Crank arm set/pair sourcing help needed


New Member
Hi there Court n all!

My ebike's left cranks thread stripped a few days back. Took it to local bicycle shop and they took it off for me. I then bought a cheap replacement of the same length but now my pedal on the left is too far out.

Thing is I've been putting off changing my cranks for ages to a smaller length. Current length is 170mm. I can find loads of left hand cranks of varying sizes but mostly 170 and 175.

I honestly want to buy 2 sets of 165mm and 160mm. 165mm at first to ride for a few months to see if 160mm is correct or too small.

So my question: How do I buy aluminium cranks in plain Matt black at a reasonable price/quality point? £30 to £50 range of possible? My cranks are, as best I can tell, diamond square taper JIS.

I read loads in the net of people going down in size but these smaller sizes are impossible to find!

Second question: Q factor is making my head spin. From what I can gather I'd like to get the Q factor as small as possible to bring pedals in for cornering. I've a Yamaha PW motor 2015/16 and 20" wheels. So how do I work out the different Q factors for each side & source shorter cranks within budget?

Please note: my drive side crank is separate from the spider so "crank sets" are no good (or am I mistaken?)
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