Bicycle Mechanics - Is this an ISIS BB? Can I adjust it?
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One guy at my LBS says that the BB on my bike is an ISIS just by looking at it. I thought ISIS referred to the type of spline pattern, but my BB has a square tapered shaft. He says that it is an ISIS BB which can be adjusted left-right to fix the chainline. Can anyone confirm or deny this? See pic below.
Looks like a cup and cone style square taper to me.
Here's a better pic:
According to the ebay seller this is a sealed bearing BB from Performance. Obviously it is square taper, but my LBS guy took one look at it and said it was adjustable, and that it was an ISIS type. I am confused. Sheldon where are you?
It might be time for a different LBS. Was your guy looking at it with the cranks on and without glasses?
dude I think he means ment that is an iso bb and you you need to find a new mo betta lbs sans druggy haffy bike mechanics
Ok, so it's obviously not ISIS. What about the adjustable part? As I understand it, "adjustable" means that you can play with the load on the bearings to smooth out the spin. The mechanic said this lets you also move the BB spindle left/right to adjust chainline. Is that true?
The chainline is fixed and cannot be changed. You are correct. Your BB has a fixed cup and an adjustable cup (shown in the pic) with loose balls inside. The adjustable cup is used to get the proper load on the bearings which is then held in place by the black lockring. Look at Phil Wood for an example of an adjustable BB. In that case the bearings are sealed and both cups are adjustable allowing for a small side to side movement.
01-20-07, 02:56 AM
As I understand it, "adjustable" means that you can play with the load on the bearings to smooth out the spin. The mechanic said this lets you also move the BB spindle left/right to adjust chainline. Is that true?
No, adjustable does not mean this. Although some axles are asymmetric. Flip it over and you can decrease/increase chainline. The majority are symmetric however...
I forgot to mention that both sides of the BB look like the pic shown and have identical lockrings. This leads me to believe they are both adjustable (I haven't played with it since I don't have the proper tools). One way that I could see the chainline being adjusted is by tightening the load on one side and loosening it on the other side, effectively sliding the bearing-spindle assembly inside the BB shell. Does this seem plausible?
If that is the case, then yes you would have the ability to adjust the chainline. I just looked at the pics again. Are you sure the drive side has a lockring?
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