does spinddle length of square taper bb really matter
I want to change my bb but i dont know exact spindle length for my crankset. so can i buy a new bb with longer spindle? or need to be exactly same length with old bb for it to works.
Longer should work, but may not be ideal for chainline.
Shorter can cause serious clearance issues.
kwakracer on
It won’t be life or death, but there are better/worse choices. The bad news is it’s tricky to measure the old one. If it’s a standard unit you might be able to figure it out.
It’ll affect chain line, and at extremes, chain ring size choices.
SSSasky on
You can sometimes / often go up or down one or two sizes without any issue. But more than that and you will likely run into issues. And some crank / frame combinations are much less forgiving. Track bikes can be particularly picky, or anything else with a single gear in the back.
Your existing BB should be labeled with the size, but you’ll need to pull it to read it. You could pull it, and then go to a local bike shop to buy a replacement. Unless there’s something unusual about your bike, a well-stocked bike shop likely has an appropriate replacement on hand.
Spindle length is generally determined by the crank manufacturer, and they will usually publish the specs online somewhere. Look up you crank model if you can find an identifying mark on the crank, and you may may find the info.
Skuggsja on
Tell me your crankset, and I shall tell you compatible BB.
Bike_and_coffee on
Yes it does. I changes once without knowing and my front mech was not working, even with fine tuning. Big chainring was useless.
BarkleEngine on
It matters to have the necessary clearance between chainrings and chainstay and to get the best possible chainline.
For me the tricky part of this dance is guessing how far onto the taper any particular crank wll be when it is fully tightened.
Michael_of_Derry on
Some BBs are asymmetrical. They might be longer on the chainring side to accommodate a triple.
Some like Shimano’s early 105 were longer on the non drive side for some unknown reason.
If the axle is too long it may mean that your front derailleur does not have enough travel to change gears
Too short and the crank arms or chainrings can rub the frame.
Some cranks have JIS taper and some ISO. Getting the correct one is important.
PrandtlMan on
It matters but it doesn’t need to be 100% precise. The longer the spindle is, the further out the crankset will sit. If it’s too far out or in horizontally with respect to the cassette, the chain will be at an angle and that can cause problems (shifting, chain rubbing front derailleur). But in my experience as long as it’s in the right ballbark (~5mm?) it should be fine.
Reinis_LV on
Take and meaure it with caliper measure. Remove the crankkset first ofc. Order in the size you currently have.
11 Comments
No, we just have that many options for fun. /s
Longer should work, but may not be ideal for chainline.
Shorter can cause serious clearance issues.
It won’t be life or death, but there are better/worse choices. The bad news is it’s tricky to measure the old one. If it’s a standard unit you might be able to figure it out.
It’ll affect chain line, and at extremes, chain ring size choices.
You can sometimes / often go up or down one or two sizes without any issue. But more than that and you will likely run into issues. And some crank / frame combinations are much less forgiving. Track bikes can be particularly picky, or anything else with a single gear in the back.
Your existing BB should be labeled with the size, but you’ll need to pull it to read it. You could pull it, and then go to a local bike shop to buy a replacement. Unless there’s something unusual about your bike, a well-stocked bike shop likely has an appropriate replacement on hand.
Spindle length is generally determined by the crank manufacturer, and they will usually publish the specs online somewhere. Look up you crank model if you can find an identifying mark on the crank, and you may may find the info.
Tell me your crankset, and I shall tell you compatible BB.
Yes it does. I changes once without knowing and my front mech was not working, even with fine tuning. Big chainring was useless.
It matters to have the necessary clearance between chainrings and chainstay and to get the best possible chainline.
For me the tricky part of this dance is guessing how far onto the taper any particular crank wll be when it is fully tightened.
Some BBs are asymmetrical. They might be longer on the chainring side to accommodate a triple.
Some like Shimano’s early 105 were longer on the non drive side for some unknown reason.
If the axle is too long it may mean that your front derailleur does not have enough travel to change gears
Too short and the crank arms or chainrings can rub the frame.
Some cranks have JIS taper and some ISO. Getting the correct one is important.
It matters but it doesn’t need to be 100% precise. The longer the spindle is, the further out the crankset will sit. If it’s too far out or in horizontally with respect to the cassette, the chain will be at an angle and that can cause problems (shifting, chain rubbing front derailleur). But in my experience as long as it’s in the right ballbark (~5mm?) it should be fine.
Take and meaure it with caliper measure. Remove the crankkset first ofc. Order in the size you currently have.
Just get [this](https://www.amazon.com/shanmashi-Andeshunk-Crankset-Integrated-Chainring/dp/B097QQ25W8/) style and be done with that old style BB.