TMC is an independent, primarily volunteer organization that relies on ad revenue to cover its operating costs. Please consider whitelisting TMC on your ad blocker or making a Paypal contribution here: paypal.me/SupportTMC

Relative handling of 85, 85D, P85, P85D

Discussion in 'Model S: Driving Dynamics' started by thegruf, Apr 11, 2015.

  1. thegruf

    thegruf Member

    Joined:
    Mar 24, 2015
    Messages:
    942
    Location:
    UK
    with a couple of comments about torque steer on the 85D after the latest update (probably s/w tunable in future) and leaving outright power aside, what is the user experience of handling between the models?

    P85/S85
    RWD
    no front motor
    weight bias to rear


    85D/70D
    AWD 50:50 split
    front/rear motors
    weight balanced


    P85D
    AWD 30:70 split
    front/rear motors
    weight to rear
     
  2. sorka

    sorka Active Member

    Joined:
    Feb 28, 2015
    Messages:
    3,256
    Location:
    Merced, CA
    The P85D is 50/50, not to the rear.
     
  3. brucet999

    brucet999 Active Member

    Joined:
    Mar 12, 2015
    Messages:
    1,302
    Location:
    Huntington Beach, CA
    So the greater weight of the larger rear motor is compensated by the extra weight of CV joints in the front?
     
  4. thegruf

    thegruf Member

    Joined:
    Mar 24, 2015
    Messages:
    942
    Location:
    UK
    221 front; 470 rear.
    That's rear biased power in my book.
     
  5. AWDtsla

    AWDtsla Active Member

    Joined:
    Mar 3, 2013
    Messages:
    2,134
    Location:
    NE
    No there is no bias. That's maximum achievable power. There is no center diff to have said bias. Actual wheel torque depends entirely on software.
     
  6. JPP

    JPP Active Member

    Joined:
    Feb 4, 2013
    Messages:
    1,841
    Location:
    SF Bay area, CA
    When you are talking about handling, are you also looking at front-to-rear weight ratio/balance? As I recall, the original S was about 50-50. Not sure what the current stats are with the various rear/front motor flavors.
     
  7. gordo

    gordo Member

    Joined:
    Jan 16, 2015
    Messages:
    213
    Location:
    CA
    My P85D definitely has some torque steer when launched. Welcome to one of the drawbacks of crazy fast acceleration.
     
  8. AWDtsla

    AWDtsla Active Member

    Joined:
    Mar 3, 2013
    Messages:
    2,134
    Location:
    NE
    Torque steer is generated from differential drive masses, usually unequal length half shafts. They seem symmetrical all the way around on the Model S, at least from any pictures I can find. Is this not true?
     
  9. thegruf

    thegruf Member

    Joined:
    Mar 24, 2015
    Messages:
    942
    Location:
    UK
    THe 470hp rear motor deliivers much higher torque than the 221hp motor. That is rear biased drive. That will affect how the car handles.

    Yes.
    However torque steer is also generated when the tire on one side loses traction before the other, usually due to localised variation in the ashphalt, which is likely the case in the S85D and is easily sorted by Tesla traction control algorithm if they deem it necessary.

    - - - Updated - - -

    Seem to be struggling to get the question out simply.

    Two factors at play with the different models.

    1. Weight

    • the rear motor only models have a rear weight bias and a lighter front as there is no motor there.
    • the P85D has a heavier motor at the back and some weight at the front with the smaller motor.
    • the 70/85D have the same motors front and back.

    Typically in a car with heavier front axle, the understeer is more difficult to control.
    So does the P85 have the sharpest turn in?
    Has anyone observed this?
    The reality may be that the car is just so heavy due to the battery that the differences are too small to observe.

    2. Power
    A RWD car is typically very different to a FWD car to drive.
    AWD is different again. (Modern ICE espcially Audi are using electronic trickery to modify the performance of the diffs and brakes to send torque all over the place to generate dynamic handling.

    The P85 is a RWD car.
    The P85D is an AWD car with a more powerful/higher torque motor a the rear
    The 70/85D has same power/torque front and rear.
    So it should be the case that the P85 is most RWD, then the P85D, then the 70/85D which should feel neutral.

    Has anyone observed this, or again is the electronics/weight masking it so much that it cannot be observed.

    (fwiw I test drove a P85+ yesterday and is felt nicely rwd, with the traction breaking occasionally on hard aceeleration leading to a nice catch by the t/c.)
     
  10. AWDtsla

    AWDtsla Active Member

    Joined:
    Mar 3, 2013
    Messages:
    2,134
    Location:
    NE
    You're just using ICE car analogies and trying to apply them to the Model S, when in fact it's a completely different beast.

    Also - losing traction in one wheel is in no sense "torque steer". Drive a high-powered ICE FWD car or even an AWD car which has an asymmetric drive train, then you will know what "torque steer" is.
     
  11. brucet999

    brucet999 Active Member

    Joined:
    Mar 12, 2015
    Messages:
    1,302
    Location:
    Huntington Beach, CA
    According to Tesla specs page (unchanged since D versions were added), MS weight distribution is 48% front, 52% rear. Adding a front motor plus CV joints and half shafts probably evens out or shifts weight bias slightly to front.
     
  12. thegruf

    thegruf Member

    Joined:
    Mar 24, 2015
    Messages:
    942
    Location:
    UK
    No it isn't

    Comonly the case on transverse engined fwd ICE cars. But mass is not the issue, it is the different angles involved leading to different torque vectors, (and a momentary potential effect of drive shaft twist from unequal length shafts).
    Torque steer is generally when the driver perceives the car pulling to left or right under hard acceleration, traction clearly is a major part of this.

    The focus of handling really isnt so much about torque steer anyway.

    More whether addition of a front motor weight increases or decreases understeer into a corner as the centre of gravity has moved forward, and how willing the car is to push the tail wide when exiting a corner espcially the models with the big rear motor. Yes, the are a gazillion other aspects too but mostly they are the same across the model range so neutralised relatively.
     
  13. AWDtsla

    AWDtsla Active Member

    Joined:
    Mar 3, 2013
    Messages:
    2,134
    Location:
    NE
    By your definition hitting the throttle on a rear wheel drive on anything other than a flat road with a steering angle of 0 is "torque steer"

    No, torque steer is caused by fundamentally different torques applies to each wheel, using different length half shafts does a great job of accomplishing this.

    Dynamic handling properties of the car under power application ARE NOT torque steer.
     
  14. thegruf

    thegruf Member

    Joined:
    Mar 24, 2015
    Messages:
    942
    Location:
    UK
    bored now
     
  15. lolachampcar

    lolachampcar Active Member

    Joined:
    Nov 26, 2012
    Messages:
    4,446
    Location:
    WPB Florida
    My progression=
    P85
    P85+
    P85D
    my experience, reasonable

    The P and P+ would tend to "roll over" the fronts on turn in to mid corner and plow (understeer) on corner exit. The PD has removed a large amount of this except at the limit by using front motor torque to pull the front of the car around. The FWD has removed a bunch of the pitch moment of the MS chassis when cornering.
     
  16. thegruf

    thegruf Member

    Joined:
    Mar 24, 2015
    Messages:
    942
    Location:
    UK
    and interested again, thanks lolachampcar ... Lola (used) to be made in my home town btw, sad to see the factory empty these days.

    This is exactly the kind of info I was looking for, having driven a P85+ at the weekend, I was quite concerned about the behaviour of the front end, not unruly but definitely unsettled with a hard prod of the accelerator, very much as you describe, setting the air suspension to low did help a bit. Nowhere near BMW or even MB levels of front end bite and stability to my (limited so far) experience.
    That the AWD helps with some electronic trickery no doubt helps control this is good to hear. But you are never going to get away from the fact this is one heavy car, nimble it isn't.

    So the question for me now is (power aside)
    S85D - same power front an rear, so probably tidy but a bit like a skateboard, or P85D and a lighter wallet, but still a more enjoyable rear biased drive?

    Just wish they would release the P85D update to increase the overall performance distance between them, as currently above 30mph the gap seems not so big as the outright 0-60 would suggest.
    Only got a week or so to update my order!
     
  17. ra-san

    ra-san Member

    Joined:
    Dec 26, 2008
    Messages:
    292
    Location:
    San Diego, CA
    I see this mentioned sometimes. Is this in comparison to a 5 series, 7 series, AMG varient or what? Some of the 7 series are similar weighs to the S. How do they handle in comparison? "Ye cannot change the laws of physics, Jim", but compared to a similar mass car, I'd hope and expect the S to out handle it (due to center of gravity, weight distribution, and possibly stance) or at least match it. Is that not the case? If it isn't, and Tesla does have catchup to do, what are the biggest elements? I thought the base versions could use some improvements, but thought the + and now the P85D were top notch, given the mass. If not, what could/ should be changed? by Tesla? By an interested owner?
     
  18. LetsGoFast

    LetsGoFast Active Member

    Joined:
    Oct 13, 2014
    Messages:
    1,342
    Location:
    Virginia
    Its so hard to talk about handling when much of it is subjective, but I have loads and loads of experience in an M5 and I'm convinced that the P85D outhandles it in pretty much every situation. Its a pretty fair comparison, because both cars have similar footprints and weights. In terms of "spec sheet" numbers, the M5 usually ran about .88g on a skidpad, where the P85D seems to test out at .91 in the one test I've seen. It has obvious improvements in understeer and body roll as compared to the P85+ in my opinion. I've not experienced the kind of torque steer I associate with front-wheel drive performance cars. I'm looking forward to making some runs at my local SCCA course just for the fun of it.

    Subjectively speaking, I feel like the P85D allows you to get on throttle earlier in the exit and will hold the line better than the M5, but getting the speed right at the apex is a bit trickier. I'm still not as confident near the margins despite a pretty extensive background driving fast cars because there is a lot going on between your input speed, steering grip and weight transfer, plus god only knows what the traction control system is doing to you. I've got the rear end loose by mistiming the entry into a sharp corner and trail braking too hard.
     
  19. lolachampcar

    lolachampcar Active Member

    Joined:
    Nov 26, 2012
    Messages:
    4,446
    Location:
    WPB Florida
    gruf,

    If it is any help, I felt the need to change out the air on my P+ to coils while I am perfectly happy with my PD. LGF, I too am a long time M5 fan although they kinda lost me at the NA V10 as the cars just got too big for me. I think the PD compares favorably to the current generation of M5s as well.
     
  20. Zextraterrestrial

    Joined:
    Mar 11, 2010
    Messages:
    3,636
    Location:
    Humboldt/Los Altos
    I was going to say that I think the P85 needs more front camber and maybe a bigger sway bar. The outside edges of my fronts are slick from hard cornering.
    also it is pretty close to an M3 equivalent in autocross for comparison

    coils should be potentially better but the loaners w/ coils I drove felt like crap. My air is much more planted and has less rebound and bounce

    I would love to see all varieties of the S on an auto X setup for comparison.
     

Share This Page