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Fit experts: What Frame brand has the shortest relative TT?(6 posts)

Fit experts: What Frame brand has the shortest relative TT?gregario
Aug 1, 2003 9:12 AM
Does anyone know which maker has the shortest relative top tube in the large (62cm+) size frames? Am I correct in assuming that if the seat tube is slack, like 72 degrees or less, that the "relative" top tube would be shorter than a frame with a steeper seat angle? So if you're comparing a 62cm frame with a 59.5 TT and a 72 degree seat angle the relative top tube would be shorter than say a frame with a 58.5cm top tube and a 73.5 degree seat angle because you don't have to move your seat back on the 59.5cm TT frame to get the proper knee position? And how does "setback" figure into the equation?
not much difference...C-40
Aug 1, 2003 10:00 AM
You won't find a huge amount of difference. Colnago TTs are on the short side in the large sizes.

To figure the difference in TT length due to the seat tube angle, add 1.5cm per degree to the TT of the frame that has the steeper seat tube angle, or subtract 1.5cm from the frame with the shallower STA. Either way produces the correct difference in TT length between the two.

In your example, subtracting 1.5cm from the TT length of the first frame yields an effective length of 58cm compared to 58.5cm for the second frame. A .5cm difference isn't very significant, when you consider that most stems are only avaialble in 1cm increments.
What he said.MXL02
Aug 1, 2003 10:29 AM
Many of the Italian frames have relatively short TT. But Look and Merckx have longer TT, but slacker STA's, so I think it really comes out in the wash. Many of the American manufacturers are going the way of Lemond, with more vertical STA's and long TT's, which, with my long femurs and short torso, fit very poorly.
I was hoping you would chime in...gregario
Aug 1, 2003 10:45 AM
I'm in the same boat. I have really long femurs. I am currently riding a 62cm Colnago with a really short stem and was wondering if a Merckx in a 62cm would be a better fit. Of course, I'm comparing apples and oranges since a 62cm Colnago is measured C-T and a 62cm Merckx is C-C. The Colnago has a longer top tube and the Merckx doesn't even list the seat angle in their geometry chart for the 62cm for some reason, but the 60cm has a 72 degree seat angle. Looks like I may be splitting hairs.
The problem is...MXL02
Aug 1, 2003 11:21 AM
that you know how the Colnago fits, and you're just speculating with the nice if you could test ride the geometry before buying...
Aug 1, 2003 10:55 AM
might be cheaper/faster/easier than you think. Some builders like Teesdale are quite affordable. Other builders like Brent Steelman have a custom tt length option that is less expensive than going full custom.