Wheel Size Advice (650c or 700c)

Bump....
I wanna see what the answer to this is as well....

My understanding is that 700c has less rolling resistance than the 650c.  Of course compact-ness is good for tri's.  Don't know any more than that!  someone will though...

My tri bike has 650c but I can't really compare to 700c as I've never ridden a tri bike with 700's. I can tell you that 650c rims are usually lighter, as are tires. The 650c wheels are suppose to be more aerodynamic since there is less spoke area. As for rolling resistance, I don't know which is better... I would imagine that the tire itself would make the most difference here.

Only bad thing about having 650c wheels is that it takes more effort to find tires. With 700c's you can walk into any LBS and buy tires... not so with 650's. I order tires online and install myself so I don't have too many problems.

I am going to have to agree with TonyWhit. I must be the only person in San Diego with 650's. I have to special order my tires and I have like two choices in tubes. If I had to do it again I would go with 700.
I have heard (not sure how true it is) that 650's are quicker. If you were on a really technical course where you are slowing and excellerating a lot then 650's would be best, but 700's are faster. That over a long distance you would be like 10 sec faster over 40K, or something like that.
So, take that for what its worth, but again I would go with 700's purely for convenience.
my 2 cents
Tom

if you are shorter than 5'3" or have an inseam shorter than 28" go for 650c..........if those two conditions don't apply then go for 700c regardless the advantages are too numerous to mention.

faster, better tire choices, neutral support is more likely to be able to help during a race, more comfortable ride (generally)

Kevin

Thanks for all your replys.  You guys rock...!

I had 650c's on my old Kestrel 500SCI and I loved them. They climbed like nothing I've ever ridden! But, I think the size/geometry of the bike should determie the wheel size.

From the Cervelo site:

650c and 700c Wheel Size

Which wheelsize is faster depends on how big you are and the position you ride in. It all comes down to putting the rider in a comfortable and aerodynamic position, and designing the bike around that.

Rider Position: If the rider rides in an aero position, the handlebars and aerobars will usually be in a relatively low position, lower than on a road bike. In a small frame size, this low position of the bars can conflict with the size of a 700c front wheel, as the big wheel and the low bars wouldn't leave enough room for a headtube. Hence for small sizes we recommend 650c wheels. For larger sizes, a good position can be obtained over either a 650c or 700c front wheel, provided that in both cases the headtube is kept short enough (shorter than on a road bike of the same size).

Bike Aerodynamics: Since both wheel sizes will work on bigger frames, the optimal frame will be the one with the lowest drag. While a 650c wheel has slightly less drag and uses a slightly more aero fork (shorter fork legs), a 650c frame will have a 2" longer headtube, assuming an identical aerobar position. Our windtunnel testing shows that due to that shorter headtube, a 700c bike will actually be slightly more aero than a 650c bike. Therefore, for the larger sizes we recommend 700c wheels, but for mid sizes the customers' current equipment and other factors will also enter into the equation.

Hope that helps...

Rob