Ask Pinkbike Anything - DH vs. AM Bikes, One-By Rings And Tire Widths
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.
DH bike to AM bike conversion?
Question: Pinkbike user Drummerwearshorts asked this question in the Bikes, Parts, and Gear forum: I was wondering if anyone has ever converted a downhill bike into an all-mountain bike? I'm off to New Zealand and I only want to travel with one bike, so I had the idea of buying a different fork and shock so that I could use my Trek Session for downhilling and on more pedally trails. Any input would be greatly appreciated!
 | While that's an interesting proposition, it is also one that I wouldn't recommend pursuing. Yes, I'm sure that there are people out there who have done exactly what you're asking about, but I'd wager that they've ended up with the worst of both words rather than a bike that works well when ridden as intended. The issue isn't weight - the Session can be built up quite light - but rather geometry. Let's say you went ahead and purchased a shorter travel fork, and even a shorter eye-to-eye length shock to match the new fork's travel - you'll still end up with a bike that sports far too slack geometry to be enjoyable on trails that require any sort of pedalling effort. The bike's seat tube angle, while being great at moving the seat out of the when it's set to a low, downhill friendly position, is also far too slack for any sort of comfortable seated pedalling. The other issue, one that is even more serious, is that a different length shock very well could cause parts of your frame to come into contact with each other at full compression, especially the seat stays and seat tube. The bottom line is that your proposed conversion isn't just going to create an awkward riding bike, it is going to be downright dangerous. My advice would be to take that money you were going to spend on a second fork and shock and put it towards a mid-travel bike that you can pedal around. There's a good chance that you can pick up something used for around the same amount you'd spend on your conversion, and then you can swap in some of the burlier components from your downhill bike - tires, short stem and wide bar, powerful brakes, et cetera - and then ride your new rig in the bike parks and on the local loops. You just might discover that your new mid-travel bike is even more fun than your slack downhill machine. Or not, but at least you won't be turning your Session into a dangerous franken-bike. - Mike Levy |
Drummerwearshorts should not be turning his Session into an all-mountain bike, and neither should anyone else.
Will a One-By Chainring Work on a Two-By Drivetrain?
Question: PB member suxfevi asks on the Bikes Parts and Gear forum: I have a bike with only one chainring and I need to put a front mech and a smaller chainring on my crankset. However, I was told that I also need to buy a new big chainring with ramps and pins to help shifting gears, ‘cause the one that I have now apparently does have them. I found a Shimano Deore FCM 590 chainring online. Will it work?
| You were well advised. Ramps, pins and specially profiled teeth are used by every good drivetrain maker to assist the front mech to lift the chain up to the larger chainring. Shimano is the king of ramps and pins, which is largely responsible for its bomb-proof, industry leading front shifting. While you can coax any good front derailleur to shift the chain up to an un-ramped single-speed chainring, the amount of excess derailleur movement required to get the job done will most certainly cause a situation where the chain will derail occasionally to the outside of the chainring when you make the shift. The Shimano Deore chainring is one of the better shifting sprockets you can buy and it is priced quite low, but you'll need to be sure that your crankset's bolt-circle diameter matches it (Shimano four-bolt XT cranks use the more common: 104 millimeters for the big and middle sprockets, and 64 millimeters for the third, granny sprocket). Once you figure out the BCD of your crankset, you can spend the big bucks for aftermarket sprockets, but my recommendation would be to save your cash and purchase the stock items for your brand of crankset. - RC |
A good explanation of how to ascertain bolt circle diameter is available on the Wolf Tooth website, and ramped, aftermarket chainrings can be found here.
Shimano's Deore XT chainrings are heavily manipulated with shifting aids like ramps, pins and profiled teeth to provide instant shifting
Should I run a wider tire in the front or rear?
Question: In the Freeride and Slopestyle forum, PB user Jackety123 asks: "Should you have bigger tires on front or rear? Was thinking of running 2.7 rear and 2.5 front, but a friend said do it the other way around.”
| I'd listen to your friend on this one. The wider tire in the front will give you a larger footprint to lean into while cornering, providing more grip and control. This will help prevent your front wheel from washing out, which has much harsher consequences than if your rear wheel were to get a sideways in a turn. It's common to run a wider tire with a more aggressive tread pattern in the front paired up with a narrower, lower profile tire in the rear. This lets you benefit from the decreased rolling resistance of the rear tire, while still having the cornering traction and flotation that the front tire provides. It's also fine to run the same tire width front and rear, but I'd recommend against running the wider tire in rear - having more cornering traction in the back than in the front could make for some awkward handling on the trail. - Mike Kazimer |
It's common to pair an aggressive front tire with a slightly narrower, lower profile option in the rear.
Have some unresolved tech questions? Jump in the Pinkbike Forum and we'll look to answer it for next time.
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to be picky, the vagina is only one part of the fanny (Fanny includes the outside anatomy too)
Personally I've never had any problem fighting a horse sized di...... Oh, DUCK(!)....., sorry.
Why is there so much emphasis placed on speed when it comes to bike reviews. Sounds like a silly question I know but, even as someone who competes regularly (in the "E" word) - I don't get it.
Of all the people out there who buy high end bikes - how many actually race and of those - how many race often? The way I see it - most people should buy bikes based on fun rather than all out speed and efficiency and therefore reviews should highlight fun factor a great deal more as it is simply more relevant.
Four strokes are faster - but two-strokes are more fun.
Some sample comments:
"This new 650b from Trek has my enduro boner raging at a stiff 7 inches!!"
"My enduro boner is a throbbing 8 inches after testing the dropper seatpost for the last 4 hours"
"Having ridden the new 29er, i have to say my enduro boner shrunk to a measley 3 inches, the bike is just too flexy and slow out of the turns
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If the air pressure in a 26" tyre was 32 psi, would the air volume in a 650b tyre with 32 psi be the same?
.
.
.
hmm
Kinda like asking if there's more air in a 1L bottle, or a 2L bottle with pressure being the same?
How can there be the same volume of air in a clearly larger item to attain the same pressure ?
I used to ride aggressive trail and really enjoyed it. Particularly shouting at strangers. However, the police asked me to stop after I bit an old woman’s jack russell.
Out on my rides, taking a shit in the woods would be a leisurely timeless affair. My DaKine Nomad all mountain hydration pack would easily swallow a NATO entrenching tool and good wad of paper wrapped up in a plastic bag. It would be me and mother nature at peace.
However now I’ve taken up Enduroing I’m running in to problems. The spade has had to go and my bum bag barely has room for an inner tube let alone a healthy stash of paper from home. On top of this, it’s just me against the clock and I’m smashing them out.
I need to just get her done. Clean. Bam. But what I’m finding is that the scant few sheets of paper I have with me aren’t enough and on top of that since I can’t afford to double fold, they’re falling apart in my hands. I’ve trialled tracing paper but at race pace, it fails to pick up.
My friends tell me: soft, tough, light – pick two. But I need the best, no compromises. What I need is Enduro toilet paper. Can you offer me some recommendations.
Agree with PBs advice here.
2 options re NZed bike holiday and bike options!
Bring yr full DH bike, money saved in parts hire an AM bike for that riding.
AM bike 150-160 def most versatile here.
Qtown hires plenty of latest high end DH and trail AM bikes.
Not many other places hire out DH bikes but do hire out trail/AM bikes.
Rotorua and CH will change this with the announcement of 2 new bike parks opening in these locations Rotorua Skyline gondala opening in our spring this year.
m.nzherald.co.nz/rotorua-daily-post/news/article.cfm?c_id=1503438&objectid=11259568
Christchurch to come and will b massive theyre aim is to have the largest bike park in the Southern Hemisphere!
i.stuff.co.nz/the-press/news/hills-and-harbour/10068513/Govt-gives-2m-for-Port-Hills-bike-park
If it was me with yr choice its a hard one it would come down to if Im travelling round NZ in a vechicle or basing myself in one or 2 locations, if travelling in van say Id bring a 160mm AM bike.
If based in Qtown then hire a DH rig.
Be aware they're is great riding on the Gondala and shuttles in Vegas but so many miss the best riding in all areas by not getting beyond the convenience factor. Which u can do at home a bike park Is a Bike park is a bike park.
Enjoy.
For the NZ holiday - an all mountain bike will be a better all rounder and allow you to ride more locations (lots of spots where you need to shuttle or pedal to get to the top of the hill)
Awesome news about rotorua and Chch!
I'm running Maxxis DHF EXO 2.5 tire in the front and a Maxxis High roller 2.3 tubeless in the rear. These are lite weight tires, so it's easier to pedal.
Also, I have Shimano Zee breaks with 203mm rotors front and back for better braking power.
I'm also interested in a head to head comparison of some of the lesser-known bikes, such as Knolly Chilcotin vs. Banshee Rune vs. Canfield The One (I know it's discontinued) and Knolly Warden vs. Canfield Balance vs. Turner Burner vs Pivot Mach 6. Many of these are difficult if not impossible to ride test (at least here in Maine) and not an inexpensive investment...
I remember when adding the larger linkage made a specialized FSR "enduro" into 6" travel ... and with a manitou xvert triple clamp fork... viola! a DH bike
alternate solution to #1's problem is a tr500 or similar adjustable geo bike. I'm getting one come September and I'm gonna save up for a 650 and a 26 wheelset as well as both an xf metric and an RV1 (speaking of which, you guys should do a review on some of their stuff... suuuper stoked on my metric hlr and vector hlr air) so if i swap wheels, swap fork and flip the dropout and pivot chips i'll be able to go from full on DH race bike to a bike that is as "enduro" as I need.
I would say that turning an am into mini dh is probably wiser than the other say around.
Wick Werks chainrings shift stupid fast and are pretty reasonably priced! I met the engineer at a race were I tried out the rings and he was super helpful and stoked on riding!
Sometimes the bike is too short for your body length
sometimes raising the bars a couple of spacers helps
Another thing to note, if something isn't right in your back, it won't fix itself, a chiropractor is worth visiting, literally 1 session is all you'll need if it's not bad and you may find you're sorted. You might be flaring up the same issue that needs fixing.
you want to go super confortabel uphill and good downhill or good uphill and scrubing down?
www.prsnlz.me/science-and-tech/the-first-fully-3d-printed-bike-frame
Travers bikes have tapered head tubes and are Ti.
www.traversbikes.com/store/p11/Rudy_29er_Frame.html
Lilshredman - I've got a Norco Range Killer B3, which you can upgrade later on and is one of the cheaper 650Bs to get into. It's been amazing.
Seriously, go ride one, then buy one.