[Closed] Interesting study looking at XC performance and wheel size....

Nothing in the abstract about trail surface?

Trail surface is everything in this debate.

[img] https://camo.githubusercontent.com/85d994904753920afca0a709cb42e994fa2dd413/68747470733a2f2f692e696d6775722e636f6d2f415748474947482e6a7067 [/img]

This is the journal article of the video that caused a small discussion on here a while ago.
[url= http://www.bikeradar.com/mtb/gear/article/how-does-mountain-bike-wheel-size-really-affect-performance-43481/ ]
Details here[/url]

molgrips - Member

Nothing in the abstract about trail surface?

Trail surface is everything in this debate.

Really? You don't think this is meaningful? Why? Cos 29er has larger contact patch? Aren't repeated question marks annoying?

Looks like a decent comparative test to me. Interesting that it goes against that one where one bloke (off here?) rode 2-3 laps of a course and found 29ers slightly faster?

@CFH: Is that the new baddie from the upcoming Bond movie?

Doctorpussy? 🙂

They used the clayton vale track. I don't know whats that like.

Accodign to the journal they used FS bikes which IMO muddies the water a bit. What I'd be interested in is an analysis of how much more time you can comfortably spend riding seated on a 29er v 650b hardtail. The greater roll-over of small bumps which is oftern mentioned with 29ers makes me think you should be able to stay seated more, reducing fatigue when racing.

what's the difference between 'trail' and non-racing XC?

Want to go faster?
Train harder, the fitter guy on the cheaper other wheel size will still beat you.

Train harder, the fitter guy on the cheaper other wheel size will still beat you.

Stupidest argument ever. Training and choosing wheel sizes aren't exclusive, are they? If you are already training as hard as you can, then the right kit is going to help. Stop trolling, troll.

Still think the trail surface is a key variable. Smooth hardpack - no difference, 26 possibly much faster due to lighter weight and faster acceleration. Rocky climb, 29 much better due to being affected less by the rocks.

They used the clayton vale track. I don't know whats that like.

From Google Images, it looks very very smooth and rather flat.

Interesting discussion already....It does look like a fairly solid study. My only concern is only 9 participants - hard to get significant difference with a small population.

I reckon there would be some big individual differences though....like it's been said before...the wheel size will suit your fitness, riding style and the conditions.

Cheers

I agree Molgrips, even on fairly rough firetrack I think the roll-over would be beneficial. I am on 27.5 but I've a feeling the next time I buy a bike it will be a 29er

mikewsmith - Member

Want to go faster?
Train harder, the fitter guy on the cheaper other wheel size will still beat you.

Anyone got a link to that test I mentioned above? IIRC the gaps were small.

cjr61 - Member

Interesting discussion already....It does look like a fairly solid study. My only concern is only 9 participants - hard to get significant difference with a small population.

Presuming each result tasked into account the power variation, I don't see that as an issue at all - its not like they are riding different/random trails.

If you are already training as hard as you can, then the right kit is going to help. Stop trolling, troll.

And if someone fitter and faster than you is training as hard as they can, you'll still lose.

Trolling? Hardly.

but if you have someone at a very similar fitness level then having faster equipment will help. If we take sundays national level elite mens race, positions 2-5 were seperated by less than 10s over a 1hr 34minute race. So thats a 0.18% difference, does an equipment advnatage really not matter?

Even at a more lowly level of me in midfield sport a couple of % faster would have had me a couple of places higher.

I've not had a chnace to read the whole paper but I think that it would be interesting to put accelerometers and load cells at various points on the bike and look at how differing set-ups afect the forces that the rider feels as thats what contributes to fatigue

0.18% difference between wheel sizes I can see.

A couple of percent - no way!

Pump your tyres up - your bike will feel faster 😛

I agree Molgrips, even on fairly rough firetrack I think the roll-over would be beneficial. I am on 27.5 but I've a feeling the next time I buy a bike it will be a 29er

I rode a trail Saturday which has its on TT ( http://www.boarsonbikes.co.uk/cake-run-time-trials-07/) where narrower bars would have made a bigger difference than wheel size... you can only go so fast through two trees with 1cm or so either side... I'm pretty sure it would be faster on my XC bike merely down to bar width...

There are quite a few places at Swinley where my kids 24er is faster than my 27.5 etc. and a 29er would be a real trial....

Anyone near me in South Wales is welcome to come and try a rocky climb on multiple bikes, see what the difference is!

Tyre size too - SaxonRider (on his B+) out-rolls me (on my 29er) by a good margin on a moderately bumpy downhill trail - despite the fact he's about 12kg lighter.

Whereas I have 2x27.5 and WHERE I ride I can't see any benefit to lower rolling resistance but plenty to smaller wheel manoeuvrability.

The selling point for me would not be rolling resistnace, but roll-over and comfort. I am very much a seated rider, by the end of saturdays race (lots of little bumps and roots) my calves and back were shot and it noticeable slowed me down on the last lap (this is with 18psi in tyres). If you bleieve the hype (and I'm not sure I do) I would ahve felt elss fatigued on a 29er and gone faster in last lap

Marginal gains, innit?

Unless you're Bradley Wiggins in which case it's a load of crap.

but if you have someone at a very similar fitness level then having faster equipment will help. If we take Sundays national level elite mens race, positions 2-5 were separated by less than 10's over a 1hr 34 minute race. So that's a 0.18% difference, does an equipment advantage really not matter?

Knowing the guy who came 3rd (he came 2nd in the last round) he far prefers his current bike and says it's faster than his previous one, (both short travel XC 29'er FS') so even with such small gaps equipment advantage that suits the rider is only a good thing.

molgrips - Member

Anyone near me in South Wales is welcome to come and try a rocky climb on multiple bikes, see what the difference is!

I'd love to - but without power data to normalise results..."feel" is meaningless...

You wouldn't need power data. You'd probably be a minute slower and a lot tireder.

As I said, first time I tried it on my light 26er FS after my rigid 29er, I thought I'd fly up it, but it took me three goes to even clear the first bit. The bike stalled on every loose rock, it was extremely difficult.

molgrips - Member
As I said, first time I tried it on my light 26er FS after my rigid 29er, I thought I'd fly up it, but it took me three goes to even clear the first bit. The bike stalled on every loose rock, it was extremely difficult.

And you think the only or main difference is the wheel size?

Size and weight yes.

Sorry but that's ridiculous.

So many other factors.

Same rider, same climb, same conditions, many many previous attempts on different bikes so intimate knowledge of climb...

Rather ridiculous of you to dismiss it like that I think. This is on my local loop, I know every inch of it.

So the bikes have geometry as similar as possible? Or will that not matter on a steep climb?

Same tyres, width, pressure?

(Ignoring FS vs rigid for now)

You do know what confirmation bias is?

I took the XC out thinking 'I'll smash my times on this!'

So it actually overturned my bias completely. And the difference was dramatic - we're not talking subtle changes here.