Crank replacement advice - sizing/clearance
Discussion
In trying to build a single speed on the cheap, firstly it's been anything but cheap, but it has been quite a lot of fun. There has been some waste though in that I've bought a few things that have turned out to be unsuitable which is not a massive blow in the scheme of things, and they will go straight onto Ebay with all the other crap I've accumulated over the years when I can be arsed to photograph them.
My latest learning point is trying to work out how to convert the crankset to a single speed. I removed the original crank because the spider was too small for mounting any SS chainrings I've found. It's an odd one, that's for sure.
So I bought a "ready to go" SS crankset for under 20 quid however the chainring fouls on the chainstay. I have done some checking and it seems I can buy a longer BB spindle but I believe I would need one considerably longer than the one I currently have, and it would push the left hand crank arm out too, which is unnecessary.
So now it's time to stop and ask. What would you do? The original crank's spider is only 72mm and there are no other mounting holes with which I could mount a SS chainring.
Advice gratefully received etc... Oh, and pics below.
My latest learning point is trying to work out how to convert the crankset to a single speed. I removed the original crank because the spider was too small for mounting any SS chainrings I've found. It's an odd one, that's for sure.
So I bought a "ready to go" SS crankset for under 20 quid however the chainring fouls on the chainstay. I have done some checking and it seems I can buy a longer BB spindle but I believe I would need one considerably longer than the one I currently have, and it would push the left hand crank arm out too, which is unnecessary.
So now it's time to stop and ask. What would you do? The original crank's spider is only 72mm and there are no other mounting holes with which I could mount a SS chainring.
Advice gratefully received etc... Oh, and pics below.
You need a longer BB!
Q factor is the technical term for the pedal spacing. It can be achieved with a long BB and straight arms, or short BB and curvy arms. You've got straight(ish) arms and short BB = fail!
What is the recommended BB length for the cranks you've bought?
Can the ring be removed and flipped, or is it pinned on? You've limited your options by going for a fixed ring, as when it wears out/you want a new ratio you will have to replace the whole shebang. You want to move both sides out tegther or it'll pedal weird!
Do you have any photo's of the original cranks with no rings on?
If you get a new BB, get a Shimano UN5x series one, they're robust and cheap.
Q factor is the technical term for the pedal spacing. It can be achieved with a long BB and straight arms, or short BB and curvy arms. You've got straight(ish) arms and short BB = fail!
What is the recommended BB length for the cranks you've bought?
Can the ring be removed and flipped, or is it pinned on? You've limited your options by going for a fixed ring, as when it wears out/you want a new ratio you will have to replace the whole shebang. You want to move both sides out tegther or it'll pedal weird!
Do you have any photo's of the original cranks with no rings on?
If you get a new BB, get a Shimano UN5x series one, they're robust and cheap.
If you need another 13mm it's definetly the wrong crank for you!
Something like this with a SS ring from On One should be fine:
http://www.ebay.co.uk/itm/Shimano-Alivio-FC-M442-C...
Something like this with a SS ring from On One should be fine:
http://www.ebay.co.uk/itm/Shimano-Alivio-FC-M442-C...
ndg said:
If you need another 13mm it's definetly the wrong crank for you!
Something like this with a SS ring from On One should be fine:
http://www.ebay.co.uk/itm/Shimano-Alivio-FC-M442-C...
I agree. It would look daft and feel awful sticking out that far.Something like this with a SS ring from On One should be fine:
http://www.ebay.co.uk/itm/Shimano-Alivio-FC-M442-C...
I've brought the original crank in and cleaned it up - and contrary to my previous "close enough" measurements, it actually has a 67mm BCD, 5-bolt spider (I measured it properly). It's really nice and light and would be nice to re-use if I could get a chainring.
In fact, it's a Shimano Alivio, so that one you've linked to would also probably fit too. Can you get it in silver? I'm trying a "thing" with the colour scheme.
Many thanks for confirming it's the wrong crank. It really is.
You will have to use a std road crank (135BCD afaik). It should be ok on something like a 111 /113 spindle. Plenty of options here and also BB spacer kits: http://www.velosolo.co.uk/shopchain.html
That's just nit-picking.
You've got one of the OLD old Alivio cranks then?
That leaves you with the new BB option, or a new crankset as said. I'd go with a new crankset, looking at the offset arms that the single speed one you have has, by the time you add in a wider bottom bracket your feet would be too far apart.
You've got one of the OLD old Alivio cranks then?
That leaves you with the new BB option, or a new crankset as said. I'd go with a new crankset, looking at the offset arms that the single speed one you have has, by the time you add in a wider bottom bracket your feet would be too far apart.
gazza285 said:
That's just nit-picking.
gazza285 said:
You've got one of the OLD old Alivio cranks then?
Yeah, the bike originated from the early 1990s.gazza285 said:
That leaves you with the new BB option, or a new crankset as said. I'd go with a new crankset, looking at the offset arms that the single speed one you have has, by the time you add in a wider bottom bracket your feet would be too far apart.
I agree. It would be horrible. I'm annoyed that I bought that cheapo crank without really considering fit (apart from the fact that it is a tapered square peg). I never even considered clearance issues.I was looking at it to see if it would be possible to remove the chainring, machine a bit more of a "collar" off the crank arm, and refit the chainring the other way around (it's "dished") but the chance of it working properly, and costing pennies were minimal.
So I thought about having a chainring made for the original crank (I have a friend who might be able to but not for free) but thought it was unlikely it would work out cost effective.
So, I want another crank but I really want a silver one.
ndg said:
Plenty of second hand silver XT cranks on ebay, or deore comes in silver, not sure about alvio stuff!
XT seems to be hollowtech. But there are some cranks suitable for a shade under £30. It's a shame I can't use my own cranks but I need to move on. I'll list my spares on eBay this weekend to compensate.Gassing Station | Pedal Powered | Top of Page | What's New | My Stuff