29/26ers and 650B - its been tried before

Darrenov

Is it just the manufacturers trying to sell to people too young enough to remember? I know they roll better over rough tracks but would they have a bigger disadvantage going uphill? Surely a bigger wheel takes more energy to move. Do any pros race on them or is it just for fun?

supersonic

Horses for courses. Some like em, some dont. Its just another option.

nicklouse

what about the other new size heading our way 27.5? we will soon a 25" as well.

John Stevenson

It's all bollocks, if you ask me.

For the size differences we're talking about, the rolling advantage is a figment of the demented imaginations of people who desperately need an excuse to buy yet another bike. None of them have ever been able to produce a single shred of evidence for the claims made for 29ers.

If we were talking a doubling of wheel size, then maybe, but a few percent? Big whoop. It's lost in the noise.

Dan Joyce

Physics and over a year of riding 'em says you're wrong!

Try this: freewheel side by side with a mate on a fireroad, one of you on a 29er, the other on a 26er. The 29er pulls away. That's because it's rolling better. I've tried this on a rigid 29er against full-suspension 26ers, and the 29er has still rolled faster. I've tried it with a hardtail 29er and a hardtail 26er both with Kenda Nevegal tyres inflated to about the same pressure. The 29er still rolled faster.

It's not hard to find evidence. You just have to ride one. Sure, it's only one element among many, but the difference is there.

The wheel isn't a few percent bigger. It's 10% bigger. That's like the difference between a 26 and 24in wheel. It doesn't make you go 10% faster, but it observably does roll better. Changing your tyres makes a difference (or maybe you leave your winter tyres on in summer cos they're ony a few percent slower? ). Changing your wheel size makes a difference.

More on this in What Mountain Bike issue 76.

John Stevenson

And yet, Dan, whenever these things get timed or measured (like the test Mountain Bike Action did a year or so ago), the effect vanishes like smoke, leaving anecdotes and hand-waving that's so vigorous it's amazing the 29er advocates doing it don't take off under their own power.

Till someone shows me some decently-conducted, reproducible tests or - even better - till it becomes obvious that you can't win a World Cup cross-country race any more on 26in wheels (just like you have no hope of winning a pro-class road time trial without an aero bar), I say it's bollocks.

If the effect was that significant, the pros would have switched in their droves, just as road pros did when aero bars came in.

Then there's all the other crap coming out of the 29er camp. 29ers fit larger riders better, apparently. It's somehow so hard to put the bars, pedals and seat in the places dictated by wrapping a bike round oversized wheels and still use sensible wheels. :roll:

29ers are more stable. Yeah, they will be. The bike has a longer chainstays, a longer front centre and different steering geometry. All of which could be achieved with 26in wheels. Those are effects of the geometry and not inherent in the wheel size.

I realise that we journalists struggle to find new and interesting things to say about regular bikes, but the attention being lavished on 29ers is completely undeserved given their microscopic total sales, substantial disadvantages and the range of claims made for them which covers the whole spectrum from absurd to unproven.

I'd say it's Biopace all over again, except that people actually bought Biopace in very large numbers - not that they had any choice.

Dan Joyce

John,
So what you're saying is: they haven't been measured or timed properly :roll:. All you need to prove the better rolling issue is roll-down testing with enough repetitions (say six or more per bike) to get a reliable mean with a small standard deviation.

I don't know if it'll ever be obvious that you can't win a world cup XC race on a 26er. The differences we're talking about are smaller than aerodynamic issues roadies face on road. But I think in time most XC races will be won on 29ers, just as most (all?) cyclo-cross races are won on 700C wheels already. It wasn't so long ago that people said that you wouldn't win an XC race on a full suspension bike. Then Paul Lazenby did exactly that. Short-travel full sus bikes now pretty much rule XC racing today. That didn't happen overnight.

I wouldn't look to the average pro for developments. Most pros ride what their sponsors give them to ride and what the UCI allows them to ride. On road, it doesn't much matter for the bunch stages. In time trials, some riders will be losing time because of the bikes they're on. (And the guy on the unfashionable but faster faired recumbent can't play.)

29ers do fit tall riders better, for the same reason that an 8 year old fits better on 24in wheels than 26. I can fit on my son's bike by jacking the seatpost right up. I could even keep the contact points in the same place by switching the stem, bars and cranks. It would fit me. But my own bigger bike with bigger wheels and bigger everything would fit me better.

29ers aren't just more stable because of frame geometry differences. A bigger wheel is a bigger gyroscope. That's inherent to the wheel size.

What I find weird is how conservative many mountain bikers are. In what's supposedly a technologically fast moving part of the cycling world, you'll prise their 26in wheels from their cold dead hands. Is there a lot of guff talked about 29ers? Undoubtedly! Will they transform your riding ability? No! Do they offer tangible differences, some of them of genuine benefit? Yes.

This isn't Biopace. It is, as 'sonic says earlier up, one more option. It's not the only option, but it's a valid one... especially for the kind of riding I mostly do.

John Stevenson

Dan Joyce wrote:

John,
So what you're saying is: they haven't been measured or timed properly.

I'm saying that whenever they are measured or timed, the effect vanishes. Feel free to do the experimentation to prove your claim.

Dan Joyce wrote:

I don't know if it'll ever be obvious that you can't win a world cup XC race on a 26er. The differences we're talking about are smaller than aerodynamic issues roadies face on road.

In which case you're admitting that the difference is very small indeed, given that the winning margin in World Cup cross-country races is one or two percent of the winner's time. As I said before, lost in the noise.

Dan Joyce wrote:

I wouldn't look to the average pro for developments. Most pros ride what their sponsors give them to ride and what the UCI allows them to ride.

True, until there's a clear and unarguable performance advantage. At which point either the UCI bans it or everyone takes it up. UCI deregulated mountain wheel size, what, three or four years ago now? (And rightly, the old 26in rule was pointless). Within a year of UCI and RTTC allowing aero bars, everyone was using them.

Dan Joyce wrote:

29ers do fit tall riders better, for the same reason that an 8 year old fits better on 24in wheels than 26. I can fit on my son's bike by jacking the seatpost right up. I could even keep the contact points in the same place by switching the stem, bars and cranks. It would fit me. But my own bigger bike with bigger wheels and bigger everything would fit me better.

The analogy with the kid's bike fails because you're not moving everything around, just the rider/bike contact points. Imagine a 26in wheel bike and a 29er with the same front and rear centres and the same contact point positions. They will fit equally well because the rider will be in exactly the same position, both in himself and relative to the tyre/ground contact points of the bike - and it's those and the weight distribution that determine handling.

If this weren't the case, then no adult could possibly fit a Moulton, when it's patently clear that they do.

Dan Joyce wrote:

29ers aren't just more stable because of frame geometry differences. A bigger wheel is a bigger gyroscope. That's inherent to the wheel size.

Gyroscopic effects of wheels make little or no contribution to bike stability. Go read Chapter 8 of the third edition of Bicycling Science: "The gyroscopic support moment [of the wheels] is tiny compared to the 'mass times acceleration times center of mass height' moment that predominantly governs bicycle balancing."

Dan Joyce wrote:

What I find weird is how conservative many mountain bikers are. In what's supposedly a technologically fast moving part of the cycling world, you'll prise their 26in wheels from their cold dead hands.

What I find weird is how desperate some mountain bikers are to be different. In what's already a fringe sport, they scurry off to its furthest reaches so they can continue to feel alternative, wacky and misunderstood.

Now we have our mutual ad hominems out of the way, can we get back to the technical issues?

Dan Joyce

While we're referencing Bicycling Science, check out the stuff on rolling resistance and how it relates to wheel size. Even on road, a larger wheel rolls better. Off road - which they don't discuss, AFAIK - it rolls better still. That's just a fact. It's why cart wheels are big, not small.

I'm happy to do a proper roll-down test as soon as I get a commission for such an article. For now, I've already got a year's worth of riding 26in and 29in wheel bikes on exactly the same trails. I've freewheeled away from riding buddies often enough to convince me. You say anecdote, I say empiricism.

The argument about a tall guy fitting as well on a 26in wheel bike is true if the 26er is built with the same wheelbase, handlebar height etc. as the 29er. Most times it won't be. And likewise, I'd argue that tall people don't fit well on either a Moulton or a Brompton and that they would not do so unless the bike (independent of wheel size) was especially made for them. Which it isn't. A 29er lets a taller rider get a bike off the peg that fits better, rather than going to The Large Man shop for a bespoke one. (However, I think even an average sized rider can enjoy some benefits from bigger wheels.)

The argument about the minimal gyroscopic effect of wheel size is true on a flat surface. Introduce bumps and it's a bigger deal. A bigger wheel will be less perturbed by a given bump, and maintain more of its forward momentum, than a smaller wheel. A 29er will, in short, be more likely to continue in a straight line over a succession of bumps simply because its wheels are bigger.

I sense that we're not going to agree. You say an improvement of a few percent is 'lost in the noise'. I think it's tangible - at race level it's the difference between winning and coming second. Even at the kind of pace I ride, it's noticeable. It is an improvement 'all other things being equal' but that doesn't mean it's not there, or that it's lost.

supersonic

Larger gyroscopic effect must mean one other thing though - slower acceleration. Placing more mass away from the hub, as with a 29er will require more energy to get it up to speed. Also the overall COG is higher on a 29er. Also the rolling issue is somewhat swayed by suspension.

Dan Joyce

Yeah, in theory it's harder to get the bigger wheels rolling. In practice, it's something you only really notice from standing starts going uphill - and even that might be more in the rider's head. Like the 29er's gyroscopic effect on stability on a flat surface, it's just a not a big deal. 'It is such a small number that it is almost impossible to measure, so don't let it worry you' is what Mike Burrows has to say on the subject.

The rolling issue is mitigated by suspension. On a sufficiently choppy track, a full sus 26er still flows more easily than a fully rigid 29er. If you're comparing like with like, the 29er rolls better. And often even when you're not comparing like with like...

Higher centre of gravity? The wheel axles are about 1 1/2 inches higher, but the bb and saddle are at the same height because the bb is dropped relative to the wheel axles, so you - the biggest and most important mass in the bike/rider make up - are at the same level as you would be on a 26er. Not that there would be anything wrong with being higher up, apart from the difficulty in getting a foot down: there's an inverse pendulumn effect going on; being higher up it's easier to balance not harder. You can confirm this by having a go on a recumbent where you're sitting much, much lower.

supersonic

Small changes cog can make large differences to handling though. To lean the bike on the same angle moves the cog a greater distance laterally - this may effect quick changes and agility.

Dan Joyce

Maybe. I don't know how you'd measure it, but 29ers don't seem as flickable or (ahem) huckable. I suspect most of this is due to the greater weight and inertia of the bigger wheels rather than the higher axle height per se, but I wouldn't rule it out having an influence. And I can't see dirt jumpers or trials riders ever using a 29er.

supersonic

The bigger front wheel just seems cumbersome to me, especially on tight twisty singletrack.

Here's one for ya: if a bigger wheel is meant to roll better, why do we have them on the front instead of the back with hardtail 69ers? The sus on the front should help, the big wheel on the back 'roll' better possibly. It cant be about acceleration purposes as some suggest, as you still have to accelrate the other wheel regardless!

Dan Joyce

69ers? Beats me. Your suggestion of a big wheel in the back is equally valid, if not more so, and would actually help a smaller rider get some of the rolling and traction benefits of a bigger wheel without the toe overlap issue that a 29in front wheel might present for a little dinky frame.

I should qualify that by saying I haven't actually ridden a 69er. But I'm struggling to see the logic in them. And I don't really understand why there are some bikes with a 29er front and a 26er rear and none the other way around.

ratty2k

I own a 29er, i cant see what all the fuss is about. Yes its a great bike, but its just different and so what? I use mine mainly for commuting on but will ride the local cross country routes on it (fully rigid). I cant see what thes "major disadvantages" are? So it may be a tad slower to accelerate and stop- but as saaid in the real world these are barely noticable anyway. To start denouncing things as bollocks 'cause you dont like 'em WTF? I'm sorry, but Brant who makes the things has the best attitude- its just adifferent way of doing it, so what? If people want 'em great if you dont- dont slag off the bikes (that work) or the people who ride 'em.

davethejackal

I've never ridden a 29er so I can't really say, but the increase in radius is more than a "few percent".

3/26*100= 11.5%

It's like saying there's minimal difference between riding a bike that weighs 26lbs and one that weighs 29, after all it's just a few percent. Clearly nonsense!

ratty2k

Again with the having never ridden one I can form a valid opinion!

Its just different people, get over it!

russ0228

john you are well and truely right. and pishie smooth land rover tracks yes 29ers might be faster. but everyone is on trails and mean trails ie bumps,rocks, sharp turns, etc,etc.
IT'S JUST A FASHION JUST AS NEON WAS IN THE NINETIES. look what happened to that. 29ers are like the ipod, a lot of people shout, up and down about the new color ooohh. but there are many better options out there. hell even half of the companies who make them believe this. it all about something the same, but really its new, however am not aloud to say who these are. i would get shot if i did
as far as statistics go, statistics show that 75% of statistics are made up, ie bull#@*$. end of i win. don't believe the hipe. lol

ratty2k

Another I've never ridden one, and can form a valid opinion! :roll: Sheesh!! what can you possibly have against a bike with different size wheels?

supersonic

I think a lot of people have a beef with the way the manufacturers portray them - while I believe, as you do Ratty, that its another option that suits some people, the manufacturers contradict themselves by teling us it is the best thing since since a sliced loaf: if that were true, they would drop the rest of their ranges!

jayson

Forgetting about the so called advantages/disadvantages of them for a second, they just look ridiculous on a MTB and are a silly fad if u ask me.

Call me what u will but I would never buy a MTB with 29" wheels im afraid.

ratty2k

'sonics right, but any of the bike makers will build up their new product. Whether it be different suspension, different frame or different size wheels. Thats just the nature of the buisness.I dont see it as a fad, they are getting more popular- witness the "big" makers getting in on the act and are very popular in America- I'm pretty sure they'll be here to stay.

rob cole

but the attention being lavished on 29ers is completely undeserved given their microscopic total sales,

this is true for the UK, but in the USA, 29ers are the fastest growing sales segment of their mountain bike market