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How do wheel size and setup affect your range?

Discussion in 'Model S: Driving Dynamics' started by RonBurgundy?, Aug 11, 2014.

  1. RonBurgundy?

    RonBurgundy? Member

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    Hey all,

    I've been doing a lot of reading and somehow cannot come up with the answer so I'm hoping someone a lot wiser than me can help me figure out how much range would be loss from going 19" to 20" to 21" to 22". Also interested in how it would affect tire wear.

    Things I understand (please correct me if I'm wrong)
    - Bigger wheels will not affect range so long as the width of the tire remains the same and the weight of the wheel is not increased. Does this mean you'll get increased range with light wheels?

    - Staggered setup will decrease your range due to more tire contact with wider wheels. I know Tesla reported earlier that their staggered 21" increased range but now it's showing that it has a slight loss of range? My understanding is more contact, more traction, less range.

    - Tire wear greatly increases with the size of the tire due to thinner walls i.e. less rubber to wear. I think 19"s get roughly 45K, the 21"s get around 10K

    In consideration of everything, I think the best way not to decrease the usage of the car would be to get 20"s for aesthetics with a non-staggered setup (though it doesn't look as good) with similar width and same size tires.

    Would any experts like to weigh in? It would be greatly appreciated.

    Thanks
     
  2. AEdennis

    AEdennis Active Member

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    Ok... Average since picking up the car with Standard 19" with Michelin Primacy - 311 wh per mile.

    Hope that helps
     
  3. HankLloydRight

    HankLloydRight Fluxing

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    Yes, but only slightly. Not really enough to worry about, IMHO. I think what would affect range the most is the rolling resistance of the tires, not the width or weight as much.

    Contact patch size is a function of the weight of the car and the PSI in the tires -- NOT the size of the tires. So given two sets of tires of different sizes and the same PSI, the sum of their contact patches will be equal (there might be a very slight difference due to the strength of the sidewalls, but that's minimal). For instance, if you measure the area of the contact patch in square inches of each tire (in In^2), times the pressure in the tire (in lbs/(In^2)) == you're left with pounds, which should be very close to the weight of the car. Notice tire size, width, nor wheel size enters that equation.


    This is more of a function of the tire compound and driving style than the size of the tires. The 21" rims come with the Michelin PS2s, which is a very soft rubber. The 19"s come with all-season tires, which are generally more durable, therefore longer lasting. The 21"s are also usually on the P85s and P85+s, so higher power, more spirited driving== higher tire wear. Again, I don't think tire wear is directly related to wheel size. And again, given the same PSI in the tires, they'll all have the same contact patch area. Also, the camber on the rears of the P85s and P85+ is set very high, so that leads to greater tire wear.

    I'm not an "expert" but this is what I've learned over the years. The best way to not "decrease usage of the car" would be to not worry so much about tire wear, get the wheels and tires you like best (for your climate), and drive the hell out of your car! So what if you have to replace tires a year more frequently? If you can afford a Model S, you can likely afford new tires a little more often than in normal, boring ICE cars.

    But one additional note -- I did change my P85+ staggaged setup to 245/35/21s on all four wheels so I could better rotate my tires (front to back) and maximize the life of them in the long run. But how much life I'll get out of them? Who knows? I certainly don't care -- when they're used up, I'll replace them. But I know I extracted as much fun as possible out of them.
     
  4. jerry33

    jerry33 S85 - VIN:P05130 - 3/2/13

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    Hank has pretty much nailed it, so I won't repeat what he said. You might note that larger wheel diameter puts the centre of mass further away from the centre of rotation so that will increase the power demand during acceleration. Also, although the nominal section width is the same, the tread width is wider on the lower aspect ratio tires. All things being equal, wider tread width requires more power to push along the road (all things are seldom equal though).
     
  5. swegman

    swegman Member

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    My P85 came with 21 inch wheels with Michelin PS2 tires. My energy usage was about 345Wh/m. My range in the car on a full range charge would be no more than 210 miles. When I discussed this with Tesla, they told me that the PS2 tires were responsible for about a 30 mile reduction in range. I have now switched to the Tsportline 19 inch wheel with the Michelin A/S3 tire. I only put about 1500 miles on the tire, but noticed on a recent trip to PA that my energy useage for the trip was "only" about 310Wh/m. With the PS23 doing that trip I would arrive with 2-3 miles range left. With the A/S 3, I had over 20 miles range left.

    A;leo keep in mind that the 21 inch wheel and tire is easily damaged by potholes (if you live in an area with bad potholes) and wears quickly, compared to 21 inch tires.
     
  6. RonBurgundy?

    RonBurgundy? Member

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    Thanks so much!

    Definitely cleared up some stuff. I don't mind replacing tires or spending the money, just scared still of range anxiety. I like to spend my weekends in places where there aren't many super chargers so i just can't give up range.

    Looks like i need to do more research into tires.

    - - - Updated - - -

    Thanks for your response. 17-18 mile difference is quite a lot.
     
  7. swegman

    swegman Member

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    Just wanted to note that the A/S 3 tire is not a low rolling resistance tire. Not sure whether there is a performance tire that is also low rolling resistance. The Michelin Primacy tire that Tesla offers is a low rolling resistance tire and would likely offer greater driving range than the A/S 3 tire.
     
  8. yobigd20

    yobigd20 Well-Known Member

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    yea that's kind of an oxymoron, right? the higher performance the better the grip and thus the more rolling resistance. that being said, I'm very happy with my aftermarket A/S 3's. :) no more squealing on full accel and yet much softer feeling and tighter grip and very quiet. I did not notice any major difference in range from the goodyear's. maybe a little less range but it's negligible. when I need more range I just stop driving @ 85mph. :p
     
  9. xray

    xray P85 6313 - X Res 3450

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    I just recently switched from 21" after about 30K miles to 19". I used the original Michelin PS2s and then switched to Hankooks for the next set. My lifetime usage is 372 Wh/mi with the 21" and so far in about 500 plus miles, I'm at about 365 Wh/mi. Of course, 500 miles is not long enough to compare it the time spent with the 21" but so far I'm guess I won't see that much improvement in efficiency between the two sizes. However, the reason I switched to 19" is because I'm planning a long distance road trip to the Oregon and 21" tires are much more susceptible to road hazards. I've already had the experience of a "blow-out" where after hitting a rock, I ended up punching a whole through the rim (with the tire remaining intact). Replacement of the original Tesla rim cost $1500 plus installation (which I had no choice since this happened in Las Vegas -- which is out of town for me). On the other hand, you can buy original 19" rims from many Tesla owners here and elsewhere who are moving to aftermarket rims. In my case, I found a set of 4 19" wheels for $850. So if you're worried about roadtrips, I would argue that the main reason to switch to 19" is not necessarily due to the increased range (since that may be minimal) but it's for the decreased likelihood of a road hazard (which admittedly could also happen with a 19" but is probably less likely).
     
  10. RonBurgundy?

    RonBurgundy? Member

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    Thanks for your observation. I'll rest assured knowing that the efficiency of 19"s vs 21"s isn't that great. Please keep me posted if things do change.

    thanks!
     
  11. AndreyATC

    AndreyATC Member

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    Wow, that's some wh/m!
    My life average on 21s with PS2 is 305whm
    Your car either had bad alignment or your driving is a bit too aggressive?
     
  12. landover

    landover Member

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    With the stock 19s I get around 295 kW with my 22s 9" in the front 10 1/2 in the rear I get about 335 kW per mile. Hope this helps.
     
  13. gdh66

    gdh66 Member

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    Don't forget unsprung weight, which is weight to overcome inertia. Unsprung weight is far more important for increased range than simply removing weight from the interior of the car (a passenger, carpet, seats for track cars, etc.). I wanted to emphasize range over performance with my MS, so I sold my 21s after getting the car (vin 2379, P85, which at the time came with 21s), and bought aftermarket 19" rims/tires from Tire Rack (OZ wheels, standard 19" size low rolling resistance Bridgestones). The stock 21" turbine wheelset (wheels + tires) weigh around 65 lbs. each! I'm saving almost 10 lbs. of unsprung weight per wheelset. Though I don't have wh/mi data, this HAS to be producing more range, but sacrificing cornering ability, aesthetics, etc. somewhat.
     
  14. Damiano

    Damiano Member

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    Folks -- Tesla provides information in the "top 5 question" section of their website comparing range for 19" and 21" wheels (presumably with the Tesla supplied tires). The site states "Range decreases slightly with larger wheels. 21" wheels have more contact with the road and are made of stickier rubber. Both characteristics increase friction." The Tesla calculator says says that at 70 mph, windows up, AC on, and 70deg outside temp, the 85kWh gets 225 mi with 19" wheels and 215 mi with the 21" -- a 4.4% range loss. The percentage range loss appears to be greater at lower speeds.
    Your Questions Answered | Tesla Motors
     
  15. jerry33

    jerry33 S85 - VIN:P05130 - 3/2/13

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    That would be normal. The tire flexes less as the speed increases. The static loaded radius is smaller than the dynamic loaded radius (which gets larger as speed increases), so the belts do not have to bend as much at higher speeds. In addition, the tread compound does not envelope small irregularities in the road surface as completely at higher speeds.
     
  16. RonBurgundy?

    RonBurgundy? Member

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    Sorry but i've read through those. I understand that 21" causes decrease in range but curious what would happen under different scenarios. i.e. 20" with same width, weight of the wheels, staggered vs non-staggered, etc...

    Just justifying my logic and everyone's responses definitely helped. I can now upgrade my wheels
     
  17. jerry33

    jerry33 S85 - VIN:P05130 - 3/2/13

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    If everything else is equal, 19 > 20 > 21. However, everything else is seldom equal, so in the end you pays your money and you takes your choice.
     
  18. omarsultan

    omarsultan Active Member

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    On the Tesla calculator, it looks like you get dinged about 4% to go form 19s to 21s. @70mph, range goes from 231 to 220. The note says its the results of a larger contact patterned stickier tires.

    O
     
  19. swegman

    swegman Member

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    Andry, I don't drive aggressively. If anything, I drive like a baby (sharp contrast to the sports cars I previously had). I use the cruise control whenever possible, stay less than 10mph over the limit (usually less), avoid flooring the accelerator, use range mode on trips, minimize use of HVAC (use seat heater when needed), etc. I have just under 12K on the car and the alignment was checked by Tesla 3 times. The first time (with about 3,000 mile on the car, Tesla determined the alignment was off and re-adjusted it. The last 2 times it has been within spec. The maximum range I can get in my P85 on a range charge is about 210 miles with 21 inch tires and 20-25 miles more with the 19 inch wheels under the same driving conditions.

    BTW, I had a 60 loaner one day and noticed that it used less energy than the P85. I asked the SC about this and they confirmed that the 60 is more efficient than the P85.

    - - - Updated - - -

    Damiano, I believe that FAQ is with respect to the 21 inch Continental tire (at least that is what Tesla told me; the standard 21 inch tire was the Continental, although some cars were shipped with PS2 when the Continentals were not available. When the P85+ was released it was fitted with PS2 as standard. The PS2 is sticker than the Continental and thus gets less range. My P85 was originally fitted with the Continental, but was then swapped by Tesla for the PS2 after 900 miles.
     
  20. HyperMiler

    HyperMiler Member

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    There is a Michelin Super Sport in the size 255/45 19 Y100 that should also fit well onto the stock rims.
    This should be the ideal solution for those preferring the 19" scenario.
    Has anyone used this possibility yet? I have seen one post on 20" with aftermarket rims.
     

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