Fit-first MTB Purchase

Discuss light weight issues concerning mountain bikes & parts.

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eyedrop
Posts: 102
Joined: Wed Jan 27, 2016 5:33 am
Location: Prescott, AZ

by eyedrop

Would it behoove me to use a fit-first approach when buying a MTB? Is it even possible to dial me in on the Precision Fit or Retul Muve when in real life, my body is moving around so much on the trail?

Or is MTB fit more trial and error, and a black art?

How does one achieve a "perfect" MTB fit? It took a few bikes, then proper knowledge to finally get my dream road bike. I want the same feeling for my next MTB. I wanna get it proper from the start.

Also, is there a way to extrapolate what is known from my road fit to getting the proper stack and reach measurements for a MTB?

Finally, are there build-a-bike websites similar to Ribble, Dolan, Planet X, etc.., where I can choose a generic carbon MTB frame with my ideal stack and reach measurements, then toss on my choice of quality components for half the cost of an equivalent Trek, Giant, Spesh, etc..?

by Weenie


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LeDuke
Posts: 1128
Joined: Sun Oct 07, 2012 2:39 am
Location: Front Range, CO

by LeDuke

It's kind of a black art, and I'd argue that your road position won't have much bearing on your MTB position. What feels good to you on the road (i.e., relation to BB) might not work for you on the dirt.

Yes, in theory, you'd move around on the bike more than a road bike. Specifically, descending, which can complicate bike fit unless you decide to go the dropper post route. Due to flexibility problems and/or bike setup, some people can have a problem getting back and low enough to make it over and down technical features.

Re: the generic frames. If you're going to go that route, you'd be better off ordering a $400 frame from the well known Chinese companies. Over on MTBR there is a 7,000+ post thread about Chinese carbon 29er frames. I have two of them (plus a Yeti ASRc) and have been pleased with my purchases.

Because there are fewer sizes for MTBs, and you're sitting more upright, most people tend to pick a frame that suits their general height/inseam/torso dimensions and build it up with stem and bars that put them in their desired position. Wide bars will feel weird to you at first, and you will probably want to cut them down. Don't do that. There's a reason that World Cup racers used to ride 560mm bars and most of them are at 700mm or wider these days. Likewise, no, a 140mm stem is never a good idea on a MTB.

Hope this helps.

boots2000
Posts: 1428
Joined: Mon Oct 15, 2007 9:28 pm

by boots2000

Hardtail or full sus?
Hardtail is easier to dial in.

A good starting point is same saddle position as road bike, reach- longer than tops but shorter than hoods, drop- start with half of road drop (be willing to adjust drop between road drop and zero drop as needed).

Don't believe the hype about super short stems-

Make your own decisions about bar width- But the wider the bar, the shifter the necessary reach.

Erwandy
Posts: 44
Joined: Mon Jul 27, 2015 2:14 pm

by Erwandy

Unfortunately, hitting it right with MTB bike fit can be notoriously difficult in first attempts. I went through 3 major transformation for my bike to get everything dialled in. The second attempt practically rebuilding the bike from scratch with custom setup. There are many sizing guides over the web to help you find the right-sized bike, but those are general guideline - you still need to actually ride the bike with specific frame size to know if it will suit your body and riding style

mattr
Posts: 3477
Joined: Fri May 25, 2007 6:43 pm
Location: The Grim North.

by mattr

LeDuke wrote:
Wed Jan 10, 2018 5:06 am
It's kind of a black art, and I'd argue that your road position won't have much bearing on your MTB position. What feels good to you on the road (i.e., relation to BB) might not work for you on the dirt.
My position is almost the same. BB to saddle and hip angles etc.
Bars are in a different place because they aren't 42cm wide and lower than my saddle. But that's about it.
I also pedal heel down, so the same saddle position (and saddle) works well. If i was one of those weird freaky toe down pedallers i'd probably have to lower my saddle, or get a dropper. :D

Mostly ride marathons now rather than XCO, so it's a lot of relatively high speed with technical interludes for a few km...... But, i don't need to change the bike for more technical courses (tyres maybe, nothing else)

by Weenie


eyedrop
Posts: 102
Joined: Wed Jan 27, 2016 5:33 am
Location: Prescott, AZ

by eyedrop

At this point, I get the feeling that an ideal MTB fitting is not quite as cut and dry as a road bike. I talked to my fitter (Paraic McGlynn and Barry Anderson at Cyclologic), and they basically told me its still a good idea to get fitted first to find the proper frame stack and reach. But for some important things like handlebars, suspension, and even seat height, it is a bit trial and error and rider preference. Getting maximum power possible to the pedals is not necessarily the end goal. There is a much bigger picture.

Still, frame geometry seems critical for MTB, due to things like center of gravity, balance, steering control, optimizing traction, etc... It astonishes me that preliminary 3D bike fittings aren't very popular with MTB'ers, and many roadies are guilty as well. It seems like most people just buy random $5000 bikes based on brand name and frame materials rather than fit. They always make the mistake of buying the bike first, then trying to "make it work", which is often a costly exercise in futility.

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