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My left knee is stiff and arthritic after 5 operations.

If I have the saddle high enough not to over-flex that knee, I can barely touch the ground ... as I am elderly and not very agile, this is not safe!

It was suggested to me that a shorter crank on the left side only would allow me to lower the saddle a bit without over-flexing my stiff knee.

Would it be practical to do this?

Thanks

(My bike is a Claud Butler Explorer 100)

Justin

  • 50 years ago this sort of personalization was quite common, but went out off style with cottered cranks. In fact, at one time a crank arm with a sort of Ferris wheel setup was used, so that the bad leg never needed to rise as high, but could still go all the way down. – Daniel R Hicks May 5 '18 at 23:58
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    Mechanically its simple to do this on the bike - you just end up with the opposite cranks spare. Physically on you? Speak to a medical professional - someone who deals with sports injuries and ideally compensating equipment. – Criggie May 6 '18 at 1:23
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    “I can barely touch the ground” are you getting out of the saddle? While sitting on the saddle it should be irrelevant if you can touch the ground. When stopping you have to move in front of the saddle so you are above the top tube. From there it should be easy to reach the ground. – Michael May 6 '18 at 7:06
  • Have a look at my question on this problem- bicycles.stackexchange.com/questions/9085/… – mattnz May 6 '18 at 7:49
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    I'm with @Criggie on this -- consult with a medical professional. Knee pain is no fun, even if you're not old. – Batman May 6 '18 at 17:07
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Seems like a reasonable idea. Two things to consider:

Can you get a crank shorter enough to make a difference? Common crank lengths are 170, 172.5 and 175mm. (measured from crank axle center to pedal axle center). Shorter lengths are also available for some cranks, in 2.5mm increments.

I think you would have to do some experiments and measurements. Say you went from a 172.5mm crank (the most common length) to a 168.5mm one. That would allow you to drop the seat 5mm and keep the same amount of knee flexion. Is that enough to enable you to touch the ground safely?

Crank availability. I looked at a few pictures of the Claud Butler Explorer. Models at least a few years old seemed to have a 3-piece crank with a square taper axle-crank interface. That's good as the square taper is an old standard, so used but perfectly serviceable cranks are available, new ones are inexpensive also. The left are right cranks do not have to match, so you can use any that you can find in the right length.

Square taper cranks need a special tool to get off, but a good local bike shop can do it for you.

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A more drastic solution, a bike with a different geometry.

The seat lower, the bottom bearing/crankset further forward and the sitting position a bit more upright.
low step bike

For example, the above photo from the vanRaam website (fair use claimed), I bet there are more models which have those basic facts.
The low step through might not be needed but will help some people.

And you can still adjust the cranks if needed.

(Not clear from the photos, but this kind of bike is available both without and with electric assist and my friend who recently rented one without was well able to keep up with her daughters on normal bikes.)

  • I edited your answer to include a photo. – RoboKaren May 6 '18 at 15:22
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One solution in addition to @Willeke’s suggestion of different geometry is an e-assist or e-bike. These have a small electric motor in the hub or bottom bracket.

The motor assist would help with starting when you need a lot of torque; with maintaining a constant speed because the motor can provide power during the half of the cycle that your leg can’t.

Be sure to try out different ebikes and you might need to get a more expensive unit such as the ones with the Bosch mid-drive. It has a torque sensing pedal sensor which reacts much quicker than rotation based sensors. This can be very important for starting from a dead stop.

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