Crank size

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9/20/2017 6:53 AM

Just curious about crank sizes. "Back in the day" 175+mm was the standard length it seems. Today it seems bikes come spec'ed with smaller cranks (170mm or less). I have seen 165mm & 160mm cranks. If this is the case, can anyone explain the reasons? Is it a "space" thing on the bike (keeping the rider more compact with the shorter CS's?

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9/20/2017 7:12 AM

Space and faster / less pedals depending on gearing etc...

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9/20/2017 7:19 AM

Shorter cranks like with just about any bmx part mean they're more responsive. hopping gets higher front end stuff is easier and the general ride feels more responsive kind of like with a higher bb.
Shorter cranks help with peg clearance but i know plenty of ppl with size11 shoes, 13in rear and 175s that don't seem to mind at all. I'd say pick what feels good for tricks and riding.
I've sampled 175/170/165/160 before selecting the size I like the best. Try it for yourself to find out!

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9/20/2017 9:16 AM

In my experience (I have 170mm cranks) It is harder to pedal and you have to pedal more to keep up with the longer cranks. When I would hop on someone elses bike, before I switched to 23/9 gearing, I would always be like "Man, your bike feels so easy to pedal". I honestly got 170's cause they were considerably cheaper on the site I got them.

Also something that wasnt mentioned is ground clearance. Thats pretty cool and its slightly lighter than the longer ones.

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9/20/2017 9:21 AM

I don't get the "easier to pedal" analogy. I mean, a longer crank arm would provide more leverage thereby making cranking easier. I get the ground clearance & other clearance issues that may be helped or resolved with a shorter crank. But I don't understand how a shorted crank would help make pedaling easier. Ever ridden a little children's bike for a laugh?

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9/20/2017 9:26 AM

Mishinn_Control wrote:

I don't get the "easier to pedal" analogy. I mean, a longer crank arm would provide more leverage thereby making cranking ...more

As I said IME they are HARDER and take MORE effort to keep your speed. But I have heard the same, people always say that shorter cranks ars easiser. I agree they are probably easier on your knees because they have less range of motion...

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9/20/2017 10:10 AM

I'm on 180's now, they're badass. Doing a crank takes less effort as there's more leverage

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9/20/2017 10:22 AM
Edited Date/Time: 9/20/2017 10:24 AM

Mishinn_Control wrote:

I don't get the "easier to pedal" analogy. I mean, a longer crank arm would provide more leverage thereby making cranking ...more

Correct, the reason people say it's easier to pedal is that with the lower leverage, you have more to push against which makes it harder to spin out. It's kinda similar to having another tooth on your sprocket. I actually didn't notice much difference going from 175s to 170s but when I get on a bike with the same gearing as mine and 175s, it feels like there's a tooth less on the sprocket. It's not as noticeable as going from 28-9 to 25-9 but I find that pedalling with longer cranks tires me out quicker.

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9/20/2017 11:05 AM

Mishinn_Control wrote:

Just curious about crank sizes. "Back in the day" 175+mm was the standard length it seems. Today it seems bikes come spec'ed ...more

Spacing due to shorted CS lengths is the main part, and a side effect is that it can give a bit more leverage with hops etc.

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