Originally Posted by ftconstruct
Regular soaps will cause the rotors to rust up and then sling orange dust all over the wheels the minute you start driving. I'm not a fan of Sonax because it smells like crap but P21s wheel gel works well and prevents rust on the rotors.
As others pointed out, rain will also make rust on rotors. I have used Sonax before, and after a good rinse, rust would build up on the rotors. I don't think it has anything to do with soap. I don't even think pH balanced soap has any rust accelerating chemicals in it.
I also minimize rust forming by drying my car with a electric leaf blower, including the wheels. I find it gets water out of all the cracks, and my waxes seems to last longer as what little water is left on the char, it just flies off withiut any rubbing. Plus all the water blows right out of the lug nut areas as well.