TCBC: Bike Ride Grab Bag

Bicycling 101: Proper Bike Fit

By Liz Sands, TCBC Ride Leader

One of the most important things you can do to be comfortable on your bike and avoid injury is to ride a bike that fits properly. There are adjustments that can be made in several different locations on your bike to make it fit your personal “geometry” better. It is also of primary importance to learn about bike fit if you are thinking about purchasing a new bike. If you buy a bike that doesn’t fit, it won’t matter if it’s the latest, lightest carbon fiber with Dura-Ace components, you are going to be miserable.

If you want to get your position on your bike checked out, I would highly recommend finding a local bike shop that knows how to do a “fit kit”. Also, ask people in the club if they have recommendations for particular shops (and employees within those shops) who are experts at bike fitting. The “fit kit” process involves taking measurements of your body, then assessing those measurements against how your current bike is set up (or if you are buying a new bike, determining the optimum frame size, handlebar width, crank arm length, stem length, etc.). There may be a charge of $50 or so to get a fit kit done. If you are buying a new bike, the shop may be willing to credit your fit kit payment toward the purchase of a bike from their shop.

If you decide to go it alone, here are some general guidelines for setting up your bike properly. First of all, never make drastic changes in your bike position. Even if you figure out that your optimum seat height should be an inch higher than how you have it currently, your body is used to the current position and it will protest if you change it dramatically. Better to raise the seat a quarter inch, ride it that way for a few rides, raise it another quarter inch, and so on. Second, find a friend to help you look at your position on the bike – it is pretty difficult to look at yourself when you are sitting on the bike.

Seat height: A longstanding formula is to measure the distance from the floor to your crotch and take that measurement times .883 to determine the distance between your pedal and the top of the saddle – but you should only use that as a starting point. The rule of thumb is that there should be a slight bend in your leg when your foot is at the bottom of the pedal stroke. If your hips are rocking back and forth on the saddle as you pedal, your seat is too high. Another general rule of thumb is that if you are experiencing pain in the front of your knee, your seat is probably too low; if you are experiencing pain behind the knee, your seat is too high.
Saddle position: Move the saddle forward or back so that when your forward foot is in the 3 o’clock position, you could drop a plumb line from the bony point just below your knee to the pedal axle. You can also adjust the tilt of your saddle – the default position would be a level saddle, but some riders (like triathletes who spend a lot of time on aero bars) like a slight downward tilt. Your saddle should never be tilted downward so much that you end up supporting most of your weight with your hands and arms. Speaking of saddles, if you are woman who bought a men’s bike and you are still riding that men’s saddle it came with, think about replacing it. You want your hip bones to be resting on the saddle – for most women, that is not going to happen on a men’s saddle.
Stem length: The stem is the part that attaches your handlebars to your frame. Sit on your bike with your hands on the brake hoods. When you look down, the handlebar should obscure the hub on your front wheel. If your stem is too long, you’re going to feel too stretched out on your bike. You can replace the stem with a shorter or longer stem for a reasonable cost.
Handlebar height: If you have an old fashioned stem that can be moved up and down in the frame, you can adjust the height of your handlebars. A starting point for recreational riding would be to have them level with the top of your saddle. If you are flexible and looking for a more aerodynamic position, you can move the stem lower. The newer threadless headsets are less adjustable, although there is a possibility of using spacers to raise the height of the stem.

There are other, more esoteric changes you can make such as changing the length of your crank arms or the width of your handlebars. Consult a fit expert at your local bike shop for advice on those.

Copyright © 2004 Liz Sands. All rights reserved.

(article orignally published in the April 2004 Activity News)

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