Just picked up a frame from one of the posters on here (thanks Josh!) Which has a square taper bb. The shell width is 68 mm but i have no idea which spindle length i require. Will be running single speed with an old truvativ e400 chainset, but no idea what the spindle width i require is and no clues on the crank itself. Does it matter? Left crank arm is about 28mm wide at point that it attaches to the spindle, if that is any help? (Calipers won't measure the right arm but looks similar)
Ta
110mm as far as I remember, makes a 50mm chain line.
It's usually written on the middle of bottom bracket itself if you take it out and it's still legible .If you don't want to do that you can pull the arms of and measure it .
Don't have the original bb to measure unfortunately
But you say the frame has a square taper BB fitted?
Why not fit the chainset on that BB then measure the chainline and then you can work out the spindle length you'll require to get the chainline that you want.
And so it begins....
Original bb won't help on a different crankset and different chainline of rear hub. Have you got another square taper bike?
I stick the crank on a bike with a square taper bb. Then measure tooth to tube centre. And work from there...
If you want to move it in 2mm you need a 4mm shorter spindle than the one used.
If you’ll be running it single speed, with presumably, a single sprocket on a freehub with spacers to take up the width then, within reason, bb spindle width isn’t that critical as long as the cranks clear the chainstays because you can adjust the sprocket position on the freehub to get a good chainline. I’d go with 113mm...
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Joshvegas ..you repeated what I suggested and don't know what you're on about saying original BB is no use. Any sq taper JIS standard BB will enable him to fit and work out what he needs in relation to his rear chainline measurement.
If Sheldon is correct,( as he normally was) ,113mm was the original bb length giving a chainline of 48.5mm .
My mistake, I meant I want to fit a square taper bb, as that's the crank I have.
There is no bb at the moment. Sorry for confusion.
Don't have a bike with another square taper bb to check. Not bothered about chainline as I can mess about with the spacing, as long as chainring clears the stay and will fit the spindle arm is all I care about.
Perhaps a better question is, putting aside the clearance and chain line issue, will any sq taper bb fit any sq taper crank? If so I'll probably get the widest one and bodge the chain lime at the hub end.
Josh, you are correct..already worked out my old bars won't fit any quill stem I have so I'm resorting to flat bars and bar ends!
Joshvegas ..you repeated what I suggested and don’t know what you’re on about saying original BB is no use. Any sq taper JIS standard BB will enable him to fit and work out what he needs in relation to his rear chainline measurement.
Because.
A. Different cranksets can have dufferent offsets and require different spindle lengths
B. I kniw more than you as
i. I gave him the frame without a bb in it.
ii. Its an italian bb shell so he's not going to have one to hand to try that.
iii. I know he's single speeding it and therefore he may, depending on what he's using out the back, require something different to a standard offset.
Anything else?
Tpbiker.
Yes all tapers are the same. As kaiser and a few others suggest.
113mm would be a good choice!
Thanks all, went for a 110 in the end as it was cheapest! It's a 70 mm, so if i stick a 2mm spacer in there I'm assuming it'll be fine.
If it doesn't work it was only 12 quid so not a huge investment!
Looking forward to getting this bad boy built up, and once again thanks to Josh for the frame...hopefully it'll soon be getting some use!
Thanks all, went for a 110 in the end as it was cheapest! It’s a 70 mm, so if i stick a 2mm spacer in there I’m assuming it’ll be fine.
It won't fit in the frame. 70mm bb is Italian threaded (both cups have the same thread) and is a larger diameter than BSA.
edit : ah, one of the posts up ^^^ suggests it's an Italian bb shell so should be fine! (although the first post says 68mm)
As above, an Italian thread BB won't fit in an English thread BB shell.
For clarity.
Tpbiker does actually know he's buying an italian bb
Yes all tapers are the same.
There are actually two types JIS and ISO.
I do..only because you told me! I'd have been having a breakdown wondering why i couldn't screw it in otherwise!
And yes, frame actually measure 70 mm, just checked.
Not all square tapers are the same.
There is JIS & ISO
Google suggests that the crank is JIS though.
Jis and iso tapers are the same taper.
They're different lengths with one getting narrower on the end which moves the crank about 2mm one way or tuther and i forget which is which.
As we've now established actual chainline isn't to worrysome this is unlikely to he a huge problem.
Before anyone says it.. the right combo might bottom out but that'd be a bit unlucky.
Joshvegas...I accidentally ruffled your feathers ..I had meant to say "I" don't know what your on about ..so apologies for that!
Thanks kaiser
I didn't need to be so snarky about it.
End of the day if its built back up into a bike it's a win all round.
I liked what you did with the teeny tiny font 😀
Arrgghh - I have an italian square taper BB here that is no use to me - I bought it to fit a bike that has a french BB thread! I think its a 118mm. Let me know if you want it.
oooh thats niche TJ!
I wonder if we could build a bike using all the wrong bits people have bought!
Really confused me. Two threads both the same direction. Must be italian BB thread I thought so I bught one and tried to fit it. Nope - different diameter. Much head scratching ensued
And to add to that is there not also a swiss bb?
most confusing thread in a while
most confusing thread in a while
..quite literally!
Sheldon Brown is /was a personal hero of mine ...incredibly altruistic with his knowledge sharing. RIP you are sadly missed.
