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Range/efficiency data on wider tires?

Discussion in 'Model 3' started by insaneoctane, May 16, 2019.

  1. insaneoctane

    insaneoctane Active Member

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    I'm considering replacing my 235/45R18 with something slightly wider for 1) Rim rash avoidance [primary] and 2) Appearance [secondary]. I'm thinking 245 or 255 but haven't seen any data on range/efficiency impact. It seems the people who have swapped for new tires don't typically care about range and don't track the difference. Obviously stickiness/tread life rating would be a factor too, so that ought to be in any data shared. I'm looking to move from the waving of hands and "oh, you'll lose 10% to 20%" guestimates to something a bit more measurable to help me decide if I can justify the change.

    With my LR RWD, I'm currently enjoying lifetime avg of 227 Wh/mi with aero covers REMOVED on my 18" Michelin Primacy MXM4's. I don't think these tires are particularly quiet, but I don't necessarily want to make them worse/noisier.
     
  2. Zoomit

    Zoomit Active Member

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    My speculation...

    If you stay with the same tires (minus T0 spec foam), 255s might be 1-2% worse consumption, plus noisier.

    If you change tires, anywhere up to +10% worse and likely noisier.

    I too would be curious if anyone has quantitative feedback on this.
     
  3. afadeev

    afadeev Member

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    I'm going to do the same with my 20" tires once the current set wears out, for exactly the same reasons.


    [QUOTE="insaneoctane, post: 3664635, member: 46237"I'm looking to move from the waving of hands and "oh, you'll lose 10% to 20%" guestimates to something a bit more measurable to help me decide if I can justify the change.
    With my LR RWD, I'm currently enjoying lifetime avg of 227 Wh/mi with aero covers REMOVED on my 18" Michelin Primacy MXM4's. I don't think these tires are particularly quiet, but I don't necessarily want to make them worse/noisier.[/QUOTE]

    Wider tires represent bigger aerodynamic "bricks" that the air needs to flow around, so they will definitely increase energy consumption. By how much is hard to guesstimate without try A vs. B comparison with the same compounds. Since peopel typically upgrade both the size and the model of the tires, scientifically valid comparisons are hard to come by.

    The noise is another matter, and much of that is influenced by the tire compound, tread pattern, and varies over different road surfaces. For example, some tires "sing" over concrete, others "hum", yet others hardly change the noise level. I would say the width is less of an influence that the above considerations.

    For what it's worth, on my other car, when I swap between 255/275 front/back tire wheels to 285 all around and drive on a highway, my mileage goes down by ~3.5%.
    However, the wider tires were much gripper (RE71R's vs. PSS), so that skews the analysis a bit.

    HTH,
    a
     
  4. insaneoctane

    insaneoctane Active Member

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    Thanks for the meaningful replies thus far.

    What is your "other" car referenced here?

    I will say that the impact to "mileage" or range is far more significant for EV than it is for ICE because of the inherent efficiency of EVs. These numbers are made up (and speed dependent), but they prove my point: because EV's are so much more efficient tire rolling resistance & tire aero impact might actually be 10% of the total losses of the vehicle, vs ICE, being less efficient, rolling resistance & tire aero might only contribute to 2% of total losses. Therefore, increasing your tire's RR and aero impact by say 25% more affects ICE far less than EV (EV: 125% X 10% = 12.5%, or a 2.5% overall increase.....vs......ICE: 125% X 2% = 2.5%, or 0.5% overall increase). Again, these numbers are made up, but they demonstrate why tire choice impacts EV efficiency MORE than ICE.
     
  5. afadeev

    afadeev Member

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    F80 M3.
    In my sig, and profile pic.


    Could well be, but intuitively, I don't see why it would be so.
    Drop in mileage will come from aerodynamic resistance and additional rolling friction.
    If an equivalent increase in tire size was applied to both an EV and an ICE car, an identical additional mileage penalty will be assumed by both vehicles (all else being equal).

    Extra torque will need to be exerted to overcome those two forces.
    You could argue that providing extra torque by an EV motor will be more efficient than by an ICE motor (maybe?), in which case the delta impact will be lower on EVs.

    This is just off the cuff. I haven't thought about this enough to have a strong opinion on the subject.
    Either way, we don't have solid A vs. B data on the additional % penalty from wider tires, but I'm pretty sure that it's > 0.
     
  6. Glamisduner

    Glamisduner Active Member

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    expect a huge hit if you go wider and PS4S.

    245 on mine was a large range reduction. over 20%, and the weights are equal too. If you go heavier expect more if a hit, if you go wider also expect more of a hit.
     
  7. insaneoctane

    insaneoctane Active Member

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    Respectfully, I completely disagree as explained in my long statement. Increasing your RR by 25% will be more noticeable if your original RR was 10% of your losses vs 2% of your losses.
     
  8. Zoomit

    Zoomit Active Member

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    #8 Zoomit, May 17, 2019
    Last edited: May 17, 2019
    I"ll let you guys duke it out, but if you *just* increase the tire width, without changing the tread/compound, the rolling resistance won't likely increase. If it does, it's a secondary effect. Rolling resistance is primarily a function of tire compound and vehicle weight. The aero drag does noticeably change by increasing the width. So I think most of the increased consumption of going to a wider tire, if the tire model is unchanged, is due to the increased aero drag. Tire weight certainly also has an effect, but that would not be noticeable during steady-state driving.
     
  9. jamnmon66

    jamnmon66 Member

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    Range is impacted more because of the significantly higher baseline efficiency. Off the top of my head, an ICE is around 25% efficient in general and the Model 3 is close to 90% efficient. If those guesstimates are assumed to be accurate, then 75% of the energy in a gallon of gasoline is lost before any energy is used to push the ICE down the road. So, if you change tires that are 20% less efficient, you'll only notice a loss of 5% on mileage (20% of the 25%). For our car (assuming 90% efficiency), the same tire change will result in a loss of 18% (20% of the 90%). On an ICE, you probably wouldn't even notice a loss of 5%. But 18% is very noticeable to us, particularly since we're paying so much attention to it. The same principle makes you really notice the loss from higher speeds.
     
  10. Leafdriver333

    Leafdriver333 What range anxiety?

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    The variable between EV and ICE on tire change is in regenerative braking.

    With more rolling resistance EV loses % of Regen.
     

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