Comparing my road bike with my MTB, when you take the tyre into account, the wheels come out not very different. The road bike is a bit bigger but I guess if I put 2.5s on the MTB it'd be pretty close.
I was wondering about this. Why don't you get 29" wheels on road bikes? I'd have thought the flywheel effect would benefit roadies like it's supposed to help MTBers.
Does this ever happen? Has it happened in the past and the debate is long over? Would it make sense if it did happen?
Etc.

What? '29er' MTB wheels are just 700c.

Why don't you get 29" wheels on road bikes?

Actually that's exactly what you do get – it's just they tend to put smaller tyres on them 😉

Woo, 10 seconds quicker 😉

Bah, it took me another 11 seconds to type all those extra words I used!

Everything is a race with you Nick.

EDIT: I think he meant rims that would make roadie wheels 29" in diameter, about 2" larger than they currently are?

no, the benifit of 29'ers is supposedly the better rolling over obstacles and lower rolling resistance due to the longer/narrower contact patch.

Even specialist roadies like triathletes/track riders/Time trial's only use 19mm tires so theres not much to be gained by going even narrower.

It would raise the front wheel furter, thereby making the riders less aerodynamic.

They weigh significantly (to a roadie) more, as the rims have to be stiffer and need more spokes.

The usual way for roadies to go it towards 650b (mtb sized) rims in order to get lower and therefore more aerodynamic.

why don't you get 29" wheels on road bikes?

Thats a crazy idea, it would never work.

Everything is a race with you Nick.

Damn right, I have to be first, much to my GFs dismay…

You won't get larger diameter road wheels because road riders are inherently afraid of change, and they've been 700c for so long!

Gary Fisher have mixed things up slightly with their new road bike though, bigger hub flanges and such, can't be arsed to find the article at the moment!

whats new about big flanges? Loads of hubs out there with a choice of sizs depending on iwhether your a climber (low flanges for lighter weight) or a sprinter (big flanges for a stiffer wheel).

big flanges for a stiffer wheel

Actually that's a myth. Literally.

The usual way for roadies to go it towards 650b (mtb sized) rims

Er, actually 650c if they're going smaller, and they were doing that well before MTBs got all nichist! As to why you don't get more different wheel sizes, that's because roadies tend to favour interchangeability over fashion.

Oh well, tell Gary Fisher who've spent years contradicting you!

Gary Fisher Chronus here.

And very very few road riders would tend to go towards 650c, they used to be more common on very small road bikes, or on TT/tri bikes, but are largely redundant now.

There's so much out there that's 700c it'd be a nightmare to change, road riders are a lot more prone to swapping wheels and such than MTBers anyway, so compatibility is more important.