Chainset and bb confusion

[its_all_calypso]

Hi all,

I'm looking for a second hand track chainset and have noticed that some websites list a specific bb spindle length that goes with the chainset. I know they don't list these specifics for fun, but if just say, the recommended spindle length is 107mm and I have a longer spindle, will the chainset still be suitable? I understand the difference between JIS and ISO, this question is more so to do with the length.

Thank you!

 

[midlife]

It's to do with the chainline rather than anything being compatible. On a track bike the chainring should line up with the rear sprocket. If the axle is too long then it won't.

 

[fossyant]

If it is a specific track chainset, then I think standard is 110mm BB.

 

[Cycleops]

Are converting a geared bike to single speed?

 

[Juan Kog]

I agree with the above comments. There are a number factors to consider in achieving a good chain line , rear hub and the frame is it the standard 120 mm OLN or a wider geared bike conversion. My suggestion is buy the chainset , fit with your existing bottom bracket , it maybe ok . If not you can calculate what bottom bracket you do need. Rather than having an unwanted 107 mm BB in your spares box .

 

[FrankCrank]

Perhaps I'm over thinking this, but would add to what JK said above. If you use the old BB first, and needed the chainwheel to be say, 5mm further out, you'd need a new BB with a spindle that was 10mm longer, as the length is equally divided both sides - if that makes sense.
On another thread recently, I alluded that perfect chainline was something to aim for, but in reality you can't always hit the exact target, and it's not something I'd worry about too much, but as always YMMV

 

[GuyBoden]

You can calculate the chainline needed by using your rear sprocket.

So, if your rear dropouts are 120mm and the distance between the inside of the dropout to the sprocket is 15mm. Then half of the dropout distance (60mm) minus the sprocket distance (15mm) is the chainline needed (45mm).

Then you need a BB that will give a 45mm chainline, some manufacturers give the chainline with their BB in their technical specifications.

But, this is easier said than done.