Tesla Tests Towing With Model S

MAR 18 2015 BY ERIC LOVEDAY 47

A Tesla Model S caught testing with a tow hitch and trailer? (via reddit)

It’s an unlikely sight, but we figure this is some sort of Tesla Model X test mule, so it makes sense then to test the towing capabilities in the real world.

We don’t expect to see the Model S get an official tow rating/capability ever, as that’s one of the biggest reasons buyers will choose the X over the S.  Giving the S this ability would certainly hinder Model X sales.

Officially, Tesla promises that the Model X will be tow-rated, but the automaker has not yet announced a pound figure.  Our guess is 3,500 pounds, or inline with what small to midsize ICE crossover can typically pull.

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47 Comments on "Tesla Tests Towing With Model S"

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I don’t think the i8 can do that! And most certainly the i3 even with the Rex in it.

That’s not a small trailer either

Thats a pretty small trailer. I can’t remember the last time I saw a smaller trailer that wasn’t attached to a bike.

Not that small a trailer… if it was filled with water or dirt it would be a giant load for most passenger vehicles.
I should think if they can keep the tongue weight low the Tesla family ought to be able to tow alot of trailer weight… just probably need to keep it under the weight of the car to keep the tail from wagging the dog.

Since the Model S has an independent rear suspension (IRS) rather than a live axle, the added tongue weight would put additional wear on the inner tread of the rear tires The added weight on the IRS would make the rear tires pitch in, putting more of the weight of the rear of the car onto the inner tire tread. That’s why all real pickup trucks still have solid live rear axles; they spread the extra payload evenly across the entire tire tread. The Model S with the bigger rims already eats tires. Towing heavy loads with the bigger rims would only make this problem markedly worse.

Model X is built differently, reinforced expressly for towing.

Reinforced or not, the additional tongue weight of the trailer will ALWAYS cause the IRS to pitch the tire inward and result in more wear on the inner tire tread.

You seem quite convinced! 🙂

Would air suspension be able to help with evening out the load?

I read it is the biggest U-Haul is renting.

According to the U-Haul website that is a 6X12 trailer rated at 2,670 Lbs load, empty weight of 1,730 Lbs total GVW of 4,400 Lbs. Mark, not really a small trailer.

Interstate 680 is in California. I can’t make out if those are manufacturer plates. Could this be just a regular Model S owner who put on a trailer hitch like K-Man did to his Model S?

On closer inspection of the pic, it looks like there are sensors attached to the wheels. It was difficult to see them on my smartphone’s small screen.

Youre right sensors front and rear attached

680 is a freeway relatively near the Tesla factory. And you can see various monitors on the car. It is definitely for testing.

why would you not tow rate the Model S.
The Outlander PHEV is tow rated to 750kg braked and un-braked.

Sorry should have said the Outlander PHEV is Tow Rated, NZ = 750kg and Aust = 1500kg

Don’t tow rate the Model S to get people to buy the Model X (which will probably cost a bit more).

Why are cars that are tow-rated in the EU with smaller engines not tow-rated in the USA?
Because it’s more profitable that way.

Looks to me like the Model X is coming along nicely and beta testing. The towing capacity could be higher if the chassis can take it. The electric motors certainly have the torque to be better at towing than ICEs. So… Tesla has proven the large EV with long range concept, then all wheel drive, now towing, soon economy 200 miler, eventually trucks and vans. When will the big 3 do something cool and not derivative.

Can’t wait for Tesla to show Ford how this is done.

(Of course if FoMOCO were a serious player in the future of transport and not so squeamish about their quarterly growth… the Aluminum F150 would have been available in a 100kWh batteried version with a monstrously strong motor or pair of motors. They could do it… they could have done it long ago.)
California Cars FTW over old industrial Detroit MI.

“The towing capacity could be higher if the chassis can take it. The electric motors certainly have the torque to be better at towing than ICEs. So…”

I would think the limitation on towing is due to the inverter, motor, and battery overheating and going into reduced power mode, especially when going up a long, fairly steep incline at highway speeds (70 mph). The Model S powertrain overheats and goes into reduced power mode after less than one lap when it’s driven hard on a race track. The same would occur if the Model X were towing its maximum load up a steep incline at highway speed for an extended period of time, such as when towing a trailer into the mountains. You just can’t drive the Tesla powertrain hard for more than short bursts. This is a hardware problem that can’t be fixed by an OTA software update. Perhaps the upcoming silicon carbide (SiC) power semiconductors for inverters will remedy the problem. Toyota is currently conducting field tests in Japan with SiC power semiconductors that it has developed.

http://www.hybridcars.com/toyota-hybrid-tested-with-sic-power-semiconductors/

Think Big! Sti!
Put in a bigger motor(still small), a bigger Stronger)inverter and more batteries, and you will tow anything better than an ICE truck.
Giant mining trucks and trains have electric propulsion because it is much more efficient.

“Giant mining trucks and trains have electric propulsion because it is much more efficient.”

And they are “hybrids” too. Usually with diesel engines…

Towing will reduce the already limited range of a BEV, and perhaps reduce the speed at which it can be safely driven. But there is a much more important consideration for Model S owners:

Towing puts added stress on the power train, and the chassis. If the car isn’t built for it — and the Model S isn’t — then towing anything but the lightest loads isn’t a good idea. The Model S already has an “issue” with misalignment between the motor and the gearbox — that’s why they’ve had the “milling noise” problem. Common sense suggests whatever stresses in the drive train cause the “milling noise” would be made worse by towing.

Bottom line: The Model S was not designed or built to tow. Hopefully the Model X will be somewhat better in that regard.

Bingo. Rated towing capacity is based on towing up a grade and addressing cooling concerns, not just how big of a boat you can pull down the freeway on a flat road.

Don’t understand why this is news, at all. Some people have attached tow bars to their Model S. Even if someone thinks it looks like somebody put sensors on the wheels, that doesn’t mean it’s an official Tesla test. I suppose Tesla does need to know how a dual drive “D” Model S will handle towing, so there does appear to be a logical reason for Tesla to do such testing. But finding a reason for Tesla to do such testing does not qualify as evidence it is -doing- such testing. Furthermore, it seems bizarre to me to claim this is a Model X test, when it’s clearly a Model S. * * * * * Is it a “big” trailer? Well, compared to a camper trailer, it’s pretty small; an open-topped trailer with relatively low wind resistance. In fact, there aren’t a lot of trailers out there with lower wind resistance than this one. I think even the smallest enclosed U-Haul trailer would have higher wind resistance. Sure, I’ve seen smaller single-axle trailers, such as ones which held a single motorcycle or a couple of bicycles. But I haven’t seen many with smaller frontal area than this actually being… Read more »

Well, it can be a Model S being used as a mule with a Model X drivetrain.

Sure, but why would we see that at this late date? We’ve already seen pictures of more than one pre-production Model X on the road. Why would they still be testing with mules modified from the Model S at this point?

Reportedly, the Model X has a wheelbase 2 inches longer than the “S”, and has a beefed-up rear suspension. Assuming that’s correct, you couldn’t put an unmodified Model X drivetrain into an “S”, due to the shorter wheelbase.

Towing tests with a modified Model S seem rather pointless to me when it’s this close to when the Model X will actually be entering production.

However, Speculawyer’s comment about this photo being taken near the Tesla factory does make it appear more likely that it’s an official Tesla test, even if that doesn’t make any sense to me.

“We don’t expect to see the Model S get an official tow rating/capability ever, as that’s one of the biggest reasons buyers will choose the X over the S. Giving the S this ability would certainly hinder Model X sales.”

Using that logic, Tesla shouldn’t have made an all-wheel drive version of the Model S. And yet they did. If the Model S and Model X cost about the same, why would Tesla care if a given person chooses one over the other?

Well, having the AWD D model probably did reduce potential Model X sales. But it did allow Tesla to get the AWD technology to market faster and allow them to raise their average sales price by providing a new toy with even faster acceleration.

That is not a light trailer, I rent that one a lot. If it’s the ramp model the trailer weighs 2,400 lbs empty.

But with 2 axle…

Also 2400 lbs even with 1100 lbs load is well within the towing capacity of the compact crossover such as CRV/Rav… Typical Class II hitch.

Plenty of folks have put a tow hitch on their Tesla-powered RAV’s. Can’t tow things far, but great for hauling stuff around town.

someone should make a trailer with regenerative braking on it.

Why? The car already has regen in it. When slowing, the trailer will push the car, which can recapture the energy itself.

Regenerative braking is “motor braking”, done by switching the electric motor to generator mode. Kinda hard to do with a trailer, which has no motor!

I’d wonder whether the X will have a beefier gear box than S’s murmering one.

If the things are wearing out with no trailer, using the same gearbox with an additional loading will be an embarrassment.

They’ve had so many problems with the S gear box it doesn’t surprise me they have actually started to endurance test the X Box before they ship it out the door. We called it “shippin’ shit” in the industry.

GM has test facilities where the can just run 10 million cycles on the transmission in a test cell 24 hours a day. Tesla does not.

So runnin’ on the road with a load is the way to go.

Funny all the yamerring about the simplicity of the Tesla design….. the “more complicated” Volt has a zero failure record.

My appreciation for the Volt, and what appeared to me to be its overly-complex engineering, certainly has grown over time. The lack of reported problems is one big reason for that. GM delivering a nearly trouble-free PHEV right out of the starting gate is an impressive achievement.

But it’s hardly fair to hold up the Model S as an example by which to compare the reliability of BEVs to gas guzzlers. The Model S is the first mass-produced car from a new car company. I daresay that the first car GM produced wasn’t as trouble-free as the Volt!

Legacy auto makers have had more than a century to work out the mechanical problems in gas guzzlers. A century from now (or even 20 years from now), I’m confident the average BEV will have significantly fewer problems with hardware than the average gas guzzler today. (But with ever more complex software, that will be increasingly problematic… especially in self-driving cars.)

I believe it’s an S with the X drivetrain. The trailer with water or solid weights is testing capability.

Probably. But if they are working on towing for the X, why not test the S as well? Could appeal in Europe where people tow all the time with cars way less powerful, and maximum towing speeds are low.

A little research:

This is a 6×12 dual axle, trailer, the largest utility trailer U-Haul offers.

This Model S was towing anywhere from 1,730 lbs (empty weight) to 4,400 lbs (gross vehicle weight), per U-Haul specs.

It looks from the photo like the trailer isn’t holding much of a load. Of course, if those are “solid weights” as one post suggested, looks could be deceiving.

At any rate, it still seems more likely to me this is part of a long-term towing test of the dual-drive Model S, rather than a belated pre-production test of an “S” modified to be a Model X mule.

The ability to cool the motors effectively is what will make the primary difference between being rated for towing or not.

Am expecting the tow-rated X to have a higher capacity cooling system than the S.

They are also likely to limit maximum sustained power output to a level the cooling system can be effective at.

This one is definitely going to require the car to be smarter than the driver. First thing some idiot is going to try to do is lead-foot it up a long grade with a heavy load.

Tow rating is one thing, what effect does towing have on driving range? You tow a trailer with an ICE vehicle, your MPG goes down substantially

Towing is going to have an even bigger impact on EV range than it does on a gas guzzler’s MPG. Plug-in EVs have rather limited energy available, and so are engineered to be as energy-efficient as possible. As a result, the extra energy required for towing will have a disproportionate effect on range.

However, most of the energy drain from towing on the highway will come from wind resistance, not how heavy the load is, unless there’s a lot of hill-climbing involved in the trip.

There is a silver lining to this cloud: It is generally recommended that drivers limit top speed on the highway when towing. For Model X drivers who do so, that will help mitigate the range loss.

Maybe Tesla Should build a line of custom Tesla Trailers for Utility towing and Camping, that are highly aerodynamic – which they could allow to be towed at higher weights/loads, and have a lower rating for towing other stuff? Since the Car can tell that it is about to be plugged in and opens the charging port when the Supercharger cable & plug approach it – they could also make a communication system between the car and their custom trailers for similar purposes – to first – know it’s their trailer, and second – to even know the weight on the trailer!! With a little bit of engineering – the trailer tongue could also tell the car what it’s tongue weight is (using a load cell in/at the ball, or in the tongue right above where it sits on the ball)! Beyond that – I would bet they could develop a future system so that a utility trailer is also a range extender – with a newly added Tesla Trailer Power Port (TTPP) that is like their supercharge port – but with live drive power transfer capabilities, that only opens it’s door when the Tesla Power Trailer is connected! (Much… Read more »