coasting 

this is like the little red riding hood thread...

Grandma, why do road bikes have such big wheels? All the better to run over you with.

ElJamoquio

Ah, the joys of being an average sized male. Everything on earth is designed for *me*.

AEO

I could be wrong.

After having my 20" front wheel slide out under me once and another time having it lock while braking, I lack confidence in corners with my folding bike.

On the other hand, with my CAAD9 and CX bikes, I can pedal through corners that are relatively sharp with confidence.

I always hear that mounting panniers lower is better for stability, so my guess is lower CoG = stabler.

jefferee

Only problem is, being average sized makes me about 35 pounds too fat for this sport.

gnome

most of us are too fat for this sport.

AEO

I'd rather be too fat for the sport than have no endurance.

Yellowbeard

Better still, the 54-56s are the best looking.

tatfiend 

The Shimano Capreo? group goes down to a 9 tooth rear sprocket. Such have also been available from Moulton too.

700C wheels are traditional and in many respects road bike enthusiasts are conservative, as is the International Cucling Union which governs racing bike legal configurations. If not racing legal most manufacturers will not likely build it and many road cyclists will not buy it.

Most bicycle wheel sizes date back to when roads were a lot worse than now and larger wheels gave a smoother ride on rough roads. 27" (630mm BSD) and 28" (635mm BSD) wheels used to be common and tires are still available for both wheel sizes. 700c wheels and tires became common in the USA due to Italian bikes using them and due to the rim size being compatible with tubular tire wheels as far as brake pad height adjustment is concerned. That makes swapping between clincher training wheels and tubular race wheels easy. 27" wheels were the commonest ones on most road and touring bikes sold here until the early 80s or so.

29er wheels are just wide700c rims with fat tires, not a different size as far as bead seat diameter is concerned.

stevegor

At last somebody has mentioned Alex Moulton.........

Perhaps everybody here with their "Big wheels are faster 'cos they're bigger" argument might spend a few moments to Google "Alex Moulton" and learn something.... just sayin'

Oh yeah, and you might find out that the Moulton bicycles were beating everything in speed records, track, road , TT and long distance cycling until cycling's world governing body banned them from competing against "normal bikes" .... sour grapes?

Phantoj

I'm not buying this; there should be an equal and opposite horizontal component on the back end of the contact patch.

alcjphil

One thing that has not been addressed to any extent: braking. I rode with a guy who had a Bike Friday, and he loved it, with one reservation. He was a big guy, well over 200 pounds and he was very cautious about descending because his rims tended to overheat during sustained braking

Campag4life

No. F1 cars ride exclusively on billiard table smooth roads. They won't do well on public roads let alone where many bicycles ride.

Campag4life

You should buy it because Fat boy is right. There are many misconceptions why a road bike has evolved with 700c wheels. The same misconception applies to mtb evolution. It is largely wheel strength relative to size...the very impediment that kept inital mtb's from having 700c diameter rims and now they do with improved technology...that and mtb's evolved from cruisers with more fat tires avaiable with 26" dia. wheels.
The thing that Fat boy didn't mention aside from angle of attack and contact patch depth is contact patch "shape". For the same psi the surface area is the same for same weight rider and bike if tire pressure is the same...but....shape is different which affects the riding dynamic of the bike.
Because the tire patch is longer for a taller wheel this affects handling and rolling resistance. The reason the other poster mentioned that his 20" bike skidded on corners is because of its short contact patch. This holds true of 29er mtbs which carve in dirt much better than 26er's for the same width tire. As to rolling resistance, it is more than angle of attack that Fat boy mentioned. Its again about contact patch shape. A longer contact patch for the same surface area translates to a more narrow patch and that means the tire deflects less in cross section which translates to lower rolling resistance. In summary the reason why road bike wheels aren't even larger is wheel strength to weight ratio and larger wheels and suitable larger frames with longer and heavier rear and front fork stays don't fit riders left of center and smaller in stature. Marketing doesn't drive trends. Good technical trends drive marketing.

cod.peace

A Moulton was raced in RAAM in 1987 and 1988 by Dave Bogdan.

Tsuru

Those disk wheels are ADORRRABLE! Who's a cutey wheel? YOU'RE a cutey wheel! Whoshabooshybooshy? Yourabooshyboosy!

AEO

there are street circuits... Adelaide for example

brbbiking

Big wheels allow you to see better over cars, and be seen :-D

Tsuru

Hey.

Are these things legal in road racing?

AEO

nope.

I think he would be better served by disc brakes.

PhilNYC

I'm the same height and ride a 56. But every "fit calculator" I've ever taken the effort to measure myself for has told me I should be riding a 57....

stevegor

Hahaha very funny.

I love it when the ignorant show their ignorance

Tsuru

It's not ignorance, it's just having fun with a pretty silly looking bike. Faster or not, disc wheels on that thing is pretty silly looking.

Dheorl

I do need to get a very marginally longer stem on my 55cm I think but only 10mm up. Not sure I'd be able to get the bars where I want on a bigger bike.

mollusk

I hope that none of the posters in this thread ever take an engineering course from me.

gnome

I'm an accountant. I wouldn't be able to handle the complex math of engineering.