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Newbie at Road - Sizing questions(3 posts)

Newbie at Road - Sizing questionsMichael Gretton
Mar 20, 2001 12:08 PM
Please Help! I don't purchase new bikes often so I want this next purchase to be just right. I purchased a Cannondale R600 Triple (2001) and I am concerned that the bike might be too large. I researched sizing more after I made the purchase and found the inseam formulas recommended by many "experts". After completing the formulas, I discover that it is recommended that I fit into a 56 cm bicycle and that if I had to error, go to a smaller vice larger bike. I am awfully concerned that I might have made mistake. It doesn't appear that I am stretching when riding my 58 (although I just bought it) and the bike feels okay now; however, I am concerned that once I start doing longer rides an improper fit might manifest itself in pain and discomfort. I am about 5'10" inches (male). The stand over clearance is just grazing my crotch (if I pull up snug, it is about a half itch clearance). What is your opinion? Should I try to get a 56? Is it that important? My elbows bend nicely (so I think remember I am new!) and when i look down, my hub is obscured by the handle bar. Any help would be appreciated. Thank you very much,

re: Newbie at Road - Sizing questionsPsyDoc
Mar 20, 2001 12:30 PM
Hi Mike.

Do not worry. If you are comfortable on a 58cm, then ride it. When I bought my first "expensive" roadbike, I was sized on a 58cm. Was it too big for me? I do not know; all I know is that I was comfortable riding it. I am 5'-9" with a 33 3/8 inseam (or 84.77cm)and I am currently riding a 56cm Merlin Extra-Light. I have about 4cm (1.5 inches) of clearance between "the boys" and the top-tube. Some of the fit formulas put me on anywhere from a 55cm to a 58cm bike. One website in particular, Rivendell Bicycles, believes that people are riding frames that are too small for them. The URL to their page where they discuss fit is:

Below is my "standard" response to questions of fit along with numerous websites with info on fit.

Good luck!

This is a standard reply as questions of frame sizing often present themselves on this board. This information is to 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.
re: Newbie at Road - Sizing questionsLBS Guy
Mar 20, 2001 5:15 PM
If the bike feels good when riding it if your not to stretched out and dont feel uncomfortable, then ride it, your the only person who will really be able to know if it feels good, and if you do feel to stretched try a shorter stem before trading bikes in, hope it goes good, later