Bicycle Mechanics - Rotor Cranks (classic question with a new twist)

I searched Sheldon Brown's site and he does not mention them, which probably is a bad sign.

From searching the forums I see that the merits of Rotor Cranks have been discussed to death since about 2002.

My question is simple though: Has anyone ever heard that these are good for the knees?

I don't just mean the marketing b.s. associated with these cranks, but personal stories, actual facts, etc. Do they reduce strain on the knees?

If so I'll buy them.

Thanks for any advice.

Rotor cranks are mainly about overcoming the dead spot, not about saving the knees.
Knee saving characteristics are usually attributed to pedals with plenty of float, pedals/shoes that allows for sideways angle adjustment, crank length (usually shorter), saddle position, gear ratio and cadence issues.

But sure, if there's something about the rotors that makes you use a higher cadence or a pedal with more float, they might "accidentaly" be better for your knees I suppose.

This is what they say on their Web site, but with no facts to back it up:

"Conventional pedalling subjects the knee to great articulatory stress when the leg is pushing on the upper dead spot. By eliminating the dead spot, the RS reduces the typical knee injuries of the cyclist, due to less stress on the knee tendons and muscles. Thanks to the variation of the development during the cycle, the push is more progressive and the articulatory stress is more uniform."

If you need adjustable cranks, what comes to mind to me are PowerCranks. They are a bit expensive ($1000-$1200 depending on model), but they can allow one to run their feet independently of each other.

Knee injuries are not normally associated with cycling. Many runners take up cycling due to knee injuries. There is no dead spot with bicycle cranks because, unlike an internal combustion engine, you are not limited to pushing down. You push forward at the top and back at the bottom - keep your feet moving in circles.

Knee injuries are not normally associated with cycling. Yeah, right. Although the knees see much less of an impact during cycling than during running, and none of those "dynamic" accidents as might occur particularly in different ball games it is still entirely possible to injure the knees through bike riding. It's a highly repetitive motion through a greater angular movement compared to running, and particularly if done pushing a heavy gear injuries can easily occur.

A quick google for "knee injury cycling" gave 164 000 hits, so it's not like it's unheard of.


There is no dead spot with bicycle cranks because, unlike an internal combustion engine, you are not limited to pushing down. You push forward at the top and back at the bottom -

But the force by which you can push forward is much smaller than the force by which you can push down - or even pull up/back for that matter. In terms of energy transfer the spot might be "comatose" rather than "dead", which hardly changes things.

p.s. Sheldon Brown only talked about and reviewed things he had known or experienced first hand. That's why there's no disk brakes, not suspension, and no weird rotor cranks.

"Conventional pedalling subjects the knee to great articulatory stress when the leg is pushing on the upper dead spot. By eliminating the dead spot, the RS reduces the typical knee injuries of the cyclist, due to less stress on the knee tendons and muscles. Thanks to the variation of the development during the cycle, the push is more progressive and the articulatory stress is more uniform."

Sounds like this description was written by a post-grad exercise physiology student on a final exam! :lol: