Ask Pinkbike: Mismatched Wheels, and What Pressure Gauge?

Dec 12, 2017
by Pinkbike Staff  
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Here at Pinkbike we get inundated with all kinds of questions, ranging from the basic "Can I have stickers" to more in-depth, soul-searching types of queries like if you should pop the question or what to name your first child. Ask Pinkbike is an occasional column where we'll be hand-picking and answering questions that have been keeping readers up at night, although we'll likely steer clear of those last two and keep it more tech oriented.





Converting to a 29" Front Wheel

Question: blackmountainsrider asks in the All Mountain, Enduro & Cross-Country forum: I'm toying with the idea of trying a 29 wheel on the front of my 650b Orbea Rallon. I love this bike. It's fast and composed already, but I love the big wheels on my XC bike (Whyte T129). I was wondering if anyone on here has tried anything similar? I can see it being the best of both worlds. The Orbea currently runs a 160mm fork with a very low BB. My issue is whether to get a 160 or 150mm-travel air shaft to try in my 29er pike. It will only really be used for 'enduro' type riding, where I'm not bothered about speed on the ups or easy flat sections.
Orbea Rallon 2016
The 2016 Orbea Rallon featured 27.5" wheels and spot-on geometry for aggressive riding. Could a 29" front wheel improve it?

bigquotesYour concept is intriguing. I've ridden three different bikes with the 29/front, 27.5/rear combination, and I think it has merit. The Foes Mixer was the most impressive handling of the bunch. The most prevalent benefit seems to be that the front wheel holds and tracks a better line around corners. Another is that you can ride a little farther forward on the bike while descending, which makes it easier and quicker to react to changes.

Converting to a larger front wheel will dictate some changes in your Rallon's geometry. Because you didn't specify size, I'll assume that you own a medium. A 160-millimeter 29er fork and a wheel with a 2.3 Maxxis Minion tire will raise your handlebar 38 millimeters, raise your bottom bracket 12.5 millimeters, and slacken your head tube angle by 1.8 degrees (these are rounded numbers). That seems like a huge change for a bike that you admit is already a great handling machine. I'd suggest a 150-millimeter fork instead. The larger front wheel will more than make up for the reduction in travel, and you'll end up with a one-degree slacker head angle, and a 9-millimeter increase in your BB height. Orbea set the Rallon's BB pretty low, so that extra 9 millimeters should not be a destabilizing factor. And, who knows, you may enjoy being able to pedal without banging your pedals every 50 meters.

You already have a 29er, so I'd suggest you first switch forks and see how the transplant works before making the sizable investment in a 29-inch wheel and a new Pike. Be sure to remove at least 10 millimeters of spacers from below the stem to maintain some semblance of your original stack height. Give yourself some time to get used to your "new" bike before you pass judgement on its handling. Riding with a larger front wheel is a different sensation.
RC


FOES Mixer
The Foes Mixer has a 27.5" rear and 29" front wheel - a combination that produced a very responsive chassis that was stable at almost any speed.




What Tire Pressure Gauge?

Question: @JHollowell says in the Bikes, Parts, and Gear forum: What does everyone use to check air pressure in Presta valved tires? I bought the SKS digital gauge and it was junk, or at least the one I got was. Worked fine on Schrader but wouldn't give me a reading on the Presta valves, so I sent it back.


bigquotesI went longer than I should have without owning a tire pressure gauge. I'd convinced myself that all those years of wrenching had turned my hands into the only gauges I needed, but then tires and rims began to get wider, and ideal pressure window began to get a little narrower. My current go-to gauge is the Topeak SmartGauge D2. It has a swiveling head with an easy-to-read screen, can quickly be switched to work with Presta or Shrader valves, and the battery life has been impressive.

As a backup, I use an analog Meiser Accu-Gage. It's about half the price of the Topeak, doesn't require batteries, and it'll measure in half-pound increments if you really feel like dorking out. As with any pressure gauge, it's best to try and use the same one as often as possible for consistency's sake.
Mike Kazimer



Tire gauges
The Topeak SmartGauge D2 and the Meiser AccuGage are both worthy options.



Have some unresolved tech questions? Jump in the Pinkbike Forum and we'll look to answer it for next time.


103 Comments

  • 38 0
 I've had my topeak smarthead gauge since about 2005, and it's still rocking. Still on the same battery too.
  • 2 0
 The battery last longer than the O-ring if you consistently check air shocks with Schrader valves
  • 1 0
 @properp: so far so good, but mine is the older, round design. Maybe they changed O-Ring suppliers? I've had a mix of valves as I use it on my cars as well.
  • 2 0
 The screen stopped working on mine, but they immediately replaced it under warranty without blinking. I still like my Meiser gauge better though.
  • 3 0
 My topeak smarthead gauge must be around 8 years old and still on the original battery. But like Mike I thought my 'feel' was as good as the gauge the other day, now I have a non sealing ding in my bikes rear tubeless rim! Bummer.
  • 5 14
flag redrider3141 (Dec 12, 2017 at 13:07) (Below Threshold)
 Two sentences and it's still a better product review then we get to see on PB...
  • 3 5
 Been through two Topeak Smartguage D2's in two seasons. Garbage as far as I'm concerned. I'll be contacting them for warranty after seeing xeren's comment.
  • 4 0
 Yep. The Topeak is good stuff. But, pumping then dealing with a gauge for 2 tires for every ride. And if you at times ride with your kids, that's a lot of messing around. So, best deal is to just make sure you've got a pump with a good gauge. My Lezyne Dirt pump works great and is very accurate. It comes with a lower pressure analog gauge - that is the ticket.
  • 2 0
 @atrokz: I think what ruined the O-rings in mine was trying to check high pressure rear shocks. The wife and I both got new rear shocks this summer and did a lot of testing with air pressure. When the rear shock has extremely high pressure in it you have to push extremely hard to get it to register. I believe this is what destroys the O-ring.
  • 1 0
 Mine has been running strong for 6 years, wound up getting my dad and my brother one as well, both have been solid for 4 years. Love the tune feature. If you currently don't use an accurate gauge I think you'll be genuinely surprised at how a 1-2 psi really makes a difference. One of my favorite pieces of kit.
  • 5 0
 @properp: they will mail you you o rings for free. Just contact them.
  • 2 0
 @pgm83: thanks for the info. I just replace them myself. Very easy. I only pointed out because if you were going to travel with this and depend on it it's nice to have a sparrow ring. Nothing's worse than showing up on a dialed bike and having to use someone else's gauge.
  • 1 0
 @pgm83: spare Oring. Talk to tex ugg
  • 1 0
 @properp: I could probably think of one or two worse things to happen. Actually three. The list probably stops at three though.
  • 36 5
 I run a 29 on the rear and 26 on the front. It sure sucks on the descents but it is awesome on the climbs. Since I spend far more time climbing than descending I thought this setup would make me happier for a larger proportion of the ride. Nailed it so much I go to the park and ride to the top and then catch the chair down. Thinking of swapping around the compression and top-out coils for extreme goatability.
  • 1 0
 Spot on!
  • 30 6
 I can't accurately gauge the pressure of making the first comment, but there's a lot.
  • 22 1
 Did you think of that pun at the BAR?
  • 8 0
 Baring such pressure, would you still be inflated about it? Hard to gauge.
  • 4 2
 This thread is going to be atmospheric!
  • 3 32
flag Jtowle1992 (Dec 12, 2017 at 11:13) (Below Threshold)
 Pinkbike needs to get a grip, 29 front with a 27.5 rear WTF!
  • 5 1
 To be fair to come up with a good pun you do find yourself under a lot of pressure
  • 11 0
 @Jtowle1992: what do you want 26 front 24 rear?
  • 15 0
 @mattvanders: Seriously, how hard can it be? Just snap your fingers and . . . presta, a pun.
  • 5 1
 @properp: Back in the day my downhill hardtail was 26" Front (With upside down triple clamps) and 24" Rear
  • 12 3
 I wonder if David Bowie and Freddy Mercury ever wonder if their tires are under pressured.
  • 2 0
 @properp: Specialized Big Hit back in the 90s had that!
  • 11 0
 @drummuy04: Freddy Mercury just wants to ride his bicycle. He just wants to ride his bike
  • 1 0
 It is all in your head man, it is all psichological. Just don't set the bar that high or the pressure is going to make your head explode. Or well, at least it is going to make you tired.
  • 1 0
 @properp: that's old school set up from the early 2000's...fun times
  • 3 0
 @mattvanders: I think a nicer line would be 'It's hard to come up with a pun under pressure '. Nice try though.
Yours,
The Pun Police
  • 1 0
 This pun run just went flat.
  • 1 0
 No it didn’t it just needed some air
  • 7 1
 Been riding my 2014 E29 with a 29 front and a 27.5 plus rear setup for the past 4 months. It feels livelier, rails corners harder, and changes directions way easier than two 29er wheels. HA is around 65deg and BB around 333mm. Other than a few extra pedal strikes, it's been a sweet set up.
  • 6 1
 Mismatched wheels is not that unusual, Dirtbikes have been that way for decades. Typically they are a 18"R/21"F but I've had 17"/21" and 18"/23" bikes too. A lot of MX bikes are 17"/21". You can't quite directly compare sizes as the aspect ratios on the tires are much different but still.
  • 1 0
 say more about the aspect ratios and how that affects size comparisons
  • 5 0
 the specialized big hit utilized this with a 26"/24" combo...but of course nobody is hucking these days like they used to...
  • 2 0
 @freestyIAM: How do you mean? Like why a 21" MX wheel with a 90/100-21 tire is 28" tall? For reference my 26" MTB with 2.25 Nevegals is 27" in diameter.
  • 1 0
 @redrider3141: Yes that. i didn't realize that when you were talking about aspect ratios you meant that some 21"tires are taller than others so factoring tire height differences aren't as dramatic. TY
  • 2 0
 @freestyIAM: Also that Dirtbike Tires tend to be taller/wider so it adds a lot more rubber to the overall height.

Hard to directly compare because while MTB tires get sold by Rim Diameter/ Width dirtbike/ atv/ motorcycle/ car tires get sold by Rim Diameter, Width AND Section Height.
  • 5 0
 @redrider3141 um, no mx bikes are 17"/21". MX bikes are 19" rears.
  • 3 0
 @dirt-unit: He would have been correct if he was thinking of a late-seventies Husqvarna.
  • 1 0
 @codypup: Yup! I forgot about newer MX bikes going 19" in the rear. Most of my bikes have been from 1975-2000.
  • 1 0
 MX bikes have had 19" rears for a while
  • 3 1
 Liteville does it too. Didn't @mikekazimer ride a Liteville to test some integrated dropper post? Was the review published already? I'm curious what he thought of the dropper, the mismatched wheels and whether the EVO6 rear wheel spacing helped that much.
  • 1 0
 @NebulousNate: You're right, about a decade earlier than I thought.

Last two bullet points:
www.dunlopmotorcycletires.com/about/off-road-facts
  • 3 0
 I've run 29 front, 27.5 rear since April this year on a Ragley Mmmbop 2017 and it works well. Running a 29 fork with 140mm (so 10mm less than optimum), and fatter rear tyre. Only thing is for pump track and tight bits of track the front end feels a bit more sluggish when picking it up and throwing it around. I've actually just gone back to 27.5 front with 2.6 tyre now that they're available. First ride the other day and I think it is staying on now as the whole bike is a bit more chuckable with negligible reduction in rollover speed.
Good experiment though and if you're not into jumping then it's a good set up.
  • 3 0
 @preach: I'm not exactly hucking like the crazy guys back in the day, but I'm still rocking the 26/24'' combo.
"24 ain't dead".
  • 2 0
 Comimg from a moto background I've always wondered why the different wheelsize concept never really stuck in MTB. Obviously a dirt bike has a lot more power than a pedalbike, but a similar dynamic exists where the rear wheel needs to put power to the ground and the front wheel needs to roll over trail garbage and not wash out in the corners. I'd think a larger diameter front wheel and a smaller diameter but maybe fatter (larger contact patch) rear wheel would make sense for both vehicles...
  • 1 0
 @ryetoast: what is the overall size if MX tyres? I thought they were similar except a rear had a larger profile tyre and smaller rim than the front.
  • 1 0
 @fartymarty: I ran a 90/100-21 on front and a 130/90-18 Rear on my XR250 and XR400. The front comes out to 28" in diameter and the rear 27.2", so close but still stepped. The 130 rear was on the larger size, especially for the 250. On a more typical 120/90-18 the overall diameter would be 26.5"
  • 1 0
 @redrider3141: I suppose relatively this is similar to 29F 275R. The guys at Mojo have been running Geometrons with 29F 275R and supposedly you get the best of each. I am surprised more MTB companys don't do it altho you can't at the moment in DH due to the silly UCI wheel size rule.
  • 1 0
 @fartymarty:
Hey, For what its worth, I'm on a 29er Spesh Camber Evo, moved up from a 26" Giant Anthem.
So a big jump in wheel size.
Partly due to the extra wheelbase, I found tight cornering required a hell of a lot more input to get the bike around.
The Camber is a really good trail bike,and the larger wheels definitely increased roll over speed,but i just did not like the handling when things got steep and tighter.
Had a fairly distinct feeling it was the rear of the bike the was having trouble coming around.
Decided to bite the bullet and got a 27.5 rear wheel.
I decided to make no other adjustments to the bike for comparison.
That was 18mths ago, and I'm never going back.
The change is massive, and in a very positive way.
Rails corners, and accelerates faster out of them.
Manuals better, better mud clearance, i do bump pedals a little more often but wouldn't swap the low BB.
As others have mentioned, I also ran 26/24 back in the 80's and it was woeful.
I would urge any 29er Stumpy or Camber riders to give it a go.
Other frame designs will no doubt benefit as well, but If they all ready have a very slack HA or low BB
it may not work as well.
  • 1 0
 @XCAussie: Thanks. I wish more companies would give it a go. Did you read the "Enduro 6 Ways" article on Dirt?
  • 7 1
 I have the accu-guage as mentioned above.
It’s really reliable and accurate to read. No batteries. Simple and reliable dial style technology. Well made too.
I wouldn’t buy anything else!!!
  • 5 0
 I agree that it functions well but it is extremely sensitive. If you have dropped it even once from any height it is no longer accurate, also out of the box two new ones side by side will give you different readings
  • 6 0
 you dont need to buy a whole new fork. just 29" pike lowers, they are $250 online, and the $30 air piston. the stanctions of 26/27.5/29" pikes are all the same lengh in all travel options.
  • 9 1
 The pressure of having mismatched wheels is driving me bonkers.......
  • 6 0
 Valves getting clogged with tubeless sealant has been my biggest issue with getting accurate readings from a pressure gauge.
  • 2 0
 take your valve core out and soak it in gt85 or similar for 5 minutes then refit and blow your tyres up , Sealant will no longer stick to the valve core ,I didn't think it would last for more than a couple of weeks but it generally lasts for the duration of the tyres life
  • 1 0
 @konacyril: what is gt85. Is it like a euro triflow
  • 1 0
 ill have to try that with the last of the GT85 we have. Our supplier doesn’t carry it anymore oddly enough
  • 2 0
 @da-yeti: its just a Teflon based spray lubricant mate ,think any oil based lube will work just as well
  • 1 0
 I just put an ARC30 29" wheel with a 2.5 DHF on the front of my Trek Fuel EX 9.8+ with a 160mm pike w 51mm offset and it definitely struck less rocks and climbed a little slower, but felt great on the "Luge" a fast and rocky S-curvey downhill in SoCal.
I didn't hate it, but to be honest, It's really hard to tell the difference.

The diameter of the rear DTSwiss M1900 with 2.8 Schwalbe Nobby Nic was around 28" and the front is about 29.5 with the DHF. I admit, it's a bit of a Franken-bike but it still seems to rock n roll pretty good.
Just saying...
#MTBeers
  • 1 0
 I got the same set up on my 2017 Fuel EX 9.8 275+ too! 29 Stans Barron 35mm internal with DHF 2.5 WT up front (140 mm fork) and rear 275 HRoller 2.8 and hard to tell the difference except i can feel its definitely slacker.
  • 1 0
 just because i felt like it, i put a 27.5 wheel and fork on my 26 hardtail. i wasn't expecting much, pleasant surprise, the cornering was sharp. the bike felt a little more planted in the rough. and i don't feel like i lost any of the pop or "playfulness"-(whatever). but RC is right, swap the fork and wheel from your xc bike first
  • 1 0
 @blackmountainsrider I currently have a set up similar to your post. Running a 26” rear wheel and 27.5” front on my Santa Cruz v10 bike. The ride quality is amazing. It monster trucks over everything, it’s fast, it corners well and it jumps surprisingly well. I love the set up tup
  • 1 0
 I was planning to go 69er on s 26" Mondraker Summum, since I have Dorado and can use really whichever front wheel size I please from 26-29". But then read Danny Harts comments about his experience competing on a 29" Summum and my impression was that he thought it was a sad development. Maybe I should go with a 67.5er (did I just invent a word?).
  • 2 0
 I run mismatched on my old Titus switchblade and love it. Other than the shorter reach and slacker seat tube than modern bikes, it rips. #26rearaintdead?
  • 3 1
 Love the Topeak, great for fork & shock pressure management as well.

Im amazed at how 5 psi can make or break my Pike. 5psi too high and it feels like crap.
  • 1 0
 I ran my 2015 enduro 29 "mullet" for a while. It's really fun and fast especially in a bike park. Now that I have the newer, slacker E29 I feel that it may be a bit too much if I run it that way.
  • 4 2
 The topeak gauge is the gauge I use. The O-ring in the end of the head wears out quickly.
  • 1 0
 I had a Brodie hardtail with a 26" front & 24" rear. seemed pretty good at the time except you had to have more spare tubes kicking around
  • 3 0
 When you're only using a tube for a spare, you can stretch them surprisingly far. I only carry a 27.5" tube because they fit a 29" and 26" wheel equally well. Have also used a 29" tube in my 27.5".
  • 3 1
 Seems like a lot of people missed out on 2005. Lot of freeride guys ran 26-24 set up.
  • 1 0
 I have Topeak which I bought after much research. Waited too long. Very good product and battery life is amazing. Very easy to use and accurate.
  • 2 1
 Chris porter from Geometron/Mojo and Damien Nosella from Production Privee both use a 29” front wheel.
  • 8 3
 and when they jump from a bridge should i also do it?
  • 4 1
 You can add Rob Metz from Zerode to the list too.

I'm 80% sure that's how he's running his Taniwha
  • 10 1
 @funkzander: yes mate why not give it a go
  • 3 1
 @funkzander: Sounds like they can clear the gap. Can you?
  • 2 1
 It says something that people with access to so many different frames, forks, wheels and options have settled on this setup @funkzander:
  • 3 1
 @dwojo: he certainly was last time i saw him
  • 1 0
 Has Brett Foes updated the geo for the Mixer Enduro? IIRC, it had really good reviews 2 years ago.
  • 3 2
 The wheel size-geo change math wrong. It's the radius change, not diameter. You're estimates need to be halved.
  • 2 3
 so many things wrong with this. first, you are wrong, because the tire needs to clear the arch of the fork. Second, how can you possibly just say he is wrong without providing your own math? How did you even check his numbers? You obviously didn't calculate anything yourself because A. you didn't show any numbers and B. you don't know how.
  • 1 2
 My OCD won't allow me to ride a bike with mis match wheels sizes. They just look wrong. The irony is that I'm not bother by dirt bikes, go figure.
  • 1 0
 The analog gauge only goes to 30? That definitely won’t work for me.
  • 3 0
 they make one in 60psi too
  • 1 1
 The Topeak gauge sucks! Best one i ever had was the old price point gauge.....
  • 2 1
 Chris porter experiment?
  • 2 1
 Unless it has the stupid saddle angle, I'd say no.
  • 4 1
 @southoftheborder: Me too, but as we're riding the wrong size bikes, what do we know?
  • 5 8
 I can't believe people are talking seriously about pressure gauge. LMAO
  • 7 0
 never underestimate the confidence 0.25 psi give to the weekend warrior
  • 2 0
 @Lagr1980: It's hard for me to tell the difference between even 3-5 psi. The only thing I really notice is dinging the rim more.
  • 1 2
 @funkendrenchman: 0.5 PSI is noticeable to me.

That said, I have to generally know first to tell what is actually different.

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