We installed a Torklift hitch system on our Model S and took pictures documenting the installation, mounting a Saris Thelma hitch rack and Trek road bicycle, including the underbody and disassembled rear of the car. The pictures also include some shots of the barn with solar panel installation:
The Torklift hitch is a custom hitch for the Model S, available with two adapter - 1.5" and 2". It has detailed instructions on how to remove the rear bodywork, bottom panels, and bumper crossbars to install the hitch receiver. The system installs without structural drilling, using existing bolts and nuts that are part of the Tesla bumper system.
Installation is complex, and for most people should be done in a body shop. However, we have a lift in the barn and all the needed tools, so I tackled it myself.
Immediately inside the bumper cover is a stamped steel bumper cross member that is attached with eight nuts, onto studs that protrude from the aluminum body. This steel cross member covers an extruded aluminum reinforcement that is the main structural element inside the rear bumper, providing crash protection for rear-facing passengers in the jump seat (in cars so equipped).
The instructions are to remove the eight nuts holdng the steel cross member with a 17mm socket wrench, then remove eight more nuts that attach the aluminum crossbar, using a 15mm socket wrench. The trailer hitch is then mounted behind (forward on the car) both crossbars using the original nuts to hold all three crosspieces (including the new hitch) in place.
As I outlined in a separate post, we uncovered loose nuts for the steel bumper liner. The linked pictures include several that show a quality control issue when assembling my car. Three of the four nuts holding the right side of the steel bumper crossmember were barely threaded onto their respective studs. They were not even hand tight, but just started onto the studs, far away fom being seated. The fourth nut was properly torqued to 40 ft. lbs. (the torque recommended in the hitch instructions).
I seated and torqued the nuts upon installing the hitch, so no harm in our case, but it is in an area that cannot be inspected without major dissassembly, and it does make one wonder what else wasn't tightenned on this or other cars.... This issue is discussed fully in the other link, so no more about it here.
Returning to the hitch installation, there is a video on the manufacturer's website:
A small fitment issue required minor grinding on the hitch, and the two stud extenders were about 1/4" too long, so I trimmed them with a Dremmel cut-off wheel. Pictures of this are in the Dropbox link. Installation also requires cutting a pretty big hole in the bottom rear body cover, including the forward part of the plastic chrome finisher at the bottom of the bumper. The provided template suggests using a 4" hole saw on both ends of the oblong hole to get it started. I do not have a hole saw that big, so masked the surface to protect the paint and chrome, and transferred the template to the tape, drilled a starter hole, and used a jig saw to do the job. Cutting the bumper cover was the scariest part of the job.
The hitch worked great but does reduce battery range. Last night we drove 170 miles with it and a bike on a hitch rack. We began with a full max range charge (272 rated at start) and drove normally, Mostly 65 mph, some 75. We had 10 miles left on arrival, so lost about 90 miles of rated range due to a combination of low temperatures, slightly above average speed, and the rear rack. The hitch/rack/bike combo seemed to affect range about 10-15%, as we averaged 404 kwh, and normally average 340-350 on that trip at those temps (about 40 degrees) and speeds. However, we did have the headlights on as it was dark the entire way, and all of our prior trips over this route were with the lights off during the day.
Driving with the bike carrier and two road bikes are akin to pulling a parachute behind a vehicle designed for least air resistance. We did this because regular strap-on bike carriers can't be used with the aluminum body, and since the car is designed with specific attachment points for a roof rack, Tesla must have testing saying exterior wind disruption isn't terribly bad. I figure that a rear hitch mounted rack is less disruptive than having two bikes mounted on the roof.
Since we had almost no range cushion with a max range charge for this trip, I am further reducing range planning allowance for this car. We now think of the 85 kwh Model S as a 175 mile range car for normal trip planning, but 155-160 with the bikes on the hitch rack.
We have used the hitch a number times of since since the original post above and have the following updated observations:
1) Quality - the hitch has performed flawlessly for both the bicycle rack and to tow a small utility trailer. We originally bought the 2" receiver adapter and later added the 1.25" receiver, which is a lot lighter and less bulky. We have had no quality issues with the hitch and good service response from the manufacturer.
2) Impact on warranty - We limit towing to under 1,000 pounds, as the car does not have a trailer rating. Most of our trips have been with just the Saris bike rack, but twice we have pulled an 8' utility trailer loaded with an ATV, about 60 miles each way to a servicing dealer. We also use it often to make 20-mile runs to the dump from our farm (we have no trash pickup in the boonies). One time we used it to tow a dual-jet ski trailer for three miles to a boat ramp, on flat roads. Basically, we limit its use to lightweight trailers that do not need or have onboard brakes. TM seems to tacitly approve of the hitch, as they provided space for presentation as Teslive and other Model S events. My car has been serviced several times since installation, and the service center techs commented on the high quality of the hitch. Although lawyers may worry more about fine print, I see nothing that towing light loads could do to damage the car, and it seems logical that prudent use will not affect warranty coverage.
3) Impact on range - this is the unhappy side of doing anything to the Model S low-profile envelope. We generally use about 290 -300 wh/mi driving the "bare" car with two occupants and a medium size dog between our houses, over mostly flat roads, 190 miles each way. In lower temperatures this climbs to about 335 wh/mi. Our average since new is 325 wh/mi, including all miles driven, with lots of full-out test drives. Unfortunately, putting the Saris Thelma bike rack on the hitch receiver, with two carbon fiber road bicycles, pushes the wh/mi up to 425-430 at 55-65 mph, under identical conditions, or about 125 wh/mi, reducing range by 28%. This cuts range on a full max range charge to below 190. The loaded bike rack is essentially like pulling a parachute behind the car. The bikes stick up slightly above the roof line and destroy aerodynamic integrity. The pictures in dropbox show how disruptive the rack and bikes can be.
Our battery charge ran down to zero miles last night at exactly 188.5 miles after a full range charge and driving 55-65 mph in moderate temperatures with no hard acceleration. This says we lose about 74 miles of range due to using the bike rack. This makes it impossible to take the bicycles back and forth between houses in cold weather, and it is risky in moderate temps despite a max charge. The bottom line is that range loss eliminates using the hitch in about 50% of the cases that we would like to employ it. However it does give an excuse to buy two more bicycles for the second house.