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Bike fit questions and answers(7 posts)

Bike fit questions and answersbadabill
Jul 5, 2001 11:20 AM
I have been reading all the posts on bike fit. For the most part they are posted by new riders and have been getting great advice on fit and where to look for more answers on the web. I am amazed at how many LBS give bad or no advice at all on fit. Now my 2 cents on fit. How many of you think top tube length is the most important measurment for fit. I believe if you get TT length correct the other factors can be adjusted. Stand over hieght is the least important, I ride my bike not stand over it ;-) To be comfortable on the bike you need good balance and center. So wouldnt it be better to size bikes from TT length.
Just my opinion...NeedySpeedy
Jul 5, 2001 11:47 AM
I believe the top tube length and the standover are equally important. (talking traditional frames). If the standover is too low but the top tube is the right length there will be more post showing out of the frame to get the right seat height. Also to get a "proper" or "comfortable" fit the use of a stem with a rise may be required. Now if the next size frame is chosen with the higher standover then that usually results in a longer top tube which also may require a shorter stem to acheive proper fit. Its a toss up. Extremes on both ends (either a too short or too long stem - or a stem with excessive rise) will result in a bike that handles unpredictable and isnt comfortable on long rides.

I believe a bike is too small if:
There is more then 6 inches of post showing and there is a need to go with a stem longer then 130mm or there is a need for a stem with excessive rise.

I believe a bike is too big if:
There is less then 4" of post showing and there is a need to go with a stem shorter then 100mm.

These are just my opinions and what I have found works for me. I'm sure there are exceptions (everyones body is proportionally different).
If the bike fits, ride it!!Cima Coppi
Jul 5, 2001 12:26 PM
When I was being sized up for my new frame, every shop expert, including the builder of the frame said TT length is the most important measurment for a proper fit. ST length was a close second, so do not discount the importance of this measurement. That being said, I have to disagree with the Lemond method of ST measuring for tall riders such as myself (Colorado Cyclist's fit page addresses this issue). For example, based on the Lemond method, with my 87cm inseam, I should be riding a 56.5cm c-c frame. Well I'm just under 6'2" in height, and I have been comfortably riding a 60cm c-c frame for 14 years. My new frame is 59cm c-c w/ a 58cm TT. Perfect fit!

So it may not be a surprise if LBS's use this method of sizing and put someone into a frame too small for them.
If the bike fits, ride it!!G
Jul 5, 2001 2:44 PM
I agree. Most sizing formulas tend to put persons 6ft+ on a smaller frame. Most formulas put me on a 58c-t frame, but I have found that a 59c-t fits me better due to a longer top tube and I am currently riding a 58c-c frame(59.5c-t) that has a 58cm top tube. And it feels so much better. I have found that the "Rivendell way" of fitting a bike suits me perfect.
re: Bike fit questions and answersTJeanloz
Jul 5, 2001 12:31 PM
To say that one aspect of a bike is more important or less important is likely to get you into trouble. Sizing is a really delicate balance of all factors, and is not the same for all people. For example, you could present me with two identically sized people who I would put on different sized bikes depending on other factors like flexability, what type of riding they're going to do etc. Most people think that there's one golden size out there for them that will be the only bike they can ride. There isn't. Fitting a bike is a balance between a bike, which is somewhat adjustable; and a body, which is somewhat adaptable. Every angle, length and size need to be considered in unison to select the right size.
Excellent points!PsyDoc
Jul 5, 2001 1:38 PM
For example, due to my flexibility, I can add roughly 1-2cm to my reach calculations.
re: Bike fit questions and answersLarry Meade
Jul 6, 2001 8:30 AM
When looking at TT length you must also consider seat tube angle. A slacker seat tube will effectively shorten a top tube as the saddle must be pushed farther forward on the rails to achieve the same KOP postion as a steeper seat tube. Just another of many things to consider when looking at frame geometry.