Bike sizing
 

Im looking at a quintano roo I found on CL for a sweet deal. It's posted as 20" for the size, which is around a 50cm? From what I read I should be riding a 54cm.

I'm 5'9" tall with a 32" inseem with my shoes on. Is this bike to small for me? The original owner is 5'8" tall with a 30" inseem and was professionally fitted. Seems close enough that the seat height and handle bar height could be adjusted for a good fit?

Any help here would be great.

Sounds like it might work. Common wisdom suggests a slightly smaller TT bike vs a road bike. One reason is that most TT/Tri events are shorter than typical road rides, so it's easier to put up with the discomfort. Also the cramped cockpit keeps you in a very aggressive aero position, and the frame weighs less than a larger frame, but weight is usually less of a problem in a TT/Tri bike.

The real key is to ride the bike for about an hour. Of course that assumes it's been kinda dialed in for you.

Competitive cyclist .com has a great tool for an initial fitting. You have to do 9 measurements, and you need the assistance of another person. You plug it all in, and choose Road or TT bike, and then it spits out 3 sets of measurements for 3 different fit types.

I got a good deal on a 58 cm Fuji 1.0 frame and built a TT bike based on it. It's a bit bigger that I would like, but is pretty close to the "French Fit" that Competitive Cyclist recommends for my size.

I TT/Tri bike properly fit can be very fast, about 10 - 15% faster for the same effort as a road bike. Most is due to the aero positon, but also (for a true TT frame) due to the more upright and forward seat position and "slammed" stem position.

Hope this helps.