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2013 Tesla Model S: Is This the Sort of Trailer Hitch He Hit?

November 19, 2013

2013 Tesla Model S

We've all heard about the most recent Tesla fire, the one that happened in Tennessee over a week ago. The driver reportedly remains a Tesla fan after hitting a "rusty three-prong trailer hitch" that was "sticking up with the ball up in the air."

As he tells it, he couldn't miss the object, which subsequently passed under the car and made hard contact. "I felt a firm "thud" as the hitch struck the bottom of the car, and it felt as though it even lifted the car up in the air."

But I haven't yet found a photograph of the actual "rusty three-prong trailer hitch" in question.

We do a lot of towing tests here at Edmunds, so we have a collection of hitch equipment in our garage. I went downstairs and inspected what we had to see if any of it made sense.

2013 Tesla Model S

The "three-prong" description immediately brought to mind a load-equalizing hitch, a very common hitch setup that nearly all travel trailers are towed with because they tend to be quite nose heavy. The 3-foot spring bars are like wheelbarrow handles that hold up the back of the truck and distribute excess nose weight back onto the trailer axles.

But it's very unlikely the spring bars were attached like this in this scenario. They're only in place if a trailer is in the act of being towed, and no one has said anything about a trailer crash preceding the Tesla incident.

2013 Tesla Model S

When the spring bars are absent, the hitch head indeed has a 3-prong appearance. Folks often leave this part plugged into their truck even when they're not towing. And it's easy to imagine someone forgetting to insert the secondary retaining pin and have the main pin vibrate loose and fall out.

Tesla or not, it'd be a formidable chunk of debris for any car to hit no matter how it wound up on the road. These things are pure steel. And that 2-inch shaft, the part that plugs into the hitch receptacle, is solid, not hollow. Each one of these weighs about 50 pounds, a figure that came from our own scale in preparation for our most recent towing test.

2013 Tesla Model S

Here's the smaller of the two we own sitting ball up, as described in the driver's account. Imagine a Tesla Model S arriving on the scene left-to-right at 70 mph, the speed the Tennessee car was travelling at impact.

Like ours, that car had air suspension, so at that speed it would have been running along in Low mode with 5.2 inches of ground clearance under the battery box. My water bottle is 8-inches high. The hitch head is quite a bit taller. The math doesn't work out well.

2013 Tesla Model S

These hitches are bottom-heavy where the absent spring bars are meant to plug in. It wants to sit this way. If hit from the left, the initial impact could tip it up like this and present a 2-inch square solid steel spear to the underside of the car.

Even if it wasn't oriented in this position, it's clear an equalizer hitch like this would do major damage to any car that ran over it. And this could easily explain why he thinks his Tesla got lifted off the ground. Why the quarter-inch battery box sheathing got torn open.

So why is he still a Tesla fan? For one, the fire didn't really get going for five minutes. After the impact he got two levels of warnings, the first of which he ignored in an attempt to make it home. He heeded the second, pulled over, got out and began to collect his things. Then the first smoke appeared underneath. At this point he says he walked about 100 yards away. Flames didn't appear at the front of the car (ahead of the battery) for another two minutes.

But he also says this: "I am thankful to God that I was totally uninjured in any way from this impact. Had I not been in a Tesla, that object could have punched through the floor and caused me serious harm."

From this I take it the size of the object he hit, the thud and the lifting off the ground made a real impression on him. It's another clue that makes me think my equalizer hitch theory is plausible. Any of the above objects could easily cause "serious harm" if hit by a standard car. After all, the sheetmetal under our heels is not much thicker than a half-dozen sheets of paper. We might not have feet left if we ran over one of these.

To his point about the impact itself, the Tesla Model S's underfloor battery box represents a 4-inch thick barrier that prevents objects like this from piercing the cabin. That's no bad thing from a direct-injury point of view. He's probably right.

2013 Tesla Model S

Am I overestimating the size of the hitch? Could it be a regular one like this? You be the judge. For my part, I don't see any "three prong" resemblance. And the above 2-inch receiver with 2-inch ball isn't quite 5 inches tall. It's quite possible one of these could pass cleanly underneath and make zero contact.

But this is all speculation. Tesla has not responded to my request to interview the driver or share these pictures with him to see if they are similar to the thing he hit. I'm hoping we'll know for sure someday, and that goes for the similar incident in Kent, Washington, too.

Dan Edmunds, Director of Vehicle Testing @ 11,923 miles

Most Recommended Comments

By stovt001
on 11/19/13
3:26 PM PST

Amazing how gasoline powered cars burn to the ground due to damage or poor maintenance literally any day of the week, but an electric car does the same thing and everyone freaks out. Heck Ferrari 458s were burning down faster than they could build them when they were first released. The fact that it took a few minutes after he stopped (and after he drove for some time with the damage) just for the flames to appear is encouraging.

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By mercedesfan
on 11/19/13
4:20 PM PST

@stovt001, I completely agree about the overreaction, but electric cars are a unique case. I feel completely safe in my Model S because it is obvious Tesla did their job when it comes to isolating the battery pack. However, Li-ion batteries in general are incredibly dangerous if they combust so some initial reaction was warranted. Working in aerospace, I have seen enough lithium fires during testing to know that I would rather be around a gasoline fire any day. However, with each of these fires it just becomes more obvious that those issues are not present with the Model S because Tesla did such a good job with their battery pack design. General discussions of electric vehicle safety are valid, but this Tesla witch hunt is crazy.

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By djwdjw
on 11/19/13
3:18 PM PST

Tesla has apparently decided to roll-out an firmware update without any supplied documenation that a) raises the LOW ride height to begin with and b) disables LOW at highway speed on all cars (previously this was the default at highway speed, now STD is). You should verify the details independently, but it appears this change was made to all Model S cars with the air suspension option. Done over the air, without owner permission/consent (the change was not documented in any release notes). Changes in secret - they must feel a sense of entitlement and arrogance to make any changes they want to owner's cars at any time. TesNSA?

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