|Re: I don't understand (archive)|
Posted by Fred Kern on October 06, 1998 at 22:05:23:
In Reply to: I don't understand posted by Z3 Husband on October 05, 1998 at 22:28:31:
There are a nunmber of problems with alloy (aluminum) wheels. First, here in Vermont, they use gravel up to 1/4 - 1/2" in size. This chips the paint finsh on the wheels. The chloride in the road salt is very corrosive to aluminum. Hydrated aluminum chloride (AlCl3*6H2O)has a high specific volume change relative to aluminum, it also hydrolyzes to form hydrochloric acid and continues the corrosion process by undercutting the finish around the original chip. I have also noted that the OEM wheels on the 1.9 do not have a finsh on the backside of the wheel. It is very likely that corrosion in this unprotected area could migrate under the finish on the front side of the wheel.
I hava also had problems with galvanic corrosion at the wheel hub --where the wheel mounts to the brake disc. You have dissimilar metals, and electrolyte and electrical contact. Corrosion of the aluminum (anodic to steel) is enhanced in this area. The corrosion products can use up the clearance necessary to remove the wheels. The result is that the wheels have to be beaten off with a hammer.
Most discount tire stores (e.g. the Tire Rack) have packages with snow tires mounted and balanced on steel wheels. If I were to drive the Z3 in the winter this is the way I would go (I drive an Audi A4 quattro and this is the way I DO go). You don't have to mount and balance tires twice a year, your alloy wheels will be preserved and if the steel (winter wheels) rust, they will (1) be behind a hubcap and (2) some wire brushing followed by Sears anti-rust enamel can repair the damage.