Autopilot and Towing

[Cottonwood]

The reality is that trailer brakes aren't strong enough to stop the trailer on their own. They are just there so that the trailer doesn't act in an undesirable manner such as passing the car towing it on the left, right, or over top.

So long as you have sufficient braking on the tow vehicle the trailer just needs stability. It doesn't have to exactly match the braking power of the tow vehicle.

Another nice signal in the 7-pin trailer connector is "reversing lights" signal. Simple surge brakes don't know the difference between coming to a stop and backing up an incline. The "reversing lights" signal can be used to disable surge brakes, even if the electric brake control is not used.

 

[Cosmacelf]

If I get a call back from Tesla about this, I'll ask about the 4 pin/7 pin thing...

 

[flar]

In the U.S. 4-pin trailer connectors are for lights only (ground, running, left, right). The 7-pin connector includes +12 Volt power and a proportional, electric brake signal. See Wikipedia: Trailer connectors in North America

I would have hoped that Tesla included a 7-pin trailer connector with proportional trailer brake controls in their tow package...

If I get a call back from Tesla about this, I'll ask about the 4 pin/7 pin thing...

The graphic of the tow package option just a few posts above shows that they provide a 7 pin harness.

Autopilot and Towing - Page 2

 

[scottf200]

In the U.S. 4-pin trailer connectors are for lights only (ground, running, left, right). The 7-pin connector includes +12 Volt power and a proportional, electric brake signal. See Wikipedia: Trailer connectors in North America

I would have hoped that Tesla included a 7-pin trailer connector with proportional trailer brake controls in their tow package...

Brake controllers usually come with a dial or other way to set braking strength. It has to be this way since the weight of the trailer varies. If you are towing something light, you set it to not give as much braking power to the trailer brakes. But if you towing something heavy, you have to tell it to give more braking strength for any given input. I have found that it takes some trial and error fiddling when you first start towing something to get the right setting (you can feel the trailer brakes dragging the vehicle back if you set it too strong).

I don't know if the brake controller gets a variable braking signal rather than just on/off. I would assume it gets a variable signal.

I got a call back from Tesla (on a Sunday no less) answering my question about the Model X tow package. Unless there is some confusion (I did ask the person some clarifying questions which she will get back to me tomorrow), the Model X just comes with a 4 pin wiring harness that you can then attach to your own third party brake controller to, just like as with other SUVs and trucks. Some people here have asked about regen braking, but presumably regen braking would also trigger the brake controller, just as it triggers the brake lights now.

- - - Updated - - -

Separate question for those that tow more often than I have. I'm looking to tow about 1,000 pounds. I'm thinking that I don't need a trailer than has brakes. I will be towing down a mountain though. What do you guys think?

Perhaps their is some confusion on what 4-pin connector we are talking about. It is the brake control 4-pin connector and not the trailer 4-pin or 7-pin connector.

I just pulled this out of my Ford Expedition before I sell it to make room in the garage for the Model X. My Expedition came with a towing package (beefier alternator, trailing pins, and brake control pin.)

Image: http://i.imgur.com/rKLlM0s.png

Image: http://i.imgur.com/bTeUKdt.png

Image: http://i.imgur.com/qgRvAHy.png

Image: http://i.imgur.com/wXQ7CN1.png

Via: Brake Controller Installation: Starting from Scratch | etrailer.com

 

[vangogh]

The X's on the test track at the Tesla Factory today had hitches : )

 

[NigelM]

Separate question for those that tow more often than I have. I'm looking to tow about 1,000 pounds. I'm thinking that I don't need a trailer than has brakes. I will be towing down a mountain though. What do you guys think?

I think you'd be hard pressed to find a trailer with GWR 1,000lbs that's fitted with brakes; so the answer is no, I wouldn't worry about it. The assumption is that a trailer that light would have a low center of gravity in any case. If for some weird reason it's tall and thin, be extra careful coming down the mountain.

- - - Updated - - -

The reality is that trailer brakes aren't strong enough to stop the trailer on their own. They are just there so that the trailer doesn't act in an undesirable manner such as passing the car towing it on the left, right, or over top.

So long as you have sufficient braking on the tow vehicle the trailer just needs stability. It doesn't have to exactly match the braking power of the tow vehicle.

Good explanation. Couldn't have put it better myself.

- - - Updated - - -

I've been thinking about towing a trailer with the Model X, and it occurred to me that AutoPilot may be disabled while towing, or at a minimum not recommended.

Thoughts?

Depends what you're towing. I regularly pull a tall 2-horse trailer with a loaded weight ~4,500lbs; I had a Model S loaner with AP last week for 4 days and although I loved it I can say that I definitely wouldn't attempt to use AP with my horse trailer. Something lighter with a low center of gravity maybe, otherwise no.

 

[santana338]

Perhaps their is some confusion on what 4-pin connector we are talking about. It is the brake control 4-pin connector and not the trailer 4-pin or 7-pin connector.

I just pulled this out of my Ford Expedition before I sell it to make room in the garage for the Model X. My Expedition came with a towing package (beefier alternator, trailing pins, and brake control pin.)

View attachment 99142
Via: Brake Controller Installation: Starting from Scratch | etrailer.com

I forgot about this thread and just caught up today. If scottf200 is right then I'm curious how much of the wiring harness is included. If a 4-pin brake controller connector is included under that dash, that is great for allowing choice on which controller to use. But the hardest part about installing a 7-pin trailer connector is running all the wires from under the dash back to the trailer hitch. Can we assume Tesla is including this wiring harness to make it easy to connect either a 4-pin or 7-pin trailer connector? If not, it is going to be quite the adventure to wire this up since there is no structure underneath the MX to wire tie to like in ICE cars.

Is anyone in a position to clarify this? I know my Honda had a trailer connector stowed away waiting to be connected to my trailer harness. Etrailer had an excellent video showing how to hook everything up for a 4-pin connector. I hope the MX is this easy.

Trailer Wiring Harness Installation - 2007 Honda Odyssey Video | etrailer.com

 

[Cosmacelf]

I've asked tesla about a wiring harness and the answer always comes back, "we don't know".

 

[CarlK]

I kind of doubt AP would be available when towing not the least is certain sensors would be blocked.

 

[Discoducky]

I kind of doubt AP would be available when towing not the least is certain sensors would be blocked.

Possibly, but only rear sensors are completely or partially blocked so the front and side are still fully unblocked.

Why wouldn't AP work with full front and side view?

 

[dhanson865]

Possibly, but only rear sensors are completely or partially blocked so the front and side are still fully unblocked.

Why wouldn't AP work with full front and side view?

I'd assume lane keeping would still work but lane change and autoparking would be disabled.

TACC (speed control), navigation, etc would be unaffected.

I'd just assume they wouldn't allow lane change because it couldn't check the blind spots to the rear and sensors even if not blocked wouldn't reach to the maximum length of a trailer. I think they wouldn't allow auto parking for even more obvious reasons.

So call it partially disabled when towing?

 

[Discoducky]

With the current sensor suite on Model S that sounds like my expectation as well, but would assume it would lane change with driver intent.

 

[scottf200]

I forgot about this thread and just caught up today. If scottf200 is right then I'm curious how much of the wiring harness is included. If a 4-pin brake controller connector is included under that dash, that is great for allowing choice on which controller to use. But the hardest part about installing a 7-pin trailer connector is running all the wires from under the dash back to the trailer hitch. Can we assume Tesla is including this wiring harness to make it easy to connect either a 4-pin or 7-pin trailer connector? If not, it is going to be quite the adventure to wire this up since there is no structure underneath the MX to wire tie to like in ICE cars.

Is anyone in a position to clarify this? I know my Honda had a trailer connector stowed away waiting to be connected to my trailer harness. Etrailer had an excellent video showing how to hook everything up for a 4-pin connector. I hope the MX is this easy.

Trailer Wiring Harness Installation - 2007 Honda Odyssey Video | etrailer.com

Ken verified it comes with the brake controller wiring but the plug is different see: Installing a Tekonsha Prodigy P2 Brake Controller in a Model X

 

[ohmman]

From another thread - AP is disabled for towing. So this is resolved. Totally understandable, but it'll be cool one day when you can tow hands-free.

View attachment 106551

 

[goneskiian]

Ken verified it comes with the brake controller wiring but the plug is different see: Installing a Tekonsha Prodigy P2 Brake Controller in a Model X

That's the one! Thanks!

I went looking for that last night but couldn't find it.

 

[don123]

Autopilot works with a light, rather un-aerodynamic trailer at reasonable speeds. We just drove for 8 hours in our MX AP2 towing a trailer with a gross weight of about 1,200 lbs. If we exceeded roughly 100 kph (60 mph), AP sensed the load was too great and turned off. We then had to stop and shift into park to re-enable AP. Firmware 17.28.c528869. Good driving Tess!

 

[ecarfan]

Thanks for your report. I thought AP was disabled while towing regardless of trailer weight. When you were towing did you have the trailer lights connected to the car at the plug by the hitch?

Autopilot works with a light, rather un-aerodynamic trailer at reasonable speeds. We just drove for 8 hours in our MX AP2 towing a trailer with a gross weight of about 1,200 lbs. If we exceeded roughly 100 kph (60 mph), AP sensed the load was too great and turned off. We then had to stop and shift into park to re-enable AP. Firmware 17.28.c528869. Good driving Tess!

 

[don123]

Thanks for your report. I thought AP was disabled while towing regardless of trailer weight. When you were towing did you have the trailer lights connected to the car at the plug by the hitch?

Yes, the trailer lights were connected to the MX trailer hitch plug and they worked properly. The trailer symbol was lit up on the driver display screen. I had to disable trailer mode in the settings. That caused the trailer symbol to turn from blue to amber (caution?), and it enabled AP.

 

[ohmman]

Yes, the trailer lights were connected to the MX trailer hitch plug and they worked properly. The trailer symbol was lit up on the driver display screen. I had to disable trailer mode in the settings. That caused the trailer symbol to turn from blue to amber (caution?), and it enabled AP.

Interesting. When you disabled trailer mode, did the lights continue to work on the trailer (signals/brake lights)?

 

[don123]

Interesting. When you disabled trailer mode, did the lights continue to work on the trailer (signals/brake lights)?

Yes, the signal/brake lights on the trailer work when trailer mode is disabled.