When you buy a used car and begin sorting it out, you’re in the “getting to know you, getting to know all about you” phase. Hopefully you remain captivated by your new purchase. More often, though, you start to run into things that make you think, “Huh… that’s weird. Maybe I won’t bring this one home to meet the family.”
A few weeks ago, I described changing the brake fluid in the ’79 Euro 635CSi. Whether I actually completed the job is debatable, as very little fluid came out the right rear caliper, a clear indication that the rubber brake hose to that wheel is probably swollen nearly shut, necessitating replacement of all of the rubber lines. However, completed or not, floor space in the garage is precious, and I wanted to get the wheels—fifteen-inch E34 basketweaves—off the floor and back on the car. As I was snugging down the lug nuts, I looked at the front wheel and hub, and saw this:
I had to stare at it for a while to understand what I was seeing. It eventually sank in: The front wheel bearing was exposed because the dust cap was missing. I immediately checked the other side: same thing. It was obviously this way when I’d bought it; I’d only driven the car perhaps ten miles before marooning it in the garage for the winter. How long had the previous owner driven it like this? Don’t know.
My mind ricocheted around before settling on a memory from about three years before. I’d bought my ’72 2002tii and was fitting a set of E30 basketweaves to it. The wheels fit fine, but when I tried to put the center caps on the front wheels, they wouldn’t fit. Upon examination, it turned out the wheels’ center caps were hitting the dust caps protecting the wheel bearings. Tii’s take a 47-mm dustcap; stock ones have a perfectly cylindrical profile whose width at the top was the cause of the clearance problem with the center cap. With a little searching, I found an aftermarket 47-mm set that tapered at the top. This solved the clearance problem on the tii.
Return to the present. I recalled that, when I bought the 635CSi, the seller had a pricy set of refinished vintage BBS RA wheels on it. I elected to divorce the wheels from the car to hold the price down, which required me to buy an inexpensive set of E34 basketweaves, show up with them when I picked up car, jack the car up, and swap all the wheels before loading the car on the trailer. I guess it’s not that surprising I didn’t notice during that wheel swap that the front hubs had no dust caps.
I made a reasonable conjecture: Either the BBS RA wheels themselves or their small center caps had a clearance problem with the dust caps on the 635CSi’s hubs, just as the tii had with the E30 basketweaves. I doubt that anyone would make a deliberate choice to run without dust caps; perhaps the previous owner, eager to install his shiny new RAs, ran into the problem, put the issue and the dust caps aside just to get the wheels on, then… forgot.
I’ve done worse.
I dug up the ad for the car. It certainly implied that the wheels and tires had been very recently purchased. They sure looked mint in the pictures. I was hoping that he hadn’t driven it without dust caps for long. I looked at the grease in the bearings, swiped some out with a Q-tip, and didn’t see or feel any obvious abrasive or particulate matter. I temporarily bolted the wheels onto the front hubs, grabbed them at 6:00 and 12:00, and didn’t feel any alarming play in the bearings. I spun the wheels and didn’t hear anything crunchy. Good enough for now.
Well, I thought; I solved this dust-cap-clearance problem with the tii. I can look through my records and find out where I bought those tapered ones. Oh, right—first I should find out what size the 635CSi dust caps are. I measured the inside diameter of the hub with calipers, converted to metric, and voilà: 47 mm, same size as the tii.
One of the nice things about using realoem.com is that, once you know a part number, you can easily see which BMWs use that part. I confirmed that the 635CSi and the 2002tii do indeed use the same dust cap. Great, I thought, I’ll just order a set of the same tapered ones I used on the tii.
Then I remembered that the 635CSi didn’t have the fancy BBS RAs on it anymore—the wheels which, at least according to my theory, had caused the problem. I wondered if the stock dust caps would have any clearance problem at all with the E34 basketweaves. I started going through the process of ordering a set of stock dust caps online. They were short money. I thought let’s just get this done.
Wait—if they’re the same size as the tii, then I, who don’t throw anything away unless it’s broken or dead, probably still have the set of dust caps I pulled off the tii. Of course, my garage and basement are such disaster areas that if you don’t find what you’re looking for in 30 seconds, you may never find it. Fortunately, in less than a minute I was holding in my hands the stock dust caps I’d removed from the tii three years ago.
In about another minute, I’d tapped one of them into one of the 635CSi’s hubs and successfully test-fit one of the E34 basketweaves on it. And about five seconds later, it was clear that the E34 center cap fit over it with absolutely no clearance problem whatsoever. I pulled it back apart, greased up both the left and right caps, and tapped in the caps for good.
I hoped that the missing dust caps are just a minor hiccup. Then I remembered that, when I was bleeding the brakes, I never bled the clutch hydraulics. I crawled under the car and found that the clutch slave cylinder is installed upside-down. I thought, “Huh… that’s weird.” The 635CSi has, however, already met the family. I’m in for an interesting ride. I can’t wait for this snow to melt so I can begin driving the car.—Rob Siegel
Got a question for Rob Siegel, the Hack Mechanic? You can find him in the BMW CCA Forums here!
Rob's book Memoirs of a Hack Mechanic is available through Bentley Publishers, Amazon, and Bavarian Autosport—or you can get a personally inscribed copy through Rob's website: www.robsiegel.com.
