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This Stupid Wrenching Mistake on my BMW Z3 M Roadster Nearly Ruined My Weekend

Road & Track logo Road & Track 4/12/2021 Aaron Brown
a car parked in a parking lot: Don't do this. © Aaron Brown Don't do this.

Prepping a sports car for track use doesn't usually require much major work. But because of a very stupid, very simple mistake, I recently almost created a much worse situation for myself.

My friends and I spent the weekend readying my recently purchased 1999 Z3 M Roadster for an upcoming track appearance at Lime Rock Park. For the most part, this meant running through basic maintenance items and tending to some small issues I'd noticed with the 190,000-mile BMW since buying it in January.

a close up of a truck: IMG_0951.JPG © Aaron Brown IMG_0951.JPG

I was ready. I’d bought an oil change kit from FCP Euro, picked up new Michelin Pilot Sport 4S tires and Hawk HP+ brake pads from Tire Rack, and was also intending to swap in a new clutch master cylinder and replacement slave cylinder in an attempt to fix a clutch engagement issue. It seemed like it should've been a problem-free weekend. And it would've been, if only I'd used a little more of my brain.

IMG_0947.JPG © Aaron Brown IMG_0947.JPG

Oil change? Done. Pads? Done. Clutch system? Mostly fixed. But when I put the wheels back on, lowered the car off the lift, and tried to drive it forward, it abruptly stopped in its tracks.

Oh no.

It was an aggressive stop, too. It felt like the parking brake was locking the rear right corner in a terrible way. Under any amount of throttle, you could feel the suspension load up and twist. It was bad, very bad, and the car was undrivable. Back up on the lift my little M Roadster went.

a close up of a car: IMG_0995.JPG © Aaron Brown IMG_0995.JPG

My friends, Road & Track staff writer Brian Silvestro and local BMW E39 M5 hoarder Mathias Rios, immediately jumped to the conclusion that the new and aggressive HP+ pads were catching on the badly lipped rotor, for which I’d failed to buy a replacement. Though this made some sense—I had expected the rotor to lightly grind and rub down the new pads in a less than ideal way—there was no reason why that should have caused the whole corner to lock up.

We took the wheel off and attempted to spin the rotor to see where the problem point was. But, miraculously, we couldn't replicate the issue. The rotor spun freely. But when we put the wheel back on, problem. After many minutes of the three of us staring at the wheel and spinning it like cavemen, Mathias asked the golden question.

"Are all your lug bolts the same size?"

"Oh," I said."Uh."

Earlier that weekend, I’d noticed my two rear wheels were missing two lug bolts. I found two replacements in our shop, which were indeed noticeably longer than the ones on the car, but they threaded on fine."Perfect!" I thought to myself."Fixed!"

a close up of a car: So stupid. © Aaron Brown So stupid.

I was wrong. This was a bad idea.

The longer lugs came into contact with parts behind the rotor, and probably came very close to creating disaster.

After pulling the longer lugs out, we lowered the car again. Everything was fine. The Z3 M rolled, accelerated, and stopped just like it should.

Let this be a lesson to all of us: Don't put random lug bolts on your BMWs. Don't put random parts on your car at all. And, yes. My friends already roasted me appropriately for this.


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