a lot of the racers have.

MattPage did a lot of experiments with 26/650/29 wheels recently.

Not sure he wants the results in the public domain though 🙂

Easy in theory. Nightmare in practice…..

For example do you give them the same tyres. Yes you say thats fair…

But is it. If the 29er has more grip then it could run a shallower tread for the same traction. Or if the 29 er is more comfortable over roots it could trade this comfort away for a thinner tyre. Which is presuambly is what a racer would do. If we are not talking about racing who cares which is faster….

Blind tests are pretty hard to arrange on a bike and as soon as the rider knows what they are riding it’s pretty much impossible to control for their preconceptions. Basically, bikes tend to feel like we expect them to and whatever bike it was that you wanted to buy in the first place will probably feel the best.

Cheers,

Andy

29-26=3.

HTH

imo, there is no maths of value aside from physical comparisons of the wheels. And that tells you only a part of it. ie roll-over angles don’t also consider tyre deformation differences at impact point. Volume variances. Contact patch etc etc. Too complex to model with any validity.
Would you try to balance variables between wheels, or keep tyres and pressures optimised for each wheel as a rider would? How do you test when off-road riding and riders themselves vary so much? I guess a rider, 2 or 3 otherwise near-equal bikes, a track and a HRM can help them decide what works best for them (many mags have done this – a feature rather than a test imo, but still, some result trends seem to appear in them), but I wouldn’t call that ‘doing the maths’ as it can’t be applied to riders or terrain equally.

I’ve done back-to-back runs on 3 wheel sizes and the only thing of value was how I felt the bikes rode differently and of that, what I would attribute to the wheels as one of those ‘princess and the pea’ kind of riders. I’ve also done roll down / along types of ‘tests’ on different tyres and pressures.
After all that, I only had more questions about accepted component designs and what we feel is important on a bike. Rim diameter isn’t as important as we may think / in the way the generalisations suggest imo. ie, why all the focus on just that aspect of the wheel? We’re happy to challenge one accepted norm yet not others, or we get distracted by one aspect and lose focus. Perhaps because (like suspension) it’s too complex to sell easily without being distilled down to easily digested ideas.

I’ve rode my Cotic Soul and Solaris back to back

It’d be easy to time a downslope roll over roughish ground (not DH, just mimicking xc riding without pedalling). Done over a few different types of terrain in terms of bumpiness, that should sort out “rolling”.

Grippiness, much harder

Handling, essentially impossible I’d think, as it’s too subjective

So we’re left with making up our own minds (as long as manufacturers allow us to, i.e. continue to supply both/either/650/wotevva)

Why do people think 29rs have a bigger tyre contact patch size?

The size of the contact patch is related to the pressure in the tyre and the weight of the bike+rider, not the size of the wheel. Do 29r tyres tend to be run at lower pressures than 26r tyres?

if all things are equal then the 29er will have a very slightly larger contact area.

Why (assuming that by ‘all things’ you mean the weight of the bike, the weight of the rider and the pressures in the tyres)?

Wow, the seconds must have absolutely flown by!

Give a Pro a 26, 650b and 29er – tell them they can ride any of the three and they’re paid on results, easy. Although they may choose different bikes for different days/course/weather etc…

Ah well spotted IHN 🙂

@Rorschach – best gif on STW for a long time 😆

Correct. 29ers and 650B don’t have a bigger contact patch than 26″, it just tends to be a different shape, elongated as wheel diameter increases. So it can feel grippier sometimes and is percieved as bigger. If the tyre contact patch actually is bigger for a given pressure it will feel firmer to ride ie you can use less pressure for the same ‘feel’ over bumps (pressure, force and area), I think that’s the only relationship. Sidewall thickness, rim width etc is a distraction though.

Static contact patch is proportional to the system weight divided by tyre pressure. Dynamic contact patch increases with wider and/or larger diameter tyres. There’s a reason supercars have bigger tyres than superminis.

Yep.
By reducing tyre width but increasing wheel size, contact patch is maintained but drag is reduced.

Humna variables aside, imagine trying to set up a computer model that included all the terrain variations and riding dynamics over a 2 hr or 12 hr ride. It’s too complicated. I think the results of the fictional test would be very easy to tip either way just by changing a small variable ie there’s not a lot in it unless you know what you want the wheel for. There is no ‘better’, just ‘more fun for me’.

If in doubt, pick the middle size )

^ True, but then consider roll-over and momentum benefit etc on those techy sections, and the ease of moving around a smaller wheel ..

We get to the point of Rorschach’s gif very quickly )

and does a 69er = 650b F+R once it’s all equated?

I’m out..