Bike Fit
If you want to ride better, stronger, and more comfortably, you need to have the proper bike fit. This starts with the frame itself and then gets more exact as you adjust all of your components around. A good fit won’t guarantee a Tour de France stage win, but it can improve power and reduce the possibility of injuring yourself. Many different ways to fit your bike have evolved througout the years, but here are a few general guidelines:
1. Get the Right Frame Size
The mathmatical way of figuring a general frame size is easy to do at home. First measure your inseam. Your true inseam is not your pant length, but it will probably be close. Stand straight up without shoes and feet shoulder width apart. Press a book or some other straight object up between your legs and measure from the top of the book to the floor. (Road frames are measured in centimeters, so you will want to do all of your measurements in centimeters. 1 inch = 2.54 centimeters.) Multiply your inseam by .67 to get a frame size.
Here are my measurements:
86.4 cm inseam * .67 = 57.9 cm frame (obviously this rounds to 58 cm)
2. Set Seat Height
You already have your inseam measurement, so just multiply your inseam by .883. This gives you the measurement from the center of the bottom bracket to the top of the saddle. This will get you within a centimeter or so of the optimal seat height.
3. Position Seat Front to Back
This is probably the most controversial measurement around today. I will tell you what the conventional rule of thumb is, and you can do some research about pro’s and con’s to this method.
Generally, the center of your knee should be directly over the center of your pedal. To make sure this is the case you will need a trainer and a plumb bob. Ride your bike normally in the trainer for a few minutes, then stop your pedal stroke where the crank arms are parallel with the ground. Have a helper hang the plumb bob from the front of the forward knee down all the way past the pedal. The string should pass near the front edge of the crank arm. If the front of your knee is over the front of the crank arm, the center of your knee is very likely to be over the center of the pedal.
4. Handlebar Position
The general rule of thumb for a fit rider is to position the top of the handlebar about half of a fists width below the top of your seat. As you ride on the hoods of your shift levers, a plumb bob from your nose to the handlebar should hang right on top of or slightly behind the handlebar. You would never want your nose out in front of your handlebar.
When positioned correctly your back should be these angles when riding in these positions:
Tops of Bar -> slightly higher than 45 degrees
Brake Hoods - > slightly less than 45 degrees
Drops -> less than 45 degrees and knees shouldn’t overlap elbows
Go See a Professional
If you don’t have the equipment or a helper to accurately get your measurements, go see a bike shop. Ask around for the best fitters in your area. Fitting is an art. Some fitters are good and some are bad. Shop around, and make sure you know how in depth the fit will be before you fork out any of your hard earned money.
You should refit your bike at least once a year. Your body may change over time, and your parts may shift around slightly. Don’t ride a poorly fit bike. I heard a good tip today on The Spokesmen Podcast that said to write down the measurements after getting fit, so that you know what a good fit is for you. You may crash, or your bike get stolen. If anything happens, having your bike measurements written down will allow you to set up the new bike very easily.
Now Get Out There And Ride!
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