I am wondering if I should give this a thought in the futur. My right leg is 1cm shorter than the left leg anatomically. It is short with both the femur and the tibia. To compensate, i have been riding with my right cleat pushed forward and put as many shim(spelling?) under the cleat. I would like to know if anyone is currently riding with a different crank size from left to right?
I am asking because I still have a lot of toe pain (left) when i ride more than 50 miles. Both feet get numb and the right foot is very cramped and painful. That was the whole problem at IMAZ… I have tried different shoes (3 pairs) and now think that maybe my speedplay pedals are the culprit. So i am about to put my old look pedals back on try triding with it. if it work (hopefully it will) i will need to figure something out with the leg lenght…
I know i am trying to do a lot of changes, but this is the time of the year to do it! along with eating junk, drinking beer and complaining that I am getting fat LOL!
My right leg is a full 1" shorter then the left. My saddle height is set to the long leg. I’ve adapted to pedaling toe down on the right side after 15 years. For about the first 10 years I used a 1/2" shim under my right cleat. I’ve since removed any shims I was using in my cycling and running shoes, too.
I’ve always thought about using the different crank lengths but never tried it. I really don’t think it would accomplish much in my case since I’ve been cycling for so long with the leg length differnce. My body has adapted to the difference.
My right leg is 1cm shorter than the left leg anatomically.
Don’t most people have some imbalance of this nature? Nobody is perfect. Are you outside the norm?
yes, I am outside the norm. i have a truly shorter leg on the right, the slight scoliosis in my lumbar spine on that side. It was all measured on x-rays. i have a lift in my running shoes and work shoes. I am always more likely to get injured because of those biomechanical differences. A leg difference less than 6mm is very common, yes. But 10mm? Anatomically? Not everyone has that!
Marisol, I would say it might be worth trying. I have a similiar situation with my arms. Due to scoliois the reach on my right arm is almost two inches longer than my left. When we first set up my tri bike we adjusted the aero bars to compensate for this. A couple of weeks later I was back in the shop to get bullhorns cut to fit. The right side is linger than the left. Only thing I have to watch for is climbing out of the saddle, if I "pull’ on the bars I have more leverage on the right side and will turn the wheel without meaning to. I really don’t see where the longer crank arm would hurt, anything that makes you more comfortable pedaling should result in better performance.
The logic of shorter crank arms for a shorter leg is a bit obscure. If you had a shorter crank on one side, it would make up the leg length difference at the bottom of the stroke only. At the top of the stroke, it would have the opposite effect. The crank on the shorter side doesn’t come up as high as the other side which means the shorter leg is having to extend further not only because of the leg being shorter, but also because now the crank doesn’t come up as high. Shims is the only way to go for a leg length problem… in my opinion anyway.
I use different crank lengths and recommend it to anyone with significant femur discepencies. This has worked for me and for many athletes who have come to me for bike fit.
I have an 8 mm anatomical discrepency that is completely in the femur and use a 5mm shorter crank for my shorter leg. My pedaling economy (watts per liter of oxygen consumption) and comfort are significantly better. If your body is not symmetrical, why should your bike be? As Andy Pruitt says, adapt the machine to the body, not the body to the machine. For large femur discrepencies, different length cranks is the only solution that provides optimal leverage at 3 o’clock and 9 o’clock of the pedal stroke - as well as at 6 o’clock.
As Andy Pruitt says, adapt the machine to the body, not the body to the machine.
Andy Pruitt may have said that, but did he say “use shorter cranks for a shorter leg?” Yes, you should adapt a bike to fit the person (that’s where shims come in). Sorry, the logic doesn’t make sense. Think about it… a shorter leg (or femur to be specific) means that leg is already at a length disadvantage at the top of the stroke. If you shorten that crank, all it does is make the discrepancy even greater. Shims correct for the bottom AND TOP of the stroke. It’s a very simple lesson in physics.
"If you had a shorter crank on one side, it would make up the leg length difference at the bottom of the stroke only. At the top of the stroke, it would have the opposite effect. The crank on the shorter side doesn’t come up as high as the other side which means the shorter leg is having to extend further not only because of the leg being shorter, but also because now the crank doesn’t come up as high. "
Uhhhmmmm… No.
This makes absolutely no sense. You’re mixing up extension and compression, and are totally mistaken as to how the leg actually functions during the pedal cycle.
Mixing crank lengths can be useful in compensating for leg length differences, specifically femoral diff. Shims are better suited for addressing a lower leg length difference. If you look at the leg as a series of connected levers, and view it’s motion during the pedal cycle, this is actually fairly easy to see. A short cut is to imagine the crank arm at rest dead parallel to the ground. If you add shims, how does this effect the leg? Now shorten the crank arm - what is the effect? If you can visualize the difference, you can see how the 2 different methods of compensation work.
If a persons upper and lower leg are shorter, the best method, if the difference is substantial, is to use a combination of shims and crank length manipulation. It may also be useful to play with saddle twist, as orientation of the pelvis/hips can be a useful tool to address this problem as well.
"Sorry, the logic doesn’t make sense. Think about it… a shorter leg (or femur to be specific) means that leg is already at a length disadvantage at the top of the stroke. If you shorten that crank, all it does is make the discrepancy even greater. Shims correct for the bottom AND TOP of the stroke. It’s a very simple lesson in physics. "
You certainly have a right to a different opinion, but I’ve studied pedal stroke economy of athletes with femur-length discrpencies and they pedal more economically with different length cranks. If an athlete consumes less oxygen at a given wattage, that is pretty strong confirmation for me.
In fact, simple physics would tell you that shims double leg length discrpencies at 12 o’clock by giving the shorter leg a longer effective crank length. The knee angle of the short leg will be more acute at the top of the pedal stroke … not good for pedal stroke economy or injury risk.
Experts disagree on this point, but my clients have had a lot of success with it and metabolic test data agrees with me. Sometimes breakintg with tradition can be an improvement.
This is starting to get where I want it too… So you are saying that both the shim and the crank lenght would help? Nobody commented on my right cleat being pushed forward to accomodate for a shorter femur. Pelvic rotation is accounted for in my numbers.
I’d have to see you pedal to be ble to make a specific recommendation, but you are right, 10 mm is huge. I would try 5 mm different crank lengths and a 5 mm shim if the discrepency is 50/50. Have you had xrays to determine the exact discrepency in each bone?
Also, cut back on volume and intensity of your riding while your body adapts. Even going from a terrible position to an excellent position puts new stresses on your tissues. Give them time to adapt.
What about a direct link? All I found was your article, I asked for dissenting opinions, because I actually thing that the concept might make sense for marisol.
In other news tonight, how many athletes do you have on your “premium” package? Just curious.
I’m not sure what Andy does with crankarm length and femur length differences. I’ll check with him and post back.
Paraic McGlynn http://www.bicycleranch.com/meet.shtml is an excellent bike fitter in Scottsdale, Arizona who I believe doesn’t use different crank length to adjust for femur length differences. We disagree on that one point, but I still highly recommend him.
I currently have 11 premium clients and 10 basic clients.
Did anyone figure out the correct way to fit someone with a femur discrepancy? I have a 5mm discrepancy in my right femur…I had a cat scan done by my doctor so we could measure everything. Also, I have a 1mm discrepancy on the right leg below my knee, but I’m not really concerned about that of course…its 6mm total. I was thinking about trying a 172.5 crank on my right and a 170 crank on my left. Any thoughts…I have been using 5mm shims on my right for a year, but since I just ordered a new speed concept 9.9 tri bike and got my cat scan I am looking into getting everything dialed in better. Thx
On my right side I hab=ve a longer pedal spindle than on my left. While pedaling my right knee would brush against my top tube, or just come closer. With the longer pedal pindle with the laser on my leg the light action (lack of a better term) is now the same as the left.