Would adding a 5mm cleat shim make the crank arms shorter in reality?
So a 160mm crank would virtually become a 155 crank arm length?
Thanks
No, it would effectively make it longer. As your foot at the top of the stroke would be 5mm higher.
You’re still going to be turning a 320mm circle, it will just be offset 5mm up from the BB. And where you’re applying peak force (at least in my case), is with the crank nearly horizontal, so its still going to be ~160mm at that point. I’d be raising my saddle 5mm to compensate, so leg extension and knee angle would remain the same. Hip angle would either be slightly tighter if I didn’t raise my cockpit as well, or overall body position would be identical if I did add an additional 5mm up front.
So I guess the real question would be whether having an effective 165mm at TDC and 155mm at BDC would make a difference…?
On a related note, several years ago I tested some wedged cleat risers that were claimed to make your pedaling more efficient. These weren’t the typical wedged shims that are supposed to correct anatomical issues, these were like a 25-30 degree angle that put the rear of your cleat about 2 cm from the sole of your shoe. The guy that developed these claimed having your pedal at an angle (huh?) rather than level would be more efficient. All it did for me was make my pedaling feel really unstable, especially if I got out of the saddle. I imagine adding a tall shim stack would feel exactly the same…
Wouldn’t your foot at the bottom of the stroke be 5mm higher as well?
I added 10mm to my cleat due to a crash and leg length difference. Still not getting to 50/50 like I was before. I am still a bit short on the affected leg. My cranks have a tri-lobe system and I am at 170mm, if I moved my short leg to 172.5 or 175mm would that balance me out or make it a bigger difference again? Can’t figure it out in my head.
Wouldn’t your foot at the bottom of the stroke be 5mm higher as well?
Yes would do that also. But given most go to short crank to open up the hip angle at the top of the stroke, that is what I focused on.
Shimming both shoes is pretty similar to lowering the saddle. Apart from lowering the saddle also lower drop to handle bars vs shim would just change legs angles.
Shim in shoes to change leg angles is worse than dropping both saddle and bars, as it would have a great frontal area, so higher aero drag.
The only reason I can see for shim in shoes would be on one side to help a leg length discrepancy.
Wouldn’t your foot at the bottom of the stroke be 5mm higher as well?Yes - The only reason I can see for shim in shoes would be on one side to help a leg length discrepancy.And a more elegant alternative for that, btw, is to select LH and RH cranks of 2.5mm or 5mm difference in length, rather than shimming the shorter leg shoe/pedal interface.
I use a varus wedge in my cleats to make up for my misalignment. This is definetly an issue for many people.
“Shim in shoes to change leg angles is worse than dropping both saddle and bars, as it would have a great frontal area, so higher aero drag”
Perhaps you meant something other that varus/valgus angles. You are not clear on this.
No. Go to a PT, and/or use strength and mobility work to address the imbalance. Mechanically forcing the difference will cause issues in the long run. While you may truly have a leg length discrepancy, most people do not and it’s actually caused by tight hips.
No. Go to a PT, and/or use strength and mobility work to address the imbalance. Mechanically forcing the difference will cause issues in the long run. While you may truly have a leg length discrepancy, most people do not and it’s actually caused by tight hips.
I am a PT. I have a leg length discrepancy after a broken and repaired neck of the hip.
My apologies, that was a bit strong. Interpreted tour post as someone wanting to use shims to compensate for injury, got worried, especially because I tend to find that shims are overused in the first place, seems that might really mess someone up.
Best of luck with your recovery, that sounds rough.