Class 3 Tow Hitch For Model S

[arman1010]

I'm looking to take on this project I need help with the electrical... How to wire the lights and power delivery.

Also thinking it might be cool to wire an Inverter to the back to get power to a Trailer

@arman1010 , You got time to help? LOL I'm in Richmond Hill....

That's great. For tge wiring harness I wanted to but actually didn't end up pulling the 12V+ all the way from the battery‚ instead I tapped into the wire for the power tailgate.

Putting inverter in the trunk is probably not a good idea (unless u put a very low powered one)‚ considering the distance from the battery‚ because for DC current the farther the distance‚ the thicker the wire required. Frunk will be the best place for it because you will need a very think wire (like 0 or 00 aws) to hook it up to the battery.

 

[Anhinvestments]

It is a shame that most responses on forums are from individuals that have no clue about a subject, but have a strong opinion.

I am a mechanical engineer that has worked for Nasa and Boeing and have been rebuilding cars since the 90s. There is one reason alone why Tesla does not have a tow rating for a Model S and it is the same reason BMW does not provide tow ratings for their cars and that is "It will take away from their SUV/ crossover sales". A model S can safely tow whatever the equivalent equipped Model X can as they have near identical brakes, drive train, frame rigidity, suspension, wheelbase, and overall weight. The model S lower center of gravity makes it less likely to flip or jack knife compared to a Model X

I have a BMW 5 series with over 400 lbft of torque and has no tow rating, but BMW will provide a tow rating for their tiny little X1 that shouldn't be towing anything. I ordered a class 3 hitch from Europe and towed my 21 ft 4500lb boat much better than my friend could in his 4 cylinder X1.

Most important things if you tow. Make sure the tongue weight is 10% of towed load, never tow more than the lowest weight rating of the hitch, ball adapter, trailer gross weight, or trailer tire max weight. If you are towing a heavy load near 5000 lbs for long distances, you may need to increase the psi of your rear tires by 5psi.

 

[Anhinvestments]

It is a shame that most responses on forums are from individuals that have no clue about a subject, but have a strong opinion.

I am a mechanical engineer that has worked for Nasa and Boeing and have been rebuilding cars since the 90s. There is one reason alone why Tesla does not have a tow rating for a Model S and it is the same reason BMW does not provide tow ratings for their cars and that is "It will take away from their SUV/ crossover sales". A model S can safely tow whatever the equivalent equipped Model X can as they have near identical brakes, drive train, frame rigidity, suspension, wheelbase, and overall weight(The Model X rear tires have a higher load rating, but even the 19" Model S tires with only a 96 load capacity can withstand the 500lb tongue load of a 5000lb trailer) . The model S lower center of gravity makes it less likely to flip or jack knife compared to a Model X

I have a BMW 5 series with over 400 lbft of torque and has no tow rating, but BMW will provide a tow rating for their tiny little X1 that shouldn't be towing anything. I ordered a class 3 hitch from Europe and towed my 21 ft 4500lb boat much better than my friend could in his 4 cylinder X1.

Most important things if you tow. Make sure the tongue weight is 10% of towed load, never tow more than the lowest weight rating of the hitch, ball adapter, trailer gross weight, or trailer tire max weight. If you are towing a heavy load near 5000 lbs for long distances, you may need to increase the psi of your rear tires by 5psi.

 

[dmwahl]

Torklift is now starting to sell an updated version of their Model S hitch rated for 4000 lbs total, 400 lbs tongue. A couple people have already ordered and received them. Model S Trailer Hitch Installation has more of the discussion.

 

[ThomasD]

What is the payload capacity of the model S?

 

[dmwahl]

What is the payload capacity of the model S?

I think around 1000lb, you'd have to look it up to get an exact number.

 

[peakay]

Well done @arman1010! I am getting ready to do the same thing and I have already marked my Drawtite Model X hitch with the holes from a Model S Ecostealth hitch.

In step 11 you describe cutting additional notches to fit the bumper panel over the hitch. Is that visible from the exterior when it's all assembled? Do you have some pictures of that?

I was finally able to finish the project. It took a while but I cannot be happier with the way it came out. I have followed the same steps as @Evoforce‚ except that all his heard work saved me from all the trial an error that he had to go through. Thanks @Evoforce.

These are the steps I followed:
1. Ordered a Class 1 Model S and a class 3 Model X Hitch( Drawtite 24958 & 76143)
2. Used the model s hitch to transfer the bolt pattern into the class 3 hitch (remember the new hitch will be installed on bottom 3 rows of bolts and the top row of bolt will remain unused)
3. Took the Class 3 hitch into a machine shop and drilled 4 new holes and adjusted the the top inner holes on each side
4. Built an isolation circuit using Optocouplers for the 7 pin trailer hitch connector so that the trailer lights donot draw power from Tesla light circuits
5. Custom built a wiring harness using the isolation circuit combined with Takonsha ZCI circuit isolator (Yah its a bit of an overkill)
6. Removed the rear outer bumper cover following the Uhaul hitch installation video
7. Removed the bumper support
8. Cut and installed a layer of heavy duty pastic over the bolts so that the hitch doesn't touch the aluminium body and cause any corrosion issues
9. Cut the plastic under panel so that the hitch receiver can stick out.
10. Installed the 7 pin plug on the plastic under panel and pulled the wires through a grommet under the trunk.
11. Cut 2 additional notches on the plastic underpanel right behind the bumper light reflectors and two more near the center so that the hitch flanges can slide into those grooves
12. Installed the bumper cover‚ pulled a 30amp positive all the way from the battery (following UHaul wiring harness video) and completed the wiring harness installation Andrew braught a few extra 12V outlet in the trunk area by afding a new fuse box.

Here are the parts I used:
1.https://www.amazon.ca/gp/aw/d/B07121N4YV?psc=1&ref=ppx_pop_mob_b_asin_title
2.https://www.amazon.ca/gp/aw/d/B0721TDDMG/ref=yo_ii_img?ie=UTF8&psc=1
3.https://www.amazon.ca/gp/aw/d/B07WWHFJKS?psc=1&ref=ppx_pop_mob_b_asin_image
4.https://www.amazon.ca/gp/aw/d/B001EP0HPI?psc=1&ref=ppx_pop_mob_b_asin_image
5.https://www.amazon.ca/gp/aw/d/B07V2MVM2K?psc=1&ref=ppx_pop_mob_b_asin_image
6.https://www.amazon.ca/gp/aw/d/B0834WD483?psc=1&ref=ppx_pop_mob_b_asin_image

I used the following rig:
1. Trailmanor 3023 popup camper (2900lb empty weight)
2. Takonsha Prodigy RF wireless break controller
3. Camco Eaz Lift weight distribution hitch with sway control.
4. Receiver height was approximately 10" with air suspension in standard mode. The tongue height when level was around 19". The ball was 3"‚ so I used the hitch shank in a 6" rise configuration.

Initial test results:
1. The hitch feels very secure.
2. The bumper feels solid over it‚ even without the stock bumper support underneath
3. The towing experience was factastic. I drove over a bridge while there was a wind gust adviaory and still didn't feel a thing. There were no swawing and had no issue maintaining the center of the lane. If it wasn't for the moaning and rattling noises coming from the hitch I wouldn't even know that I was towing something.
4. The auto pilot performed beautifully.
5. My weight distribution hitch was distributing very little weight because it wasn't properly setup (as I didn't have the required torque wrench). Nevertheless‚ the load was very steady and the experience will only get better when I set it up properly
6. Energy consumption without the rig that day was about 180Wh/km. Considering that I was pulling a flat box befind me these were the numbers:
A) at110km/hr I was burning 352Wh/km
B) at 100km/hr it was 340
C) at 90km/hr it came down to 320

Lessons learned:
1. Must use a backup camera behind the camper
2. The rattling noise from the receiver can unsettled inexperienced drivers. Use a tie in bolt clamp to address that (Trimax THC200 Univeral Anti-Rattle Clamp Fits 2" Hitch, Chains, Clamps & Hooks - Amazon Canada)
3. Use Lithium Dry Grease on all hitch friction surfaces

Next Step:
1. Continue gathering range data in different driving conditions
2. Properly configure the weight distribution hitch and measure each axle wieght by taking the rig into a weighing station
3. Program different breaking profiles for the prodigy break controller in order to maximize the regen from forward momentum but still having full breaking ability at the finger tips.

For anyone who maybe interested but cautious about this mod‚ consider the following:
1. All components that impacts towing performance or parts that are impacted by towing are identical between Model S and Model X.
2. Your Model S is even heavier than certain year models of Ford F150
3. Tesla cannot deny any warranty unless they can prove that the claimed damage resulted directly because of the mod.
4. Range will be severely impacted by towing. For my use case‚ I am hoping to get at least 50% of the rated range while towing.
5. Even if I don't tow with the vehicle‚ having the class 3 hitch will allow me to use up to a 500lb cargo carrier on the back.
6. Most importantly‚ consider your local laws regarding towing and follow them

Hey @arman1010 couple questions:

1) Did you just leave your bumper support out? Any issues

2) Your hitch looks like it sticks out further than @Evoforce 's does. Is that just due to facelift vs non facelift rear bumpers? His looks like it sticks out just past the little chrome rib on his.

Thanks!

 

[peakay]

Well done @arman1010! I am getting ready to do the same thing and I have already marked my Drawtite Model X hitch with the holes from a Model S Ecostealth hitch.

Hi @jjvan - Can you describe this process? Did you just mate the two back or back or ? I wasn't sure if they are truly symetrical side to side or not, so wasn't sure if back to back would work. Thanks.

 

[jjvan]

Hi @jjvan - Can you describe this process? Did you just mate the two back or back or ? I wasn't sure if they are truly symetrical side to side or not, so wasn't sure if back to back would work. Thanks.

Instead of modifying the Model X drawtite hitch, I ended up installing the new version Model S Torklift Ecohitch Stealth Stainless x7201s that is rated for 4000lbs. With that hitch all 8 bolts per side are used and the original bumper support is not re-installed.

Before that when I marked the X Drawtite hitch, I put the old version Model S eco hitch back to back on the drawtite hitch to mark the holes. I never drilled out the holes and sold that hitch to a Model X owner after the new version of the Model S eco hitch came out.

 

[arman1010]

Hey @arman1010 couple questions:

1) Did you just leave your bumper support out? Any issues

2) Your hitch looks like it sticks out further than @Evoforce 's does. Is that just due to facelift vs non facelift rear bumpers? His looks like it sticks out just past the little chrome rib on his.

Thanks!

1. Yes. I left out the bumper support as well as the additional 'so called' bumper reinforcement that comes with third row bucket seats option. Without the support the plastic bumper cover is a bit mushy in certain places but my kids stood on that many times when getting in and out of the trunk and I never had any issues.

2. Not sure. May be a refresh thing. May be just a visual illusion. When I look streight down from the bumper edge I cannot see it. Here are two pics from the side. One standing up and one sitting down. Sorry its a bit dark but u can zoom in and check.