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bike fitting(6 posts)

bike fittingDavid T
Aug 1, 2001 12:15 AM
I'm 5"7 with 29 inches inseam, should I go for a 50cm bike or 52cm bike. Some people tell me that a 50cm road bike will be a bit short for my body, while with the 52 cm, the clearance between the top tube and my body is very small.

Thanks for the advice =)

David
re: bike fittingPsyDoc
Aug 1, 2001 3:47 AM
Which one feels better? As for standover height, as long as you have at least 1" (2.54cm) of clearance you are fine. But, we are not talking about being able to see 1" of daylight between the top tube and your crotch area. The 1" difference refers to the clearance found between the top tube and your pubic bone. Assuming you took your inseam measurement correctly, I am inclined to think the 52cm would be a good fit as long as you are comfortable with the reach to the handlebars with a stem no shorter than 10cm. When you measure your inseam, you want to measure to the pubic bone so pull you have to pull up hard on the book binding or whatever you are using to help you determine this measurement.

For another perspective on sizing, go to http://www.wrenchscience.com/WS1/main.asp and click on "Road." On the new page that loads, click on "Frame" and then click on "Help Size Me." You will need a friend to help you take the measurements.
Agreed DocJim Burton
Aug 1, 2001 1:20 PM
My new bike doesn't have much "crotch clearance", but I feel that it fits me perfectly when I am actually on the bike. David, we are about the same size. I think that in smaller people like us, it is very important to make sure the top tube, not standover hieght, is the deciding factor in buying a bike. In fact, it seems to me that top tube length is the most important factor for everyone in buying a bike.
re: bike fittingJohn S.
Aug 1, 2001 9:59 AM
David:

I too, am 5'7" with a 29 inch inseam. I have owned a GT with a 52cm seat tube, and a 54cm tt, and found it to be a bit too big. You are probably aware that finding a perfect fit for persons with shorter legs (and arms) can be difficult. I can't tell you which bike will fit you best, but based on my own experiences, I can recommend some places to start:

I will assume that if you are 5'7", and have short (29" legs), that your height comes from a long torso. I had a professional fit done ( on a serotta cycle), and the recommendations were as follows: 50cm seat tube, 53cm tt (with a 100mm stem), or a 52cm tt with a 110mm stem), and a recommendation for a slack seat tube angle (around 73 degrees) -- this slack angle was important for me, because it allows me to stretch out on the bike, without being too far forward. Oh yeah, and don't touch a crankset longer than 170mm.

With that said, Here are a few bikes that fit me very well: Lemond Zurich - it has a 51cm seat tube, and a 53cm tt and slack angles! Note: all Lemond frames share this geometry, so if you don't have $2,000 for a Zurich, you can try one of their other models.

Also, if you have some extra cash, look at Independent Fabrications. They have lots of sizes, and make one of the best steel frames anywhere.

What did I end up getting. . . . ?

My solution for a perfect fit was to go custom (got a fantastic frame from Landshark), however, you should check out the Lemond and IF . . . you will not be disappointed!!

Good Luck!!

John S
recheck inseam...C-40
Aug 1, 2001 10:12 AM
The inseam measurement that you have posted is shorter than I would expect for a 5'-7" rider. I'm your height and have an 83cm (32-5/8") inseam. I ride a 55cm frame with a 54.3cm TT and 74 degree seat tube angle. I use a 110mm stem.

Measure your inseam as described at coloradocyclist.com, or use a bike with a horizontal top tube as a measuring device. Block up the wheels (equally), until you get very firm, crotch pressure when you straddle the bike in bare feet. The distance from the floor to the top of the top tube will be an accurate inseam measurement. The proper frame size, measured center to top of top tube, will be 27cm less than your inseam. Subtract 2 to 3cm from your inseam to get maximum standover height.

If you are truly 5'-7" in height, you need a top tube length in the 54-56cm range. The top tube on stock frames in the 50-52cm range will be too short. This top tube length is common for frames in the 54-56cm range. A custom frame may be your only option. Check that inseam and post again for additional guidance.
recheck inseam...Egyptian Magician
Aug 1, 2001 9:40 PM
To measure standover height, should one be barefoot, in socks or in cycling shoes?