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Special Owners! Check Your Rotors!
I thought I'd throw this out here, as this may be the reason why some Special owners have had trouble aligning their rotors/calipers. This shouldn't apply to standards, but may be something to look at if swapping rotors around, particularly between models. I mentioned this in another post, but though it might be good to call more attention to this.
It's been stated here many times that all XS rotors will interchange and are dimensionally identical, with the only 'different' ones being the slotted versions. The parts fiche backs this up, as it only lists three kinds; 'standard' non-slotted rotors and the two left/right slotted ones. But this may not be true, as I have two rotors (out of ten) that are not identical to the others. The difference is in the 'dish' or 'offset'; the majority of mine measure as .750" from the mounting face to the outer friction surface, while the other two measure at .810", for a difference of .060". This can't be accounted for by wear, as all check within .015" of each other for disc thickness.
Here's my thought; the Specials require you to align the rotor and caliper by moving the fork slider one way or the other in the axle clamp. But this can put your fork tubes out of parallel, introducing 'stiction' and wear problems. I think this is the main reason the Specials have bushings on the bottom of the fork tubes and the standards don't; the bushings help reduce friction and reduce wear. But what if the tolerance 'stack-up' requires a large movement of the fork tube to get alignment, maybe more than the engineers intended? I suspect this was an issue and the fix was these 'different' rotors (only used on the production line) to prevent problems on the new bikes. So if you have replaced or swapped around your rotors and had trouble with this, check for this. I'll note that one of these 'oddballs' was off a low-mile unmolested Special, and the other was on a standard that did show signs of having had bits replaced, so who knows on that one.
Maybe someone could verify this on some other rotors...
It's been stated here many times that all XS rotors will interchange and are dimensionally identical, with the only 'different' ones being the slotted versions. The parts fiche backs this up, as it only lists three kinds; 'standard' non-slotted rotors and the two left/right slotted ones. But this may not be true, as I have two rotors (out of ten) that are not identical to the others. The difference is in the 'dish' or 'offset'; the majority of mine measure as .750" from the mounting face to the outer friction surface, while the other two measure at .810", for a difference of .060". This can't be accounted for by wear, as all check within .015" of each other for disc thickness.
Here's my thought; the Specials require you to align the rotor and caliper by moving the fork slider one way or the other in the axle clamp. But this can put your fork tubes out of parallel, introducing 'stiction' and wear problems. I think this is the main reason the Specials have bushings on the bottom of the fork tubes and the standards don't; the bushings help reduce friction and reduce wear. But what if the tolerance 'stack-up' requires a large movement of the fork tube to get alignment, maybe more than the engineers intended? I suspect this was an issue and the fix was these 'different' rotors (only used on the production line) to prevent problems on the new bikes. So if you have replaced or swapped around your rotors and had trouble with this, check for this. I'll note that one of these 'oddballs' was off a low-mile unmolested Special, and the other was on a standard that did show signs of having had bits replaced, so who knows on that one.
Maybe someone could verify this on some other rotors...
) I had previously removed the rotors to clean and paint this winter, so they may not be replaced on their original side. Could that be a problem, or could I have something else screwed up?
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