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shorter crank arms

Old 05-16-15, 11:26 AM
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thylton48
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shorter crank arms

I am a male aged 67 and had knee replacement 2 years ago and never recovered complete bending motion. About a month ago began riding my hybrid again and am experiencing some pain at the top of my pedal stroke(maximum knee bend). I have 175mm crank arms and was wondering if changing to 170mm cranks would help, what do y'all think.
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Old 05-16-15, 11:30 AM
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Sure. I would make sure that you have proper leg extension at the bottom of the pedal stroke first. The usual rule of thumb is that your legs should completely straighten when riding with your heels on the pedals. If your saddle is too low, that will exacerbate the issue of your knee bending too much at the top. Hope this helps.
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Old 05-16-15, 11:37 AM
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^ Yup. Make sure you have proper seat height adjustment first.
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Old 05-16-15, 11:39 AM
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Depending on your height, maybe try 165s. 5mm is noticeable but not dramatic--a 10mm change will give you a better picture if shorter cranks is helpful for you.
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Old 05-16-15, 11:52 AM
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This might help. How to Fit a Bicycle
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Old 05-16-15, 03:11 PM
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If the problem with your knee is limited range of motion, shorter crank arms will help. 175mm arms are really quite long for anyone unless you're over 6' tall. I'd go with 165mm or even shorter.
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Old 05-16-15, 03:30 PM
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Originally Posted by JohnDThompson View Post
If the problem with your knee is limited range of motion, shorter crank arms will help. 175mm arms are really quite long for anyone unless you're over 6' tall. I'd go with 165mm or even shorter.
Agreed. My bikes have cranks of 175, 170, and 165mm and I hardly notice any change at all switching between the 175mm and 170mm. The 165s feel a little different, but not dramatically so. I'd recommend changing to at least 10mm shorter to experience a significant change in the range of motion.
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Old 05-16-15, 03:47 PM
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+1 on check seat position first. but a shorter crank (170) will help with knee bend, your leg will be 1 cm further from your chest at the 12 o'clock, which might help
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Old 05-16-15, 04:10 PM
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I have a limited range of motion in one knee and 165mm cranks were a savior!

175mm 60 RPM
170mm 80 RPM
165mm 85 RPM
160mm 80 RPM

Believe me- 5MM CAN be very noticeable!
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Old 05-16-15, 05:10 PM
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I'm 67 ,too. (FWIW) have 1_180, and several 175 & 170... not a speed/performance ambitious guy , I just pick a confortable Gear .

saddle to pedal spindle height is relatively consistant .. a bit higher with the shorter, and lower with the longer crank-arm. but equal in total.
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Old 05-16-15, 08:28 PM
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Originally Posted by thylton48 View Post
I am a male aged 67 and had knee replacement 2 years ago and never recovered complete bending motion. About a month ago began riding my hybrid again and am experiencing some pain at the top of my pedal stroke(maximum knee bend). I have 175mm crank arms and was wondering if changing to 170mm cranks would help, what do y'all think.
I think you need to consult a qualified bike fitter who can look at your physical situation and make proper recommendations.

This sounds too serious to just toss out to a bike forum for random opinions...
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Old 05-16-15, 08:34 PM
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Not an expert but I would recommend trying out at least 165 mm cranks for people with range of motion issues. I am a very short rider who tried out shortened custom cranks (153 mm) and they made a big difference to my comfort and performance vs. 170 mm. They're just so much easier to spin. The difference was very noticeable especially when climbing.
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Old 05-16-15, 09:26 PM
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Could be Q factor is part of it too ? Somebody here said most bikes are actually built for a narrower person across the hips than the average American. If I recall right he said speedplay has a correction system that was a great help for him. Pedal washers can help some but this sounded like a series of different axles for the pedals to correct Q factor.

Bill
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Old 05-17-15, 09:22 AM
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What is Q factor?
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Old 05-17-15, 09:24 AM
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Thanks for all the information and suggestions. Gives me plenty to research and experiment with.
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Old 05-17-15, 11:40 AM
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Originally Posted by thylton48 View Post
What is Q factor?
The distance between your pedals...
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Old 05-18-15, 01:55 AM
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Speed plays are expensive though
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Old 05-18-15, 05:11 PM
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Keep your knees straight (don't side load the joint, it reduces ball and socket contact area, concentrating force).

Be a spinner and use less pressure per stroke (keep pressure down).

Take it real easy and warm the joint up slowly. It takes me about 3 miles before I am ready to put my max effort.

I must manage my knees. If I over do it I inflame the joint. Then its NSAID after dinner.

YMMV
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Old 05-28-15, 03:23 PM
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Originally Posted by thylton48 View Post
I am a male aged 67 and had knee replacement 2 years ago and never recovered complete bending motion. About a month ago began riding my hybrid again and am experiencing some pain at the top of my pedal stroke(maximum knee bend). I have 175mm crank arms and was wondering if changing to 170mm cranks would help, what do y'all think.

Ditto. How did it go for you?

This is my situation as well: http://www.bikeforums.net/fifty-plus...l#post17835324

I am looking forward to having my new machine shortly... perhaps tomorrow.

Cheers!
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Old 05-30-15, 08:01 PM
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My ride came in. 165mm cranks are not bad at all when that's all you can turn over. But, it does make for a tad taller seat height.

http://www.bikeforums.net/fifty-plus...l#post17850950

This is my first aluminum road bike and it's pretty well thought out. Reviews of earlier years were positive. With the 2015 Z85 Felt switched to 105 components so I lucked out there. I'm looking forward to learning how to use aerobars.
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Old 05-31-15, 12:42 PM
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Originally Posted by cpach View Post
Depending on your height, maybe try 165s. 5mm is noticeable but not dramatic--a 10mm change will give you a better picture if shorter cranks is helpful for you.
Agreed. 10mm will show more results.
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Old 06-04-15, 08:40 AM
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Originally Posted by Willbird View Post
Could be Q factor is part of it too ? Somebody here said most bikes are actually built for a narrower person across the hips than the average American. If I recall right he said speedplay has a correction system that was a great help for him. Pedal washers can help some but this sounded like a series of different axles for the pedals to correct Q factor.

Bill
As it turns out, putting in nearly 2 years on a recumbent exercise bike introduces the Q-factor by a matter of inches not mm when transitioning to a road bike. I am switching out the clunky pedals on the trainer with a pair of MTB pedals to reduce the width between the pedals. My plan is to meet in the middle by also using Zero-axle Tioga pedals on the Z85 to widen things up a bit.
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Old 06-04-15, 03:35 PM
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Originally Posted by McBTC View Post
As it turns out, putting in nearly 2 years on a recumbent exercise bike introduces the Q-factor by a matter of inches not mm when transitioning to a road bike. I am switching out the clunky pedals on the trainer with a pair of MTB pedals to reduce the width between the pedals. My plan is to meet in the middle by also using Zero-axle Tioga pedals on the Z85 to widen things up a bit.
Yea I was reading up on it a little and they mentioned going narrow on Recumbants for a narrower fairing, lower cross section, etc.

Bill
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Old 06-10-15, 09:46 AM
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Definitely an effective way of increasing the Q factor:



That big sealed bearing adds a bit of weight: Tioga's Zero-axle peddles are a bit heavier than I expected. However, they are very well built.

This seem to me to be a very good design idea. Perhaps Tioga should consider extending the Zero-axle line to accommodate clips and for use as clip-ins. Otherwise, if I ever transition back to clipless, Speedplay seems to be the only Q factor savvy peddle.
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