Tesla Motors Club

As winter arrived I was excited to strap a roof rack on my Model 3 and take it to the mountains. I quickly discovered little information out there about how it would impact the range. Given the long cold uphill drive and variable weather conditions, I was determined to find the highest efficiency setup and characterize it for route planning. I started with a stock TM3 LR AWD, keeping as many variables constant as possible, and did 20+ runs up and down the highway gathering data. I tested with both the SeaSucker Monkey Bars and Tesla's Roof Rack, with various configurations of snowboards, carriers, and fairings.





Additional pictures, charts, and raw data: Model 3 Roof Rack Options - Comparing Efficiencies

TL;DR compared to stock TM3 LR AWD 18":

• Tesla Roof Rack -- 1.6% range loss
• Tesla Roof Rack + Yakima FatCat 6 Evo -- 17.3% to 19.6% range loss
• SeaSucker Roof Rack + Thule 91725 Flat Top Ski Carrier -- 26.7% range loss
• Aero Wheel Caps Removed -- 5.4% range loss
  

Test Procedure

1. Get on the highway going 70mph with autopilot engaged and reset the trip meter.
2. Drive 6.5 miles south, gaining about 130 feet in elevation.
3. Log the Wh/Mi, disable autopilot, and get off the highway
4. Get back on the highway going north and do the same thing again. This time losing about 130 feet in elevation.
5. Average the north and south results together.

I avoided traffic during the trials to not skew the data and threw out any significant outliers due to road conditions. I tried to test when the wind was at a minimum but this seemed to be the most significant variable I couldn't completely control.

Controlled Variables

• 55-60°F outside temperature
• Dry highway road, minimal wind
• 70mph on autopilot
• HVAC off
• Radio @ 25% volume
• Tires @ 42 psi cold
  

Configurations Tested

• Baseline: Tesla Model 3 Dual Motor Long Range, 18” Wheels w/ Aero Wheel Caps
• Config 1: Aero Wheel Caps removed
• Config 2: SeaSucker Monkey Bars, Thule 91725 Flat Top Ski Carrier, 2 snowboards bindings down, Yakima Wildshield Fairing 46” [Picture]
• Config 3: Model 3 Roof Rack, Yakima FatCat 6 Evo T-Slot mounting, 2 snowboards bindings up (T-Slot mounts too low to put bindings down) [Picture]
• Config 4: Model 3 Roof Rack, Yakima FatCat 6 Evo standard mounting, 2 snowboards bindings down [Picture]
• Config 5: Model 3 Roof Rack, Yakima FatCat 6 Evo standard mounting, 2 snowboards bindings down, Yakima Wildshield Fairing 46”
• Config 6: Model 3 Roof Rack

Results and Real World Impact
At the end of the day I care about how much time I spend on the road. To that end I plugged the Wh/Mi figures for each config into ABetterRoutePlanner to see how they would impact the round trip driving time to my favorite ski resorts.

Wh/Mi Δ / Range Δ / Time Δ

1. No Aero Caps
+5.7% / -5.4% / +7 minutes

2. SeaSucker
+36.4% / -26.7% / +44 minutes

3. Tesla Rack + T-Slot
+24.4% / -19.6% / +28 minutes

4. Tesla Rack
+23% / -18.7% / +26 minutes

5. Tesla Rack + Fairing
+21.0% / -17.3% / +24 minutes

6. Tesla Rack Only
+1.6% / -1.6% / +2 minutes

Accuracy
For each config I did two or three round trip trials. On average the trials within a config varied by 2.2%.

Cabin Noise
I measured cabin noise for each config using the iOS app Decibel X. The absolute values are probably not too accurate, but the deltas are somewhat interesting. The baseline measured 83dB.

• Config 2 (SeaSucker) measured 84.5dB. Without the fairing the app measured lower but the sound was much more unpleasant. Likely due to the frequency of the noise and concentration at that frequency.
• Configs 3 and 4 measured 86.5dB and 86.1dB respectively. Config 5 (fairing) measured 86.7dB and was actually more unpleasant due to a small gap between the fairing and the rack+boards.
• Config 6 (Tesla Rack Only) measured 85.1dB but didn't sound too different from the baseline in practice.

Speed Impact
I repeated testing of Config 6 going 65mph instead of 70mph. The Wh/Mi decreased by 9.9%, causing the range to increase by 11.0%. No big surprises here, but always interesting to verify physics.