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fit question seat tube v. top tube(5 posts)

fit question seat tube v. top tubemoschika
Jun 10, 2003 2:37 PM
i recently completed restoration of a vintage lightweight, pics coming soon in retro section, and have a question about fit.

i currently have a 54cm LeMond, the vintage is 58cm Ruegger but the top tube lengths are roughly the same. when i ride both i don't feel any more stretched out on either one but i feel i'm higher up on the larger frame. even though my legs aren't reaching any more then they would on the LeMond and i don't think the bb is any higher.

when looking at frame sizes it seems that seattube length is usually identified while tobtube is less given, yet i would think both are important. but is one more or less important?

what's the verdict on fit? tube lengths? how it feels?
Some things to considerKerry
Jun 10, 2003 4:24 PM
First, just because two bikes have the same TT length does NOT mean they will fit the same. Seat tube angle has to be considered as well. Increasing the STA by one degree will move the head tube roughly 1 cm forward, since your saddle position stays the same relative to the BB. The perception of being higher up on the larger frame may just be that the TT is closer to you. However, it's really easy to measure BB height, so why not KNOW the difference. Assuming you have roughly normal proportions, TT length and STA are at least as important as seat tube length, because they are what get the bars in the right position relative to the saddle without having to use unusually short stems. If you have an extra long or extra short torso, then TT length and STA become more important. Within reason, longer or shorter seat tubes just change the amount of seat post showing. All that said, there isn't that much difference between frames in the TT/ST relationship.
some real life measurementsmoschika
Jun 10, 2003 10:10 PM
ok the bb hieght is the same 27cm. the seat-bue c-t on Lemond is 54cm, Ruegger 58cm. top tube length c-c on Lemond is 54cm, on Ruegger 56cm. from center of seatpost to center of handlebar where it goes thru the stem on both is 66cm.

angles i don't know how to measure effectively. but i'm thinking the head angle of the Ruegger is shallower then the Lemond because the stem is longer but the length between center of seatpost and end of stem is the same. is this right?

body wise i have a longer torso then legs. i can stand over the Ruegger but it does get a bit close for comfort.
hey, it's okdesmo
Jun 10, 2003 8:39 PM
to ride a 70's vintage race bike that's on the big size. 3" of seat pin and zero drop to the bars looks right at home on those babys. I ride a 54cm in modern custom steel but my '73 Italvega, stamped "58" which mesures out at 56 c-c seat and 55 c-c top fits me just fine as well. If I park them next to each other the relative seat and bar height and distance to each other is very close, even though they do not share any of the same tube lengths, angles, or wheelbase. both bikes offer great, but totally different rides.
Jun 10, 2003 10:13 PM
it's good to hear that the 'right' fit isn't always going to be the same 'size'. i don't feel any less comfortable on the larger frame just different. and bending down to shift on the downtube takes some getting used to, especially on a bumpy road.