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Discussion Starter · #1 ·
I'm a first time poster and relatively new to biking having started about 5 months ago. I am currently riding an older Trek road bike that was given to me and is a 58cm frame which I know is too big for me. I am considering buying a new road bike (Motobecane Le Champion SL). From all I have read and also from having been measured at two local bike shops it seems the ideal frame size for me would be 55cm which of course is not offered. Would it be better to go up to a 56cm or go down to a 54cm? Help!!
 

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Discussion Starter · #3 ·
I'm 5'8" and weigh 155. I wear 32" length pants and a 31" waist (if that is a help?!) and probably am average build as far as leg and arm lengths for my height.
 

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not much...

jrz1 said:
I'm 5'8" and weigh 155. I wear 32" length pants and a 31" waist (if that is a help?!) and probably am average build as far as leg and arm lengths for my height.
I'd suggest reading up on fit basics at www.coloradocyclist.com/bikefit. In place of a cycling inseam, a measurement from the center of the crank to the top of the saddle. parallel to the seat tube should gives us a good idea of the appropriate frame size.

Another important measurement is the handlebar height, vertically, from the ground to the top of the bars. While you're at it you can measure the saddle height vertically from the ground to the top of the saddle. The difference is the saddle to bar drop. This can affect your choice of frame size.

The other issue is the fact that different brands measure "frame size" differently. A current "58cm" Trek for example, measure only 54.5cm center to center. That's probably not too tall for someone wearing 32" pants, but it might be too long, since Treks have some of the longest top tubes and what little info you've posted indicates a short to average torso.

http://www.motobecane.com/lsl_geometry.html

From looking at the geometry chart, it appears the Motobecane is another oddball, measuring the frame size as the entire seat tube length. A "56cm" only has the standover height of a 54cm, measured center to top. It also has a long TT, which may not make it an ideal choice.
 

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Discussion Starter · #5 ·
Thanks for the great info, especially the sizing chart for Motobecanes. If after all the measuring I still find that the "perfect" fit is a size not offered is it better to go one size up or one size down in general? What are the advantages and/or disadvantages of either?
 

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lots of varibles...

Beginners tend to adjust the handlebar height fairly high, since it takes a pretty fit person to tolerate an 8-10cm drop from the saddle to the bars. This can be accomplished with a high-rise, 96 or 100 degree stem to start with. Later, the stem can be slipped over, lowering the bars 2-3cm. If you need 3cm of spacer and a high rise stem, then the frame may be too small. Motobecane doesn't list the head tube length, but IMO, it's every bit as important as the TT length. You need to figue out what kind of stem angle and spacer combo will be required, before you buy the bike.

Take some measurements and post again with more info.
 
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