170 vs 175mm cranks

[BaBaBiker]

Hello everyone.

What's the deal with 170mm and 175mm crank arm(?) lengths? DO I need longer if I'm taller? Is it a design thing? What crank length do you have?

[Sagan97]

(10-15-2019, 05:31 PM)BaBaBiker Wrote:  Hello everyone.

What's the deal with 170mm and 175mm crank arm(?) lengths? DO I need longer if I'm taller? Is it a design thing? What crank length do you have?

Hi, I believe that it makes more difference on road bikes where you pay extra attention to position & leg length/stretch. I've a friend who recently replaced 175mm arm to 170mm on his commuter bike because the bottom bracket (BB) is positioned relatively lower than other city bikes (or my urban fixie bike), he'd have moments when the pedal hits the ground or rocks on sharp corners, which is nasty. I have 175mm crank on my old road and 170mm on fixie bike, honestly can't tell the difference

[BaBaBiker]

(10-18-2019, 10:43 AM)Sagan97 Wrote:  Hi, I believe that it makes more difference on road bikes where you pay extra attention to position & leg length/stretch. I've a friend who recently replaced 175mm arm to 170mm on his commuter bike because the bottom bracket (BB) is positioned relatively lower than other city bikes (or my urban fixie bike), he'd have moments when the pedal hits the ground or rocks on sharp corners, which is nasty. I have 175mm crank on my old road and 170mm on fixie bike, honestly can't tell the difference

Okay,makes sense, I am not into the hardcore road cycling yet. But I remember having the same issue taking corners back when I was a kid on kids bike, crashed once badly.

[ManBearPig]

Was surfing on reddit the other day and clicked on this, immediately remembered about this thread. Some reading there about crank sizes; might help:

https://www.reddit.com/r/bikewrench/comments/e3sbyj/how_much_does_crank_length_matter/

[meamoantonio]

(10-15-2019, 05:31 PM)BaBaBiker Wrote:  Hello everyone.

What's the deal with 170mm and 175mm crank arm(?) lengths? DO I need longer if I'm taller? Is it a design thing? What crank length do you have?

Longer crank arms generate more torque which helps with climbing but spin slower compared to shorter crank arms. There's a sweet spot that you're looking for that balances torque and being able to spin the crank, youcan check with your local bike fitter which one will suit you better

[Talha]

Crank arm length affects a lot of things. Most importantly, comfort and riding. 170 mm arms are generally better for most riders, but if you're a tall person take the 175 mm arms.

Use this calculator https://bikefaff.com/crank-length-calculator/

It is actually a design 'thing' but it has a lot to do with your aerodynamics and range of motion. Lookup cadence as well. shorter cranks are better for higher cadence. If you happen to pedal a lot, 170 mm is better.

If you don't cycle professionally or daily, you won't even notice the 5 mm difference. So, ultimately, it just comes down to which one is a better fit for you (comfort)

[ReapThaWhirlwind]

I've used 165mm 170mm and 175mm.

Shorter crankarms allow you to stay seated while pedaling and the longer offer more leverage, but can provoke you to leave the saddle to get up on it. Depending on your riding style, the longer can be better, but for shorter people, they can cause stress on your connective tissues. Eventually, they will strengthen, but this can be a stressful endeavor. If you're taller, you could still benefit from a shorter crank if you want to focus the tension into upper parts of the legs. Note they also offer 172.5mm for a happy medium.