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When changing my tires sometimes my rotors start rubbing more and have to adjust the shims. Is this normal because in my mind the tires shouldn't affect the angle of the rotor unless a higher volume tire is causing the rotor to be higher in the caliper than it was with a smaller volume tire? Anyone noticed this as well?
 

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Assuming you take the wheels off before switching tires (which unless you're a magician, cant think of any other way of doing it haha), this can happen and its because of the tiny changes when fixing the hub back on the drop out. Eg. like if you tighten the quick release with a different torque than before, it can ever so slightly change the alignment in the rotor.
 

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The rubbing is probably caused by varying quick release pressure when you remount the tire. You can easily test this by adjusting the quick release tighter or looser and see the rotor position change in the caliper. A different volume tire shouldn't affect brake alignment.
 

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In addition...

even the position of the hub end caps or lock nuts against the drop out can cause small changes in hub alignment. You have to remember that you are only taking (in most cases) a couple of milimeters of clearance between the rotor and pads. Add to that the fact that no rotor is ever perfectly true, and the variation in torque on the qr, and you have the perfect recepie for rotor rub when reinstalling a wheel from one time to the next. And that doesn't take into account other subtle variations like paint flaking off the drop outs, hub bearing wear or change in adjustment over time, etc. Also I've found that some brakes are more sensitive than others as well.

Anyway, with experience and experimentation you can find methods that will lessen the need to adjust after wheel reinstall. One of the major factors, qr torque, is pretty easy. Simply use the lever angle method when reinstalling the wheel to set the torque of the qr. You'll have to experiment at first. Hold the qr lever at a 90 dgree angle in relation to the skewer and tighten the nut frimly by hand. Then close the lever. Not tight enough, then open the qr back up and hold at a 100 degree angle and repeat. If it's too tight then simply decrease the hold angle and try again. Once you find the hold that allows you to firmly tighten the nut and results in a good tight lock. Simply hold the qr lever at that angle everytime you reinstall the wheel. It's simple and it works pretty well. It's not that accurate if you where able to actually measure the torque, but it's much more consistant than just tossing the wheel in and fiddling with the lever till you get it tight. From there it's just a matter of practice to become as consistant as possible. I rarely have to adjust calipers anymore using this method. It doesn't totaly elimate the occasional adjustment. But I do adjust less than I used to.

Good Dirt
 
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