I need to check my crank length. How can I accurately measure it? Do I just use measuring tape as I was nervous of this because of the small difference between sizes I.e 172.5 175
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4Sometimes it is written on the back side of the crank.– rvil76Jul 29 at 11:13
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Thanks, I will check that– CharlieJul 29 at 11:34
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If your bike is worth less than $1000USD or so, you can be pretty sure it's either 170 or 175. 172.5 and the other more exotic lengths aren't regularly found below that price point in my experience.– MaplePandaJul 30 at 6:48
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2 Answers
Crank length is measured from the centre of the bottom bracket axle to the centre of the pedal axle.
It's explained here
Measuring tape should do, crank length goes in steps of 0.25cm (one tenth of an inch).
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You're totally right. I'm getting old. But still, it's not hard to measure with a tape measure or a ruler. Jul 29 at 18:34
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When measuring, check the measurement a couple of times to be sure, to verify that you did not move your starting point/frame of reference.– Ted HohlJul 29 at 20:24
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2Another trick is measure the largest distance between the hole edges, then smallest distance, add together and divide by 2. Removes need to find the center of both holes.– mattnzJul 29 at 20:59
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But I'm with rvil76, I checked my Ultegra cranks, it mentions 175 on the back, I checked a 105 crank, also has it stamped in the back of the crank. Jul 30 at 14:49
Measure it by looking around for where the length is written or stamped into it. Usually on the inboard side near the threads for the petal.
No tape measure required.
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True, but is it possible that some low cost bikes may not have the length stamped on the crank? Jul 30 at 22:14