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frame size(3 posts)

frame sizemerryrita
Apr 30, 2001 2:21 AM
thanks for your replies below. i am re-entering the riding world and find it totally different from 20 years ago. i use to ride a 23.5 inch schwinnn paramount i thought fit well. but, now the new kestrel i am looking at is a 56cm. can that be a good fit, i know the conversion # now, and it doesn't seem correct.I am 5/11, average leg length and wondering if other factors fit in to change my measurements, or did i not drink enough milk? thanks again for any help
re: frame sizePsyDoc
Apr 30, 2001 3:35 AM
There are numerous factors that can come into play when trying to get a good fit. For example, the length of your tibia, femur, arm reach, torso height, body height, etc. I am 5'-9" and I used to think that the 58cm Trek 2300 I had a number of years ago fit well least that's what the LBS manager told me. I really do not know if the 56cm is a good fit or not in your case. How does it feel when you ride it? How does it compare in comfort to a 57 or 58cm bike. Ride a few different sized frames and see which one feels the most comfortable.

If you run just your height measurement (I am assuming it was taken as accurately as possible), then the bike fit analysis at BSN (link listed below) suggests a starting point for frame sizing, measured center of bottom bracket to the top of the toptube, of 56cm to 59cm. In order to find the "right" size, a good bit will depend on the frame builder as toptube length, angles, etc. will have an impact.

Good luck.

The following is my typical response to sizing questions:

This is a standard reply as questions of frame sizing often present themselves on this board. This information should be used as a good starting point for frame sizing. Frames differ not only in their size, but also in the angles that are used which may influence your choice of frame size.

A typical solution is to take your inseam measurement from your pubic bone to the floor in bare feet about 6 inches apart. Place a book with a 1 1/2" or so binding between your legs and pull up until you cannot pull up any further. In other words, you want to measure to the pubic bone so pull up hard. Make sure the book is level. Have a friend measure from the floor to the top of the book binding.

Then, take that number and convert it to "cm" by multiplying it by 2.54. Next, take the converted measurement and multiply by .67. That will give you a good estimate of the frame size (measured center of bottom bracket to the top of the top tube; commonly referred to as c-t) you would need to get. But, someone commented that this could put riders over 6-feet on a frame that is too small (c-t) and they may be best served by subtracting 27-28cm from their inseam length for a c-t frame size.

In order to find the frame size you would need from a manufacture that measures frame size from the center of bottom bracket to the center of the top tube (commonly referred to as c-c), you would multiply your inseam by .65 or you can subtract 1 - 1.5cm from the c-t value.

Once you have a good starting point, then you really need to go out and ride a few different sizes to see which one fits you most comfortably. I have a 33 3/8" inseam (or 84.77 cm). I ride a 56 cm (c-t) Merlin Extra-Light and a 19" Specialized mountain bike. I chose the 19" over the 17" because the 19" just felt more comfortable.

I found that the more I knew about frame sizing, the more confused I became. Here are a few links on sizing information that will benefit you.

Note: click on "Ergobike: Competition Bicycle Size/ Proportions Analysis" and at the bottom of the new page that opens, you can choose your inseam measurement. The program then calculates all the other measurements that are "average" for someone with your inseam. You will get a plethora of information back.
Having said all that . . . 56 seems sort of small for 5'11"Cory
Apr 30, 2001 8:01 AM
There are lots of factors besides height involved in bike fit, as has been exhaustively pointed out. Before I wrote the check, though, I'd ask the bike shop to fit me on something big enough that I could get the handlebars up level with the saddle, or very close to it. Left on their own, they'll set you up with the bars 2" to 4" lower than the seat. There's no real advantage to it, especially if you're not going to be racing seriously, and lots of benefits to raising the bars.
It may require a stem change (possibly angled up and shorter) to accommodate your proportions. It's well worth the extra time in terms of comfort, endurance and your ability to stay on the bike for long periods. If you want to get aero, you can always go down on the drops. check for more...