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Bike size(4 posts)

Bike sizeLucid
Nov 25, 2003 8:05 AM
I'm wanting to get into road biking in order to raise my fitness level for mountain biking. I've ridden (mountain bikes) for about 6 years, and I've found that in order to increase my times I have to put in around 50-75 miles a week. This has been quite a challenge trying to log this many miles on a mountainbike every week (transport, cleaning etc.. At anyrate I would appreciate it if someone could help my with sizing. I'm 6' tall and have a 33'' in seam (wow, it sounds like I'm writing a personal ad!)
fit website...C-40
Nov 25, 2003 9:47 AM
Take a look a Good info on fitting there.

I doubt that your cycling inseam is only 33 inches. It's meaured from the floor to very firm (saddle like) crotch contact in bare feet.

One of the most basic rules is to maintain 2-4cm of standover clearance in bare feet. For instance, even though I'm only 5'-6.5" tall, I have a 32-5/8" or 83cm inseam. I ride a 54cm frame (measured center to top) which has a standover height of 79cm.

Another guide is saddle height. Measure from the center of the bottom bracket to the top of the saddle, along the seat tube. Subtract 17-18cm from this dimension to get a reasonably accurate frame size, measured center to top. My saddle height is 71cm, so I subtract 17cm and get a 54cm c-t frame size.

Keep in mind that all frames are not measured the same way. Trek and Fuji measure to the top of the seat tube, which makes their frames 2-3cm smaller than those measured c-t. Lemond and many others are measured center to center (c-c) which makes their frames 1.5cm larger than a frame measured c-t. Standover height is often a better indictor of the actual frame size, when comparing frames mesured by different methods. To add to the confusion, many road frames now have sloping top tubes, making the standover height irrelevant. When comparing these frames, you have to go by the top tube length and the head tube length. Unfortunately, many manufacturers fail to list the head tube length in the geometry charts. If you have access to the frame at a store, then it's best to take a tape measure and measure the frame yourself.
Thanks C-40Lucid
Nov 25, 2003 12:57 PM
I appreciate the reply; that website is a big help. Thanks for the indepth knowledge!
Just for comparison, you might try RivendellCory
Nov 25, 2003 5:16 PM
I haven't looked at the site C-40 recommended (and I wouldn't question a guy named C-40 anyway). For comparison, though, you might look at the fit information at It's designed to size Rivendell's bikes, which may fit a little differently than others. FWIW, though, it put me on a frame 2-3cm bigger than I would probably have bought on my own, and it's WAY comfortable.