What is available to whom it suits
Two examples from professional sport show just how important the right crank length is: Former professional cyclist Rolf Aldag used 180 millimetre long cranks on his road bike due to his height of 1.90 metres. Special requirements can also make a different crank length sensible: The Spaniard Miguel Induraín (1.88 metres) even used 190-millimetre cranks for his world hour record in 1994. However, the most important indicator for determining the optimum crank length is not body height, but leg length. Basically, in order to achieve the same joint angles for the same movements for short, medium and tall people, the crank length should grow proportionally with the leg length. However, with most manufacturers, the cranks do not grow proportionally with the frame size - simply because of the limited range on offer. The market leaders Shimano, Campagnolo and SRAM mainly offer three crank lengths: 170, 172.5 and 175 millimetres. Very tall or very short cyclists will not find anything suitable in the range offered by the mass-production manufacturers, as deviating crank lengths are not lucrative for mass production. Only occasionally are slightly shorter cranks fitted: for example, even Canyon's endurance women's bikes only have 165 millimetre cranks on frame sizes XS and smaller. Some smaller manufacturers have specialised in the production of such cranks.
Manufacturer of special cranks
- The French company Spécialités T.A. offers cranks with lengths
between 155 and 185 millimetres
https://specialites-ta.com/pedalier/manivelle/manivelles.html
- The Dortmund frame builder Uwe Marschall offers in its product
"Big John" range of crank lengths between 150 and 220 millimetres.
http://www.marschall-framework.de/produkte/
- US manufacturer offers the widest range Tin Cycles. The specialist
for customised frames offers cranks between 130 and 220 millimetres
http://zinncycles.com/Zinn/custom-cranks/
Rules of thumb
1. trust your proven system!
If you have physical limitations, changing the crank length can help you to cycle without discomfort. If you have not had any problems for years, there is no reason to vary the crank length.
2. adjust your wheel settings when you change the crank length
A longer crank means greater extension in the pull phase and greater flexion of the knee in the push phase - and therefore a more intensive load. Check whether you need to readjust the seat height, horizontal saddle position, handlebar position or pedals to avoid pain. However, a change of 2.5 millimetres is at the limit of what can be felt and therefore generally poses no danger.
3. special cranks do not fit every bike!
Crank lengths beyond the usual standards - i.e. well below 170 or over 175 millimetres - require an adapted frame geometry so that ground clearance does not suffer and cranks or shoes do not collide with rear stays or the front wheel. The solution for very tall or short riders is usually a customised frame.
