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Can your wheels be too light?

Discussion in 'Model S: Driving Dynamics' started by tdiggity, Mar 18, 2013.

  1. tdiggity

    tdiggity Member

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    #1 tdiggity, Mar 18, 2013
    Last edited: Apr 1, 2013
    I switched to some really light wheels and am noticing that I may be using a lot more energy driving around. I was hoping less weight would equal less energy used!

    I need to do some more driving on them with my regular commute, but 40 miles in mostly city driving was about 400 wh/mi :(. I'm pretty sure my 21" didn't go that high. Then, I reset the trip computer and drove to work, that was 23 miles and it's showing about 330 wh/mi which is an improvement, but not too far off from my lifetime average of 340 wh/mi. But, I feel like I need to press the pedal down more often to maintain speed. It feels like the car is lighter off the line, too. Could be all in my head though.

    Wheel: 19 pounds
    Tires: Michelin Pilot Sport A/S (F: 245, R: 255) - ~29 pounds
    Total: 48 pounds

    Stock 19" weight: 57 pounds
    Stock 21" Weight: 61 pounds

    Starting wh/mi: 340 wh/mi
    After 1000 miles: 325 wh/mi
     
  2. smorgasbord

    smorgasbord Active Member

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    It's probably more tire design and pressure that determine efficiency than wheel/tire weight. Reducing unsprung weight (weight before the springs/shocks) helps handling as the wheels have less momentum when bumps lift them off the ground. Although, the air suspension in Model S may be tuned for a certain amount of unsprung weight that you've now changed with lighter wheels.
     
  3. mnx

    mnx 2013 P85

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    Just a thought, the 21" conti's are 26 lbs, your Michelin's are 29lbs. You may now have more mass concentrated on the outside of the wheel/tire combo, which would be less efficient.

    edit: I sure hope they can't be too light since I ordered a set of aftermarket 19" wheels that are 19.8lbs. I'm hoping to get a little better performance/efficiency. :)
     
  4. tdiggity

    tdiggity Member

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    Quoting the latest data point from the Lifetime Average wh/mi thread:

    Battery Wheels Wh N Miles
    1 60 19 330 8 12359
    2 85 19 362 21 58859
    3 85 21 370 15 49365

    Ok, so i'm not too far off from average, but I'll still cross my fingers for closer to 300 wh/mi w/ the new wheel/tire setup.

    In any case, the experiment continues....

    - - - Updated - - -

    That saddens me to find out that the 21" Conti's are lighter than my 19" Michelin's...
     
  5. nrcooled

    nrcooled P#8946 VIN 03225

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    #5 nrcooled, Mar 18, 2013
    Last edited: Mar 18, 2013
    Here's a WAG...is is possible that the lighter wheels require more energy to keep them moving? Heaver wheels require more energy to get them moving but less to keep them spinning. Lighter wheels don't maintain the energy as well and require more energy to keep them spinning. [/WAG]

    disclaimer: I am by no means (and probably very obvious from my guess) a physicist and this is just a complete guess on my part.
     
  6. mnx

    mnx 2013 P85

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    Also the width of your wheels is 9.5 in the rear right? (Are you running 265's in the back)?

    That would decrease your efficiency as well I believe.

    Where's Jerry when you need him. :)
     
  7. tdiggity

    tdiggity Member

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    Actually, I went safe and did 255's in the rear. Was too scared about fitment issues w/ the +30mm offset. This next weekend I'll do some investigating to see if 265 or 275's will fit. It seems like they would from a few other reports, but no one has had the low offset yet.
     
  8. mnx

    mnx 2013 P85

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    What about the front? 255's as well?
     
  9. tdiggity

    tdiggity Member

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    245's in the front. I am getting some parking lot rubbing when I am at slow speeds turning the wheels to the very ends. It's actually really a really loud and kind of scary. But a quick visual check didn't show that it was rubbing on any of the suspension components.
     
  10. wycolo

    wycolo Active Member

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    Rims can only enter into the efficiency equation if there are aerodynamic effects. Like those 'turbo' rims that either suck air into or blow air out of the wheel wells, whatever your choice is here. Lighter rims would accelerate quicker but not coast as far, so momentum issues balance out. Unless we are on a dragstrip.

    I've grinched before about flimsy aftermarket rims being fitted to one of the most powerful production cars in the world, but here I go again: new thread = renewed entitlement. :rolleyes:

    Question: Which nut would you prefer to keep your wheels from flying off your axles??

    LugNuts-S_vs_aftermkt.jpg
     
  11. tdiggity

    tdiggity Member

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    I would argue with you on the part about flimsy wheels. My forged wheels are a very strong 1 piece design.

    Regarding lugs, I do have a genuine question: What about M5's, panamera's, or high powered cars like ferrari's getting away with using Gorilla lugs? are they also in danger?
     
  12. wycolo

    wycolo Active Member

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    > I would argue with you on the part about flimsy wheels. My forged wheels are a very strong 1 piece design. [tdiggity]

    Today's presentation was about lug bolts/nuts. So, show us your nuts! (that fasten those forgeries).
    We'll decide. :smile:
    --
     
  13. tdiggity

    tdiggity Member

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    Oh no, you're right, I am using Gorilla lugs. Because there is no other choice when using "tuner" wheels :(. But, I was being genuine when I asked what other high powered cars are using. Are they concerned? and what are the alternatives.
     
  14. 7racer

    7racer Member

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    your new tires keep the stock diameter correct?
     
  15. tdiggity

    tdiggity Member

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    #15 tdiggity, Mar 18, 2013
    Last edited: Mar 18, 2013
    The rears are off by about 2% on the speedo.

    Stock: 245/45-19
    New: 255/40-19

    This is my play-it- safe setup on 9.5" wide tires. If all works out, I'll upgrade to 265 or 275's and get even better ratio.
     
  16. nrcooled

    nrcooled P#8946 VIN 03225

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    I think the better question is "has anyone validated the 'strength' of the stock wheels?" As long as you go with a reputable company for aftermarket wheels you will be fine. Enkei/Rays/HRE/BBS etc make factory wheels for a lot of manufacturers. This assumption on the Tesla forums that there is NOTHING better than stock is just full of fail. This is coming from someone (me) that has actually raced cars with tons of aftermarket wheels with zero failures. All of these wheel manufactures test their wheels and construction technologies on racecars. Where the heat, abuse, and loads put on the wheels don't come close to what they would experience on the street.

    Have I seen failures at the track? Yep, I've seen 4 wheel failures over my time and 2 of them were on stock wheels. Of the 2 aftermarket wheel failures one was due to the fact that they were indeed cheap knock-offs and the other was due to the fact that the guy was trying to get a faster time by hopping EVERY curb at VIR. This caused the car to literally lift two wheels off the ground every lap. Eventually, one wheel failed.

    I challenge you to find a flaw in the manufacturing process for reputable aftermarket wheel makers and then show where the Tesla stock wheels exceed. Just throwing out your "grinching" with no empirical or evidentiary evidence doesn't help the community.
     
  17. wycolo

    wycolo Active Member

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    > As long as you go with a reputable company for aftermarket wheels you will be fine. [nrcooled]

    Phone jockey @tirerack fits rim to your car (or from your specs) and what does it mean? That it will fit on the car, at best. And here: "you have to use these skinny nuts". NO warranty as to fitness of purpose for your newfangled vehicle. Ordering by phone or in person at a big tire chain you are basically on your own- there is no 'reputable' here, just whether or not it fits. Unless, that is, they can say: 'It is an OEM replacement rim'.

    Then you have to ask: "Will it work with my OEM lug nuts/bolts?" If the answer is yes, then you have something of true value, a thing of beauty. Photos please! More likely it will FAIL that test, as you say. Cannot be OEM unless it uses OEM (or better) mounting hardware. Simple as that. Why are Tesla OEM lugnuts so huge? So they will not pull out of the aluminum rims. So they will not work their way loose due to miniscule contact area. FAIL.

    The lead time on a newly designed & commissioned rim from China shops is at least three months. Soon we might be offered Tesla oem-spec'd aftermarket rims of various tasty choices. Hopefully will be made nice & stout and drilled for the big Tesla nuts. They've seen the car & the shoes it comes with. Its not rocket science to make knock offs of sufficient quality for the Tesla. I just put a pair of MOMOs on the Roadster front: 20 lb very strong & well made (in China). Accept Roadster lugbolts. Half inch wider than stock, I have no idea what car they were made for. I don't care since the stock rim size is unique to Roadsters, and maybe a couple rare euro exoticars. For the Roadster rear you can use oem G6 and HHR rims from MOMO that match, and I've been running G6 rims all winter. Meet or exceed oem specs in every way for the Roadster. Next step Model_S.

    Today's focus is on the mounting hardware. Thats the easiest way to tell if a rim might be moral enough for a Tesla. Your assignment, if you should accept it, is to look at other powerful cars to see exactly how the rims are attached to the hubs. Grab some photos! I'm 200 miles away from any exoticar dealers or I would have already taken a stab at this. Should prove very interesting.
    --
     
  18. tdiggity

    tdiggity Member

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    If you know the answer to this, you should tell us all. I don't think there's any point in beating around the bush like you are doing here. We're all here to learn about the Model S, or at least I am, and I find this type of response kind of insulting. It's one thing to say that small diameter tuner lugs are unsafe, and it's another thing to ask us to find out this information without admitting that you don't know the answer. It's fine to not know the answer, by the way. But like I said in my first sentence, I feel like you know the answer to this and have very strong feelings about this but you don't provide any proof (which is what everyone is asking for).
     
  19. artsci

    artsci Sponsor

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  20. nrcooled

    nrcooled P#8946 VIN 03225

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    The strength of the mounting hardware is directly related to the (based upon my research) strength of the threads and the amount of threads that are attached to the lug studs. I have used Gorilla lug nuts in the past and never had an issue. I have also used light weight Volk (Rays Engineering) aluminum lug nuts too. The design of the lug nuts are made to properly seat in the holes of aftermarket wheels. Of course matching the lug nuts to the wheel is important but they are designed to fit properly.

    My question to you is have you used a set that failed? Do you have direct experience with a failure?

    OEM does not equal perfect and that is why there are recalls done by manufacturers. Reusing the stock lugs does not give me any additional feelings of security or benefit. Properly matching the lugs to the wheels, buying from a reputable company, and ensuring that they are torqued properly does give me additional feelings of security and benefit.

    As for powerful cars and their setup I ran a 400+hp Evo VIII at many trackdays with gorilla lugs and NO problems. It ran on proper track tires, aftermarket wheels, and properly matched lug nuts.
     

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