You may be able to get away with reusing the pads, but it isn't a good practice. I would look at them and make sure there were no contaminants on the friction surface. Then, if I reused them, I would test them to see how the pedal felt, and if the vehicle stopped straight once the pads were bedded in. Any hint of any problem, and I would throw them out. And because of that possibility, and not wanting to do brake jobs multiple times, I would probably just change them when I installed the rotors.

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2007 X3 3.0si, 6 MT, Premium, White

Retired:
2008 535i, 6 MT, M Sport, Premium, Space Grey
2003 X5 3.0 Steptronic, Premium, Titanium Silver
2002 325xi 5 MT, Steel Grey
2004 Z4 3.0 Premium, Sport, SMG, Maldives Blue