Yes, I know you can ride anything, blablabla, whatever.

The question is specifically does anyone *choose* 27.5 over 29 for XC racing? If so, why?

Nino does (and he ain’t slow neiver)

27.5 – dual suspension – WC champion

George Budd does.

Does Nino choose 27.5? Or is that his employers marketing department making the choice?

I suspect as reigning xc champ and sho-in for the olympics he can ride what (and for who) the hell he likes.
Also he’s ridden 27.5 from pretty much the start of 27.5 coming out.

Only he really knows but I can’t see why Scott would object to him riding a Spark 29er instead if that’s what he wanted to instead as it’s still a Scott XC race bike.

It’s cos he’s not massively tall isn’t it?
I’m sure I read somewhere that he can’t get as aggressive position on the scale/spark 29?

I read the same, he couldn’t get the position he wanted on a a 29er.

So it’s not because he can’t afford a new race bike but thinks 27.5 might fit in his old 26 frame?

I thought his was going to be a topic by Kryton trying to justify selling his 26″ birthday present to fund a new XC HT. I feel somewhat let down 🙁

Perhaps it’s the domain of shortarses??

I did. I’m 5’7 and 8 1/2 stone and I felt a 29er would be too tall and unwieldy. I’ve never ridden one in anger so purely based on sitting on one and reading too much on t’web.

You’re way taller than Emily Batty then

Yes I have since 2012… So I quite like it.

Seems big enough to roll well, quick enough in the corners and also a bit lighter as everything is smaller.

Me! Probably could go 29 (5’11) but with short little legs the bars always feel really high on the big wheeled bikes I’ve tried. More used to riding road and TT bikes doesn’t help either.

Will see how well they roll at Charlie’s gravel dash next weekend it will be the 650’s first (semi, kind of) competitive outing! Hoping to race more XC and Xterra events later in the year and into the winter.

Reigning Nat Champ Beth Crumpton works in my shop, she’s ditched 29ers for now and on 27.5 now and happier with it. She is 5ft4 and very slight though, she found although she was quick on the non technical stuff on a 29er, she couldn’t muscle it about as much as a smaller wheel in the technical stuff.

Horses for courses innit. I’m of the opinion if you’re big enough that a 29er doesn’t feel too unwieldy, you’re likely to be quicker on it A2B, but it the wheel size starts to get in the way because of your physical size or strength then go for the smaller wheel.

So it’s not because he can’t afford a new race bike but thinks 27.5 might fit in his old 26 frame?

That is what he did at the start. Apparently he could’t notice any difference with the massively (13mm) bigger wheels but as he had already bought the wheels and tyres he kept with it.

mboy – Member
Reigning Nat Champ Beth Crumpton works in my shop, she’s ditched 29ers for now and on 27.5 now and happier with it.

What did she won the nationals on?

Here’s my unscientific, unsubstantiated and entirely hypothetical take on why it probably makes f-all differnece over the course of a race.

typically gearing changes with bike wheel size so the gear inches are similar, plus when racing you’re goign to be pushing as hard as you can anway.

If the terrain is flat (fire road, tarmac) the greater roll-over of a 29er is irrelevant

If its rutted, rooty and fairly straight then the roll-over of a 29er probably is a bonus but this gets negated by the manouverabiliy of smaller wheels whe it gets twisty and properly technical

When up to speed the momentum of a 29er may be an advantage but this is probably cancelled out by the faster acceleration of 650b.

Given that whichever way, there are probably seconds in it, none of it matters as I’ve yet to ride a perfect race without screwing up my lines somewhere on the course and loosing way more time.

If its rutted, rooty and fairly straight then the roll-over of a 29er probably is a bonus but this gets negated by the manouverabiliy of smaller wheels whe it gets twisty and properly technical

This.

My 26er has light wheels and tyres, and it’s all closer to the centre of rotation. Consequently it’s incredibly fast in acceleration and twisty bits. I’ve seen the back to back comparisons of 29 vs 26, but Id’ be interested to see that done on different courses and for different riders. As a heavy bastard I gain most of my time on the twisties, knowing this mentally I hit them harder than some other riders seem to.

Thinking about it though – good acceleration seems to help passing people much more, and being stuck behind someone slightly slower on any given section probably costs you more time than anything else (besides fitness!)

When 29ers first became more common a few years ago all of the magazines ran 26″ v 29″ articles, experiments, and all sorts of analysis to try and quantify the difference.

Basically there was sod all in it in pure performance terms (time), even with elite level athletes, hardly anything, a handful of seconds over several k’s – and that was 26″ v 29″.

So the difference between 650b v 29″ is not even worth talking about. People should just ride the bike they like the feel of the most of the terrain they normally ride.

I have a 26″ and a 29″ bike, I like them both, the 29er feels faster, but it’s a lighter frame (alu v steel) and general build, I’ve no doubt my 26″ bike would feel almost as fast if I put it on a diet.

But, I’m 6ft tall and pretty well built and am actually leaning towards preferring the 29er these days, though the 26″ is a lovely bike I feel a bit on top of it (large soul) and can feel it get more hung up on little obstacles than the 29er, which I have no problem muscling about.

mboy – Member
Reigning Nat Champ Beth Crumpton works in my shop, she’s ditched 29ers for now and on 27.5 now and happier with it. She is 5ft4 and very slight though, she found although she was quick on the non technical stuff on a 29er, she couldn’t muscle it about as much as a smaller wheel in the technical stuff.

Horses for courses innit. I’m of the opinion if you’re big enough that a 29er doesn’t feel too unwieldy, you’re likely to be quicker on it A2B, but it the wheel size starts to get in the way because of your physical size or strength then go for the smaller wheel.

I’m a big fan of 29ers. They work for me even though I’m not giant (5’11” and a bit!) However, I’ve been looking to replace my wife’s bike for her and tried to convince her to give big wheels a try.

She is 5’5″ and slim build and made comments similar to what you are saying here Mark. Albeit from someone at the entry level of mtbing rather than a national champ. So for her, the rolling stability was a plus but anything more than that and it felt like (her words) the wheels/bike controlled her not the other way round.

Next stop will be to try the Kona Tika in 650b and see how that feels for her.

I ride and race a 27.5 (the same frame as Beth for what its worth). I went from a 26 to a 29 to the 27.5. I chose the 27.5 because I’m pretty short (5’6″ ish) and the 29er I raced (sponsored) was just too big. The smallest frame I could get was a 17″ with a 120mm head tube and so get the front anywhere near low enough meant using a 40 degree negative stem. All that happened then was everytime it went downhill, I went over the bars.

The 27.5 fits me much better but it has its disadvantages in ny eyes…I usually get a cracking start from the gun which I put down to the bike but by the time the race hits anything flat and straight, the 29ers just swamp me. For example, at the first Welsh series race at Llandegla, I got the holeshot into the first corner and led the race to the foot of the big climb, I then got mugged by the 29ers which just seemed the go faster and climb better for less effort on that long straight section.

In my case, I’m not sure exactly how much faster (or if) I’d be on a 29er but it’s done my technical riding the world of good and I certainly feel like I can throw the bike around far better than I ever could on the 29

Basically there was sod all in it in pure performance terms (time), even with elite level athletes, hardly anything, a handful of seconds over several k’s – and that was 26″ v 29″.

Hmm, I thought it was more conclusive than that. One thing I’ve noticed on my 29er is that it’s much easier to find traction on loose stuff. However it’s also noticeably slower to get going and correspondingly has more momentum when you do. Ok so it’s 5lbs heavier than my XC race bike, but a fair chunk of that is in the wheels and tyres.

So based on that, and a course with scrabbly bits in it, it might be easier on a 2er if not that much quicker. But the acceleration could be a factor. Next time I’m prepared to enter an XC race I’ll let you know how I get on on my 26er 🙂

Didn’t realise Gee was still on 650b thought the Pivot was 29er?

No they’re both 27.5 – the LES and Mach4.

They do a 29 version of both (Mach 429SL and LES 29) but I preferred to stick to 27.5.

I usually get a cracking start from the gun which I put down to the bike but by the time the race hits anything flat and straight, the 29ers everyone just swamps me. For example, at the first Welsh series race at Llandegla, I got the holeshot into the first corner and led the race to the foot of the big climb, I then got mugged by the 29ers which just seemed the go faster and climb better for less effort on that long straight section.

That describes Wednesday race for me. Molgrips I’m outsprinting people from the gun on a 29er, but I upgraded my wheels (AC Race) & rotors to quite light ones which might may the difference there.

Hmm, I thought it was more conclusive than that. One thing I’ve noticed on my 29er is that it’s much easier to find traction on loose stuff. However it’s also noticeably slower to get going and correspondingly has more momentum when you do. Ok so it’s 5lbs heavier than my XC race bike, but a fair chunk of that is in the wheels and tyres

I reckon that if you lost 5lbs off the 29er it ride like your race bike or added 5lbs to the race bike and it’d ride like you 29er.

Message? Lose some weight off the 29er.

Well no, cos a 29er wheelset that weighs the same as a 26er (if that were possible, which I doubt) would still have quite a bit more angular momentum and hence still be slower to accelerate, cos it’s all further from the centre of the wheel.

If its rutted, rooty and fairly straight then the roll-over of a 29er probably is a bonus but this gets negated by the manouverabiliy of smaller wheels whe it gets twisty and properly technical

I’m not convinced there’s enough in it, or maybe I’m just used to the fat bike. But I can barely feel the weight of my 29ers wheels when turning and they’re ‘only’ crests (shod with relatively heavy Purgatorys).

I race a 27.5 – I never found a 29er I really liked more than my 26. However on the advice of gee I tried a 27.5 and loved it. Been racing them since about 2013ish, and really like it.

It was more my stupid choice of gearing that held me back at Dalby rather than wheelsize – I managed to race hard enough to get into Expert riding a 27.5, but I reckon its more the engine than wheel size.

Well no, cos a 29er wheelset that weighs the same as a 26er (if that were possible, which I doubt) would still have quite a bit more angular momentum and hence still be slower to accelerate, cos it’s all further from the centre of the wheel.

For a given mass, a 29er wheel is only harder to accelerate to the same rotational speed. To reach the same ground speed the wheel doesn’t need to rotate as fast so the effect of radius cancels out.

Does wheel size make a difference then? 😉

This all sounds a bit like alcoholic’s anonymous confessions!

Hello, my name is Paddy and I race a 650B. I’m really enjoying it, although I probably will be after a 29er next year for a slightly more versatile bike. I’ve got a very stiff hardtail, so some of what I’ve found will be characteristics of the bike, not something true of all 650Bs.
Compared to the 29ers I’ve had over the past couple of years: It climbs like a dream on anything smooth or steep; I lose out a bit to the 29ers on flat bits or shallow climbs when it’s rough; my wheels/tyres are awesomely light, and seem a lot stiffer than 29er wheels of the same weight; I’m descending technical stuff and cornering faster than last year; I haven’t noticed any problems with instability on rocks etc.

I was also worried about an XL 650B looking weird and out of proportion, but it looks fine (a lot better than tiny little 29ers with -30deg stems).

TL;DR: great on everything except rough flat bits.

Well no, cos a 29er wheelset that weighs the same as a 26er (if that were possible, which I doubt)

Mine are 1450g, and you can get lighter 29er wheels than that, and heavier 26er wheels than that.

Mine are 1450g, and you can get lighter 29er wheels than that, and heavier 26er wheels than that.

But using the same rim and spokes means the 29″ will always be heavier than the 27.5 which will always be heavier that the 26.

That is the reason I am on 16″ wheels. Really light, although have to admit the BB height is challenging.

When 29ers first became more common a few years ago all of the magazines ran 26″ v 29″ articles, experiments, and all sorts of analysis to try and quantify the difference.

…and you have the leading author of one of these already replying to this thread 😉 So the big question is…. 27.5er Pivot also or 29? 🙂