You’re all wondering what the hell happened with that Kia Soul that launched way up into the air after running into the tread of a rolling wheel that fell off a pickup truck. Specifically: How did the wheel fall off the pickup in the first place? I just pored through dozens of parts diagrams and repair videos/photos to come up with what I think is a strong theory explaining what sent that wheel into the path of that poor Kia Soul.
By now, many of you have likely seen this video of a Kia Soul using a rogue wheel as a ramp:
Witnessed and recorded the most INSANE car crash yesterday, you can see Autopilot also swerve and avoid the rouge tire for me $TSLA pic.twitter.com/csMh2nbRNX
— Anoop (@Anoop_Khatra) March 25, 2023
If you’re wondering “How the hell did that happen,” the answer is simple: The tire’s ability to deform and grip allowed it to grab hold of the Kia Soul’s front fascia such that the Soul began to “ride” up the tire. That happening at highway speeds made it appear as though the Kia was launching off a jump.
How did the wheel fall off the adjacent pickup truck? Well, the answer to that is a little less clear.
The California Highway Patrol says its officer’s initial assessment implied that lug nuts or studs had broken, but the official investigation hasn’t yet been completed, and even when it’s done, we may never know what the actual cause of the tire-detachment was — that’s at least what the California Highway Patrol’s media contact told me over the phone. (This issue is a private matter between the people involved, so the police may never publish the root cause of the failure).
But even if we never hear it from the police, there’s enough info in the video to help us determine some possible causes of the wheel detachment. So let’s talk about them.
Before we start, it’s worth pointing out a key bit of information in that clip. The screenshot above shows a shiny silver surface on the backside of the errant wheel. This will come into play later.
(With that said, some of you who pointed this shiny disc out when you first saw the clip, and think it’s now obvious what the cause was, may end up surprised by my conclusions).
Let’s Talk About The 2011 Chevy Silverado’s Front Suspension Setup
We need to talk about what the 2011 Chevrolet Silverado’s front suspension looks like — specifically, how the wheel is held onto the vehicle.
How Your Wheel Is Held Onto Your Car
Let’s begin by having a peek at a typical “spindle” design on an older vehicle. A spindle is the part of the suspension that holds the “hub” that contains the threaded studs to which the wheel mounts. On an older car, like my Jeep J10, the spindle is a pointy pipe that bolts to the steering knuckle, which is attached to the suspension control arms (or in my case, the axle) via ball joints. You can see all of that below.
Those ball joints are just greased steel balls that allow the steering knuckle to pirouette when you turn the steering wheel (turning the steering wheel pushes and pulls the tie rod shown below, which yanks and shoves the arm on the knuckle), thus turning the front wheels.
Onto that spindle sits a brake disc, which has inner and outer tapered roller bearings inside of it. The inner race of each bearing rides on the spindle; the outer race is pressed into that rotor. Here’s a look:
Tightening the castellated nut under the grease cap is what sets the bearing “pre-load” (i.e. made sure there wasn’t too much play so the bearings last).
Here’s what those bearings look like in my Jeep J10:
The point is that, on an older design like the one above, the rotor itself is what houses the replaceable wheel bearings, which rotate on the spindle (called the “stub axle” above) as the wheels rotate. The spindle itself does not rotate with the wheel, but it does pivot/pirouette on the ball joints as you turn the steering wheel left and right. The vehicle’s front wheel bolts up to the studs on the rotor (labeled in the diagram above).
The Hub Assembly/Unit Bearing
The way wheels are mounted to cars changed sometime around the 1990s with the implementation of the “wheel hub assembly,” also called the “unit bearing.” This is a single part that incorporates a lot of the functions done by multiple components in an older spindle/wheel bearing system like the one presented before.
Instead of the brake rotor carrying the wheel via studs, and that rotor housing two bearings, with those bearings riding on a stub shaft/spindle hooked to the knuckle, the hub does a lot of this work.
A unit bearing contains two bearings built in (see below), it mounts directly to the knuckle (no stub shaft/spindle required) via three bolts in the outer case of the hub assembly, and it features studs that hold both the brake rotor and the wheel. The rotor now only has to handle braking loads, not the entire load of the car.
Let’s look specifically at the hub assembly of the 2011 Chevrolet Silverado involved in the now-viral video. The hub is shown in the 1A Auto YouTube video above, but here are some screenshots:
You can see that in the image above, the steering knuckle is attached via ball joints to the suspension control arms, which hook up to the vehicle’s frame.
In the Silverado, the knuckle has three holes in it; bolts enter those holes from the back (inboard) and thread into the three threaded holes in the wheel hub assembly, holding the hub (and that thin brake dust shield) tightly against the knuckle, perfectly flat so that the hub face/flange is situated vertically.
You can see the three bolts holding the hub assembly to the knuckle here:
Here’s the hub assembly all tightened up. Notice that the hub’s face/flange is basically vertical:
Onto that hub face and over the hub’s studs slides the brake rotor:
Once the rotor is on, the brake caliper is mounted to a bracket that is bolted to the knuckle via two beefy bolts:
Below is how the caliper looks from the front: Notice that the caliper and caliper bracket are both slid over top of the rotor. The rotor isn’t yet fastened tightly to the hub flange just inboard of it, since the lug nuts (which go over the lug studs) aren’t squeezing the wheel against that rotor yet.
Still, even though the rotor can wobble a bit in this setup, it isn’t going to slide off those studs since the caliper and bracket are mounted over top, holding it all in. This will become relevant when we talk about how that hub and rotor (that’s the shiny thing shown in that screenshot early in this article) might have escaped — that rotor wouldn’t have easily moved axially outward from the truck, as the caliper and bracket would have held it in.
To finish off the Silverado’s wheel setup, let’s peek at the image below. It shows that the wheel goes on over the six studs, and lug nuts squish that wheel and and the rotor below tightly against the hub face.
Why Did The Wheel Fly Off?
Now that we’ve got a good understanding of the Silverado’s front suspension/steering setup, let’s talk about possible causes of the truck’s tire evacuation:
- The lug nuts came loose/the lug bolts sheared
- A wheel spacer failed
- The ball joints failed
- The knuckle failed
- A wheel bearing separated
- A wheel bearing failed catastrophically (sheared)
- The bolts holding the unit bearing to the knuckle failed
Let’s just go through these one by one:
The Lug Nuts Came Loose/The Lug Studs Sheared
Take a look at the image just above, which shows all the wheel’s lug nuts. Imagine if those came loose. What would happen is the wheel would start to wobble with a severity proportional to the number of loose lug nuts and the extent to which each was loose.
It’s safe to say that a scenario where all nuts come loose at the same time is unlikely, and it’s even safe to say it’s unlikely that they’d all shear at the same time. And if they somehow did, the wheel would fly off, and the rotor would flop around between the hub flange and brake caliper. Even if the rotor somehow fell off the car, there would certainly be nothing holding it to the ejected wheel, since the rotor simply slides over the same now-sheared studs that the wheel slides over.
A Wheel Spacer Failed
One thing I haven’t yet mentioned is wheel spacers. These have become fairly common in the automotive world as a means to improve a vehicle’s “stance.” Specifically, they push wheels outboard to make a car look wider and more aggressive.
Though it’s not clear that the truck in this video used wheel spacers, it is clear that it has had its stance widened — something that can only easily be accomplished with new wheels that have a different offset/backspacing or with wheel spacers.
The way wheel spacers like the shiny aluminum ones at the top of this section work, is they bolt to the wheel hub’s studs. This squishes the rotor against the hub assembly. The wheel, instead of being bolted to the hub assembly’s studs like it normally is, now bolts to the spacer. In this way, the spacer just acts as a middle-man, creating more space between the brake rotor hat (and thus the hub face/flange against which it sits) and the wheel, pushing out the wheel. Here’s a look at the setup courtesy of eBay seller brakeautoparts_20:
As you can see in the image above (the spacer is black in the image above, whereas it’s silver two images up), the studs that normally tighten your wheel up against your hub, squeezing the rotor, are now just being used to squeeze the spacer and rotor against the hub. The spacer has its own studs built in; the wheel slides over those, and the lug nuts tighten that wheel against the spacer.
Here’s another look:
The question many people have is whether the spacer failed.
If the spacer’s own studs failed, the wheel would have just fallen off. The brake rotor/disc would still have been attached to the vehicle via the nuts in the spacer’s bored holes. Now, if the spacer itself had failed, it would have come off and remained attached to the wheel. The rotor, though, would still be attached to the wheel hub.
And though I’ve looked at this screenshot a number of times, I have concluded every time that what fell off the truck is a wheel with an attached shiny brake rotor, not a shiny wheel spacer. A wheel spacer would have a smaller bore at its center, and there would be holes in it to accommodate nuts:
So thus, I don’t think a failed wheel spacer failure is what caused the wheel to fall off.
The Ball Joint Failed
Failure of ball joints holding the knuckle to a vehicle’s control arms is one of the primary causes of wheel detachment on modern vehicles, but I don’t think it’s what happened to the Silverado in the video.
A ball joint failure means the knuckle detaches from the suspension, which is bolted to the chassis. The wheel would still be carrying the unit bearing and the knuckle, since the six lug nuts would still be creating a clamp load between the wheel, rotor, and. hub, and the three bolts would still be holding the hub to the knuckle from the backside.
Given that there’s no evidence showing the knuckle still attached to the rogue wheel assembly (the screenshot clearly shows that there’s no big steering knuckle still attached to that wheel — there’s just a rotor), I don’t think this was the failure mode.
What’s more, a ball joint failure rarely happens suddenly, and it certainly won’t happen to both ball joints simultaneously (typically only one ball joint fails at a time, causing the tire to simply “tip”). Even if one failed and put increased stresses on the other joint, causing it to fail shortly thereafter, the steering tie rod from the steering rack would still hold the wheel in place.
In any case, ball joint failure is rarely something that happens suddenly without warning, and when it does, the wheel usually doesn’t fly completely off. This just isn’t likely what happened to the 2011 Silverado in the video.
The Knuckle Failed
What if the steering knuckle fractured? This isn’t unheard of, especially if a vehicle has been in some kind of collision, either with a curb, another car, or some off-road obstacles.
But a failed knuckle isn’t likely to violently throw a wheel out into the road. As mentioned before, the knuckle is held to the vehicle via three joints — two ball joints and a tie rod end. The wheel is attached to the hub (via its lugnuts) and that hub is bolted to the knuckle through those three holes shown above. I see no single fracture that would completely release the wheel.
This was clearly not the issue.
The Wheel Bearing Separated
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Have a look at the clip above, and you’ll see what a typical wheel bearing failure looks like. The wheel will start becoming loose as the inner and outer parts of the wheel hub (called inner and outer rings — I’ll show a labeled wheel bearing in a moment) want to separate, since the bearings that typically wedge between those parts to keep them tight have ground into dust.
If a wheel bearing gets bad enough, the center part of the hub (the part with the flange that the wheel bolts to) will actually be able to pull itself out of the bearings and outer ring, which is what’s attached to the knuckle. Have a look:
Here’s a screenshot of me pulling the inner ring out from the hub flange:
And here it is completely extracted:
That’s scary even on a driven axle where the axle’s outer shaft helps hold the bearing together via a big nut; on a two-wheel drive vehicle (like I suspect this truck is), it’s even scarier.
Indeed, since the detached flange (shown above) includes the hub studs, if this were to fall apart, it would take the rotor and wheel with it. So you’d end up with a sandwich made up of this hub flange, the rotor, and the wheel, which is being squished by lug nuts that thread onto that hub’s studs. This is not unlike what we see in the screenshot.
So this is it, right? The wheel bearing just failed — that explains the wheel coming off completely, and the rotor remaining attached.
Possibly. You see, for that inner bit of wheel bearing to become detached from the rest of the hub, it has to slide out axially, and that means it has to push the rotor out axially. And remember, that brake caliper and bracket are the way:
Not only that, but when a wheel bearing fails in the way I just described, it usually causes the wheel to wobble quite violently before failure. The video does not show the truck’s tire wobbling prior to it falling off. Here’s another look:
Witnessed and recorded the most INSANE car crash yesterday, you can see Autopilot also swerve and avoid the rouge tire for me $TSLA pic.twitter.com/csMh2nbRNX
— Anoop (@Anoop_Khatra) March 25, 2023
But it’s sometimes hard to tell from the outside if a wheel is wobbling at speed. So this failure mode isn’t entirely implausible; it’s possible that the unit bearing could have separated, and either snapped the caliper bracket right off or the rotor could have slid radially out from the caliper’s pads.
A Wheel Bearing Failed Catastrophically (Sheared)
My primary inkling is that the wheel bearing failed catastrophically. Specifically, I think the inner ring sheared, possibly as a result of fatigue — but in any case, I think it broke into two pieces.
I’m going to assume that the truck was two-wheel drive for this specific example (since it was in California, and since the screenshot does not show an axle shaft attached to the escaped-wheel and rotor), but a four-wheel drive wheel hub isn’t much different anyway, so this all still applies.
Imagine if the inner part of the hub (green) fractured, especially if it happened far outboard, not far from the hub flange. Now the wheel is no longer supporting the rest of the vehicle vertically (in the previous section where I assumed the ball bearings had worn out, you’d still have that inner tube running up against the outer ring, thus supporting the truck’s weight). This could help explain why the wheel launched the way it did:
If you look at the video, it’s not like the wheel just detached and rolled just beside the pickup — it was launched sideways. And as you can see, the bottom of it was shoved out first and the tire seemed to turn towards the left lane. Why would this happen? I have a theory.
Let’s say the wheel bearing fractures like I just mentioned. Now the bearing is no longer supporting the weight of the car. This means the caliper, which is bolted to the knuckle (which is bolted to the truck’s suspension), is going to want to fall down relative to that rotor. Again, at this point, the rotor (and the broken-off hub flange to which it’s bolted and of course the wheel) is not attached to the car at all, it’s just got a caliper hovering over it and a knuckle (with a broken off hub section) behind it.
If you look at the image above, and imagine the caliper wanting to push down, it’s going to create a load on the edge of that brake disc with a component pointing downward and a component pointing towards the front of the truck. Watch this little clip below and you’ll see that the downward force of the caliper pushing the rotor (which is inboard of the tire — the pivot point) creates a moment arm that wants to “tip” the tire such that the top moves inboard. Since it can’t move inboard due to the knuckle being there, the bottom moves outboard, just like in the clip.
The caliper also pushes the rotor forward, and since the rotor is inboard of the tire tread (again, the pivot point), this makes the tire want to pirouette about its axis, rotating outboard towards the Kia. This also would cause the wheel/rotor/broken hub to be “squeezed” and violently shot out of the truck.
The Bolts Holding The Unit Bearing To The Knuckle Failed
Another very plausible cause of this wheel leaving the Silverado is the failure of the three bolts holding the hub assembly onto the knuckle. If this were to have happened, the wheel hub would still have had to move outward towards the caliper and caliper bracket (since the back part of the unit bearing bearing sits inside the center bore of the knuckle about an inch), which would have wanted to hold the rotor in.
But I could see the back of the unit bearing escaping the center hole of the knuckle just enough to slide out radially away from the caliper in a way similar to what I described in the “sheared unit bearing” scenario above.
If all three bolts were broken, and the unit bearing were just sitting in the knuckle’s hole, the weight of the vehicle would, via the knuckle, push down on the back of the unit bearing, and this would create a moment arm around the tire’s contact patch that would tend to want to rotate the top of the tire inboard and the bottom outboard. There would be a lot of force that could break the caliper off (the caliper isn’t with the wheel nor is shown flying down the road, but it could stay with the vehicle since it’s attached via a brake hose), or – with the unit bearing now out of the knuckle’s bore – the caliper could just shove the wheel/rotor/entire unit bearing out and away and towards the Kia like I described in the previous example.
How would three bolts break at exactly the same time? Wouldn’t you expect some kind of chain reaction? Well, it’s possible two had threaded out all the way already (or broken), and the hub was just being held in by one. That would be enough to let the vehicle drive smoothly, since the back of the hub slots into that knuckle’s center bore, keeping things centered. It’s possible that what we’re seeing is the final bolt letting go, as there is substantial stress on it from the aforementioned moment arm.
My Conclusion
My initial hypothesis is that the unit bearing sheared. I spoke with The Autopian’s own suspension engineer, Huibert Mees, and he agrees, telling me:
Here is my take on it. I think it is a 2WD truck and the spindle failed. You can clearly see the brake rotor still attached so it is definitely not a lugstud failure. The rotor is still connected to the wheel by the lugnuts so it must be the spindle that failed. It is possible the bearing retaining nut came off, especially since it is the left wheel (which means the rotation of the wheel would want to unscrew the nut), and the wheel simply came off the spindle. I’m fairly sure it cannot be a 4WD truck since the driveshaft (or at least the outer CV joint) would have had to come out with the wheel if the bearing failed.
OK. I just looked up what the front bearing for the Silverado looks like and it is a bolt on unit like the one in the picture you sent (called a HUB III style). A failure of that type of bearing is very unusual. I’ve never seen it before but since the rotor was clearly still inside the wheel, it is the only explanation I can think of. The hub flange that holds the studs might have fatigued off. I still think its a 2WD truck though.
Last month Huibert wrote the article “Our Suspension Engineer Talks About The Effects Of Wheel Spacers And Wheels With Different Offsets.” In it, he talks about how a wheel spacer (or a wheel with different offset/backspacing) can affect bearing durability by increasing a key moment arm, so that may have played a role in causing the bearing failure in the first place. From that article:
…look at where the bearing load line now sits. It is way outside the ball bearing races and will cause a significant increase in the loading of the bearing — loading that it was not designed for. The life of the bearing will be reduced, and you can expect to have failures in a part that would normally last the life of the car.
And if you look around the internet, a number of Silverado owners (not of the same generation, but with the same basic suspension design) have had similar wheel failures happen.
Check out the post on Chevrolet Forum titled “Wheel assembly fell of while driving down HWY…” It includes the images above and reads, in part:
As we are on vacation driving down the HWY going 70mph, we left as if we got a blown tire. Luckly my husband had good control over the truck, which is a 2007 chevy silverado 1500, we got the truck pulled over and the tire, gas sideways under the truck! The lugs and tire with brake assembley were all together in the wheel! It looks as it the axel just broke completley in half. The man who towed us said he has never seen anything like this before.
Looking at the images, it appears that the unit bearing sheared on what looks like a two-wheel drive truck.
Another Chevrolet Forum post titled “wheel assembly came off at 60mph” is even more dramatic, features the images above and this description of events:
as i was driving home i was going 60 mph down a 3 lane road and i was in the middle lane. all of a sudden it felt like the front left tire blew out…the truck slowed down and started pulling to the left. i mashed the pedal and it straightened back out, but when i left of the pedal again it started to drift to the hard left again. i thought i had a flat so i decided to pull over and see whats up….as soon as i hit the brake pedal the truck dropped down to the ground and sparks were flying and i looked over and saw my tire flying next to me about 10 feet in the air. the tire took off, bounced over 2 cars, hit a stop sign, took some guys chain link fence out and went through his trailer and ended up in his living room. (trailer park was right next to the road) i had no brakes considering my brake line was ripped and all the fluid came out. so i was skidding down the road and hit the median…(luckily it was only a curb!) then bounced off and finally came to a stop in the turn lane.
Notice how this truck is four-wheel drive, and the bearing doesn’t appear to have sheared, it appears to have fallen apart, unlike my initial hypothesis. I don’t think the 2011 truck was four-wheel drive, and I’m not entirely sure the bearing “fell” apart.
As this forum post shows, if the bearing does fall apart, the rotor tries to move outward but is held in by the caliper; the truck straightens up when the driver touches the brake (see in bold), which clamps the caliper and pulls the rotor and hub back inboard, straightening the vehicle. Eventually, enough of this actually tore the caliper off with the rotor.
Though I can’t completely discount this type of bearing-separation as a possibility, there’s no obvious wobbling happening to the 2011 truck in the initial Twitter video. I’d expect that if the bearing came apart (whether due to an axle shaft breaking and no longer holding the bearing together in the case of this 4wd truck or just wear and tear) instead of shearing, the outer bit of the unit bearing would try to move outboard and hit the caliper; the driver would hit the brakes, it would straighten out, and this might happen a few times before the caliper just snapped off the knuckle and the wheel went rogue. That behavior is not obvious in the Twitter clip.
So based on these forum posts, and based on my look at the system in question, I still think the unit bearing sheared, though it’s similarly likely that the three bolts holding the unit bearing onto the knuckle were the culprits. These are just theories, of course, so let me know what you think in the comments below.
UPDATE (March 30, 2023 6:30 PM ET): We have new footage from the Tesla driver who released the original video clip! Check it out:
Found some additional interesting footage pic.twitter.com/OV9aeeZ1jU
— Anoop (@Anoop_Khatra) March 30, 2023
A close look shows the rotor attached to the wheel, and a small circle at the axis of rotation:
That circle looks silver, indicating that it’s clean. What would be this clean underneath a vehicle — in an area that sees dirt and grime regularly? The brake disc is clean because it gets wiped by the brake pads, but what about that little circle? The answer could be that this is a shear surface that is clean because that bit of metal is being exposed to the elements for the first time. This could be a sheared axle (but again, I think this truck was two-wheel drive), though I think it’s a sheared unit bearing.
The shiny bit in the screenshot could also be the shiny cap on the back of the unit bearing (in the case of the three bolts holding the unit bearing to the knuckle being the culprit), though that would get dirty not long after installation. Also, the the triangular-ish flange with the three threaded bolt holes — the part of the back of the hub bearings that actually touches the face of the knuckle — is nowhere to be found in the grainy screenshots. But again, they’re grainy screenshots.
UPDATE (March 30, 2023 10 PM ET): This story has been updated to discuss the likelihood of the three bolts that hold the unit bearing to the knuckle being the cause of the failure. Hat tip: VermonsterDad!
Seems logical to me. . .I had to replace these around 70K on my ’09 Silverdao. Drivers side was a fight to get off, distroyed the backing plate doing it. Bought a new one, but never put it on, got a new truck, so this part just sits in a shelf in my garage. . . But given the extra torque on the wheel offset, I would agree
OK, thinking about this a bit more. . .I kinda think maybe it was not the hub assembly that failed, the the 3 bolts that hold it on, and here is why.
1. Definitely, I think 2 wheel drive, otherwise the axle shaft would have came out too most likely. That said, I think the silver in the center is the 2wd cap. If the bearing failed, I don’t think you would see that, as it is the back of the bearing assembly. (though I suppose you could argue the failed bearing bear metal would be silver).
2. As mentioned above, a failed bearing would have vibrated or wobbled. This didn’t, it just goes. . .if those bolts fail, that thing will just pop out.
3. The police report indicated that the studs failed. . .maybe they meant the 3 bolt that hold the bearing assembly on, not the wheel studs. Maybe over torqued??
Three bolts failing all at the same time seems a bit unlikely. Obviously, the hub failing is also highly unlikely, but three bolts without any wobbling? Maybe two came out all the way, and then only one was holding it on, and then that one finally gave way? Actually, I could see that.
I’ll append the article to address this, as I think it’s plausible.
All 3 failing simultaneously would be unlikely. But 2 of the 3 could easily have backed out previously. The hub to knuckle is a close tolerance fit and I don’t think the weight of the truck is supported by the bolts as much as by that fit. It’s obviously a much larger diameter then the bolts and would therefore be much stronger. I too have had to fight to remove those hubs and destroyed the backing plate in the process. Much later I was under the truck for something unrelated and noticed one or two of those bolts were loose. They are poorly placed for access and do not have any sort of locking feature to keep them from backing out. No doubt the hub had been replaced due to the modified wheel locations and that it’s probably seen some sort of truck use in the 12 years since it was built.
on every Honda and Subaru i worked, the CV knuckle is larger than the mounting hole for the bearing, so you don’t actually lose the wheel assembly. Also, bearing on subarus seem to be shit, especially the 5×100 ones, but very easy to replace.
Even when one spends a lifetime driving on urban highways, it is extremely rare to witness an accident right in front of you. So I think it says something that I have personally witnessed THREE instances of a tire ejecting from a pickup truck into travel lanes at speed. Each instance probably had a different root cause, but regardless it sure as hell indicates a “problem area” to me.
So the first documentation of a soul ascending into heaven on YouTube and you science it all away? I mean, it was obviously the rapture. Right?
Does anyone else see it?
https://www.dropbox.com/s/ztbpi4hrevyrtfw/LeftRear.jpg?dl=0
yes, that is common on the solid rear axles. One strut is in front and one in the rear of the axle. It is one of the reasons i hate being in trucks, every time you hit a bump you also get side to side motion along with the up and down motion. This shows that much movement because it dropped a good 18″ in the front right corner.
Thanks, great explanation. However, I have to ding you a couple of points for “that may have played a roll,” which should be “that may have played a role.” Yes, it’s quite nit-picky, but after that article from Torch about grammar I had to point it out.
Maybe it was meant to be a pun.
Too much stuff rolling in this article! Trust me, I know the difference!
Why did the chicken cross the road? He lost his bearings.
He would be a rooster. Well maybe a capon I guess.
Yes I agree on the hub failing. GM trucks went to this modular design with the GMT 400 in 1988, on the 4wd K models. In 1999 when the next generation GMT 800 design was released, the 2wd models had changed to this style as well. This was done for parts interchangeability; the ‘800 models all have 6 lug wheels on the 1500 and 2500 LD models, whether 2wd or 4wd, instead of 5 lugs like the half ton 2wd ‘400s and square body trucks have. The hub replacement is fairly easy as long as you have the correct tools; I’ve done the job on my dad’s ’06 GMC. On the ’07-’13 trucks (GMT 900 in GM designation) the hub is the same between the 2wd and 4wd models, except for the 4wd models having the splined hole in the center for the axle stub shaft to go through. Those axle nuts are 35mm hex on the ’06, and are torqued to around 200 ft/lbs. So if properly installed, shouldn’t be coming loose easily!
I also agree on the use of wheel spacers loading the wheel bearings in ways they’re not designed to handle. This video is a great illustration of that….
How the heck does anyone know this kind of hyper specialized esoteric fact?
What are we if not a community of people who know hyper specialized esoteric facts?
Like knowing the difference between spacers and adapters! 😛
Your conclusion is the only reason that makes sense to me. Especially highlighting that this is likely a 2WD truck.
If you look down further in the replies to the video, one of the Tesla’s other on-board cameras caught the wheel bouncing by, and gets a pretty good look at the inside of the wheel:
https://twitter.com/Anoop_Khatra/status/1641303843697983488
Yup. You can definitely see that the rotor is still attached to the wheel. Good looking out.
Yes! I wish I had seen this before. Now the instantaneous bearing failure seems more likely to me because I can see what appears to be a protrusion the center of the wheel.
This would seem to require an instantaneous failure. Could unevenly torquing an adapter/spacer cause enough stress to the hub? I’m picturing someone going to town with an Earthquake impact wrench.
Correction: That is a wheel adaptor, which is completely different from a spacer. A spacer is just a disc of metal with holes in it, which cannot cause a failure like this. Adaptors = have their own studs, and the wheel mounts to the adaptors studs, which can or cannot be a different bolt pattern.
While you’re technically not wrong, in automotive parlance the term “spacer” is commonly applied to both the slip on and bolt on styles. Go do a Google Image Search of “wheel spacer” and you’ll see plenty of both.
The term “adapter” is generally only used when talking about spacers that convert from one lug pattern to another, hence the “adapting.” That can only be accomplished with a bolt-on style since it has to carry its own lug studs in the new wheel pattern.
Yes, but “Commonly incorrect” is still bullshit. A spoiler is not a wing, a spacer is not an adaptor. Let’s be better and help educate and use the correct words. Words have meaning. If we start using words incorrectly just because everyone else does, nothing means anything anymore.
Adaptor = has studs
Spacers = Disc with holes
2 different things. And I put 60k on adaptors to run 911 wheels on my old VW. Was fine. Used highquality hubcentric ones.
Well unless your name is Merriam and/or Webster I don’t think you or anyone else here is the official arbiter of this, so I’m still gonna disagree with you and say that “adapter” only refers to when you are changing lug patterns. Otherwise, what are you “adapting?” But I’m not about to bear this cross, have at it.
It’s adaptEr, not adaptOr
You do make a convincing argument. And you are probably correct. However it is California, and considering how Californians love to do mods and how some people never do maintainence on their vehicles I wouldn’t put money on it.
Thanks for the deep dive here and I agree with your conclusion. As a Monday morning automotive CSI agent I’m truly intrigued by stuff like this. It was disappointing to see so many people who apparently don’t understand how hub bearings work thinking it was sheered wheel studs despite seeing the brake disc still attached to the wheel. But I think a valid case can be made that aggressive wheel offset caused the hub to fail prematurely.
If this was a 4WD truck there’d be a chance the wheel would stay on since the axle nut retains the hub bearing, but more likely the CV shaft would pull out too.
As you mentioned wheel bearing failures are common on GM trucks. When I worked in internet automotive parts sales I processed probably thousands of orders for GM truck wheel hubs. It’s certainly possible the hub had been noisy for a while but the driver never noticed due to loud off road tires. Last weekend I couldn’t hear my own V8 engine with Magnaflows on the freeway over the drone of the M/T tires on a bro-dozer driving next to me.
If this was a 4WD truck there’d be a chance the wheel would stay on since the axle nut retains the hub bearing
The nut will hold for a while, but as things start flopping around, the stub on the CV can break off, or the bearing can seize and unwind the axle nut.
Yeah, it could be an instant catastrophic failure of the bearings, but I still can’t help but wonder if the hub studs were torqued so far that they snapped. If such a thing happened, then the broken studs could have been mangled enough to keep the rotor from separating. That would neatly explain what we saw in the video.
I still want someone to explain what happened to the left rear wheel. It toes in and such cannot be due to the rear axle shifting from the drop lest every time a live axle vehicle hit a bump on one front wheel the rear axle would steer the truck. Talk about bump steer!
Also, a small correction I believe is required in discussion of spacers: The original lug nuts are still used to attach the wheel to the spacer studs and new nuts are used to attach a spacer to the rotor/hub. The reverse is stated in the article and is seemingly wrong.
That is not the case with many spacers I’ve personally used. The provided nuts were low profile (shorter than stock) and meant to be used to attach the spacer to the wheel hub. Low profile nuts are required because the stock lug nuts would protrude past the face of the wheel spacer and interfere with the wheel.
Also many wheels require special lug nuts, meaning the nuts that came with the spacers may not be compatible with all wheels, but they would absolutely be compatible with the spacer. Admittedly that may not be the case with all spacers, just my own experience.
Adaptors have studs. Spacers are just discs with holes in them for lugs. Let’s please be better than the rest of the internet and use the correct words.
See my response to you above. You’re not wrong but everyone and their dog uses the term “spacers” for both styles, whereas “adapters” are used when converting lug pattern using said bolt-on style spacers. So I’m gonna keep using “spacers” interchangeably.
IDK. I think he got us cold. When making technical arguments, it’s hard to justify inaccuracy.
I’m gonna Torchinsky here and pull the “language and terminology evolves over time” card. Y’all are welcome to die on the “this is not a wheel spacer” hill while the rest of the world has agreed that it’s fine.
In fact if I wanted to be even more pedantic I’d insist he’s wrong because “adapters” only refer to a specific type of bolt-on spacer that is designed to change lug pattern (or even lug count in some cases). Go Google “wheel adapter” and you’ll see all the results change lug pattern like I just did.
No, stop, [inappropriate word]
Use the words that MEAN the things you are talking about. Spacers just space the wheels out. Disc with holes.
Adaptors = thick chunk of metal with studs, that CAN have a different bolt pattern, but don’t have to.
Stop defending using the wrong word. Words have definitions, and allow us to communicate. Using the wrong words just because idiots do is a great excuse to call tires wheels, brakes breaks, camaros cameros, and all the other stupid shit people who barely passed high school type out. USE THE RIGHT WORDS, PLEASE.
/rant
Fuck off? Really? It’s one thing to hold a passionate opinion about something and engage in spirited debate but you lost all my respect with this unnecessary outburst.
I still fundamentally disagree with your opinion on the term and unless you can point to something like an SAE paper that explicitly states what you’re saying, this is largely subjective.
BTW on my own car I have what you call “adapters,” but I pressed the built-in studs out and just use the remaining holes for my extended length wheel studs in my rear axle to go through. Does that mean they’re no longer adapters in your mind?
Yeah that is what I did with the spacers I used on my car, tossed the studs that came with the spacers and installed longer studs in the hubs/axles.
I don’t mean like F OFF MAN I mean like “f off with that bs man”. We friendly. I was just like 3 drinks in and more passionate than normal, sorry for the swears 😛
I think if the studs come from the original hub, it’s a spacer. If the studs are mounted to the disc, it’s an adapter.
Come on now, this is The Autopian. Let’s be civil; no point in being mean.
I also disagree with your point. Multiple reputable companies call them spacers, and I agree with them.
The part’s sole job is to create SPACE, and not to adapt a different bolt pattern, which is why when you type in “wheel adapter” you end up on the manufacturer “U.S. Wheel Adapter” website. That company has this on its front page:
Wheel spacer is correct in this context, but it’s totally fine if you don’t want to agree.
Preach
I do like the idea of being able to differentiate them by whether there are studs or not (adapter v spacer), but then again, I forgot about shims because I’m an idiot.
Yes. Completely different things.
Wasn’t trying to be mean, my bad. Was a few drinks in, that’s just how I talk. Anyway, they’re still different things. You could get an adapter made in the same bolt pattern if you wanted to.
Regardless, there is a MASSIVE difference in reliability/safety/aesthetics between a 10-20mm disc with some holes in it vs a 2 inch + CHUNK of billet of questionable quality with studs built into it.
Calling them the same thing just confuses everyone and then words have no meaning and you have people that don’t know anything claiming your 15mm wheel spacer is ‘dangerous’ because they saw a truck with 5″ spacers snap a wheel bearing. They’re different things, we should use different words.
I agree; it IS confusing! Those little thin plates are a totally different animal, and that should be clear.
Also, it’s totally fine! Glad to have you here contributing to conversation and being part of this community.
It happens, especially when you’re a few drinks in!
One could argue that the slip-on style is potentially just as dangerous as the bolt-on style because the slip-on style reduces the number of threads left for the factory lug nut engagement. In fact on many vehicles you simply cannot use a slip-on because the lug studs are just long barely long enough stock, in which case the bolt-on style would be the only option. Some racing organizations actually require using open ended lug nuts for this reason so you can see how much the thread engages.
If your whole argument hinges on all spacers (yes, I’m gonna keep calling them that, deal with it) being a “CHUNK of billet of questionable quality with studs built into it,” your argument doesn’t hold water. As is the case with pretty much all automotive products, quality and durability spans the whole spectrum. There are junk products, and there are quality products, and usually the price is reflective of that. High quality spacers installed properly can be totally fine.
I have plenty of personal experience using wheel spacers of both styles but I never went cheap on them. Admittedly my use of spacers is to put high offset wheels on a car in order to place the wheels roughly where the stock ones were. I made this distinction on the last article from the engineer about wheel spacers, because using spacers (of any kind) in the way I am does not place any extra load on bearings. It’s only when you change the effective track width through spacers or wheel backspacing that you run into problems, just like Mr. Silverado here.
Sorry, couldn’t understand you, you’re using the wrong terminology and I don’t know which kind you’re talking about when. 😛
I don’t give a [poopy]. This place should be better than the rest of the internet, using the wrong words for things.
https://xkcd.com/386/
Sorry, yes, I am triggered. I have over 100k on “spacers” without any wheel bearing issues or handling problems or anything, yet people will say they are dangerous, and think of the brodozers with 22s sticking out 8″ past the fenders. They’re different things. Use different words.
And today’s Pedantry Winner is…
You are indeed 100% correct. Compliments. 🙂
Yes, that exactly what I’m saying. The
spaceradapter provided nuts are used to attach thespaceradapter to the hub, not the wheel to thespaceradapter.Why do you and others keep ignoring what the police said? There’s no wobble, no smoke, and now we’re making excuses as to why no one heard a failing bearing. Either a bearing/hub failed totally and instantly or the studs failed. Both are viable, but only one has any supporting statement.
My bad, I completely read this backwards. I 100% agree with you here, and the article should be corrected.
I don’t believe the police here because:
Yay, we agree! 🙂
#4) I think it is possible. If the studs sheared, they would not be clean cuts and as such could retain the rotor. Unlikely yes, but I think indeed possible. Additionally, if the studs failed, they would also get twisted pretty hard in that moment and thus be more likely to hold the rotor.
Also, I don’t see any wheel hub or bearing parts flying out, which is another reason I find stud failure to be a viable explanation.
We have no information as to the provider of the information. They might now know anything, or they might know more than us put together.
I have yet to hear any plausible explanation for the rear. It was absolutely not the axle shifting forward. I still believe a second failure was cause by the first.
If the hub bearing failed the only things you’d see flying out are the actual bearings in the middle which could totally be amongst the debris flying through the air in the video. The wheel side of the hub flange would still be attached to the wheel (with the brake rotor sandwiched in between), and the spindle side would still be bolted to the spindle.
I simply don’t see what you do in the video regarding the rear axle, so I’m not going to address it. To me it looks like both rear wheels are solidly attached to the rear axle and I don’t see the shift in axle angle you do – my previous replies about that were just explaining how that could possibly happen. But admittedly it’s very hard to tell what the rear axle/tires are doing in a grainy video while debris from the front is flying around.
It’s the later part of the video. Something funny definitely went askew back there. I can’t un-see it.
Becuase there are not spacers on the truck, just high offset wheels. You can see that when the wheel is spinning around after hitting the car again. Even if the studs failed either those in the hub or spacer then the rotor would not still be attached to the wheel.
One MORE reason to add to my long list of reasons to not use wheel spacers.
ADAPTORS. Spacers are fine, disc with a few holes in it, bumps it out 5-25mm or so, completely safe, have well over 100k on some without issue. Adaptors, if improperly torqued or poor quality, are a completely different thing.
Bruh let it go
Never.
Yeah, especially not the spacers that have their own studs. Those spacers are a mess. I dislike those spacers.
Those are adaptors. They are fine if used properly and not EXTREME. I put 60k on a set, no issues.
seeing the long distance it took for the silverado to stop I think that, just as the guy you quote in the forum, something happened to his break lines. Meaning damage was further in than just the lugs or a spacer.
I love how you chose the rustiest example photos I think I have ever seen.
I’m sure they’re from one of DT’s favorite fetish sites…
Thanks David, I learned something today.
I’d just shrugged this off as a spindle failure.
I nearly had this experience recently on my wife’s 2005 Yukon. She had complained of a random noise, and I drove the thing a few times but never heard it. We took it on a trip an hour+ away from home on the highway doing 80 the whole way, and when we were almost home we went around a curve with a bump and suddenly the car was growling horribly like it was about to die. I slowed down and limped it home after stopping to make sure all of the lug nuts were still on. Put it up on jacks and found that the dust ring on the inside of the bearing had come off at some point exposing the bearings, and now there were a few missing and some cockeyed. Tons of play in the wheel, obviously.
Ran out to the parts store at 8pm and had it fixed by 9, but as soon as I saw this video I knew exactly what it was.
These are the kind of deep dives that make this site GREAT.
For anyone who read David’s stuff on the “old” site, just imagine how hot your phone/laptop would be right now if you had read this there!
Agreed! This is good Jal- I mean good Autopian!
Aliens, didn’t mention them at all
It doesn’t matter if there were spacers or just wheel with the incredibly wrong offset… The bearings were loaded in a way they were never designed or intended to be loaded. All the stills of the truck show that the inside edge of the tire is approximately where the centerline of a stock wheel/tire combo would be.
I have a Silverado and read the forums and FB groups and they’re FULL of people complaining about “lousy quality” of the wheel bearings, and they all come from people running stupid offsets just so they can get “the look”. I just laugh.
Being on the mechanical side of things, wanted to see what you thought about it. I would agree it was wheel bearing failure and that this was a 2wd truck. The axle shaft would have been ripped out of it or at least the outer cup would have been visible in the remaining part of the wheel. Contained wheel bearing assemblies are nice to change but they do have that one big flaw. I would consider it possible the lugnuts could have also been loose enough to cause uneven stress on the bearing and instead of the studs letting go, the whole assembly came apart. Failing that, these vehicles were not designed to have such large wheels / tires. They were not built with that in mind despite it being a very common thing to do. Engineers think differently…
One of my front unit bearings is “shushing”. Not growling or roaring, but “shushing”, like one “shush” each revolution.
After reading this, I’m ordering a new one tomorrow.
my car is currently on 3 tires and a jackstand as I await a new hub. I decided to do the wheel bearing myself as I don’t currently have a trusted mechanic (and the shop I would have used by default caught fire yesterday!), and, when I got the hub out of the bearing I wasn’t happy with the state of it. No autocross for me Saturday
Are you sure it’s not just your rotor hitting the pads at a certain point in the rotation? Is there any lateral or vertical play in the tire/bearing?
This article is why I check the Autopian multiple times a day. Any website can post the video and say “wow look at this!” but only David will dive this deep and try to explain what we saw/why this happened. I suspect that this article will eventually be used as evidence in a court of law.
The police report will just say “visit the Autopian for further details.”
Great write-up, as usual, David!
I know it’s likely an “ongoing investigation”, but given the scope that this incident has taken I wish that CHP would release photos from the scene, if only to limit speculation and misinformation. There’s only so much “zoom and ‘enhance'” that one can do.