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I bought a 2020 Vitus Vee SS from Wiggle on ebay, virtually new but missing the left hand crank arm.
The original unsurprisingly isn't available to buy, so they advised a bog standard 170mm diamond from amazon.
Dutifully bought it, but when slotted onto the BB (square taper) it sits about 1cm further out from the frame than the right hand crank arm. Wiggle say once fitted it will move in a bit (is that right?), but "if you have any concerns visit your LBS".
Compared to original crank this one has a more curved profile hence it sits further out. Bought another generic one just to see and that sits closer but it doesn't match the bike very well. For black 170mm crank arms in general, the choice is hugely limited.
TLDR - On a single speed bike that is just going to be used for knocking about on, is assymetry between the crank arms a big deal? I've read stuff that says it is, stuff that says it's not!
Thanks 🙂
In what crazy world would it move in a bit? That's BS.
There are 2 types of square taper fitment, it sounds like your fitment is okay but the cranks are made for different bottom bracket widths.
I don't know if there is a database of crankset and BB combinations anywhere, but if you can live with it, crack on.
It would drive me nuts and you might find it's probably easier to get a new BB and crankset combination rather than luck into the correct combination.
You've had some shoddy advice there, I think, unless they recommended a specific crank which they've checked is designed for the same spindle length *and* Q-factor.
If you're just offering it up to the taper then the comment that it will move inboard once fitted is broadly correct—though I would expect a few mill, not a full centimetre. There's a fair amount of force going through that bolt and you won't get the same position lining it up by hand. But given the previous point, I wouldn't be fitting it to try it out because it then probably won't be returnable.
And stepping back a moment, why didn't it come with a crank? Did you know it wouldn't come with one when you purchased it? If not then I'd expect them to sort it out (not "buy one yourself and then bugger off to someone else to sort it out if we told you to buy the wrong one"); if so then I'd just buy a cheap pair of cranks so they match… they're not hard to find or expensive.
Only you can tell whether the offset will be a big deal or not. Humans aren't symmetrical anyway, so…
BTW: https://www.spacycles.co.uk/m8b0s109p3953/SPA-CYCLES-TD-2-Left-Hand-Crank
Thanks for the replies.
"...but the cranks are made for different bottom bracket widths"
Didn't even know this was a thing! First one I bought actually seats further onto the spindle, but has a more pronounced curve so ends up further out overall.
And stepping back a moment, why didn’t it come with a crank? Did you know it wouldn’t come with one when you purchased it?"
Yes I was aware at the time and price reflected that (160 vs 300 new). Thanks for the link, though that looks identical to the second one I bought. Like I said, very few options without just buying a whole new crankset like you say.
I've mixed and matched cranks, no issues.
I even spent a few months of 30km a day commuting with one crank 5mm longer than the other (using one from my spares box while waiting for the correct new one) - and couldn't feel the difference.
Thanks. Yep I've heard of people using different length cranks and not noticing the difference. I guess I was worried about whether assymetry the other way, same length/different 'q factor' (if that's the right term) would have more of an impact.
I doubt I'd notice the difference in spacing. Some might.
Is the BB 67mm with spacers? If so, you could remove the BB and refit with all three spacers on the drive side. This would move the drive side out ~3mm and the non-drive-side in ~3mm, reducing the asymmetry from 10mm to 4mm.
Thanks. Based on all the replies, think I'm going to try the easy option and fit the crank. Worst case, can just get a whole new crankset if doesn't feel right. Will report back either way for anyone else searching in the future!