serotta trail/rake determination

[Geoff]

I just got the build sheet from andrew for a used frame I bought. they have 4.3cm rake and 5.59cm trail. To get this they used a front wheel radius of 34cm. To get 34 cm you would have to have a 29mm tire. Is this normal to use such a large tier diameter for trail or rake determination by frame designers?

Geoff

[cpg]

A 29mm tire would have a larger radius than 34cm. A 34cm radius is a typical 23mm tire. Everything looks normal.

Curt

[Geoff]

I thought bead seat on a 700 wheel was 622? If that is the case to get 34 radius or 680 diameter that would require an aditional 58 or 2 x 29 to get the 680 diameter.

Am I wrong here?

Geoff

[cpg]

You're correct about the bead seat thang. 700C = 622. But not correct about the tire bit. 23mm refers to the tire's width. Not it's height. So the radius is an actual measurement with the tire mounted up. In this case a 700c with a 23mm tire mounted physically measures 34cm. Capiche?

Curt

[Geoff]

roger that, tire not round... so easy a cave man could do it.

Thanks

G