Aside from what the LBS tells me…btw - which are two different things from two different shops. And while I wait for them to build a bike to demo. Looking for some ST input.
Want to get on a Kuota K-factor but don’t know if I’m a M or L. Basically I’m 5’11" with 34.5" inseam:
Height 180cm
Trunk 62cm
Inseam 88cm
Arm 74cm
One LBS measured only my torso (62cm) and said that the top tube fit is the most important for a Tri bike…so I should be on a MEDIUM. Another said that because of my inseam (88cm…34.5 inches) I COULD be on a LARGE…
then…Kuota’s on-line configurator tells me I should be on an XL! The following is their calculated output…
Seat tube 57,8 cm
Top tube 57 cm
Saddle height 77,8 cm
Stem 13 cm
I think the top tube and head tube are the two important measurements since you can always extend the seat tube with a longer post. As long as the head tube isn’t too short, you’re probably better off with the smaller bike. If the smaller bike ends up having a top tube that is slightly too short, you can add a bit to the stem. I wouldn’t want to go the other way and have to shorten the reach by going with a 5cm stem or something crazy like that. Your handling would be awful.
My dimensions are nearly the same as yours, which means you will likely need to buy a bike frame that is smaller than your height would indicate. By chance I measured my Yaqui (Ves calls it a 57) last weekend and the actual bottom bracket to top tube dimension is something like 51 centimeters. A friend loaned me a 51 P2C and I figured it would be too small but the seat tube dimension was nearly the same. I managed to get the same drop by using a flat stem and taking out all the spacers on the fork and from the Vision bars.
So, yes, the top tube is the important dimension, as is the head tube if you are looking at any type of decent drop.
Chad
I measured it center of the BB to top of the tube. That is not a true tube dimension, but gives you an idea of how tall the tube measures. Both top tubes are level, but the Yaqui has a little more stack height in the headset, while the Cervy has an integrated set. To arrive at the same drip I used a steep downsloping stem on the Yaqui and a straight stem on the Cervy. The handling on the Cervelo is not great, so probably the optimum for me would be a 53, but then I probably couldn’t get the seat far enough forward.
Chad