ive had debilitating arthritis since I was five and whilst I was younger I enjoyed riding a bike. Unfortunately due to degradation of my hip and lower back joints I am unable to use bikes with long cranks as my hips and back don't allow for the upwards movement.

There is some rotation and upward movement within my hips and back still - I'm able to climb stairs just about for instance.

As I say, would it be possible to adjust the crank length? Would this need to be specialist or would my local second hand dealer be able to do this?

Any help would be greatly appreciated!


  • I quite possibly mean the pedals. The long 'leg' that connects the bike to the pedal.
    – Ryan
    Aug 4, 2015 at 10:32
  • 3
    Yes. You can change the crank arms to be longer or shorter (though too much longer and you get ground clearance problems). You can even have two different lengths. But need a bike with a 3-piece crank unit, not the 1-piece seen on inexpensive bikes, and parts for some fancier bikes may be expensive or hard to find in the desired lengths. A decent bike shop should have the technical know-how to do the swap, but you probably should try to find a physical therapist or what ever to advise you. Aug 4, 2015 at 11:35
  • Welcome to Bicycles @Ryan. I'm voting to close this question as a duplicate. While the question is not exactly the same, it leads to the same answer. All the best with those cranks.
    – andy256
    Aug 4, 2015 at 11:51
  • 1
    Just to be sure: Is your saddle high enough? The usual range for crankarm lengths is between 165 and 175mm, which is not all that much difference.
    – Michael
    Aug 4, 2015 at 16:31
  • @Michael is right: if the saddle is too low, the hip and knee articulations are much likely to be overloaded. Be sure to have your saddle height correctly set up by a specialist. The correct position would be sitting on the saddle with the pedal most down and the leg almost extended being able to rest the heel on the pedal.
    – Carel
    Aug 4, 2015 at 17:59

1 Answer 1


Yes, you can change the length of the crank arms. If you are going to replace crank set, you need to make sure it is compatible with your frame. There are a number of different interfaces between the cranks and the bottom bracket.

Some common sizes are (many cranks will have the size stamped on the back of one or both of the arms):

  • 165 mm
  • 170 mm
  • 175 mm

The size is the distance from the center of where the crank attaches to the bottom bracket to the center of the pedal axle.

If that is enough, you can just swap your crank set for different one. If not there are companies selling specialized shorter cranks or crank shortening devices

Lastly, kids bicycles have much shorter cranks, maybe it would be possible to use some of them on an adult bicycle.

  • 4
    You often have a few more dimensions, like 172.5 mm and stuff.
    – Batman
    Aug 4, 2015 at 15:16
  • 3
    The unit is mm (millimeters) and it specifies the distance from bottom bracket axis to pedal axis.
    – Michael
    Aug 4, 2015 at 16:30

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