Originally Posted by
Gonzo Bob
Ahh, that makes sense. In the early days of 650C triathlon bikes (late 80's), many folks called them 26" wheels so I though you still meant 650C. I know there are some fairly narrow 26" (559mm BSD or "mountain bike" size) rims out there (I have a pair that are 22mm wide). But tire selection is probably the limiting factor.
And doing a little math: a 650C rim with 23mm tires will have a radius of ~571/2+23 = 309mm and a 26" rim with 28mm tire will have a radius of ~559/2+28 = 308mm. So clearance on the sides (forks and chain stays) will be the limiting factor. But since the bike is for TT, my gut feel says that it may not have enough clearance for 28s, but that it should for 25s. The other likely issue is that the brakes are almost certainly short reach and you will not be able to drop the shoes down by 6mm for a 26" rim - so you would need to get new brake calipers (or is the Cannondale just a frameset at this point?)
I thought of adding those factoids to my post. Glad you did. Skinny road tire choices for 559 are indeed limited. I can think of Conti Gatorskins in 26x1.125, Conti Grand Prix in 26x1.125, and Primo Racer in 26x1. After that they're all 26x1.25 (32x559) or larger. The main reason for going to 559 wheels is to use fatter tires, not for availability. A TT bike is unlikely to accept the wider tires. When I got my highracer, 700c wheels was at the top of my requirement list because I didn't want to deal with the limited choices inherent with either flavor of 26" wheels.
Unless friend is planning on doing sanctioned racing, she could easily find a LWB bent to fit, AND with easy stepover.
"Easily" being a relative term since most bike shops don't sell them.