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New Snow and Regenerative Braking

Discussion in 'Model S: Driving Dynamics' started by ecobon, Jan 4, 2017.

  1. ecobon

    ecobon Member

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    In the Denver area and it has started to get very cold today and with snow falling, the salted roads do not help much for loss of traction. I noticed that once I got over 50mph and feathered the accelerator to keep a safe distance with the cars ahead of me, my car started to lose traction in the rear and was getting a bit squirrel-y to say the least. I slowed down with hazard lights on and exited the freeway. I noticed that the car handled much better once the regenerative braking was set to LOW for this particular circumstance.

    I am guessing that this will mainly apply to rear wheel drive vehicles as all-wheel drive variants have braking applied to all four wheels. A constant speed using the accelerator would also provided much better results in the snow as the regenerative braking would not have kicked in. It was rush hour and not quite possible to drive that way in this case.
     
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  2. Blissedout

    Blissedout Member

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    Low in snow is the way to go.
     
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  3. Blissedout

    Blissedout Member

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    Sorry, I couldn't resist.
     
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  4. weradln

    weradln Member

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    Am a new 60D owner in Fort Collins, CO. We had 2" new snow two days ago and I had to drive to Denver early morning. I25 was surprisingly icy half way to Denver, then got much better. Passed at least five slide offs. n
    Nebie here forgot about turning down regen. Don't know if it was because of the Michelin X-Ice snow tires or the dual motor but didn't have any hints of losing traction. My first winter drive with the car and I was impressed with the handling.
     
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  5. ecarfan

    ecarfan Well-Known Member

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    Are you running winter tires like @weradln is?
     
  6. ecobon

    ecobon Member

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    No. A new set of Michelin MXM4s just like my 85D that seems to handle the same snow without issues, like weradln.
     
  7. Doug_G

    Doug_G Lead Moderator

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    Get snow tires. I don't use "no season" tires.

    Also feather the pedal - don't just lift off.
     
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  8. ecobon

    ecobon Member

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    Yes. I agree. That's my driving behavior in the snow. I also don't jam on the brakes and progressively press them until I feel loss of traction. ABS is not as good in the snow as manual, if done correctly. Again, after I changed the setting for regenerative braking to LOW, all seemed fine. On the 85D, I left the regenerative braking at STANDARD, and suffered no ill effects with the same tires/wheels. I am guessing that the regen comes on all 4 tires instead of just 2 for the RWD cars.

    Snow tires are a bit of hit/miss during the Denver winters as it often hits 50-60F for a few days a week. Sometimes, 70's. The snow doesn't stay for more than one afternoon in most cases due to incredibly sunny afternoons. All the snow is up near the mountains, but not too much in the city. I do carry a set of chains in the trunk just in case. Snow tires wear pretty quickly in 60-70F and are noisy. So, there are some drawbacks to having them on. Of course they have their advantages, too.

    * I let the secret out about Denver and I'll probably get stoned by the locals now. *
     
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  9. AWDtsla

    AWDtsla Active Member

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    It should be reducing regen automatically due to stability control, but who knows what Tesla has done in whatever version of software you are running.
     
  10. Barry

    Barry Member

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    Whenever the road is snow-packed, I put regen in low. That solves the problem. High regen can be like stomping the brake pedal with subsequent loss of traction.
     
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  11. fallen888

    fallen888 Member.. hehe, I said "member"

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    Yes, this is the lesson I learned this morning. o_O First winter with my MS.
     
  12. skitown

    skitown Supporting Member

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    Interesting. My experience thus far with my classic S with Michelin X-Ice snows is that I much prefer Standard regeneration vs. Low. I find that feathering off the accelerator lightly and engaging regen to slow down is much less likely to cause loss of traction than having less regen and requiring more use of the brakes. Perhaps I'm in the minority. To each his own. To my mind, this is quite analogous to simply gearing down (reasonably and gently) when driving on slick roads in an ICE, vs using the brakes. This is how I was taught to drive on slick roads and it's carried over to my Tesla, I guess. Yesterday coming back from the ski resort, regen was disabled due to cold temps and I really disliked how the car performed until it was back up to full regen. It felt like a very heavy ICE without the ability to gear down and it was unnerving to me. FWIW!
     
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  13. skitown

    skitown Supporting Member

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    I will also state for the record that I am super impressed with how well this RWD car performs on slick roads, especially with only quality studless tires. People around here are blown away by it. The meme these days that all RWD cars are bad in the snow really goes out the window when it comes to Teslas. Don't get me wrong, I would love to have an AWD Tesla, I can only imagine that it would easily be far superior on snow to any other vehicle I've owned, including my last WRX. But the classic S holds its own for sure. Heavy, perfectly weighted, low-center-of-gravity, and smart traction control, really makes a big difference. And good tires.
     
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  14. ecobon

    ecobon Member

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    Yes. The RWD is very controlled in most situations. Traction of your front tires is sometimes more important than the rears for RWD due to the need to change direction being dictated by the front wheels. With the traction control on, fishtailing is also greatly reduced to the point that it becomes somewhat effective and controlled.

    AWD has been point and shoot even during a couple of tough driving days here in Denver. The RWD has been more fun for me to drive. I also drive a Carrera 4 in the winter and although it's AWD technically, it shows a bit for RWD fun-experience in the snow.

    When my battery pack is frozen in the cold mornings, the regenerative braking is disabled and the car feels a bit out of control because I'm so used to the regenerative braking. Driving that way for a few miles gets me used to it and it feels like any other car. The degree of laying off of the accelerator is key here and if you have a fine tuned foot, you should be able to keep the STANDARD setting without worries. Also having tires that bite into snow and ice can greatly diminish any unwanted effects.

    I usually run all season tires unless we are subject to a week-long snowstorm. I might opt to swap wheels to those that have the X-Ice tires on them. About 30 mins to swap each way so I don't do it too often--just once to drive up to the mountains for the weekend. Then swapped back.
     
  15. skitown

    skitown Supporting Member

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    @ecobon, you are fast at swapping wheels! I think I muttered something like, 'don't quit your day job' (computer jockey) to myself and brother after painfully & slowly swapping on my snows this season for the first time to get comfy with the Tesla lift points/procedure, etc. Practice makes perfect, I suspect. As do muscles and muscle memory however. :p
     
  16. ecobon

    ecobon Member

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    #16 ecobon, Jan 7, 2017
    Last edited: Jan 7, 2017
    I'm also in IT and ran through the same. Then decided to wear gloves, have a mirror, good floor jack with rubber pad, cordless impact driver, long breaker bar, and large torque wrench, tire crayons, long socket 21mm 6 pts.

    One wheel at.a time. Mark tires with crayon. Breaking lugs *slightly* then jack up at each corresponding jack point.
    Use impact driver to remove all lugs and pull off the wheel. Toss other wheel on using your foot to elevate the tire to align studs with holes.
    Use fingers to put on lug nuts to studs nice and smooth with no resistance to avoid cross threading. 60-90lbs/ft on the impact wrench. tighten in a star pattern. Lower jack. Repeat 3x on other wheels.

    Finish using your large torque wrench at 90lb/ft and 129lb/ft. You can just end it with 129 lb/ft, but I start all lugs at 90lb/ft to make sure my wrench is acting properly before hitting final torque value. Drive on the freeway and come back and check torque again. Done.

    Remember to bring back your torque wrench close to zero so that it stays close to calibration values.

    * jack on level and hard surface, and use wheel chocks for safety. I got this down to about 5-6 mins per wheel (on all my cars) The impact driver saves a bunch of time here. But nothing wrong with going slow and taking your time. Really helps avoid duplicate work and injuries. I have a No-Mar Pro tire changer and static balancer mostly for motorcycle tires, but I have changed a few sets of car tires on it as well. Main reason for messing with all this in the first place and not going to the service center like most sane individuals.
     
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  17. ⚡️ELECTROMAN⚡️

    ⚡️ELECTROMAN⚡️ Fritterer and waster of hours in an off hand wayer

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    I was wondering about this last month. I also have a rear wheel drive with "no" season tires on. It felt very stable and controlled when I hit full regen on the snow and ice. I only tested this in safe open areas. Does anyone know if it applies varying amounts of regen to individual wheels when regen braking just like it would when applying the standard brakes? It felt like it did.

    P.S. have you guys felt winter tires? They are surprisingly squishy and squeezable compared to all season tires. I can see why they would work much better in snow and ice.
     
  18. Saghost

    Saghost Active Member

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    With a single motor on the axle driving the wheels through a conventional differential, there's no way to vary the amount of regen on one wheel relative to the other - both will always have the same amount, though the car can vary what that amount is hundreds of times per second.

    The only way to vary it is with ABS releasing one wheel independently as it starts to skid.

    I don't have much snow experience with the Tesla yet, but in past EVs I though regen was useful for retaining control because it is smoother to apply, without less likelihood of a jolt breaking things loose and it doesn't bring the wheels to a complete stop any way.
     
  19. ⚡️ELECTROMAN⚡️

    ⚡️ELECTROMAN⚡️ Fritterer and waster of hours in an off hand wayer

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    #19 ⚡️ELECTROMAN⚡️, Jan 7, 2017
    Last edited: Jan 7, 2017
    With a little research I see that the Model S has an open differential, but is able to simulate limited slip differential behavior by applying the brakes in varying amounts to either wheel during acceleration. So it wouldn't be changing the amount of regen to individual wheels, but most likely applies the brakes independently to each wheel during regen to keep the rear end from sliding out. Stability control during regen braking. Maybe it also reduces the overall regen braking too, at the same time? Do you know if that's what it does?
     
  20. AWDtsla

    AWDtsla Active Member

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    Can't fix over braking with more braking. The only option is to reduce regen under direction from stability control. I've never felt that car cutting regen because of this reason.
     

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