Measuring you and your bike to do the right bike fit adjustments.
Measure the length of your inseam to the floor with bare feet placed 15 cm apart.
The result is a bike fit recommended size of a road frame to you, measured from the centre of the crank to the joint of the seat tube at the joint of the seat and top tube. This calculation is based on the top tube to be horizontal.
Some frame and bike manufacturers give you the size of the frame measured from
If your current or your desired frame has a sloping top tube you should measure starting the anchor point from the middle of the head tube at the joint of the front and top tube to the middle of the seat tube in a horizontal line. Mark the point at the middle of the seat tube with tape. Measure from this point to the middle of the crank.
The Bike Saddle Height must Fit to your Inseam Length.
You can find different methods to calculate this crucial distance. You might need a friend to help your with all the measuring.
Begin the by standing on a hard surface with your (cycling) shoes on and your feet about 15 cm apart. Use tape to help you and measure from the floor to your inseam and push with the same force as a saddle does. Multiply this figure by 0.883. The result is your saddle height, measured from the centre of the crank axle along the middle of the seat tube to the top of the saddle.
Add 2 or 3 mm if you have long legs compared to your height. If you suffer from knee pain caused by damage to the back side of the kneecap adjust the saddle a bit higher. But the saddle height should never be so high that your hips bobbing over the saddle when pedalling around. If this bike fit formula results in a big change from your current settings you must move your saddle 2-3 mm per week until you reach the new position on your bike.
If the top tube is horizontal you can do a double check to make it fit your inseam. The distance from the top of the seat tube up to the saddle should be about 12-15 cm when the saddle is set at the correct height. When the crank arms are horizontal and you have clicked into the pedals wearing cycling shoes your knees should be at the top tube of the bike when you squeeze them together and the pedal shaft should be in a vertical line below your knees. Then you know you got the right fit for your bike.
This bike fit recommendations to the saddle height is based on a crank arm length of 170 mm. Adjust your saddle height in relation to whether you are using longer or shorter crank arms than the 170 mm which this calculation is based on.
Length of Crank Arms is important when dealing with bike fit
Based on the length of your inseam you should choose the correct length of the crank arms.
Follow these bike fit recommendations to the length of the crank arms:
The length of a crank arm is measured from the centre of the crank fixing bolt to the centre of the pedal fixing hole. The length is usually stamped on the back of the crank arm. If you use the crank arms longer than recommended you will be able to pedalling at higher gears, but will lose the speed of your pedalling. In some cases the large gears can course injuries to your knees. With shorter crank arms you will improve your short sprint skills and loose a little to your top speed.