cycling utah March 2000
Proper bike fit as important as the latest components
By J.R. Smith
One of the most important things you should do when going to purchase a new or used bike is to make sure it fits properly.
There are a number of methods available for road bike sizing:
1. Inseam x .65 = frame size (center to center). Used by Greg LeMond.
2. Inseam x .883 = measurement from center of bottom bracket to top of seat.
3. Stand over bike and if you have 1-1 1/2 inches in clearance then it is O.K.
4. "You are 5' 9" so you will ride a 56cm bike because my brother is your size and he rides a 56."
As you can see from above the LeMond method appears to be the most accurate but not everyone is Greg LeMond and if you were to measure everyone on the Pro Tour you would probably not find too many with that exact formula. If someone tells you any of the other methods you should probably seek professional advice.
Many bicycle shops offer professional bike fit. This is one of the most important decisions you can make to have your riding enjoyable, efficient and injury free. This is equally important to the casual rider, touring rider or racer. It is well worth the expense. The approximate cost is $30 - $50 and a shop may reduce the purchase price by that amount if you purchase a bike from their shop.
If you are someone who feels they have to mail order it is still worthwhile to make sure you are ordering the right sized bike. Manufacturers measure their bikes differently. Some are measured center to center, center to top, center to top of seat tube, center to top of lug, etc.
A professional bike fit will take into consideration your leg length, pedaling stroke, torso length, arm length to get you sized to a proper bike with correct seat tube, top tube, stem length and angle, and handlebar width. They will also take into consideration seat and head tube angles to make sure of proper knee positioning and handling. This is especially important for persons under 5' 4" who may require a 650c wheel sized bike for proper fit. They will also help you with proper crank length based upon leg length and type of riding. They should also check for leg length differnces in the case that lifts or orthopedic inserts might be needed.
As you can see a proper bikesizing and fit takes time to do properly and in my opinion is well worth the expense.