Tesla Motors Club
An often asked question is how do the 20" induction wheels impact efficiency compared to the 19" gemini wheels. I found a handful of anecdotal accounts of people driving long ranges with both wheels to compare, but no well controlled experiments.
To gather some better data I test drove two LR MYs back to back, one with each wheel size, aero caps on the 19". I took them 5 miles up and 5 miles back the same stretch of highway. 70mph autopilot the whole time, no vehicles in front to slow me down or draft behind. Both happened to have 42psi in the tires and 70mi of range left on their batteries at the start. I would have liked to do multiple runs to get a better average but test drive beggars can't be choosers.
19" MY: 335Wh/mi northbound, 251Wh/mi southbound, 293Wh/mi average
20" MY: 328Wh/mi northbound, 263Wh/mi southbound, 295.5Wh/mi average
Less than 1% difference
I also tested my M3 with 18" wheels, aero caps, roof rack, and brand new Pilot Sport All Season 4 tires (known to reduce range) as another datapoint.
18" M3: 315Wh/mi northbound, 269Wh/mi southbound, 292Wh/mi average
My biggest takeaway from this is that I suspect the 19" wheels without aero caps would have worse efficiency than the 20" wheels. There's surely some error in my data, but I doubt it's more than the known efficiency reduction of removing the aero caps.
To gather some better data I test drove two LR MYs back to back, one with each wheel size, aero caps on the 19". I took them 5 miles up and 5 miles back the same stretch of highway. 70mph autopilot the whole time, no vehicles in front to slow me down or draft behind. Both happened to have 42psi in the tires and 70mi of range left on their batteries at the start. I would have liked to do multiple runs to get a better average but test drive beggars can't be choosers.
19" MY: 335Wh/mi northbound, 251Wh/mi southbound, 293Wh/mi average
20" MY: 328Wh/mi northbound, 263Wh/mi southbound, 295.5Wh/mi average
Less than 1% difference
I also tested my M3 with 18" wheels, aero caps, roof rack, and brand new Pilot Sport All Season 4 tires (known to reduce range) as another datapoint.
18" M3: 315Wh/mi northbound, 269Wh/mi southbound, 292Wh/mi average
My biggest takeaway from this is that I suspect the 19" wheels without aero caps would have worse efficiency than the 20" wheels. There's surely some error in my data, but I doubt it's more than the known efficiency reduction of removing the aero caps.