Time trial bike - 650 or 700 wheels?

[oldguy00]

For a tt bike, is there any real difference in performance in terms of whether the frame uses 650c or 700c wheels??

[Fixed]

I am no expert on t.t. but I think 700's would ride better for most riders i.m.h.o. Cheers

[Argos]

This could be a LONG thread, as opinions abound, but I'll start off with the basic simple reasons, then jump from there....

Simple, 700c is legal in all district stuff, 700c is more common to get parts (tires) for. Get a flat, grab a wheel from another bike (in that sort of Situation) or if you want to go training, you do not have to have two sets of 650's when you probably already have more then one set of 700c.

More in depth. Much thought towards 650 was that they are lighter and have a smaller frontal profile, but we know that over 10k aerodynamics is much more important. And for the sake of argument we are talking about flat, as opposed to uphill TT's....

A slightly heavier 700c will give a better "momentum effect", keeps itself rolling, that is. Moreso, since it is going around less to cover the same distance, there is less over the top drag, where the front wheel comes, well, over the top as it is rolling forward, less rolling resistance also since the bearings (if of equal quaity) are producing less drag.

And yes the frontal area is more of a 700, but then the headtube is bigger on a 650c bike.

All of these factors are small compared to position and frame, but those are some arguments. The fastest times are ridden on 700c, but so long as you are not going for Nat'l Title's get what you want, and what you want is 700c!

[Sandy]

I know almost nothing about the subject. You seem to know just about everything. We sure do have some smart and knowledgeable cyclists on this forum. Very informative.


Sandy