How do I know if I need shorter crank arms?
05-26-23, 07:31 PM
#26
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Thread Starter
To determine if you need shorter crank arms, you can consider the following factors:
Leg angle at pedal strike: Are your legs hyperbent or hyperextended when your bike's pedals are perpendicular to the ground? If yes, you might be more comfortable with shorter crank arms.
Flat vs. uphill difficulty: If you're struggling with uphill or you need to use more force to complete the climb, shorter crank arms can make the climb easier.
Comfort: If you experience discomfort in your knees or other joints, it may be because your crank arms are not the right length for your body size and proportions.
If you're not happy with any of the above, you can try shorter crank arms to see if another length works better for you. It's best to consult a professional bike mechanic and ask them to help you measure the crank arm length you need as it will depend on your body measurements, seat height and pedal style etc.
Leg angle at pedal strike: Are your legs hyperbent or hyperextended when your bike's pedals are perpendicular to the ground? If yes, you might be more comfortable with shorter crank arms.
Flat vs. uphill difficulty: If you're struggling with uphill or you need to use more force to complete the climb, shorter crank arms can make the climb easier.
Comfort: If you experience discomfort in your knees or other joints, it may be because your crank arms are not the right length for your body size and proportions.
If you're not happy with any of the above, you can try shorter crank arms to see if another length works better for you. It's best to consult a professional bike mechanic and ask them to help you measure the crank arm length you need as it will depend on your body measurements, seat height and pedal style etc.
05-26-23, 08:17 PM
#27
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I rode my K2 again today. This is the bike with the 175 cranks. This is also maybe my favorite bike, although not because of the crank length. But after talking about this, I was paying more attention to my knees and hips today. I'm arthritic in both hips and knees although it really hasn't been a major concern biking, but today I did notice a little more tension in the left knee at the top of the crank stroke, right when the knee is closed at the tightest angle. I think this bike is going to be my candidate for experimenting with the 165mm crank arms. It's a Ritchey crank set so I'll just have to keep my eyes open for suitable 165 arms.
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05-26-23, 09:03 PM
#28
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I am 5' 5" and have an inseam of 29 inches. I used to ride with 170 mm cranks, which came with the bike. I didn't think much about it until I bought a new bike that came with 165 mm cranks. I immediately felt like I was able to pedal more smoothly. Just a single data point, but I thought I'd share it with you.
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05-26-23, 09:31 PM
#29
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I know what you mean. I used to be almost 5'6" myself...
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05-27-23, 02:28 AM
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All my bikes are pretty much off-the-shelf offerings, so I think they're all standard cranks (170mm?). I don't think I'm particularly short, but I do have a shorter leg to torso ratio. My inseam is something ridiculous like 26". And all my bikes are on the small frame size anyway, 49 or 50cm for my road bikes. My two tri bikes are 51cm, which I think is about as small a frame as I've found in a tri bike that still runs a 700 wheel.
But I have to wonder how do I know if I need shorter crank arms? Like 165 or even 160mm? Short of dropping a few hundred dollars just to try it out, is there something I could measure that might inform me? And what are the advantages/disadvantages to going with shorter crank arms?
But I have to wonder how do I know if I need shorter crank arms? Like 165 or even 160mm? Short of dropping a few hundred dollars just to try it out, is there something I could measure that might inform me? And what are the advantages/disadvantages to going with shorter crank arms?
Having a 29" inseam, the "normal" crank length made me move my hips too much causing rubbing on the saddle and sores not matter what fitting, saddle, cushion, butt cream, or other solution.
I purchased 160mm cranks for my mountain bike and it was perfect for high torque applications.
I cut down my 175mm crank to 155mm and my 170mm to 150mm for my road bike and folding bike respectively and it worked out really well.
The shorter cranks allowed me to hold higher cadence without fatigue and encouraged me to shift more to maintain the ideal cadence. Mashing in the seat at lower RPM's became less effective. So, shifting vs mash. Out of seat was still fine.
Generally, if you shorten your crank by 15-20mm you should expect to raise your saddle by a similar distance.
You'll also use slightly different muscles which will require a few rides to adjust to.
Also expect your position to change noticeably and possible handle bar adjustment accordingly.
With a 26" inseam, consider a maximum of 160mm and very likely 155 or 150mm
All of that said, FINDING shorter cranks is a problem all on its own. As stated above: I modified 2 sets of crankarms, which can only be cut by a minimum (generally) of 20mm for safety.
If you're just buying new cranks, square taper cranks have some 150-160 availability, the newer standards are much more rare and waaaay more expensive.
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05-29-23, 06:36 AM
#31
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It sounds like you could either use shorter crank arms or raise your saddle.FWIW, I was having some sciatica and shorter crank arms helped with that. I am 5' 10" with a 32" inseam and usually take a size 56 bike which usually come with 172.5mm crank arms. I went to 165mm crank arms and I am liking them.
