Tarnished wheels need to be professionally refinished

DRIVE IT FOREVER

Dear Mike:

The alloy wheels on my truck have developed these ugly, scablike discolorations on the spokes. It looks like some sort of mineral from the road has collected on them.

I tried to wash them off with water and then with bug-and-tar remover. They’re raised up, and have an orange-peel texture. What can I use to remove them? Can I use a Scotch-Brite pad? Bug-and-tar remover didn’t touch it. — K.McD., Grand Rapids, Mich.

A: Those discolorations are far more than mere discolorations — they’re corrosion. And that means that Scotch-Brite won’t cut it.

Aluminum-alloy wheels are almost always painted with a silver paint, after which a thinner layer of clear paint is applied. Sometimes an area of the silver paint is machined off for a shiny accent before the clear paint is sprayed.

If the wheels are not kept clean, the two layers of paint are attacked by road salt and brake-pad dust, and eventually they start to peel. Then the corrosive salt and dirt attack the aluminum wheel itself. Your “scab” is made up of corroded aluminum and the remains of the paint.

Here’s the bad news: The scabbing will have to be removed mechanically, ideally by glass-beading or walnut-shell blasting. Maybe you’ve caught it soon enough that it can be sanded off. It’s probably not necessary to remove all of the paint on the wheels, but only the part that’s damaged.

Removing the scabbing is only half the job, however. If the wheels aren’t properly refinished — that is, if the surface of the aluminum isn’t sealed — they will corrode again. The weathered aluminum is a field of tiny stress risers that will substantially reduce the ultimate strength of the wheels.

What’s a “stress riser?” It’s a discontinuity in the surface of a crystalline solid, such as aluminum, that allows tiny cracks to start readily. Tiny cracks become large cracks, and eventually your wheels could fail.

Most body shops can properly refinish wheels, but ask beforehand how they plan to remove the old paint and corrosion. Sandblasting is not an appropriate method of stripping alloy wheels. It leaves stress risers which, as I mentioned, make the wheel weaker.

To do this properly, the shop should demount the tires from the rims. Why? The corrosion almost certainly reaches down into the bead area of the rim, and if that area isn’t treated the corrosion will let air leak past the tubeless tire’s bead surface.

In the future, how can you keep this from happening? Treat the painted surface of the wheels like any other painted surface: Keep it clean, dry and waxed to repel dirt. Use the same wax that you would use on your car or truck’s bodywork.

Dear Mike:

I have a 1994 Chevrolet pickup. When I start the heater blower, there’s a flapping noise for about 15 seconds — it sounds like clapping hands, then it stops. If you turn the switch off and back on, it claps for 15 seconds again.

What’s the problem? — N.L., Seneca, Kan.

A: Are you missing a credit card or maybe a parking tag that you left on your dash a while back, by any chance?

I think there’s a foreign object in your heater plenum that’s flapping for a few seconds as the fan speeds up. Or perhaps some blend-air door is loose. Take it apart and look.

Dear Mike:

My pickup has zerk fittings on the steering linkage. When I pumped grease into them, I discovered that the rubber boots over the joints were broken, and the grease had leaked out.

Do I need to replace these, or is there enough grease going into the joint? — H.F., Lake Charles, La.

A: Those boots are there to keep mud and foreign matter out of the tie-rod ends and ball joints, as well as to keep in the grease. You need to repair this ASAP, or you’ll soon be replacing a worn-out joint.

You used to be able to buy the rubber boots as a separate part, but good luck with that, because the last time I tried to buy some I got stupid looks at the auto-parts store. You may need to buy the whole joint, in which case a salvage lot might be a way to save a few bucks.