Originally Posted by
63rickert
Just use short cranks on both sides.
Wrong! Short on both sides is the usual answer for RoM issues.
But only as long as both legs are the same length. About 1/3 of my customers have RoM issues and maybe 5% have leg length discrepancies. When they are combined we end up with short,
but unequal length, crankarms. Please read
Range of Motion Limitations & Crank Length The results from the test described there, plus knowing the leg length difference, will allow me to make a recommendation.
The OP should contact me off-list. If I know of an Off-The-Shelf solution that's cheaper than having me shorten cranks, I'll let him know.
Early on I would recommend that the difference in crank length = the difference in leg length. But that often lead to back trouble because the customer's body had adapted to the discrepancy. Now I usually make the crank difference equal to 2/3 of the leg difference.
BTW I recently got a gent back on the road with a 1.5" difference, and such severe RoM that he could only lift the left foot a bit over 7 inches off the floor, even though it had a 1.5" head start.
http://www.bikesmithdesign.com/Short...ay_w-swing.jpg Pedal swings are only needed for extreme RoM issues
Though it’s written for shorter riders,
Crank Length, Leg Length and Power can help you understand why a reduction in duration and intensity of the “dead spot” can more than make up for a slight loss of leverage.
Mark Stonich; BikeSmith Design & Fabrication
Shortbikecranks@gmail.com
5349 Elliot Ave S. Minneapolis, Minnesota 55417 USA
Ph. (612) 710-9593
http://www.bikesmithdesign.com/Short_Cranks
https://www.flickr.com/photos/bikesmith/ (Mostly Wildlife)
