Size yourself for a bike without fancy gizmos

Seat Height:

In the interests of health and safety, choosing the correct frame size is absolutely essential when building or buying a bike. Frames are typically measured from the centres of the top tube. This is fine providing the top tube is horizantal but does become more complex when sizing with sloping frames. In the case of sloping frames, it would be adviseable to measure the seat tube as a gauge for choosing the correct frame size. Typically, a 52cm frame would probably measure 53cm from the centre of the bottom bracket to the top of the seat tube. I would advise 2-3 inches or 5-7 cm clearance on the standover.

As an example, Lets say the rider in this case is 5' 10" (approx 178 cm) with inside leg 32" (approx 81 cm) and a typical crank length is usually around 17cm.  As a starting point, add 7-8 cm to your inside leg and set the saddle height (from the top of the pedal to the top of the saddle) to this measurement. In our example , the red line in the image below measures 89 cm; the seat post and saddle make up the remaining 19cm.

This is the one every bike shop owner will tell you whenever you climb onto the saddle:  Place the heel of your shoe on the pedal and set the saddle height so your leg is straight at the bottom of the pedal cycle with the pelvis remaining in a horizontal position. The optimal angle of your knee should be 25-35 degrees.You can check the angle using a decorators angle tool or a rule protractor from a stationery supplier if you can get hold of one.

Seat Position:

The ideal low-cost tool for this job is a Decorators plumb bob.
With the crank in a horizantal position, the front of the knee cap should be inline with the the centre of the pedal mounting bolt as in the image below.

Stem Length:

This does not need a tool, just a simple visual check.
Unfortunately, the stem cannot be adjusted and must be replaced with one of the correct length.



When riding with hands on the hoods, look down at the front wheel hub - if it is inline with the handlebars ( invisible, hidden by the bars), the stem length is correct.


If you can see the hub and it is in front of the bars, the stem is too short.
If you can see the hub and it is behind the bars (closer to you), then the stem is too long.

Mike Leggiero