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73 vs 74 degree seat angle and position over BB(12 posts)

73 vs 74 degree seat angle and position over BBweiwentg
Nov 6, 2002 6:38 PM
how much farther back am I going to be with a 73 degree angle?
I ask because there's a 49cm IF Crown Jewel in my size. they have 73 degree angles. my TCR has a 74 degree angle. my TCR has the saddle all the way forward.
re: 73 vs 74 degree seat angle and position over BBgtx
Nov 6, 2002 6:56 PM
I think in your size it will be right around 1 cm. I'm sure a math wiz can tell you for sure. Is your saddle all the way forward on a layback post? Or on a non-layback post? I believe the stock TCR post is a layback post (correct me if I'm wrong). If so, you should be fine with something like a Thomson post (non-layback). BUT, if you like a forward position like that, you might not like the IF geometry. Good luck.
thought notweiwentg
Nov 6, 2002 7:08 PM
I'm on a USE Alien, which has a little layback. I probably won't get the bike, Thomson or no. add to that the fact that the TT is rather short (IF: 51.5, TCR: 53.5), and that I need a really forward position since I have short legs.
c'est la vie. the paint scheme the guy had was nice, though.
Did you realize that your only talking about...Juanmoretime
Nov 7, 2002 1:53 AM
the saddle being back 1 & 1/2 centimeters further from where it's currently positioned to have the same distance from the saddle position to the handlebar due to the top tube and geometry differences?
Did you realize that your only talking about...Spunout
Nov 7, 2002 5:01 AM
I'd look at this closer! Because of the slacker seat tube, the corresponding(shorter) TT length should accomodate your fit.
oops. didn't realize thatweiwentg
Nov 7, 2002 6:13 AM
I was indeed talking about position over the BB, not along the TT. if I was only half a cm back, I could perhaps swing it (and let the cross bike inherit the USE post), but one cm ... hrmph.
you got it backwardsgtx
Nov 7, 2002 7:19 AM
if the TCR has a STA of 74 and a TT of 53.5 and the IF a STA of 73 and a TT of 51.5 then effectively the TCR has a 3cm longer cockpit.
this sounds about right. (nm)jtferraro
Nov 7, 2002 8:43 AM
Not sure of thisTrekFurthur
Nov 7, 2002 11:21 AM
Trying to picture it, but wouldn't 74 degrees be closer to 90, closer to vertical, thus putting him forward of the BB more; if the IF is a 73, then it brings him back over the BB a bit. Also, if the TT of the TCR 53.5 and the IF is 51.5, then that's two centimeters. Where does the third come from? Not flaming, but curious.
Not sure of thisgtx
Nov 7, 2002 1:12 PM
To achieve the same saddle postion relative to the bb, on the bike with the 74STA you would have to push the seat roughly one cm farther back that you would on the bike with the 73STA.
Ah, the missing piece--danke (nm)TrekFurthur
Nov 8, 2002 5:50 AM
Y'all are doing something funny....timfire
Nov 8, 2002 10:34 AM
I'm a little confused about where this thread is going.

First thing to note: the seat angle does NOT effect TT length significantly. Think, the TT is only about 6 inches (give or take) from the top of the seat. One degree times 6 inches... not sure the math but I would guess around 1 or 2mm.

Second, if the figures given were correct that the TCR has a 2cm longer TT than the IF, given the same length stem then he will need to move his seat 2cm BACK from where he has it now to achieve the same seat to handlebar position.

Going back to the original question, in the end he will end up with a saddle that's about 3cm farther back relative to the BB than it is now (maybe that was what Juanmoretime was trying to get at). That's going to significantly change change his hip angle. With his saddle all the way forward on his current bike, he was probably running an effective STA of about 75.5-76 degrees I would guess, but with the new bike it will be closer 72.5-73 degrees.

--Tim Kleinert