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Bike Sizing/Fitting(3 posts)

Bike Sizing/FittingJohn P.
May 22, 2001 8:32 AM
Hi,

Last year I got into road cycling in a big way. I bought a leftover '99 Klein Quantum. Its fast has beautiful paint and I really like it.

The store threw in a pair of SPD pedals which I did not care for and I just swapped them out for Speedplay Frog's. I did not want to have to go buy new shoes as I bought Sidi MTB shoes which looked pretty much like a road shoe with lugs. At any rate they are super stiff and and with the Speedplays they are great.

Between changing my diet, the cycling, lifting weights and the Spin classes at my gym 2x a week I have dropped like 30lbs and my BP is down at 112/60.

My question is I want to dial in the fit of the bike. The reach and the knee position . Are there any resources on this? I have the seat pushed as far forward as it will go because I feel like I am to streched out on the bike. But than the bike shop told me it changes your kneed position which I didn't realize. They said you should not push the seat forward. They suggested swapping out the stem. How long should the stem be relative to the rest of the bike? The shop said you should be able to look down and not see the front axle?

So since I am going to be swapping out the Icon stem (not to impressed with this Icon stuff - seatpost and handlebars are next) are there any recomendations for a good stem? I was looking at getting one of those quill adapters so I could use ahead style stems. Or just I just stick with the quill. The Cinelli Frog looks pretty nice.

Any opinions?

Thanks in advance.

John
re: Bike Sizing/FittingPsyDoc
May 22, 2001 9:02 AM
There are resources out there for determining knee position. One such resource is Colorado Cyclist (see http://www.coloradocyclist.com/bikefit/ ). REI has a resource on bike fit that may help: http://www.rei.com/EGA/clinics/bikefit2f.html

As far as stem length, you typically want the stem long enough so that the handlebars obscure the front hub. But, this is just a guideline that seems to work pretty well for most healthy people. The place you bought your bike should have fit you to your bike.
The resources PsyDoc has mentioned are good starts; there arebill
May 22, 2001 9:39 AM
others. In sum, you should start out with your cleat position on your shoe (under the ball of your foot), then find a saddle height that leaves your knees comfortably bent without either rocking in the saddle or overextending your knee, then find the right fore/aft saddle position that leaves you able to pedal comfortably. Although criticized as simplistic and overly formalistic, the saddle position most often recommended is to place the saddle so that, at the 3 o'clock position, you can hang a plumb line from your knee (from the top of the tibia -- I think that's what it's called, anyway -- right under the patella) to the ball of your foot. This is supposed to be a good starting point for an effective mechanical stance.
Now, stem position. Again, the hub obscuring method most often recommended has been criticized as simplistic (fork rake being an unknown variable in the method). I just changed out my stem, and, to be honest, I don't even know whether the hub is obscured or not, but I can tell you that I am comfortably arrayed on the bike, with my elbows bent, fairly well balanced (and MUCH more comfortably stretched out than when I started riding). I started with a 100 mm stem (which the shop where I bought the bike said was good) to a 110 mm stem (with a professinal fit) to a stem that, although 110 mm nominally, actually is about 1 cm longer than my previous stem. All progressively more comfortable.
Fitting is a process. Because your stance will change as you become more used to the riding position and your muscles develop and your flexibility increases, you start to realize that there is not one perfect fit for all time. You also will learn that the margin for error in certain dimensions is relatively small compared to some others, and much is subjective. Experiment. A simple minimal twist of the handlebars in the stem of a couple of degrees can create a huge difference. Saddle angle can create a huge difference, probably more critical, in my opinion, than saddle fore/aft position or even saddle height.