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General Category >> Technical >> shorter cranks
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Message started by FlyingLaZBoy on Dec 13^th, 2018, 1:49pm

Title: shorter cranks
Post by FlyingLaZBoy on Dec 13^th, 2018, 1:49pm

I've switched the crankset on my SprintX from 170mm to 160mm, to reduce the max knee bend... the first few rides feel pretty good with it, however, I think I'm feeling the ~6% reduction in torque when accelerating from a stop, or climbing a hill....

Interesting...

PB

Title: Re: shorter cranks
Post by catroad254 on Dec 13^th, 2018, 1:58pm

There is always a price to pay. The shorter cranks help with knee pain but you have to spin at higher rpms to compensate for the lower torque. It's worth it to me to have less pain- but I don't really care about speed.

Title: Re: shorter cranks
Post by jrob_bent on Dec 17^th, 2018, 11:40am

Aurelien Bonneteau used 123mm and 135 mm cranks during his hour record run and his 78.95 mph BM run. He is over 6'-2". Micah at Easy Street has adjustable cranks on his personal bike. Use an Allan wrench and slide the pedal up and down into whatever crank length you like.

Title: Re: shorter cranks
Post by diannalightning on Dec 18^th, 2018, 9:59am

Since Jay cut my cranks down on my VRex, I've not had knee pain on that bike. I can't do high RPM's so I just use the large front chain ring more than I used to. It's worth it to not have knee pain and to be able to ride. At least that's what I tell myself. ;D

Title: Re: shorter cranks
Post by Phantom Rider on Dec 20^th, 2018, 10:24am

Short cRanks have made a huge difference for me. I’m running 150’s on my Cruzbike V with a set of Q rings and my knee pain has been eliminated, I spin more and run 99% of time on the 52 big ring. When I ride the trike a couple days in a row I certainly feel the difference as I have not yet made the change on it.

Title: Re: shorter cranks
Post by jayg on Dec 20^th, 2018, 11:24am

Phantom Rider wrote:

Joe, I switched to 150 mm cranks years ago. They eliminated my warm weather knee pain. I've always experienced stinging pain around my left patella, during cold weather. Have recently eliminated it by wearing a knee brace with chemical heating pads on both sides of the patella. Short cranks definitely work for people that have range of motion problems with their knees. I've installed chain rings with lower tooth counts on my bikes and trikes to compensate for the slight loss of torque experienced with shorter cranks. For example, I changed the 60T big ring on my GS Aero trike to a 53T. I ride mostly in that ring (trike has a 20" rear wheel).

Title: Re: shorter cranks
Post by jrob_bent on Dec 22^nd, 2018, 7:41am

Rob Hague and Mark Mueller run 110mm cranks on their racing trikes. Rob told me this on FB and Ian mentioned it on his company page. That's close to 2 1/2" shorter than 170's.

Title: Re: shorter cranks
Post by aikigreg on Dec 24^th, 2018, 3:53pm

I bet they ain't going up to many hills with those though.

Title: Re: shorter cranks
Post by jrob_bent on Dec 24^th, 2018, 4:08pm

I went from 172.5mm cranks to 150mm cranks and go up hills easier with the 150mm cranks. Phantom Rider Joe uses short cranks and it doesn't look like he has any problems with hills either. I'll let him tell his story though.

Title: Re: shorter cranks
Post by jrob_bent on Dec 24^th, 2018, 4:20pm

Studies have shown you don't lose power or use more oxygen with shorter cranks. https://bikefitadviser.com/crank-length-research/

Title: Re: shorter cranks
Post by square_corners on Dec 26^th, 2018, 7:56am

My velomobile has 155mm cranks. That is in part due to my long legs and lack of room for my shoes at the front end of the velo. My Bacchetta, Catrike 700, and road bikes have anything from 165 to 175 cranks and while I don't get knee pain with those, I can't say I feel any difference in power with the 155 cranks in the velo. I was very concerned when I ordered it that way but I can't tell any difference at all. I use the big ring 95% of the time - around here the hills aren't significant enough to require a change. The big ring is a 61. If I had a smaller big ring, it would be 99% of the time.

Title: Re: shorter cranks
Post by Bud_Bent on Dec 30^th, 2018, 5:06pm

I went to 165 mm cranks in the WAW, because of limited foot room inside. I've stayed with longer ones on everything else. Longer cranks require you to use a greater range of motion in your knees. I have to believe that helps me to retain more range of motion in my knees in my old age, and that is a good thing. So, as long as I don't get knee pain, I'm staying with the longer cranks.

Title: Re: shorter cranks
Post by FlyingLaZBoy on Jan 8^th, 2019, 2:32pm

I'm starting to acclimate to the 160s on the trike, but I "feel" that I'm still climbing slower... other than that, it's all good. I didn't ever HAVE any knee pain, it was more a preventive decision than anything else, since I've started to hear my knees crackling a bit climbing stairs at home.

I've still got 170s on the Rocket, which is on the trainer, so I may change that out, too. If I do, I'll have at least one set of used FSA SK-light carbon cranks available to an interested party.