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New tires, now 'crabbing" and lower efficiency

Discussion in 'Model S: Driving Dynamics' started by efusco, Nov 12, 2013.

  1. efusco

    efusco Moderator - Model S & X forums

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    About a week ago I had new tires put on, same Goodyears as OEM. Since that time I've noticed significantly lower efficiency despite comparable temperatures (it's been a bit colder, but even on warmer days my efficiency was down). Pre-new tires I was getting around 280-290Wh/mi on my usual commutes. Since then I'm closer to the 320-330Wh/mi range.

    Now, I might just attribute that to the new tires alone, and perhaps it still is just that, but since the new tires there's a bit of a shimmy/wobble sensation I can just barely notice. It reminds me of the crabbing of an all-wheel drive car at low speed. It's only noticeable at low speeds (up to maybe 35mph) and it's very subtle, no visible steering wheel movement or anything like that.

    My question...is this more likely a wheel out of balance--seems sort of likely since the only change is new tires?
    Or is it an alignment issue--seems more likely with the wobble/crabbing and lower efficiency?
    Or is it just new tires breaking in and I need to shut up and be patient?

    Or something else.

    I could take it for an alignment, but there's no local SC, so I have to use a local shop and go through the process of teaching them how to deal with the car and pay out of pocket. I have another 4000 miles (~2 months) before my next service appt. with Tesla and don't really like the idea of sending the car away for just an alignment that it might not need.

    Looking for logical advice on how best and most economically to proceed.
     
  2. Todd Burch

    Todd Burch Electron Pilot

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    Not sure, but if a local tire shop did the change--is it possible they torqued the wheels back on using the old specs? When I used a local tire shop, they were about to use the numbers they had--which were the originally published numbers. Good thing I mentioned the new higher spec to them. The newer lug nut specs are a significantly higher torque setting.

    I don't think this would affect efficiency much. It is worthy of note, however, that Fall tends to be a windy season (to point out the obvious). Temperature probably has much less of an impact than the wind.

    For instance, yesterday temperatures here were in the mid 40s to mid 50s (F) yet my commute still averaged to 271 Wh/mi...the same as it was in the peak of summer. Yesterday was not a windy day at all...
     
  3. Doug_G

    Doug_G Lead Moderator

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    Check your tire pressures first. Most tire shops screw this up 100% of the time.

    Balance would only cause vibration. Alignment definitely could be an issue. It would affect driving dynamics, and could possibly affect efficiency if really bad.

    Cold does dramatically affect efficiency so be very sure you are comparing under similar conditions - not just current ambient but also whether the car is cold soaked or not.
     
  4. FlasherZ

    FlasherZ Sig Model S + Sig Model X + Model 3 Resv

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    I'd like to understand where the "old specs" numbers came from, I keep hearing about them, but I can tell you that when my wheels were worked on last December, the ranger (before the St. Louis service center even opened) had the specs that are used to this day. I don't recall the specs ever being different, but I could be wrong.

    Do you know what the "old" number was and where you saw it?
     
  5. RoverS

    RoverS Banned

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    wth is "crabbing". god what an awful word, whatever it means...
     
  6. drees

    drees Active Member

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    Don't forget that new tires are less efficient than old tires, so you'll see an efficiency hit from there, too.
     
  7. efusco

    efusco Moderator - Model S & X forums

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    I mentioned that in my post and that may well be all it is, so I'll keep an eye on it, but I wouldn't expect the 'crabbing' sensation.

    thanks, I meant to check the pressures when I first got the car home, and it's been in the back of my mind, but I hadn't done it yet, will make it a point this afternoon.

    They used the new torque specs
    As a long time hypermiler in my Prius and careful observer in the Model S, I'm very familiar with the impact of weather/temp, so I have been taking that into account, and even so, the efficiency numbers are clearly impacted.
     
  8. efusco

    efusco Moderator - Model S & X forums

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    Tires were 40psi all the way around (35F outside temp, about 20 min. after a drive home). I pumped them all up to 45psi. Will be tough to judge improvement given the cold spell we're having then I'll be out of town for a week. But hopefully that's all it was and I can wait a couple months for that alignment and rotation.
     
  9. kevincwelch

    kevincwelch Active Member

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    Where are the new specs located?
     
  10. efusco

    efusco Moderator - Model S & X forums

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    There's a thread somewhere here, but I called the St.Louis SC and they told me over the phone. 129 ft.-lbs I think.
     
  11. Jason S

    Jason S Model S Sig Perf (P85)

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    My local Sears shop did the alignment check and diagnosis when I was having some trouble. Took a bit of work to convince them to put new tires on it -- discussion with shop head, etc. But now they are all like old buddies and know the car. :smile:

    There is a little bit of fear around such an expensive vehicle. But we got it up on a lift and they saw it wasn't really anything that special, so no big deal. Any shop that can handle a Corvette can handle a Tesla, imho. (The stories they told me about some of those Corvettes... *shudder* :scared:)
     
  12. huntjo

    huntjo Member

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    I wonder if this is due to new software calculation compared to last year. For example, in exchange for less "vampire drain" when the car is not in use, it now has to warm the battery pack for the first several miles you drive, increasing your Wh/mi.
     
  13. mnx

    mnx 2013 P85

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    That definitely sounds like your problem right there. Be sure to check them in the morning or before the car has been driven.
     
  14. efusco

    efusco Moderator - Model S & X forums

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    I don't think so, I was getting sub-300 Wh/mi with pressures close to 38psi earlier this year (albeit in the summer). The numbers I'm seeing are much higher than I've seen in my nearly 1 year driving the car. I'm over 400Wh/mi on my usual commute to work this morning where I'm typically in the 280 range...again, the freaking cold weather is throwing off any accurate comparison, but I averaged in the 330-340 range last winter even with snowy/wet/icy roads. The more I drive it the more I'm convinced there's a significant alignment issue.
     
  15. Todd Burch

    Todd Burch Electron Pilot

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    Very cold temps (Ottawa, perhaps?), yes. Use of cabin heat, yes. I haven't found "a bit colder", as Evan put it, to dramatically affect efficiency. I took this to imply temps around the 40s...maybe that was a bad assumption, but Missouri is a similar latitude to me. When I drive with temps in that range, I only see a slight hit to efficiency. For example, today I pulled out of the garage and it was 35°F. When I came home temps were in the mid 40s. My energy usage for the commute was ~285 Wh/mi, and I used the seat heater. Normally that trip would consume about 270-275. Yesterday, with temps in the low 40s, my usage was only about 10 Wh/mi more than usual. So at those temp ranges, yes there's a hit but i wouldn't call it dramatic.

    Tire pressures and balance seem like likely culprits.

    - - - Updated - - -

    I don't think this is accurate. Tesla has indicated that active pack heating while parked will only occur in the extreme cold. The pack won't be warmed in "chilly" temps while parked. After all, how would it know when you want to drive? The warming has always occured once you've started to drive...at least as long as i've had my car (since December).
     
  16. Doug_G

    Doug_G Lead Moderator

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    Yes, in my experience temperatures a few degrees above freezing have a very small effect on efficiency. The big drop happens below that.
     
  17. huntjo

    huntjo Member

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    See my post last year re: parking unplugged at the airport for a week at Xmas. It was definitely heating the pack and using battery while I was gone. Was it below 20F? Yeah maybe for some of it. But I lost 100 miles of range, so I think it must have been heating continuously. I think they later programmed more tolerance for getting cold when not in use, at the (minor) expense of taking a little longer to get the limiting lines to disappear while it heats up during driving. Granted there was definitely increased Wh/ mile for the first 15-20 minutes last year as well, indicating some degree of heating on demand. My contention (or supposition, since I have no evidence) is just that we are noticing more pack heating while driving because the car is doing less while parked. I think there were some moves they made last year to decrease vampire losses, and that was my explanation for how they did it.
     
  18. efusco

    efusco Moderator - Model S & X forums

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    Just a quick preliminary follow up. I finally got back to the Sam's Club who installed the tires and asked them to do a rebalance of my wheels. With around 100 miles today since the install (yea, I run my kids around to activities a lot) in temps in the low 50s and I've averaged around 315 Wh/mi where I've seen closer to 330-340 daily for the past 2 weeks since the tires were initially changed. They did say that the wheels were out of balance and the 'crabbing'/steering wheel wobble I was experienced has essentially resolved (still feel some, but it may just be the road and/or my imagination).

    If these numbers are sustained I won't do anything more until my 25,000 service where I'll ask the SC to do an alignment.
     
  19. tomas

    tomas Traded in 9 rep bars for M3, used to be somebody!

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    I'm on 5.6 and also doing much worse than last cold season but have had at least 3 sw releases since then. Guessing something changed and only seeing it now that it's cooling. Forum consensus is that 5.8 whammy much better so waiting to see how that compares.
     

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