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Frame fit ? Is there a right choice?(5 posts)

Frame fit ? Is there a right choice?CrazyMan
Jun 26, 2003 8:45 PM
Looking on purchasing a new frame. Got fit before my last frame for a 57.5 top tube. I need a long seat tube. That bike was with a 130 stem, and felt a tad long.
The new frame has a choice of 57, 57.3, and 57.7 sizing.
Do I want a 57 with a 130 stem, a 57.7 with a 120, or to be caught in between. How will the difference affect ride characteristics? Length wise, it'll just affect number of spacers, though longer seat tube is nice.
Ultimately, do I want the larger frame, or smaller, or smallest, assuming they all fit closely.
Thanks for the help.
not enough info...C-40
Jun 27, 2003 4:41 AM
You are making the mistake of concentrating on the horizontal fit and ignoring the vertical fit, which is just as important.

In addition, the (vertical) "size" of most frames changes at twice the rate of the TT length.

Getting the right head tube length is also very important. The front-center dimension is less important, but a short F-C can lead to toe overlap with the front wheel. For riders with large feet, toe oeverlap may be unavoidable.

The three TT lengths that you have posted are insignificantly different. At the extreme, the 57.7 TT would require 1 size longer stem. The other two would use the same stem, IF the seat tube angles are all the same. This is another major mistake often made. The TT length of frames with different seat tube langles cannot be compared directly. I can provide the formula to make an accurate comparison.

What brand are we discussing?
not enough info...CrazyMan
Jun 27, 2003 10:49 AM
specific bike will be a kuota khan.
angles are the same.
and all headtube lengths are fine.
smallest may require a flipped stem, but no biggie.
This isn't so much about fit, as it is about handling and ride of 3 different frame sizes that seem to all fit.
Mike
not much difference...C-40
Jun 27, 2003 7:08 PM
According to the geoemtry chart, the front-center distance changes as insignificantly as the TT length. No chainstay length is given, so I would presume it remains constant.

The smallest frame might feel a bit stiffer, but the handling should not be significantly different among the three.

I would pay more attention to the head tube length. I'm very picky about HT length. I won't buy a frame with a HT that's more than 1cm shorter than the "optimum" length that allows me to use an 84 degree (Ritchey) stem with no spacers. A frame with a 1cm taller than optimum HT can yield the same bar height with an 80 degree stem and no spacers.

Buying a frame that's too small and requires a big stack of spacers and/or a flipped stem is not necessary when you have the option of selecting from 3 sizes that have very little variation in horizontal fit.
Ok, thanks for the help!CrazyMan
Jun 28, 2003 12:35 AM
I've issue