How The Left Front Wheel Almost Came Off My Dream Car

Here’s the thing about cars. The vast majority of them have four wheels. This is the correct number of wheels. If you take a wheel off, the car generally scrapes on the ground and/or crashes, and you’ll have a bad time. Due to some rather weird circumstances, my Audi nearly ended up with three wheels and a great deal of damage. I’m very glad I avoided that ugly scenario.

The car I speak of is my dream car, a gorgeous 2000 Audi TT in the proper roadster body style. It’s been a year since I first fell in love with the little turbo AWD scrapper. In that time, I’ve roadtripped it to the big city, nearly wrecked it on a dirt road, and left it sitting for three months while I sorted out paperwork with the authorities in a new state. Unfortunately, upon returning the Audi to the road, it started displaying all kinds of ugly symptoms. Vibrations, warning lights, and horrible noises that promised doom.

Naturally, as a car enthusiast, I decided there was no better way to diagnose the issue than to keep driving it. I knew that the problems would eventually reveal themselves if I just had enough time out on the road. I just didn’t expect to find out that one of the front wheels was hanging by a thread.

Misdirection

When last we spoke, I had just gotten the Audi back on the road after a few months, and I was tangling with an annoying problem. Every now and then, the Audi was triggering the anti-lock braking system (ABS) in conditions where it made absolutely no sense. I’d be slowly coming to a stop at a traffic light, and suddenly the brake pedal would rumble beneath my foot. This was characteristic of the ABS pump modulating braking pressure to try and prevent a lockup—except it made no sense, because I was braking with full traction at less than 5 mph.

I did the usual research, with owners forums indicating the likely culprit was a bad wheel speed sensor.  These sensors determine speed with the aid of a toothed ring fitted to the wheel itself. As the toothed ring rotates past the sensor, the presence or absence of a tooth changes the magnetic field around the sensor. The sensor picks up these changes and by reading their frequency, it’s possible to determine how fast the toothed ring (and thus the wheel) is spinning.

This explanation made a lot of sense to me. The Audi was 25 years old, and owners have been complaining about these wheel sensors going bad for almost 20 years at this point. Forums indicate it’s a common failure point on these cars, so it seemed to make sense that it had happened to my car, too.

Further evidence soon supported the theory. Traction control started randomly cutting in when I was accelerating, even quite gently. It was an intermittent problem, but a worrying one. I could turn off the traction control and drive relatively normally, but it was clear to me that this problem wasn’t just going away on its own.

I knew in my heart of hearts that I should buy a VAG-COM diagnostic cable to figure out which wheel sensor was bad, but life got in the way. Hospital visits and housing woes kept me too busy to figure out what was going on. I contemplated just dumping the car with a mechanic to get the problem sorted. Even though I had no time and nowhere to work on the car myself, I just couldn’t do it. I find it really hard to find workshops that I trust, and I hate not doing the work when I can fix a problem myself.

I ended up doing the stupid thing. I kept driving the car on short little trips, hoping the answer to my problems would naturally reveal itself. Maybe it would become clear the problem was metallic debris in the wheel hub, or a broken wire to the sensor, and I could fix the problem on my own. As you might expect, the problem didn’t magically go away. Instead, the car got worse.

I was driving across town on a sunny day, with the roof down and my partner riding shotgun. It was a nice ride, right up until an ear-splitting “SKREEEEEE” erupted from the car. It was a metal-on-metal sound that really pierced the skull, like nails on a blackboard on methamphetamine. It lasted just a second… and I wanted to pretend this problem wasn’t a new one.  Only, it kept happening again every few miles, setting my teeth on edge every time, and we could never quite pin down where it was coming from. I started questioning everything. Was it brakes? Something stuck in the suspension? Was the cam belt tensioner letting go? Fear wracked my brain.

At this point, I steeled my resolve. I absolutely couldn’t be one of those people who take their car to the mechanic because of “a noise.” I had to know what was going on.  My Audi became my go-to car. Any small trip, I took it out, trying to identify the noise. My partner helped, too, listening in from the passenger seat. It was hard to locate the intermittent sound, but she was pretty sure, she told me—the scraping noise was coming from the rear left of the car.

Living in the inner city, I still had nowhere to work on the vehicle. However, I happened across some luck—I’d found a multi-story carpark that was mostly empty on the upper floors. I figured if I whipped in all quiet like, I could jack the car up, whip off the rear wheel, and see if I could find the problem. The standard scissor jack did the trick, and I had the wheel off in short order.

Only… I couldn’t find anything wrong. The brake shields were fine, everything was where it should be… even the handbrake cable seemed to be in fine adjustment. Nor did I find anything that might explain a dodgy wheel sensor, though there was only a one-in-four chance that the problem was coming from this corner of the car.

Dejected, I decided to take car out for a longer drive. I went up a few road works with temporary barriers, and things became much clearer. With the sound reflected right back to my ears by the hard concrete walls, I could hear a continual dull grinding noise coming from the front left. Interspersed with nice loud SKREEEEETS here and there.

I hurried back to my secret short-term workspace in the multi-story car park. I jacked up the front left, and … oh no. Oh dear. The second the front wheel got off the ground, it was obvious it was barely attached. I rattled it back and forth, quite easily. It had to be a wheel bearing!

That’s not right…

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— Lewin S. Day (@rainbowdefault.bsky.social) May 15, 2025 at 3:44 PM

Rocking the wheel like that is the usual way to diagnose play in a worn-out wheel bearing. Only, I was confused. In the miles I’d racked up, I hadn’t heard continual graunching or any whining that would normally indicate a bad wheel bearing. And yet this one had almost half an inch of play! It didn’t add up. I’ve changed bad wheel bearings before; a worn one should have been way noisier and more obvious before it got this bad.

I pulled the wheel off, and I got down to the truth: It was the axle nut. You know, the one fastener responsible for keeping the wheel on the car. It was barely finger tight, hanging on by a thread.

Ah. That is not supposed to happen.

Glad I didn’t lose a wheel!

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— Lewin S. Day (@rainbowdefault.bsky.social) May 15, 2025 at 3:46 PM

I was aghast. If that nut had come off just a little earlier, I might have lost a wheel at 40 mph and gone spearing off into opposing traffic or something. What really astounded me was that the Audi design didn’t appear to have any secondary retention mechanism. A lot of cars have a split pin setup, or a notch in the axle nut so you can hammer a dent in to stop it winding itself out. There was nothing of the sort here; just a six-sided nut that had worked itself almost totally loose. I shot a quick video to old mate Laurence, who summed it up pretty succinctly—”Wtf!”

All along, this was the problem. I didn’t have a bad wheel sensor or any ABS issues. I had a wheel hub that was slowly coming off the car. The misalignment of the hub caused the intermittent wheel sensor issues, presumably because the toothed ring wasn’t where it was supposed to be relative to the sensor. It was also the cause of the terrible noise; occasionally, the hub would misalign and moving metal parts would hit static metal parts and make that horrible squeal.

The temporary fix was easy. I snugged the nut back up, and would you believe it, suddenly all the play in the bearing was gone. I dropped the car back down onto all four wheels, and did my best to hit the proper torque spec with a breaker bar. Taking the car on a test drive, the problems were gone. No ABS kicking in. No traction control interventions. And crucially, no horrible squealing noise. Despite the fact I’d been driving around on an improperly assembled hub, there wasn’t even any obvious noise from the bearing. It was rewarding to figure out the problem on my own.

Realistically, though, this never should have happened. The front axle nut shouldn’t just be coming undone by itself if it’s been torqued properly. My guess is that whoever last replaced the front wheel bearing didn’t do a very job. Peeking through the front rotor, it looks like the hubs have been swapped out at some point. I can only assume that when it was done, the nut wasn’t torqued properly.

A further smoking gun? The fact that the axle was fastened with a six-sided nut. Everything I’ve seen online is that early Audi TTs use a 12-point nut, not a six-sided fastener. Indeed, the rear hubs are fitted with the proper 12-sided hardware. Did the previous owner or mechanic lose the proper hardware and just sub in some random fastener?! If that’s the case, it’s not much of a leap to assume they didn’t follow the proper multi-step torquing procedure to ensure it doesn’t fall off, either.

Recurring Pain

The temporary fix worked for about 1,000 km (600 miles) or so before I got the same symptoms once again, with the ABS occasionally cutting in under braking. Maybe I didn’t do a good enough job torquing the axle nut back up. Maybe the wheel bearing is toast, or there’s something else damaged in there that’s causing the nut to untorque itself. Either way, I want no part of any of this.

I’m going to get the front wheel bearings replaced out of an abundance of caution. After all that, I just don’t trust them. Plus, I have to drive many hundreds of kilometers for a secret project with Laurence soon, and I don’t want a wheel coming off on the highway. That would spoil all my plans, and my partner indicated she’d be quite upset if that were to occur.

I’m leaving the work up to a shop, because – would you believe it? – the multistory carpark doesn’t have a bearing press on site. I’ll probably get the timing belt and a few other ancillaries handled, too. I’m a lot more comfortable handing the car over now that I know what is (and isn’t) wrong with it.

It’s funny to think how wrong I was from my initial assumptions. Anyone would have said, “Oh yeah, that’ll be a bad wheel sensor. There’s your problem.” And they’d have been wrong! It was an altogether weirder issue that had nothing to do with the wheel sensors at all! Never assume, and all that.

Ultimately, I learned it pays to do the work. I’m glad I put in the effort to diagnose this one properly, and I’m especially glad I figured it out before the wheel came off. I’ll take the W.

Image credits: All images Lewin Day except where stated