I have done a bit of research, and thinking that I may replace the 21” Slipstreams, on my 2016 S90, to get longer range.
Have any of you done this? If so, how much of an increase did you get?
That would depend on how much lighter your wheels are. Meaning, the light weight wheels someone put on their car may not be the same weight as the ones you are thinking about.
Probably helps acceleration more than range.
I just did this with VMR rims, 804s IIRC. They are .5” wider than stock rims but weight something around 8#+ lighter each wheel.
Right now I can’t really say, I’ve had my S 90D for just over 1 year and a couple months. The wheels that I had on it prior were the 19” rims from a 2013 P85. Same tires from the old wheels too, so no more expense buying tires.
My expectations are that I’ll do a little better with these wheels, but probably not when I drive to Phoenix and back on the highway. At high speeds I think a wheel cover is better than spokes, just look at the aero wheels the 3 has. Or even the new LR+ S.
If you wanna go REAL light spend 15k on carbon fiber wheels :)
FWIW I think my wheels are +30mm, which pushes them out to fill up the wheel well a little without rubbing. I may have that number wrong, I can look up the deets if you like.
Lighter wheels mean perceptibly improved handling. Car feels more nimble in turns and quick transitions.
They mean increased range too, but if you are frequently stopping and accelerating. Steady state like interstate cruising is aided more by aero wheel covers.
I have both on my 2013 S. Each wheel is about 8 lbs lighter than OEM, and I have self designed aero covers as well. Helps highway range by about 3-4%.
Converted last April from staggered 21s on Contis to TSportline TSS 20s with a square setup (245/40/20) on Conti DWS06 rubber. My S75 averaged 327 Wh/mi over 75,000 miles on the 21s. I've now done 22,000 miles on the 20s and have averaged 315 Wh/mi. I'm now saving 0.12 kWh for every mile of travel with weight savings of 8 lbs per rear tire and 6 lbs per front tire. Have I gained more range? No. Does it accelerate significantly faster? No.
Only real-world benefits after dropping down 1" in wheel size: 1) slightly more ride comfort and 2) longer tire life because I can finally rotate tires.
Picky, but 0.012 kWh/mile and probably more and cheaper options for tires. My efficiency has improved over the years without a rim change, so confounders, also.
@BH, true that. I truly expected huge energy savings going 21 to 20, but in my example, it wasn't anywhere close to being significant because my wallet hasn't lost weight. (And yes, 0.012 kWh/mi saved, not 0.12 kWh/mi).
Sure you could get lighter wheels for more range, but here are some factors to consider that may impact your range more than wheel weight:
Wheel design - Some are reduce drag more than others based on design. Just look at the results from Tesla's Aero wheels vs non-Aero wheel range.
Wheel/tire width - Generally the more patch contact, the less roll resistance you'll have. Think about how thin road bike tires are compared to Fatties or mountain bikes.
Tire compound - This is probably the biggest factor when you compare a "sticky" summer performance tire compared to a touring or grand touring tire.