I drove the winter beater 1600 home from work 40 years ago this winter after swapping the winter wheels and snow tires earlier that morning. I heard and felt a vibration in one of the wheels. As my brain began to wonder if maybe I hadn’t snugged down the lug nuts (like that would ever happen), BAM! The left rear wheel fell off; the car skidded on the brake drum, the rolling wheel rocketed past me, and I headed straight for a house with a big plate glass window in the front. It hit a curb, bounced higher in the air than I ever thought possible, and landed in a shrub a few feet to one side of the window. I collected my thoughts and the scattered lug nuts, extricated the wheel from the shrub, jacked up the rear corner of the car, put the wheel back on, and resolved never to let this happen again. That meant being sure to stomp down on the lug wrench; I didn’t use a torque wrench for anything except head gaskets in those days.
But it did happen again. Well, I never reached the point of having a wheel fall off again, but several times, I’ve heard that tell-tale whubba-whubba-WHUBBA that becomes alarmingly loud alarmingly quickly. As my experience 40 years ago showed, at low speeds, you may have 30 seconds before all hell (and the wheel) breaks loose. One of the times was on my 2002tii, where clearly it was operator error (again) on my part. Another time, it was on my E39. I had gotten into the habit of using my impact wrench on a low setting to install lug nuts, having checked it against my torque wrench and found that it resulted in about 90 ft-pounds. Unfortunately, the dial that sets the torque on the impact wrench had gotten jarred, or my compressor didn’t deliver as much pressure to the impact wrench in its old age, or both. I heard The Sound Of Impending Chaos on the highway. I beat it into the breakdown lane in time, but the window may have been more like 15 seconds. My toolbox was in the trunk, so I went for the ratchet handle and socket instead of the car’s lug wrench. After that near-incident, I vowed never to let it happen again (again…!) and assiduously checked lug nuts from then on with a torque wrench.
But it’s still surprisingly easy to get it wrong. The vector for error can come from a number of places. One is cars laid up for projects. With cars on my mid-rise lift, wheels always come on and off for brake work, wheel bearings, tie rod replacement, etc. I don’t necessarily re-torque the nuts whenever the car touches back down. You see how the door is opened for catastrophe.
Of course, there’s simple, good old-fashioned operator error. Maybe you swap wheels curbside with a jack; your routine is to tighten lug nuts as you do each wheel, and you get interrupted.
That’s likely what happened with my latest faux pax. The first snow of the winter was forecast, so I swapped the winter wheels onto both Maire Anne’s Honda Fit as well as my E39 530i. I hated to do it on the BMW, as I’m using mismatched alloys that are embarrassing to be seen driving and a set of Craigslist-purchased used Toyo snow tires with all the sidewall stiffness of a bowl of oatmeal. In fact, since I now own the 2008 Nissan Armada, I entertained leaving the regular wheels and the three-season 235/45ZR17 rubber on the E39, figuring that if it snows, I’d just use the truck. But then I remembered that without the snows on, the E39 becomes immobilized in the driveway if winter so much as coughs a frost. And, of course, sometimes you or a family member is out in a car when unexpected weather moves in. The responsible thing to do was swap on the winter wheel set.
The garage was full with the E9 and both Lotuses, so I did the wheel swap curbside with a floor jack. I used the small light one I take on road trips. It doesn’t have the reach necessary to lift the front or the rear, so I did one wheel at a time. I was very efficient about it and, of course, tightened the lug nuts down with a torque wrench when I was done. While swapping the E39’s left front wheel, I examined the rotor, as I’d felt some shimmy on braking coming from it. People often say, “That’s warped rotors,” and we can have an academic discussion on whether rotors on passenger cars actually ever warp from heat or whether the lack of flatness is a distortion from micro-deposits from the brake pads sticking. On modern cars, shimmy on braking can also be control arm bushings. I find that simply jacking up the car and spinning the wheel is a decent diagnostic. If it spins without the pads binding, then the rotor is nice and flat, but if the pads lightly bind and release, there’s some distortion coming from somewhere. It may be that the rotor isn’t sitting flat on the hub, or it may be that the rotor needs to be replaced. The right front wheel was fine, but on the left front wheel, there was some binding. I made a mental note that if I had reason and opportunity to put the car in the garage with the nose up, I’d look at it further.
A day later, while driving the E39 back from the hardware store, I began to feel a shimmy in the left front wheel. Initially, I brushed it off as the just-verified non-flatness of the rotor.
But it got worse. Still, I thought it couldn’t be loose lug nuts because I knew that I had tightened them all. I made a note to re-check them when I got home, which was maybe two miles away.
But then it got so bad so quickly that I pulled over. I opened up the trunk to pull out the lug wrench, and was reminded that this car, for whatever reason, doesn’t have one—it has no trunk-lid-mounted tool kit like my other BMWs of yore. I discovered this a few years ago when the car’s alternator died and I couldn’t find the towing eye, but had forgotten.
So, no lug wrench.
Then I realized I was maybe an eighth of a mile from The Tool Shed on Main St. in Waltham, this wonderful little old-school shop where a guy sells used tools. I hoofed it there, went in, and said to the owner, “You may not remember me, but I’ve occasionally bought tools here for years; I have a car parked nearby with a loose wheel. Can I borrow a breaker bar a 17mm socket, and a short extension, I promise I’ll bring it right back.” He immediately pulled the stuff out of the bins for me.
“I’ll bring it right back,” I repeated.
“I know,” he said. “I trust you.”
Sure enough, all five lug nuts were slack, and the wheel was grab-it-and-shake-it loose. I snockered them down, checked the ones on the other three wheels (they were fine), and then returned to The Tool Shed.
“You know,” I said, “I’ll just buy this.”
“You don’t need to buy it,” the owner said. “You probably have five of them at home.”
“Two,” I said.
“Really,” he said, “You don’t need to buy it.”
“Really,” I said, “I do. I want to leave this one in the car.”
Fifteen bucks. You gotta love old school.
Not kidding about the fifteen bucks.
But I’m not sure how it happened, and that spooks me. While doing projects on the lift, sure, sometimes I pull off only one wheel, or only the fronts or the rears, but I thought I’d beaten into my neurons and muscle memory that when I swap wheels, I mount all four, then torque down all four. I think it’s likely that I slipped into wheel-at-a-time mode and missed this wheel while scrutinizing the pulsating rotor. Or maybe my phone dinged. I don’t know.
When it happened, I posted this story to social media and got a hail of responses. Several folks said that before swapping wheels, they put the torque wrench on the driver’s seat so they’re viscerally reminded not to drive the car until the nuts are checked. One friend offered that I might be wrong—that I might have knocked it down, but the hub-centric wheel was slightly askew on the hub, or \corrosion was preventing it from sitting flat (although I had wire-brushed both the wheel bore and the hub), so it seemed to tighten up with the torque wrench, but once driven, it settled into a new deeper seat. I have had this happen once, but I don’t think that was the issue here. Others chimed in that their routine is to mount the wheels, drive the car forward and back a hundred feet, then re-torque the nuts.
—Rob Siegel
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