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Driving on mis-matched tires

Discussion in 'Roadster: Technical' started by smorgasbord, Mar 7, 2014.

  1. smorgasbord

    smorgasbord Active Member

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    SF Bay Area
    I got a flat this past weekend on my right rear, and took the wheel down to my local tire place to get it fixed. Of course, I'm down to the wearbars so they wouldn't fix it. I ordered the Yoko AD08rs, but since it was going to take a few days to come in, they put a newish tire on the wheel so I could drive around. The new tire is a Continental DWS.

    It's been interesting. I would not want to drive on mismatched front tires - ever.

    Although I have a v2.5, I didn't do the "New Tires" thing on the mismatched set. I wish I had time to do that on the mismatched set, but the new Yokos are in so I'm going to get them installed later today.

    Anyway, I notice the difference mostly on regen. On accelerating, the TC does kick in somewhat more frequently, but the front tires maintain their grip and so I'm able to control things. However, TC almost always engages while regenning. And as we know, when you lose traction while regenning, the result is that you lose braking power. It's a bit scary. So, I use the brakes and that gives me more control.

    Driving with the mismatched set confirms for me that regen is harder on tires than pure acceleration. Even light regen makes the TC light come on now, but fairly hard accelerating often does not. And, turns are a whole 'nother thing. On right turns, the inside wheel (the Conti) just loses traction on any kind of regen and even on acceleration it's not great.

    The original rears (AD07) lasted only 5697 miles
    The first replacement rears (AD08) lasted 11,885 miles
    The second replacement rears (AD08) lasted 11,700 or so (and I would have gone a few hundred more miles on them if not for the flat)

    And now I'm going to put AD08r's on.

    While the AD08s seem to have lasted longer than the AD07s, I also think my driving style has improved. Early Roadster owners drive binary: hard on the accelerator, then complete lift-off. I now still drive hard on the accelerator, but I don't completely lift off. I often have my foot down just enough to coast (power guage on 0). That's easier on the tires and gets better miles/kW. Your passengers necks appreciate it, too.
     
  2. hcsharp

    hcsharp Active Member

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    Easier on the tires yes but not necessarily better miles/kWh. It depends on your speed. At some point using regen to slow down faster is more efficient than coasting at 0 kW because it reduces losses from wind resistance. You can read more details about this, including the math and physics behind it, in this thread:
    Regen-vs-Coasting
     
  3. smorgasbord

    smorgasbord Active Member

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    For the situation I described (stomping on the accelerator then completely lifting off), it is necessarily, absolutely, and positively better miles/kWh to coast instead of regen.


    Back on topic - I now have the ADO8r's on my car. Might be a reasonable time to do a "New Tires" thing. I know what Tesla says about it, but anyone in the SF South Bay area have a suggestion as to where to do it? Any tips?
     
  4. hjr

    hjr #1291

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    I also had a right rear tire blow out. The other tires are still OK. Given your experience is it better for the handling to replace on the blown tire, to get 2 new rears, or all 4 new tires? The blow out happened before the winter so I put on the winter Yoko's and have left them on. Now I am thinking about performance tires again before iit gets too warm and I wear out the snows really fast.
     
  5. smorgasbord

    smorgasbord Active Member

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    Sorry so late here - but you only need the 2 rears. If the other tire is new-ish you might be OK, but I'd probably suck it up and replace them both.
     

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