Tech Tuesday – Wider Rims Are Better and Why Tubeless Tires Burp Air

Dec 13, 2011 at 5:57
Dec 13, 2011
by Richard Cunningham  
 
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Normally, this spot is designated for a how-to feature, but we are going to break tradition for this Tech Tuesday and cover some new ground with a think piece on how rim width affects tubeless tire performance. If you don’t care about tubeless tires and future rim design, then this one may not be for you. If you are running tubeless, or have an interest, then I invite you to consider that significantly wider rim designs are the future of tubeless in all disciplines of the sport.

We mounted a set of monster-sized Schwalbe Muddy Mary tires to 21-millimeter (ID) DT Swiss EX 5.1D rims and burped them right away at 35 PSI - a pressure that makes a 2.4 inch tire almost rock hard. Big tires on narrow rims - bad. The same tires rocked on 25-millimeter (ID) AM wheels. Big tires on wide rims - good.

Burping Air

Burping air happens when lateral forces on the wheel distort the tire and momentarily unseat the tire’s bead. The tire loses about half its pressure and then the bead magically reseats, leaving the hapless rider with a tire that is neither full nor flat – and absolutely useless for riding purposes.

Having been a first adopter of tubeless, I have experienced the litany of complaints about the subject that readers have posted on Pinkbike, and can say with confidence that two percent are valid technical issues and the lion’s share are generated by well meaning blokes attempting to air up a tire designed by someone who doesn’t give a damn about tubeless, on a wheel that was manufactured by his evil twin. Burping air, however is a complaint that is aired by the most respected riders and mechanics in the sport.

This article is not about wrestling with the impossible. It’s about proper tubeless rim and tire combinations, and a suggestion that we dump the narrow rim standard that cross-country riders adopted in the 1980s. The skinny rim was probably a mistake – especially for tubeless users.

Watch Mavic's Short Video That Explains the UST Tubeless Tire and Rim Interface
Views: 100,671    Faves: 21    Comments: 15


First, A Word About UST

Universal System for Tubeless is a patented interface between the tire and rim, as well as a set of standards that determine utilitarian functions. A UST tire has a square bead that interlocks to a matching groove in the rim flange and its inside has a layer of sealing rubber to allow it to be aired up and run dry. Among other items, the standard requires that the tire be mounted and aired up by hand or with minimal tools. Watch the Mavic video shown above to see how UST works. The bottom line is that UST is tough to beat for reliability and ease of use. It’s the best tubeless system in the bike industry by a long margin. If you ride XC or trail and run UST wheels and UST tires up to 2.3 inches, you probably won’t experience many of the problems outlined in this test. Presently, you can’t beat the UST system for hassle-free tubeless, but the best can always be improved upon.

Mavic SX wheel and Weirwolf tire
Mavic's Crossmax SX rim measures 21 millimeters inside to inside and is a UST certified tubeless design. The WTB Weirwolf tire is a 'Tubeless Ready' design the requires sealant. When we mounted it to the wider rim, it changed the profile of the 2.3-inch tire and improved its cornering performance.

Why Rims Need to Be Wider

There are a number of valid reasons that make wider rims a good idea. This is my short list:
• Weight savings is number one. Consider the tire and wheel as an integrated unit. The tire weighs much more than the rim, so a wider rim, though slightly heavier, adds volume to the tire without adding additional rubber and tire casing. This could be especially beneficial to 29ers because the big wheel already spins way too much rubber.
• Stability is another. Wider rims add a significant amount of lateral support to a tire – especially large-volume tires like the 2.35 and 2.4-inch rubber that has become regular fare for XC/Trail and AM riders. A tire casing could be made lighter weight and boosting the tire’s lateral stability should eliminate burping.
• A wider rim puts more of the tread in contact with the ground in a straight line and while cornering because the tread deflects less dramatically under lateral loads and remains more parallel to the rim.
• Finally, advances in materials like carbon fiber and aluminum alloys have made it possible to manufacture wider rim profiles without significant weight penalties.

drawing one
"Bicycles make their own gravity" a cycling luminary once told me. Because it must be leaned to turn, the loads almost always go through the contact patch (A) and up center-line of the tire and wheel. In normal riding mode, both wide and narrow rims can equally handle the stress.

What We Know From Experience

Experience has shown that switching from skinny, 22-millimeter (OD) rims to 27 -millimeter (OD) width versions dramatically increases the lateral stability of a wheel and tire in corners and in technical terrain. Riders who could burp 22 millimeter tubeless wheels simply by pounding out a climb out of the saddle can hammer away on 27 millimeter rims and never lose pressure. That is a delta of only three millimeters. Once the realm of downhill and freeride, 28 - 30+ millimeter width tubeless rims are now appearing in trail-riding weights. Lightweight high-volume tires like the 2.4-inch Schwalbe Rocket Ron might feel wiggly on narrow rim, but they shred on a wider profile wheel like the Mavic CrossMax SX. I found I can run one size smaller tire casing on a wider rim and it feels like a completely different tire. The 2.3-inch WTB Weirwolf comes to mind. So that got me thinking.


Why Narrow Rims and High-Volume Tires Are Bad for Tubeless

A tire may be made from a flexible material, but once it is pressurized, it acts much like a solid object to a surprising degree. Sure, it can flex and rebound when deflected, but the casing is quite stiff and when you put a lateral load on the wheel, one side of the tire tries to lever the opposite side off the rim. Clamp the tire in a vice and pull the wheel towards you and discover for yourself.

Physics dictates that the same sized tire imparts more leverage on a narrower rim than on a wider one. This probably accounts for the feeling of instability when aggressively riding large-casing tires on narrow rims. The difference of three to five millimeters in rim width only amounts to about an 18-percent change in the moment arm (leverage) of a 2.4-inch tire acting between the rim flanges. The abrupt feeling of a tubeless tire folding underneath you and burping air is a far more dramatic event than an 18-percent difference in lateral stability. There had to be more to the puzzle.

Drawing two
The imaginary tires and rims are flexed laterally at 15 degrees to illustrate that the contact patch (A) has shifted to the right. The wider rim's contact patch is still comfortably within the confines of the rim flanges (B), while the contact patch of the narrow rim has shifted to the danger zone over the right flange. The Green lines depict the moment arms of the tire and its fulcrum point at the top of the rim flange exerting an upward force (C) on the opposite bead (D). The tire probably would hold pressure at this point.

Turns out there may be another culprit that may be to blame for the thorn in the side of tubeless. All pneumatic tires flex from side to side under lateral load shifts – it’s in their nature. One reason that wider rims give tires more lateral support is that a wider rim ensures that the tire’s contact point hovers between the rim flanges. It is possible for a tire’s contact point to migrate outside the rim flanges and in such case, the line of force between the tire and rim would go over-center. In the same way that a quick-release lever generates an exponential amount of clamping force when it goes over-center as it is closed, once the tire’s contact patch moves outside of the width of the rim flanges, the tire’s ability to support the rider is significantly reduced, while the leverage it imparts to lift the opposite side bead from the rim would substantially increase. This effect would explain the feeling of a tubeless tire burping – the tire suddenly collapsing under the weight of the rider or the G-force of a turn and then losing pressure. Of course, a narrow tire could not flex far enough to allow the contact patch to get near the danger zone, but a big, flexible 2.35-inch tire on a 22-millimeter (OD) cross-country rim certainly could.

drawing three
At 20 degrees of imaginary lateral distortion, the wide-rim tire's contact point is just nearing the danger zone over the rim flange (B), but it can still support a load. The narrow rim's tire has flexed to the point where the contact patch is over center (B) and the bending forces are creating tension across the tire casing which pulls on the opposite bead, drawing it up and away from the rim flange (D). The seal has been broken and air may be already leaking.

Why Wider Rims Are the Future of Tubeless

So, by now it seems clear that, if a slightly wider rim is good, perhaps a much wider rim could offer even more benefits. In the illustrations that I drew up, I exaggerated the widths of the rims to give a clearer view of the concept – that the first benefit of wider rims for tubeless is to reduce the moment arm between the tire and the bead interface. Secondly and perhaps more important, the wider rim keeps the tire’s contact patch between the confines of the rim flanges under high deflections. Considering that a wider rim is proven to reduce the effects of lateral forces on a tire, it is unlikely that the tire on the wider rim would distort equally as I depicted in the comparison to the narrow-profile rim.

Drawing four
Still at 20 degrees, when we add more down force on the tires, the one on the wider rim can still transfer the extra load to the wheel because its contact point is hovering over the rim. Only a small amount of additional down-force collapses the tire on the narrow rim, pulling the opposing bead away from the rim flange and spraying bystanders with a noxious combination of crusty old Stan's sealant and sweat infused floor pump air. With the pressure reduced, the tension is relaxed from the tire casing and the bead returns to the sealed position against the rim.

Another potential that a wider rim may bring is a suppler ride over small bumps, and at higher pressures than expected. Tests with wider rims and similar road tires by Mavic and HED shows that the subtle change in the tire’s profile made a dramatic improvement in its performance. The switch from the classic “lightbulb” clincher shape created by confining the tire within a narrow rim, to one resembling a continuous arch made a dramatic reduction in rolling resistance over rough pavement at any tire pressure value. Cornering performance was also significantly better. Similar gains are.probable with mountain bike tires as the tire casing scribes a more relaxed arch over a wider rim, and can flex in a more uniform pattern when the tire is deflected.

DT Swiss AM wheel and Hans Damf tire
The 2.35-inch Schwalbe Hans Dampf is perfectly matched with the DT Swiss AM 10 rim. It mounts up with a hand pump and rides like it's on rails. This matchup is standard fare on the 2012 Scott Genius LT.

TubelessTips For Today's Riders

What all this information suggests is that riders who run tubeless and plan to use UST or tubeless ready tires larger than 2.125 inches should consider pairing them with tubeless compatible rims with an inner flange-to-flange measurement between 21 to 25 millimeters. A number of lightweight AM wheels in that category exist from Easton, Mavic, DT Swiss and Wilderness Trailbikes. After testing numerous combinations, we know for a fact that the wide format pays massive dividends in the handling department, and the tubeless fuss factor is reduced to almost zero. As far as getting rid of the burp, we recently ran 2.4-inch Schwalbe Muddy Marys on a set of old-school narrow DT Swiss XC wheels and they burped flat at 35 psi. We shredded for a few months on the same tires, mounted to wide-format DT Swiss All Mountain wheels without a single fault. The weight penalty of the wider rm seems insignificant when balanced against its performance gains.

Bontrager Mavic re-roll
This is an original Keith Bontrager re-rolled Mavic road racing clincher rim mounted to a Fisher (the real one) 1.9-inch Fattrax skin-wall tire - a popular XC racing tire in the mid 1980s. This is the rim that spawned the skinny, 22-millimeter (OD) mountain bike standard. Keith cut some of the circumference from a 700C 36-hole rim and rolled it smaller to make a 32-hole 26er rim. The Mavic rim is pressed together over an internal sleeve.

So, Where Do We Go From Here?

The old school 22-millimeter (OD) rim was a product of Keith Bontrager cutting and then re-rolling Mavic road clincher rims to fit 26 inch MTB tires. His creations were so lightweight that it was an overnight game-changer. Every brand that made or wanted to make a mountain bike wheel copied Bontrager’s re-rolled 700C hoops. Nobody really thought it through. Then, however, a 2.125-inch tire was considered huge and tubeless was only a dream. Tire technology has advanced so far, it’s a wonder why rim makers have only recently responded – and who beyond UST has considered tires and wheels to be an integrated system?

For the near future, I say the wider the better. Considering that carbon fiber rims are well proven and silly light, the possibility of an XC race-competitive rim at 23 millimeters between flanges is easily attainable, and rims in the upper 30s – maybe mid 40s – for AM and DH might be the game changers of 2013. If there’s anyone out there making custom rims, I’m thinking that 28 to 30 millimeters is the perfect width for trail riding. Make mine tubeless, please.

Final Notes

It's worth repeating that this Tech Tuesday is based upon my observations and theories in an effort to get an industry wide dialogue started to explore the possibility that wider rims are a better format for tubeless and to investigate the performance potential for significantly wider rims for all modes of MTB riding. I'd love to hear any opinions or theories that relate to the subject. So please weigh in. - RC



Can wider rims enhance the performance of tubeless tires?





Past Tech Tuesdays:
TT #1 - How to change a tube.
TT #2 - How to set up your SRAM rear derailleur
TT #3 - How to remove and install pedals
T #4 - How To Bleed Your Avid Elixir Brakes
TT #5 - How To Check And Adjust Your Headset
TT #6 - How To Fix A Broken Chain
TT #7 - Tubeless Conversion
TT #8 - Chain Wear
TT #9 - SRAM Shift Cable Replacement
TT #10 - Removing And Installing a Headset
TT #11 - Chain Lube Explained
TT #12 - RockShox Totem and Lyric Mission Control Damper Mod
TT #13 - Shimano XT Crank and Bottom Bracket Installation
TT #14 - Straightening Your Derailleur Hanger
TT #15 - Setting Up Your Front Derailleur
TT #16 - Setting Up Your Cockpit
TT #17 - Suspension Basics
TT #18 - Adjusting The Fox DHX 5.0
TT #19 - Adjusting The RockShox BoXXer World Cup
TT #20 - Servicing Your Fox Float Shock
TT #21 - Wheel Truing Basics
TT #22 - Shimano Brake Pad Replacement
TT #23 - Shimano brake bleed
TT #24 - Fox Lower Leg Removal And Service
TT #25 - RockShox Motion Control Service
TT #26 - Avid BB7 Cable Disk Brake Setup
TT #27 - Manitou Dorado Fork Rebuild
TT #28 - Manitou Circus Fork Rebuild
TT #29 - MRP G2 SL Chain Guide Install
TT #30 - Cane Creek Angleset Installation
TT #31 - RockShox Maxle Lite DH
TT #32 - Find Your Tire Pressure Sweet Spot
TT #33 - Three Minute Bike Preflight Check
TT #34 - MRP XCG Install
TT #35 - Stem Choice and Cockpit Setup
TT #36 - Handlebars - How Wide Affects Your Ride
TT #37 - Repairing A Torn Tire
TT #38 - Coil spring swap
TT #39 - Trailside help: Broken Shift Cable
TT #40 - Installing a Fox Float Air-Volume Spacer
TT #41 - Replace the Seals on Your 2011 RockShox Boxxer World Cup Fork
TT #42 - Clean and Lubricate Your Fox F32 Dust Wiper Seals
TT #43 - Thread Locker Basics
TT #44 - Install a SRAM X.0 Two-By-Ten Crankset
TT #45 - VPP Suspension Bearing Service
TT #46 - Rotor Straightening
TeT #47 - Finding and fixing that creak
TT #48 - Bleed and Service Magura Marta Disc Brakes
TT #49 - Cup and Cone Hub Basics
TT #50 - Install and Adjust Pedal Cleats
TT #51 - Cup and Cone Hub Rebuild
TT #52 - Converting Mavic Crossmax SX Axles
TT #53 - Cassette Removal and Installation
TT #54 - Cane Creek AngleSet Installation

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180 Comments

  • + 64
 So we should all ride surly pugslys?
  • + 0
 or doublewide, DX-32, Big Mamoth Fat, Seems like wide rims were really popular 8-9 years ago, but then dissapeared
  • + 6
 That could be because the really wide rims were usually meant for DH racing, and were made with either softer alloy grades or less-post manufacturing surface treatments (ie, no hard annodizing) with the reasoning being... they dent easily from an impact but the tube doesn't blow in the process. That's great when you're racing professionally for six minutes and a flat kills your race. Not so good for the rider who has to pay for all his own repairs and replacement parts and especially not for freeriders hoping to make their wheels last a couple seasons. In fact, that's exactly the answer a Sun Rims rep once gave to the question of why the doublewides were so soft compared to the doubletracks. The DW's were meant for racing and the DT's for general freeriding.
  • + 3
 BIG FAT LARRY on LARGE MARGE!!!
  • + 5
 Well Richard thank goodness you didn't bring up 29er tubeless........could've been another online meltdown.....
  • + 2
 Richard. I've been on 24mm wide rims for quite some time and ride a 2.2 tire tubeless at 20psi for the front and 25-28 on the rear. I have never rolled a tire off once and I am 185lbs and maybe 200lbs with gear...either something ain't working here, or pressures are being ran too low. I ride mainly XC/Trail and 2.35/2.4 is wide enough...no need to go so wide sometimes. I don't even use UST, I run Spesh 2bliss tires and/or Bonti TR tires. Never had an issue. I guess I am part of that odd few though. I just think it's like the whole bar width thing. It's all preference, some have pros and cons man. Don't stir the pot so people won't get confused and think running wide bars and wide rims on their XC bikes is the best idea. To some, it's not.
  • - 1
 Old DH rims dent easily? REALLY? That has to be about the most bogus statement ever deee. I've had endless flats in absolutely gnar rock gardens and have never seen a single "dent" in one of my rims, including the time it took me probably 50 feet to slow down with the tire completely off the rim. I have no clue what 'old school' rims you are talking about, but they sure aren't "old school", because ones like me who still run old school rims on some of our bikes have never seen an issue.
  • + 5
 Lucky you. You of course didn't identify what your rim was but I have been riding mountain bikes for 25 years now and I've not only dented my own rims simply from XC riding, I've known lots of pro-elite DH racers who've dented their rims during races. Just because you cling to some belief that rims cannot be dented doesn't make that in any way reality.
  • + 1
 Intense mag 30 front and rear for many years, now I'm running a different rear. IMO I could take a freakin hammer to my mag 30's and they wouldn't dent.

And XC rims are not DH rims. Old school XC and "multi purpose" rims SUCKED. the DH rims were awsome, minus a few, such as the double wides.

And cool stuff on the 25 years of riding. DH how we have it now only existed from the mid 90's and on, all before was fireroads and typical old school riding.
  • - 2
 And pro-elite racers are not average riders. Heck, 90% of the "pro elite" racers from the 90's couldn't even compare to the ones who rode plow bikes through stuff that makes current WC courses in "gnar factor" look like the old fireroad days did.

Watch the vids of the Avalanche mTn forks and you will quickly see the conditions real old downhillers rode in with their old school rims.
[Reply]
  • + 38
 I'll stick with tubes. Anything that offers filling tires with what looks like man jelly as a solution is a probem that has still not been fixed in my opinion.
  • + 10
 well said...
  • + 8
 Kenda downhill tube 2.25mm thick! Only had a flat once!
  • + 1
 I just use xc tubes to save weight as i use dual ply dh tyres to ward of snake bites/pinch flats,i'm also running 25mm width rims and have to run slightly more pressure to stop them folding under heavy cornering but will be getting wider rims later to support the side walll better.
  • + 5
 I agree with how terrible all sealant products are, but I gotta say tho, the right combination of tubeless products can make a deadly combo..

Ive been racing shimano xt tubeless wheels with mavic tubeless tires for 3 years now, Never flatted, and I DO NOT run sealant. Means I pump my tires up before most rides, but you should be checkin your tire pressure anyways right?
  • + 8
 Mavic ex823's wiith any maxxis ust tyre, simply spin the rim in soapy water, mount the tire, pump up and you're set. Mine hold pressure acceptably for about 3 weeks 4 at a push and thats plent for me!
  • + 3
 Mavic makes MTB tires???
  • + 3
 @Boo86:

Read the article more closely. We are discussing UST systems that are designed to "run dry", (ie. no sealant), and not retro/ghetto tubeless systems.
  • + 5
 stever I would but I'm supposed to be working, shhhh..... don't tell the boss.
  • + 3
 ^^^^ ha ha ha ha
  • + 1
 most companies have been making wider rims for a while. I had some 31mm wide halos. I run a 27 eqqualizer in the back and a 28 pimplite in the front. They are as wide as I need to go. The trick is getting tires that cut a lower profile. Miaxxis minions are pretty good. Michelin not so much.
  • + 4
 Hey Boo, have you tried tubeless? it may seem odd at first, but it's pretty nice, when you can reduce your tire pressure, and get fewer flats.. more time riding, with more traction. it's worth going through the learning curve. I'm happy I switched.
  • + 3
 Two weeks ago I was racing and I hit a G-out in a creek bed and pierced the tread of the tire on a pointy rock. Had I not have had Stans in the tube, it would have been race over. UST rim + UST tire + Stans = gold.
  • + 1
 anyone who doesnt like stans sealant havnt used it properly, as far as boos comment, you dont fill your tires with it, one or 2 ounces, and if you cant figure it out , it seals punctures
  • + 5
 yeah but calling it man fluid was brilliant
  • - 2
 Boo.....tubeless is a whole nother world if you haven't tried it. It's also cheaper in the long run.
  • + 4
 Tubeless is a whole nother (lol at the spelling) world if you haven't tried it. Yea a world of PITA tire changes. Use tubers can generally change a tire on the trail in less than 2-3 min (even the ones of us with crazy proprietary axle designs).

And cheaper? How? Tubless tires are much more than tubed tires, and being you can get crazy dh or good thorn resistant tubes that cost about 10$ of less these days, I don't see how they are cheaper, being the tire life is exactly the same btw the two, so with the additional cost being even more than the difference btw tubes and tubeless I don't see how it's cheaper. Also, people rarely blow out front tires, and many times can use the same tube for multiple - many tire changes.
  • + 2
 what he said ^^^^^^
  • + 1
 I make my own sealant, it kicks stans ass, who wants to buy some?!?
  • + 3
 Does it involve meth, methdog?
[Reply]
  • + 24
 All I know is trying to mount a DH tire on a XC intended rim blows donkey sack
  • + 5
 Discovered that the other day. Was weird.
  • + 6
 agreed, but not enjoying that visual
[Reply]
  • + 14
 Wider rims are better to a point - any old school DHer would remember there was a point where rims were so wide they ended up having a weak profile and were unstable laterally. Anyone remember Sun Phat Alberts? That's a mistake that should not be repeated.
  • + 3
 Sun double wides had the same problem ( same rim maybe ? ) , they also gave the tire a really flat profile and made them wank for cornering
  • + 4
 gotta love the 24 inch intense mags there like \ /
\ /
\ /
\ /
\---/
  • + 4
 awwwe it didnt work
  • + 1
 the sun phat alberts were a failure because of the design of them not the size of them. they were single wall. you could easily build a rim that wide that isn't a failure if you used modern rim design.
  • + 2
 Eeek, sun double wides... one thing all of us hope to forget. Now the intense mags were legendary. My front rim is going on almost a decade in age, and my rear 24 was swapped to a 26 not long ago. The 24 had a cracked seam, and it never failed, never came un-true etc, but maybe it was due to the 0 dish 165mm hub it was mounted on =]
[Reply]
  • + 12
 Thank you Richard Cunningham. Your insights into not only tubeless tires\rims but with bar width and stem length are invaluable. There are too many people out there who base their opinions on just one event or on some stubborn idea that they refuse to let die. I've worked in the bike industry off and on since 1996 and the amount of misinformation that is being slung around by consumers, shop employees, and , yes, even manufacturer reps is astounding. It really is nice to see someone looking at the mechanics of mountain bikes in an objective way.
  • + 3
 Yes- rationality good, marketing bad.
  • + 1
 Hear, hear.
[Reply]
  • + 8
 1st, thanks for the article. I love all the work you guys are doing!

I've been a huge fan of wide rims since Salsa brought out their 28mm Delgado Disc (sp) about 5 yrs ago. I can't see going back even with slight a weight penalty.

In my tubeless experience, I have yet to run UST (too much cost and too many limitations of choice), but have used Stan's rims, (my fav. the 29" FLOW) with ZERO issues. I've used tires from Maxxis, Panaracer, and Kenda without issue.

A plus, I love being able to run 2.1 tire and having them fit 28-30mm rims with increased volume that you think you are on 2.3's!
The traction you get running pressures of 20 - 23psi in gnarly East Coast terrain at 210lbs is a huge beni too.

I can't wait to have the funds to built up some XC 35-36mm rims.
  • + 1
 every one should props this so the creator can see that people care about all the work they do for us
[Reply]
  • + 4
 Informative article RC. The design of the tire is crucial in how it behaves on a rim, but wider definitely seems better for tubeless. I would like to see more experimentation done with integrated tire/tube systems designed around each other; tubeless tires designed for specific types of rims to maximize performance.

I'm not convinced on tubeless for DH, especially for the rear tire. Seen too many failures and it's an embarrassing mess to be associated with. It's not like xc where you have a tube and a pump and can fix it on the spot.

Also, what about all the Stans fluid being spilled out of tubeless tires onto the forest ground when people get flats and have to put a tube in. Especially with 29ers or AM bikes that have 2 or 3 cups in them. It is probably pretty bad for life in the ground and the run off I'm guessing. I haven't heard a any discussion about this, but it should be a concern for ecologically-minded mountain bikers.
[Reply]
  • + 3
 In first image description says, that 21mm DT Swiss EX 5.1D rim is not wide enough for 2.4 tire and thay had burped them at 35 PSI... but next image had a description, that 21mm Crossmax is UST certified... so what is difference? Is it rim bad, that makes it?

Actually I run same rims, DT EX 5.1D and Bontrager's XR4 2.35 tires converted into tubeless (with tape and sealant) and I run them at 30 PSI (as written on them as a minimal recommended pressure). Once I had a quick burp on front wheel and now I'm not so confident in that solution.

So I just thinking about Crossmax SX, but will they help against burping with tha same rim width as DT 5.1D?

I also tried to run tubeless on my DH bike this year (combination of Deemax and UST Minion), and have to say I'm not really so much confident in them after few burps on rear wheel.
  • + 1
 Hey Rich, Thanks for the great article. Do you think that in part, the burp on the muddy Mary's (using the American Classic tubeless set up on DT 5.1's) could have been because of the rim tape? The tape seems quite thin, and a film is pretty smooth and slippery, making it easier to displace the bead..

I have the same rims and set mine up using 2 wraps of 1" wide Guerilla duct tape.. It's thick, and slightly textured from the inner fibers, especially when compressed.. I believe that the added thickness help it to stay in place.. When the bead puts pressure on the tape, it compresses, creating an additional seal holding the bead in place.. after time, this acts like the split inner-tube on a traditional Ghetto set up..

I'll bet you a pack of FishClips ( www.shrockie.com ) that if you mounted the Muddy Mary's onto the same rims with 2 wraps of Guerilla duct tape ($2.50 roll at home depot) that they stay in place under the same conditions.. here's a link to a vid I shot to show friends. if they burp, send me an address.. =)
www.facebook.com/video/video.php?v=2517657694375
  • + 1
 I'll speak on this because these are actually my rims we're discussing. Once inflated and seated the tire bead doesn't come in contact with the rim tape, so that's not an issue. The film is quite thin, but it's also almost indestructible, it took a bit of effort to put a hole in even with a hot soldering iron. These rims will be completely fine with a smaller tire, they are working great with 2.35 UST High Rollers, no burping problem at all, so I'm going to guess that the noticeably larger Muddy Mary tire is partly to blame. As another note I originally tried to put 2.4 UST High Roller II's on these rims but couldn't get them to seat, even with soapy water and 100PSI. Your duct tape trick may work, but IMHO the Muddy Mary's are still too big for these little rims. I'll let Richard make his own comment as well but this was my experience with them.
  • + 1
 Thanks for the input, Ian. I didn't realize the rim tape would not contact the inside of the bead. hmm. is that because the tape is so narrow that it rides down the center channel, and not up to the edge of sidewalls of the rim? or when seated, the bead doesn't actually touch the inside of the rim, only the side walls?

my impression, and I may be wrong, is that the tire 'pops' when seating because the bead has pressure on the inner diameter of the rim, so it resists seating.. once there's enough air pressure to overcome the resistance, they forcefully slide into place and make the sound..

My thinking was: if there's a little extra pressure between the bead and the wheel, that will help things stay in place.. kind of like the original Stan’s strips, but in a cheaper version that doesn’t require tossing the gunked up strip in your pack if you get a flat.

Thanks again for the input. Cheers - Joel
  • + 1
 Exactly, the tape is narrow enough that while it does go outside of the inner channel it doesn't make it to the sidewalls. Yes the bead seats when it pops up out of the channel and into place against the rolled edge of the rim, as in the short video above. Of course non UST tires and rims don't quite lock together the same way as in the video... Your thinking may be correct, it's something I haven't tried yet...
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  • + 3
 I run ghetto tubeless on transition 32s with non-ust 2.5 minions with 2 scoops of stans. In the last 4 years I've had 2 flats. One was because I had about 18 psi in the back and dropped about 5 feet in to a rock garden, by mistake, and bent my rim bad enough that the bead would not stay on. The other time was when I tried a single ply exo casing and put a inch long tear in the casing. I live in Arizona and the stans is a must have for cactus and thorns. Tubeless is the way to go.
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  • + 2
 I think the biggest clincher here (no pun intended) is keeping tire beads seated on the rim when run tubeless. Everything you say is good, RC, and wider rims help tires stay on, better, but I still think the key is having some form of bead lock. I'm running Mavic EN521 rims, and they cannot be run tubeless, effectively, because there is no ledge for the tire bead to sit on. That's a major point of the UST format: the interlocking bead aspect. Wider rims are good, but I think rim manufacturers have been failing us in not getting that locking bead aspect down.
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  • + 2
 In terms of DH application of this theory it demands a balancing point to be achieved with rider preference there is too wide and too narrow. Yes a wider rim means a flatter profile. And yes that gives you good straight line traction. BUT it doesn't always mean better cornering traction. At high speed you will do 2 things when leaning a bike in to a turn with a tire that has a flat lateral profile. 1 you will have a reduced range of angle in relationship to to the surface the tire is on do to the flatter profile having less roll. Now for those of you who would say well i doubt many people achieve that kind of lean in a corner well fine there is my 2nd point to come. 2 With a flatter profile the tire will break traction much harsher under hard cornering because its like winding up a spring. with the "improved" traction at a now more limited angle of attack you are going to break traction latter once you have built up more energy in the side wall of the tire which makes it a less predictable and much harsher break-away-point. With all that said there is a reason that Dirt Bikes have a rounded profiles to there tires and they have offroad racing history all the way back to the 60's. Do they really think they have figured something out that motocross hasn't already.
  • + 1
 Norm, motos are much heavier and are ridden in a different way so there is reason to believe mtbs could benefit from different tire designs. Rider style and ability is an important consideration too. With the weight of the moto and the stiffness of the tire it will easily dig into the ground, while an mtb tire will roll over the top more often. It may need a sharper edge if it hopes to really bite into terrain. This design only works for the relatively few elite riders who are comfortable leaning their bikes very aggressively.
  • + 4
 The point he's trying to make is, with the right tire, a wide rim is better. Tire manufacturers will start producing tires with lower sidewalls, so the result when paired with a wide rim, is the same rounded profile on the tire. Tires and Rims need to change together. Using a current tire, with an overly wide rim, and you get a squared off tread. Take that same combo, and redesign the tire with less sidewall, and you've got the optimal setup. Tire manufacturers will have to change their tires, to get the desired effect. But, I do see this being the future. Less rotational weight, lower psi, rounded tread = bad ass setup.
  • + 2
 Ridgeline you nailed it. And that's exactly how moto tires are already the side wall is lower.. the psi is at like 12-16.. and the rim is wider. with current tires the folding over issue would decrease with a wider rim but too much profile and angle of attack is lost . Also papapendrel I ride both enduro and moto as well mountain bikes. I used to work as a mechanic in the industry and race in all disciplines. I know a thing or 2 and i can tell you there a 100 kids in whistler below the age of 16 that can lean a bike hard enough to achieve the circumstances i spoke of and the weight difference is addressed in scale in this issue. A dirt bike alone weighs 250lbs and even though the tire casings are built to be stiffer on scale to a mtb tire standing still when you get one up past 60kph the rotational mass that is generated by a tire that is that much heavier to begin with gives it quite a bit of flex in a corner. With all the rotating parts of a dirt bike you go from a 250lb bike with a 200lb rider kitted out on top at a stand still to the equivalent of probably in the 600lb range over the contact patches of the tires when running at speed. the rotational mass is the only thing keeping the tires centered and from flexing beyond control not to mention they run at a lot lower psi also allowing them to flex quite a bit. the flex issue and generation of energy that can be released at the break away point in traction for tires in both sports is of very similar science and math just on different scales.
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  • + 2
 Really interesting article , gets you thinking .
Has anyone got any experience with Muddy Marys in wire bead being used tubeless ? I bought mavic EX823's with mind to going tubeless but could not be bothered with swapping tires all the time , now I have found these Muddy Marys which have turned out to be a true all year round tire.
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  • + 2
 Bought a pair of dee max rims last season for my DH bike, decided to use tubes rather than go tubeless, went from having 3 flats, in the past 8 seasons to having 11 flats (mostly snake bites, plus 11 walks of shame in the park) by mid season, plus one nasty spill due to a rolledover front tire wash out. Lost a ton of confidence for the remainder of the season. Decided from there to put an older wider rim on the front non UST, while at the same time opting to try tubless on the rear, also aced the fold up UST tires replacing them with the ones that come round off the shelf. Frick that was one costly, time consuming, emotionally draining, experiment.
-wider rims are better
-UST works, choose your tires carefully, triple compound tires give you more flexabillity, folding something that should be round and stuffing it in a square box WTF.
-reducing grams is expensive in MTB, but the gains can be rewarding, especially when you focus on unsprung weight like your wheels and tires, just don't forget that stability and traction are priceless.
-Thanks Tech Tuesday for addressing this very very important issue, I would love to here more in the future.
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  • + 2
 From my experience, I've spent a day on DT5.1s with 2,5" minions, converted to tubeless and on a first bigger mistake it lost most of the air. I was wondering, if atual UST without conversion would help, but this width makes a lot of sense as well. Anyway I'll rather see what 2013 will bring and run my tubes for this season..
  • + 1
 i think it is all preference. i tried tubeless and burped the tire @35- 38 psi even on a wide rim. i think tubeless is great for the dh racer who has the perfect setup or xc riding but in my experience, i find tubeless way to expensive and too much of a hassle for the everyday dh rider or freerider. But as far as wide rims go, theyre great for both tubes and tubeless setups because even if ur running tubes, the tire will still fold over under harsh lateral forces, so wide rims all the way!
  • + 1
 Well that's certainly true, when i was riding somewhat well (ok that's a lie, I never ride well, but i wasn't failing that hard for a while), the tire held air very well, and it was maybe better than tubes overall in terms of grip(that's very biased, comparing SX trail with V10 syndicate), but once i went a bit too much to the front on a steep section, ended up going over the bars and after that my front tire was empty.

That said, for clean riding or just anyone who has some skill, it could work (we've all seen that), but when making mistakes, or probably on landing large jumps I'll rather wait for something more forgiving.

About rims width, I've used to run 23mm, now I'm down on 21mm and can't notice it, but that'll come with time i guess..
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  • + 2
 Before I switched everyone told me how much trouble tubeless was and that it wasn't going to work with my wide AM wheels and tires. I didn't listen though and went for it anyway and I couldn't be happier. No flats, no burps, no problems. I can get them to seal with a hand pump and some soapy water.
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  • + 2
 Richard - keep in mind that tire design plays a huge role in the leverage effect that causes tubeless tires to burp under load. Sidewall height varies from tire to tire, as does true casing width. I would argue that the careful choice of tire plays as big (or bigger) role than rim width does. A tire with a comparatively low sidewall height, narrow casing, firm casing and firmer compound will maintain its shape and break traction before burping the sidewall. Taller sidewalls, thinner/wider casings and sticky compounds are more prone to pulling off a narrower rim. The taller the casing, the longer the lever.

All that being said, I run a 28mm I9 EN wheelset and ride it hard, no problems. The weight savings of a 24mm rim are not worth the potential hassle of losing air even once IMO.
  • + 1
 Good points g123. Experience supports them. RC
  • + 1
 Continental tires in particular tend to be taller in casing height for a given "width" stamped on their sidewalls than most every other brand.
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  • + 2
 I am running tubeless Stans Flow rims with Maxxis Minion EXO 2.5 No problems so far after 5 rides over rocky high speed trails.

Previously I ran Crossmax SX (UST) with UST tires and it requires no 'juice' but mounting requires a compressor; I needed to inflate to 70psi to get them to snap on to the rim. Once on it was great... then...

... Maxxis came out with my favorite DH tire, the Minion, in a single ply 850g tire 2.5". For an AM bike, this is the perfect front tire. But, no UST option without gaining a pound in the tire. So I was back to tubes just so i could run this tire.

Now I have Stans rims (not UST) they are made for regular tires (read: lighter and more options and I can run my EXO tubeless!) and yes with messy juice but overall performance is awesome. I now have DH feeling grip with near XC weight. So good.

I know of guys that run this on their DH bikes for the resort riding for jump trails; light wheels make H U G E difference to your ride. There is nothing I can think of that has a bigger impact to the feel of your bike and ability to go fast with confidence.

Great topic.
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  • + 1
 Good article.

So wider is lighter and less burp prone; but there must be an upper limit. Any gain usually means a compromise on some other aspect. So what to you compromise by gaining less tyre-burps? What is the ideal tyre width to rim width ratio?

What would happen with a rim as wide as the tyre (i.e. the tyre cross-section a semi-circle)? If the rim was even wider than that, you'd basically have no sidewall!

I can think of three considerations:

(1) As you increase the rim width the tyre volume increases, but only up to a point; then further increase in width the tyre reduces the volume.

(2) An equal tyre/rim width (i.e. semi-circle tyre cross section) seems to be the optimal shape for the air pressure pressing the bead directly against the rim; with any wider a rim the air pressure is going to be pushing the bead more outwards off the rim.

(3) If you picture a wheel with a huge rim width to tyre width ratio, it becomes obvious that when the wheel is leaning over (i.e. when cornering) you have less space between the rim and the ground than you would have if the rim were narrower. This would presumably mean less bump absorption, less traction, and more 'pinching' of the tyre.
  • + 1
 good points, also the edge of your rim is less protected by the tire and more prone to rock damage, I've seen this with too wide of rims on rock crawler trucks.
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  • + 1
 never had a doubt that wider rims are better for most DH/ AM use, especially when running single sidewalls with the new Maxxis EXOs : at only 140 lbs i have an advantage over heavier riders with these pinch 'resistant' tires, but i ride with a couple of guys that are over 180lbs using EXOs and they are both using wider rims than me to compensate for the extra weight on these thinner sidewall tires - i can see significant merit to wider rims for anyone wanting to lighten their ride up [ 1.5 lbs with both tires ! ] but still have the same durability as a Double sidewall. and BTW, have had 3 pintch flats w/ the EXOs [ once at Whistler and 2x on Burnaby Mt. DH trails ] but EVERY time i was running way too little air - never had a flat since running at 28 - 30 lbs rear & 26 - 28 Front so a heavier rider could run a little higher
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  • + 1
 Richard
how about an article expanding on the tubeless concept?. you stated that UST was the best, period. what about tubeless ready? especially since there are no UST tires for 29s. why not? too heavy for one reason and UST tires have thicker casings meaning less supple. SInce 99% of UST users use sealant, then the reality should be UST rims and tubeless ready tires are the best. I think if you do some personal testing you'll agree
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  • + 1
 "The 2.35-inch Schwalbe Hans Dampf is perfectly matched with the DT Swiss AM 10 rim. It mounts up with a hand pump"

I would love to see this happen.... Not saying it's not possible, but it's pretty rare, as in never happened for me, that a tubeless tire will bead with a hand pump.
  • + 1
 Mounted 2.35 High Rollers to Easton Haven rims with a floor pump no problem, no sealant either...
  • + 1
 most any specialized 2bilss tires will
  • + 1
 Also should note that 90% of the tubeless set ups I've done in the last year were on non-tubeless tires..... My bad.... I'm sure proper tubeless works fine
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  • + 1
 I didn't realize they still maiking skinny rims until I saw my buddy get a pair of sun disc jockey wheels. He said they looked wide in the picture lol. Now they in the trash and he on 33mtx. Anything under 28mm shouldn't be on a mtb. 32-28 mm all mtn, 32 and up freeride/dh. Dj peeps try getting away with skinnies but usually handle like crap.

Now they going to make doublewide tubeless 29ers son
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  • + 1
 Totaly agree with you Rich, wider rims up to a certain point would definetely will improve the tire behaviour. We need wider rims than 21 mm (internal width) for even a better behaviour on tires above 2.35 width maybe even 2.2 width. I have a DT SWISS 2200 (22.3 mm) internal width on my Marin Wolf Ridge 2009 and the handling on the tires improved from the old hoops I had Mavic 321(21 mm) internal width. Bring some 25 - 27mm internal width trail- all mountain hoops on the market and for 2.35 and upsized tires. Sorry for the grammar english is my 2 language.
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  • + 1
 i used too ride 3 inch nokian tires on double wides on 10psi or less w/ out tires flexing side too side
then when i switched too my first set of 729 is was out w/ the nokians cause they couldnt handle the narrow rims at low PSI
ive always told people that wider rims let you run bigger tires at lower pressure
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  • + 1
 What I dont understand is in their photos they do not show a UST tubeless rim and how well a Tubeless Compatible Tire interface. A square edge bead locks into a UST rim or a UST approved rim diameter for a perfect fit. In the fail position this is a real example of a Stans tubeless system applied to any rim that is not UST. This is why Stans doesnt approve a perfect fit for any match tire on any match rim. With a UST ERTO rim and any UST or TCS, 2Bliss, or TLR tire system is consistent and will fit perfectly for a no fail situation. I will say if you are all about boostin big air and huckin, forget tubeless. If you are a racer and/or want speed, traction and more control go for tubeless. Do not run a Stans system if you like to be agro, you will burp and break your collarbone. If this doesnt make any sense go to www.wtb.com and watch Jason Moeschler and Mark Weir explain why they created a new standard so everyone can have consistency in their tires!
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  • + 1
 I've been running wider rims than the norm since 1999. My XC bike back then used Mavic 521 28mm with 2.1 tires. Now I run 32mm with 2.2-2.3 for XC and my DH bike rocks 42mm trial rims with 2.6-2.8 tires
I'm able to run less pressure 22psi (single ply) for XC and 15-16psi for DH, have more grip and fewer pinch flats (XC). AND the bike looks so much cooler, more moto!
Haven't switched to tubeless cause I like to switch tires frequently for different terrain, though I have used it for trials back in the day (loved it).

www.pinkbike.com/photo/6853305
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  • + 1
 so i finally couldnt understand could someone help me please! I bought a pair of those same white crossmax sx wheel set with two specialized 2bliss tires which by the way suck but came stock on my enduro, i need to change them because on a burp today they passed away, so which would be the recommended tire for the crossmax on all mountain riding? and are the rims any good???!! i didnt know they had a 21mm width when i bought them so i kinnda regret it?
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  • + 1
 So why does a 47mm trials rim burp when ran tubeless? Is it the silly low pressures?

Do you think the UST standard if applied to a modern trials rim would be viable?

Just a technical question because I'd love to run front and rear tubeless for trials!
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  • + 1
 tested with a friend of mine trials rims on a DH bike (44mm wide rear) with tubes. Problem is that the tire is not as round as it used to be on a narrower rim ( a high-roller is almost square edged in the section). When you lean into the turn the bike will not turn as it used to. Has to do with inner/outer tire diameter ratio. My point: rims alone will not do it. Tire profile will have to change too.
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  • + 1
 I can the see reason you are striving for, but making a tyre square will make it handle like a bag of shit when on the shoulder. this is an extremely misleading article to back up your opinion not fact! Tubeless is the way forward though.
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  • + 1
 total mess up with the widths of rubbers and rims.

1: muddy mary: 2,35" or 2,5" there is no 2,4" muddy mary. do you even know what you're writing about?
2: in the very beginning it says:

We mounted a set of monster-sized Schwalbe Muddy Mary tires to 21-millimeter (ID) DT Swiss EX 5.1D rims and burped them right away at 35 PSI - a pressure that makes a 2.4 inch tire almost rock hard. Big tires on narrow rims - bad. The same tires rocked on 25-millimeter (ID) AM wheels. Big tires on wide rims - good.

and in the end it says

As far as getting rid of the burp, we recently ran 2.4-inch Schwalbe Muddy Marys on a set of old-school narrow DT Swiss XC wheels and they burped flat at 35 psi. We shredded for a few months on the same tires, mounted to wide-format DT Swiss All Mountain wheels without a single fault. The weight penalty of the wider rm seems insignificant when balanced against its performance gains.

3: so non existing 2,4" schwalbe tires suck on a 21 ID rim like the pictured EX 5.1. thank god they managed to mount the same tire on a dt swiss "all mountain rim" what certainly means it is a brand new (and very allmountainish) dt swiss EX 500 rim.
some might know that this is actually the same rim with different stickers on it. great work richy. and please don't tell you mounted a 600+ grams dt swiss "freeride" rim and name it somewhat allmountain with little weight penalty.

yesterday the cockpit height, today rim width, whats up for tomorrow? i'm sure to wake up, willing to follow a new trend!
  • + 0
 Maybe he actually measured them....they measure about 2.4. Unfortunately Schwalbe has skewed sizing, so they call it a 2.35....
  • + 1
 i do not want to flame, its just when someone tries to tell me that a few millimeters of rim width make a difference, then a few mm of tire width do the same.

schwalbe has not skewed it. take out your caliper and measure a 2,4" schwalbe (for eg big betty) and afterwards the muddy mary. you will notice a 2mm difference. fortunate me: i own the mentioned ex5.1/ex500 rims as well as big betty and muddy mary tires. the different sizes are even visible, especially in terms of tire volume. just sounded fishy to me.
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  • + 1
 Wider rims may be better, but only up to a point. Everything is a compromise, and what I think this article fails to address is the other side of the story: What if you make the rim too wide? Imagine a stupidly wide rim, and it becomes apparent what the downside of increasing rim width is. The centre of the tread may still be a good distance from the rim, but when cornering the part of the tyre in contact with the ground is closer to the rim. This effectively results in characteristics of a narrower tyre, namely: reduced bump absorption and hence less traction, and more prone to 'pinching' of the tyre.
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  • + 1
 According to this, if we use wider rims, it prevents leverage. which means you can also correct burps by having shorter sidewalls on your tires. or higher sidewalls on your rims. or maybe even a inner side wall on the rim with a bigger hook.
  • + 3
 I spoke with Stan (the Man) at the Interbike Expo about this and he agreed, that running shorter sidewalls on the rim actually reduces the tire's ability to lever the opposite bead up and burp the tire. All Stan's rims have this feature. The European ETRO tire and rim standards do not allow Stan's low-flange rim design (and many other good design improvements suggested in previous comments) to be sold OEM on bikes.
RC
  • + 1
 If only they would have thought about all this before big companies ruled the bike world and set standards. any big changes in cycling are hard to get accepted by riders. unless someone comes up with something you can just add with out having to change any sizes, like a sealant that remains really stretchy and flexible even when dry. that would be wonderful, but it seems unlikely.
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  • + 1
 Some interesting info here, but not really, pretty obvious
Hardly a complete gathering of all the information required to know all you need to know about tubeless.
Sorta seems like he's focused on the obvious basic stuff, and not really mentioned anything that applies to the real choices of running tubeless.
Such as
The various and unpredictable size standards of tubeless tires
The various sizing standards of rims that are tubeless, or aren't, or are called good for both(bullshit)
The reliability of the mavic eyelet style rims meant for normal spokes and hubs. They're expensive, and aren't void of eyelet stripping problems, Burping, Etc.
It'd be nice to hear more about ghetto tubeless
And it would be nice to hear more about Stans

Not because i need the info, just in the interest of a more concise article.
I've already made my decisions. Stans for trail bikes, always with LUST tires. And forget about it for downhill.
Almost none of the world cup pro's use it so why should I?
Seems like the Athertons got a few flats this year. I'm not racing but flat tires piss me off. especially tubeless style flat tires where instantly your tire has no air and you're lying on the ground in pain wondering what the hell happened

What sounds very interesting however is the tube/tubeless system that some of the teams have experimented with.

Most importantly, finding what works for you and your style of riding, and where you ride is what matters most. Because theres a lot of stuff out there that doesn't work well (kinda like most bike part situations) and could hurt you seriously.
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  • + 1
 Great article - love to see some tech thought going into things rather than just emotive 'feelings'.

Can someone tell me why Mavic only make UST rims in either super skinny (X819) or super fat (X823)?

From experience, the Mavic UST system is the best (Stans just didn't work for me). However, the 819 is too narrow for anything other than XC duties and I concur with the problems identified above. I've used the 823s for DH racing and found them to be brilliant - however just too heavy for general trail use.

If Mavic are supposed to be at the vanguard of tubeless rims (UST), then why don't they make an 821 aftermarket rim?!

Bah!
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  • + 1
 Wider rims may be better, but only up to a point. Everything is a compromise, and what I think this article fails to address is the other side of the story: What if you make the rim too wide? Imagine a stupidly wide rim, and it becomes apparent what the downside of increasing rim width is. The centre of the tread may still be a good distance from the rim, but when cornering the part of the tyre in contact with the ground is closer to the rim. This effectively results in characteristics of a narrower tyre, namely: reduced bump absorption and hence less traction, and more prone to 'pinching' of the tyre.
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  • + 1
 I run a slightly wider rim with a tube type set up. I found that this kind of set up improves wheel strength and tire stability when it gets gnarly. and you don't have to worry about that white "man jelly" stuff. I also got 0 flats during the 2011 season.
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  • + 1
 You're preaching to the converted here RC. I've been running wide rims on my bmx bike since the 1980's and for the last 6 years on MTB. 28mm Mavic XM321 and 31mm Sun singletrack rims. Good article - especially for XC and Trail riders who tend to run skinny rims. Freeride and DH riders are usually on wide rims anyway.
  • + 1
 Ditto. I'm happy on my Araya 7X rims and Mitsuboshi CompIIIs on my Kos Kruiser... :-)
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  • + 2
 This all makes huge sense. My really wide Spank Spike rims worked perfectly tubless. But I'm now running DeeMaxs (although with tubes), where does this leave DeeMaxs? too thin for tubless?
  • + 1
 deemaxs are 29mm wide, its still wide enough.
  • + 2
 You sure? I read that the Deemax is actually 23mm (inner width) which would make it only half decent for UST-purposes and my new bike comes with a Deemax/Minion-UST-combo.
  • + 2
 internal yeah, they are 23mm, i was on about external. the are basically the mavic ex823 rim (the latter 2 number on mavics denotes internal rim width). i thought they were on about external in this article.
  • + 5
 So it's even more ridiculous that the Deemax Ultimate is only 21mm wide and Mavic has inveted UST.
  • + 4
 The only reason that Mavic and DT Swiss and others all have such skinny inner width rims is that they are obsessed with advertising the lowest possible weight wheels/rims. This comes at the expensive of reliability and performance for us buyers. Spank is one of the very few companies making decent-width rims, and they aren't even that heavy. Excellent article Richard C!
  • + 2
 True that wheel-addict, the Spank Spikes are 35mm external and weigh 595g. The Spike Race is 28mm/23mm and weighs 510g. That's a ton of width w/o a lot of weight. One major difference is Spank MAKES their own rims and is not a rim extrusion rebadger. Wider is better but Mavic and others in their search for lightweight have forced us down a narrow road.
  • + 1
 I have 823s and when running tubless with 2.4 UST tires the rear would still burp sometimes when doing 180s, even at 40psi. My rear wheel has a tube in it now.
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  • + 1
 You lost me at lighter weight. Can't remember the last time I ran tires narrower than 2.2. Are you suggesting that I can get a wider rim and downsize to a 1.9 and enjoy better tire performance at a lighter weight? Kind of hard to believe...
  • + 2
 In the case of AM/enduro type riding.. whatever you want to call it... I think a 2.35 tire on a wider rim is better than a 2.5 tire on a narrower rim.. you'll get similar volume with a better profile that won't roll over and at a lower weight (maybe marginal depending on rim comparison)... this is true whether you're running tubes or tubeless... and both options set-ups are fairly common.. so i think there's a valid argument to be made.
  • - 1
 When RC makes an article, you have to assume it's more about XC than DH. He may claim he's more trail/AM oriented, but many other people's AM likely makes his AM look like XC.

I'm already on wider rims, but when I saw that part about going wide for weight weenie purposes... LMAO.
  • + 3
 Apparently it's the author of the article you take exception to and not the content. So be it. The logic is perfectly sound in theory and in practice.
  • + 0
 Rotational weight is the most noticeable weight on any type of bike....why do you think the syndicate has been rocking carbon wheels....last time I checked, WC downhill isn't XC riding. To me, wheels, pedals, and bars are the most important part of any bike, no matter what style of riding it's for. If you take weight off your bike, it is most noticeable in the wheels.
  • + 1
 "• Weight savings is number one. Consider the tire and wheel as an integrated unit. The tire weighs much more than the rim, so a wider rim, though slightly heavier, adds volume to the tire without adding additional rubber and tire casing. This could be especially beneficial to 29ers because the big wheel already spins way too much rubber.
• Stability is another. Wider rims add a significant amount of lateral support to a tire – especially large-volume tires like the 2.35 and 2.4-inch rubber that has become regular fare for XC/Trail and AM riders. A tire casing could be made lighter weight and boosting the tire’s lateral stability should eliminate burping."

I am arguing the content and, to better understand it, you need to know where the author is coming from. RC is talking about XC/trail/AM. He doesn't make any true mention of DH nor 2.5 tires, besides predicting 30-49 rim widths.

You say you *think* a 2.35 tire on a wider rim is better than a 2.5 tire on a narrower rim. Put some numbers to those rim sizes--should I assume 24mm inner width for the 2.35 tire and some 19mm inner width for the 2.5 tire or 25mm inner width rim for the 2.5 tire and a 28mm inner width rim for the 2.35? I said I find it hard to believe that you can enjoy a better tire performance from downsizing a tire and putting it on a wider rim, with weight savings in mind. The tire performance will go down and putting it on a wider rim will not restore that performance; you can't say restore, since it won't ride like the 2.5 tire. It will *alter* the performance, but whether that's good or not is up to the user. What you're trying to argue is that it's optimal for a specific use, such as what you see as AM/enduro type riding.

It's best to ask true experts, such as tire R&D team members, rather than rely on some journalist or some random nobodies. They have the scientific knowledge to understand the properties of everything that goes into a tire and the tools to confirm it.
  • + 1
 My point is, 2.5 tires are not only wider, but taller. You cannot match the volume of a 2.5 tire, with a 2.35 tire on a wide rim.

Here is an illustration of the cross section of a tire mounted on various width rims:
www.pinkbike.com/photo/7493994

Trying to find the area of these individual shapes, you can get an idea of the volume of the tire according to how wide you mount it (actual volume depends on the rim inner cavity too). Summing all the data up, you will find the volume difference of mounting the tire on a rim that's 2-5mm wider is very insignificant compared to the volume difference of a larger size tire. The altered performance comes more from altering the shape of the tire, to a shape that the tire manufacturers did not intend for it to have. There's a reason for rim standards. It's basic geometry, according to the tire size.

This article is an overglorified rant about how tubeless conversions have more issues than UST or other tubeless solutions, and how wide rims *may* reduce burping, along with a bunch of other opinionated reasons, some rather silly, about why rims should be wider in general. If you want to use wider tires, mounting them on wider rims than you usually mount your narrow tires on for better performance should be obvious, just like saying going true UST is obviously better than a relatively ghetto American Classic conversion is better for tubeless performance. The tighter a tire fits, the less likely it is to burp. Another post here, from the owner of the rims pictured, says the tire bead doesn't even touch the rim tape (read: doesn't even touch bead shelf) on the DT rims when inflated. That's what I call a loose fit...

I admit I dislike RC's articles, even during his MBA days, but this is only one of the few times I spoke out against it. I'm actually surprised I'm spending so much effort trying to explain myself, when I could be spending my time doing something more productive, including riding.
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  • + 1
 Only problem I see might be getting the tire to air up on a wider rim. I've got 19mm Crossmax STs & had no issues running non UST 2.1 Nevegals(30-32psi) in B.C, and non Ust Psyco Genius 2.3(28psi) when in Arizona for 3 weeks. Stan's in both setups. No burps, no flats in the cactus, but a bit of squirm with the bigger Psycos.
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  • + 3
 I run "Ghetto Tubeless" with cheep Ruber Queen 2.2's on a mavic 729 and sunn singletrack. Yet to have a burp. Or a puncture, after 8 months.
  • + 1
 I'm with you.
Run "Ghetto Tubless" on my kids DH race wheels on Syncros DPS32 rims and never had a pinch flat or burp in 2 years or so. Put tubes in their thrash wheels and get pinch flats even with good pressures Frown
Only just saying today that I'm going to run even those ghetto Smile

It's a cheap simple alternative that works, rather than converting to proper tubeless rims and tyres.
  • + 0
 your name says it all
and if you need to fix a tire on the trail? good luck getting a ghetto tubless setup redone
  • + 3
 Apart from there is no difference between changing a tube mid ride, and swapping the ghetto liner for a tube mid ride?
  • + 1
 @Shodan54
Read and make an effort to 'comprehend' what has been written rather than just flame it.
Take note of what I wrote.
* DH race wheels. (not out on a trail in the middle of nowhere)
* No pinch flats or burps in 2 years + (who carries a tube and changes it on the side of the track mid run at a DH race anyway)
Fair to say that there is NO issue here at all.

It's a race meet so I take spares.
If they cut a tyre which has happened before I put in a spare wheel.
If they are having that bad a weekend with cutting tyres I put on a new tyre with a tube.

Oh, and as for the name, who cares what it is. You do not know the story behind it anyway.
  • + 1
 In my experience, ghetto tubeless doesn't work because there isn't the correct tyre bead/ rim interlock that you get with the patented UST system. Yes, ghetto works when the bike is in a straight line, but land the bike sideways or push hard in a corner and non-UST tyres tend to roll off the rim.
  • + 1
 @mackeroo
I understand what you are saying, but will have to disagree.
Both my lads are around the 100kg mark and hammer down a DH track, corners, berms jumps and drops anything and never rolled a tyre.... We have tried it and found it to be more than successful and will continue to run them that way.
I can only think that anyone having trouble may not be seating the tyre initially with a high enough pressure before putting in the latex, wrong tyre pressure or wrong mix of latex/water.
But hey, each to their own what works for some may not for others Smile
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  • + 1
 Totally agree, wider rims make sense in every way, regardless of tubless or not. In MX you don't see skinny rims with tires on them like balloons either. Their rim widths are relatively close to their tire widths.
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  • + 1
 Can't wait for the wide format war to start! I ride in a rock garden backyard so it's either to much pressure to prevent smashed rims or constant burping...bring on the wider trail rim!!
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  • + 3
 I get the vibe that over half of the people who dismiss tubeless haven't used it before.
  • + 1
 word to your mother...
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  • + 1
 25-26mm inner width is perfect! I use 26mm on my dh and street bikes and it works great. Tire profile is wide enough and round enough and it doesn't roll too much either. 26 width is perfect! Try it and you'l see!
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  • + 1
 Is there compagny that makes 24 inch downhill tubes because my DMR Moto Digger are super nice but the side of the tire is so gay I always get punctures when I land or bump a bit whippy ahahah !
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  • + 1
 No mention of the new hookless tubeless rims and why they work better? Also my mates CX bike burps tubeless tyres like heck... tyre width to rim width is way down on a CX bike...
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  • + 2
 Thought provoking article that would very likely have been edited down for space if put on a text-based magazine. See why web publishing is the future? Thanks for that RC
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  • + 1
 I run Easton havens with Kenda nevegal 2.3 with Stan's sealant. I have not had one flat in two years, best investment I have made. Corners awesome no burps. Ido check my air psi ever ride, works best at 23 psi for me
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  • + 0
 "That is a delta of only three millimeters" delta! Ha. Why not just write change!? Or if you wanna be really mad draw the triangle, or lower case delta that looks like a musical note.
  • + 5
 HAHA! Delta. I just like the way the word sounds. When you write tech stories for a few years, you get tired of using the same 200 words over and over again. Plus, it's fun to toss a fish into the seal tank now and then. RC
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  • + 1
 I run 2.35" Schwalbve Nobby Nic's tubeless on 21mm rims with Notubes' sealant at 1.7 pressure and it works fine. There is no answer in the list for me to choose from.
  • + 1
 It depends how do you ride your nnics. I was blown away about mine on 21+ (dunno exactly) XT AM rims. They seemed fanstastic until I rode them in proper mountains, until I took them to the pump track, until I wanted to whip a bit on dirt jumps. I'm not a best rider, yet I found their edge. A flexy edge. Then trying Rocket Rons which are even skinnier was really a head shaking experience, even as for a rear tyre.

There are other factors to take into account than just rim width like tyre stability dependent vastly on sidewall thicnkess. Then it's not only about tubeless, super thin tyres will provide terrible handling even with dh tube. Then different rims have different ability to hold the tyre tight. Ghetto conversions will definitely not hodl the tyre as well as virgin-tight Mavic UST rims.

Both tyre and the rim have to come together to fit the specific use and riding skill. Sure it is better to put your trust on wider rims, but this discussion is completely pointless for someone who hasn't come the level of being able to take any tyre off the rim, because he just can't ride aggressive enough. XC riders on XC races riding with their saddles high, not being able to lean the bike enough or "foot it out" can ride 2,8" on 17mm rims.
  • + 2
 " virgin-tight mavic" Waki you should write greeting cards...........awesome!!!
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  • + 2
 that was great.... This is a solid article and we need to see more of these since they are very very informative.
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  • + 1
 wider rims do wonders for normal tubed tires, nevermind tubeless. i will never again ride a sub 25mm rim, not even on a xc bike, PERIOD. ztr flows for me.
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  • + 1
 I ride 823 and I don't have air burping problems...but I do have freakin problems with flat tires...I ALWAYS get a f** hole in my tire, and byebye brand new minions...
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  • + 1
 I can't believe I still hearing people say that tubeless is the way forward. Tubeless is the only way to go. Any discussion is backwards.
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  • + 0
 "Weight savings is number one. Consider the tire and wheel as an integrated unit. The tire weighs much more than the rim, so a wider rim, though slightly heavier,... "

Negating statement...
  • + 2
 simple math- 100g adfditional rim weight. Subtract 100g going to a 2.25 tire from a 2.4 and keep the same air volume. Now add the 50g sealant. You need rim tape either way, so +5g for sealing tape. Finally subtract the tube weight 200g+. You lose approx 1/3 pound doing this, and have better rolling performance, traction, and flat resistance. I have used these conversions on my bikes from DH to cross county for the past three years and have had one flat, and it was traced to a faulty rim strip which was replaced free of charge. I would use tubeless for my BMX, but the pressures are too high. If you take your time and learn to do the conversion correctly, these systems work awesome. If you slap it together, you will have nothing but trouble.
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  • + 1
 Excellent format for this Tech Tuesday. I enjoy the how-to, but this tech-opinion piece is well done and significant.
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  • + 2
 Are the rim widths in the article external or internal widths?
  • + 1
 good point
  • + 1
 Late in the article he says " with an inner flange-to-flange measurement between 21 to 25 millimeters" so I guess all measurements are internal. One of my sets are 21mm external and 17mm internal and that is narrow as all hell, I doubt RC is wanting us to go to 17mm internal.
  • + 1
 When RC was discussing a 22mm standard, he meant external. When he said 21-25mm for AM he meant internal.
  • + 1
 Yea, It got a bit confusing there. I went back in and cleared up the ID/OD references.Thanks rsuske.
BTW, there are a lot of riders out there rolling on 17mm ID rims. Seems funny after riding wide for a year.
RC
  • + 1
 Much like my Mavic 819s ... too narrow!

The rim manufacturers need to get on it and make a light, wide, strong XC/AM rim - unless I'm missing something obvious, I can't think of one.
  • + 2
 17mm is not too narrow, its just too narrow for AM bikes. They are designed for XC tires on XC courses and to be light as hell, which in an XC race matters more than supreme cornering capability. In a loop you spend much more time climbing than descending. And the start can mean everything.
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  • + 0
 There should be one called i have no idea what they said at all. but since there is not one im going with milk is for cereal not tiires Razz
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  • + 2
 Just wish there was more UST tyres out there???
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  • + 1
 I've trying to install Schwalbe Rocket Ron on my bike's wide rims using Stan's but they leak on sidewalls... and flat.
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  • + 1
 i have always ridden pimp rims.
i got pimp lite rims on my trance x now Big Grin
with tubeless fitted
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  • + 1
 That is obvious. Problem is that carbon rims should start to get cheaper and they are not. So I wait
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  • + 1
 as long as my wheel keep turning i dont care
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  • + 1
 Are ztr flows good for minion 2.5s?
  • + 1
 I've got Flows and have run lots of UST tyres including Minions and have been very happy. I ride very rocky terrain and about 20 PSI and have never burped any UST tyre. Maybe I'm not riding fast enough!!
  • + 1
 Ive run flows with 2.4 purgatorys and just about any other tire you can think of, never any issues. I even ran my Nokian 294 gazza extreme wire bead tubeless on it all winter if you want a bomb proof setup get them
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  • - 1
 I vote tubes, so many of the professional downhill teams still use tubes, even the Athertons, find a good setup you don't get pinch flats with and stick with it!
  • + 4
 Athertons used tubless this year due to new Mechanic they had, and look how many flats/torn off tyres Gee and Dan had between them.. I think it's all well and good in practise for them,but as soon as they hit warp speed (race run), it's a lot more abusive to the wheels.
  • + 5
 The Athertons was a bad example to choose... Razz
  • + 0
 The problems Gee had was more to do with a tire that is not intended nor any good at being tubeless being pushed on him with sponsors. Still an amazing tire though with tubes , one of the best.
  • + 4
 Nothing to do with their mechanic, he's been with them for more than a while now....
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  • + 1
 mavic ex 823 tubeless + michelin dh16 2.2 ...god's recipe.
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  • + 1
 I don't know, I'll gonna wait.
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  • + 0
 So all of the cool kids go and buy new stuff in the latest trend, so I can get deals on your old out-of-date parts please.
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  • + 0
 That's a funny looking moment arm
  • + 4
 Indeed. This article is psuedo-science...

I wonder if RC contacted any actual tire engineers when he wrote this? Because certainly they would talk about things like bead seating, bead compression, bead shape vs. rim shape, etc.

Can't argue with his conclusions though. Wider is better, but there is a lot more to the story when you get into the actual engineering involved.
  • + 1
 especially if you look at Stans superior bead design.
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  • + 0
 this is why i need to get rid of my Dee Max's... sigh
  • + 1
 incorrect! I had a deemax wheelset with ust maxxis minions sealed with stans on my dh race bike and i never ever burped air...and I ran as little as 18psi at time for certain trails. From my experience the deemax are the best tubeless dh wheelset, along with being ridiculously strong, they're a killer item. As for mavic's terrible hubs? well we wont go there haha
  • + 1
 maxxis minions here no Stan and it burps at every turn... Ridiculasly strong is true tho...
  • + 1
 thats weird, maybe i just got lucky with my deemax's because even with some respectable dents in the rim they never burped
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  • + 0
 When you refer to a size of the rim, is that the inside or outside width?
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  • - 3
 Thank you Captain Obvious!
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