Inspection Failure #3 - Tires (Original Post: Dec 23, 2011)

I suppose this should have been failure #1, since it was obvious I'd need tires before I bought the car.  However, it has taken this long to get this failure fixed, even though I bought the tires on Sep. 26, 2011, one day after I bought the car.


I have traditionally been a "Michelin Man."  No, I don't mean I'm shaped like Bibendum, the Michelin Man in the ads!  Incidentally, I just learned recently that his name comes from their original Latin motto: Nunc est Bibendum, which means "Now it's time to drink!"  Only the French!

Anyway, I was on the Tire Rack web site, looking at Michelin tires that would fit the Z3.  The front and rear tires are different sizes, wider in the back of course.  While looking, I noticed a sale on the Kumho tires - that's a South Korean brand which has had great reviews lately.  In fact, I had seen a comparison test where the Ecsta 4X tires beat the Michelins.  The price was right, a set of four came with a $50 rebate Visa card, and the Tire Rack will ship the tires directly to Jack's Auto and Aero.  I bought them.  As it turns out, they would sit there so long that Jack forgot whose tires they were!

You see, if you are going to ever refurbish your wheels, the right time to do it is while the tires are off.  My wheels were not bad, really, but the clear coat was peeling in several spots.  On the picture below, you can just see a few freckles - that's the places where the clear coat was missing:

John Zimmerman had told me of a vendor he had used a couple of times to powder coat aluminum wheels.  Powder coating is a process where a sort of plastic is baked onto the surface, yielding coating much harder than paint.  You can get the coating in many different colors, and the price was actually cheaper than having the wheels stripped and painted.  I paid $240 for all four wheels, including chemically stripping the old finish, repairing some minor curb damage, and the new powder coating.  I chose to go slightly darker than the stock finish, to a color called "Smoke Chrome."  My Z4 Roadster had darker wheels, and they didn't show brake dust as badly, so I wanted that for these as well.

Jason is the guy's name, and this is a side business for him.  That means that it gets done when he has time, and with Thanksgiving and other distractions, it took over three weeks to get the wheels back.  Luckily, I had some other things to keep me busy while waitng.

You may remember the picture on the left below - that is the hub of the brake disk after removing the wheel.  Galvanic corrosion between the aluminum wheel and the steel hub had literally welded them together, and it took some serious pounding with a rubber mallet to separate all four wheels. The picture on the right is the same hub after some major cleaning with a wire cup-style brush chucked in an electric drill.  It took 15 to 20 minutes per hub to clean things up, and I also had to do the same process on the matching surface inside each wheel before delivering them to Jason.

The lug bolts were in bad shape too - the paint was chipped and the metal rusted after 12 years and 197,500 miles.  John's son Bob has a media blast cabinet, and he kindly cleaned all 20 of them for me.  See how nicely they cleaned up in the right picture?

Of course, the bare metal started to rust almost immediately, so I put three good coats of a rust-preventative paint on them.  At first I was only going to paint the head, but Mike Miller, the BMW guru for the BMW Car Club of America, recommended that I paint the entire bolt too.  I painted the tops, and then turned them over and painted the threads.

Finally, the wheels were ready, and John and I took them over to Jack to get the tires mounted.  That's probably the most expensive place to do it, but Jack has some very fine no-touch equipment to mount and balance, and he took extravagant care in both.  In fact, for two of the tires, after the initial balancing spin, he took them back to the tire machine, broke the bead loose from the wheel and rotated the tire 180 degrees on the wheel.  In one case, that reduced the amount of weight needed to a quarter of an ounce.  He balanced all four to 0.0 ounces - perfect.

I remounted the wheels with a thin coating of copper-based anti-seize compound on the hubs. That should forestall the recurrence of the galvanic corrosion problem between wheel and hub.  The same compound was used on the lug bolt threads for the same reason.  I was able to reuse the original BMW wheel centers, which were still in good shape.  Here they are on the car - looking good!