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Handling at the Limits: 19" vs 21"

Discussion in 'Model S: Driving Dynamics' started by SDRick, Apr 23, 2016.

  1. SDRick

    SDRick Member

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    For those of you who have an opinion, how much if any handling is lost with the smaller wheel? How close are the slalom and skid pad specifications between these two options?
     
  2. CHG-ON

    CHG-ON Still in love after all these miles

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    I'm no racer at all. Though I am pretty aggressive. Fortunately, I get to drive completely awesome winding mountain roads every single day, so I get to play. I expect that I would only occasionally notice the difference between the two sizes. But I can say that with my 21's, I am always surprised at just how planted that car is. Especially for carrying so much weight. I love it. The unfortunate part is that I can't seem to get more than 10K out of the rears.
     
  3. tmyl21

    tmyl21 Member

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    @CHG-ON Have you ever lost grip with the road on your 21's taking a hard turn or corner? Do you like the Hankooks?

    I just had the Conti 21's switched back onto my MS for the summer from the 19's. I can also attest to the grip and shear confidence in the feel of the 21's vs. 19's. Maybe it's me or it's just in my mind, but it does seem to hug corners and turns with more vigor with the 21's.

    I can recall an afternoon last month in which I was accelerating hard on an on ramp to a highway on the 19's and the feel was noticeably different from the 21's. The grip was there in the turn of the ramp before it straightened out just not as crisp handling the weight of the vehicle. I felt maybe even drifting a tad to the left not grabbing the road as well as on the 21's. It has been my first season or winter on the 19's since acquiring them as I have been accustomed to the feel of the 21's for over a year.
     
  4. 3mp_kwh

    3mp_kwh Member

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    It's confidence, not handling, that is lost in the 19". The car is heavy and any sidewall flex is going to get loaded during transitions/corners. I don't think there is any evidence of a single thread on TMC that resolves this to be an understeering, or oversteering, car because about the only way a Tesla will let that happen is if you have RWD, and deliberately turn off traction control, or go into a turn so fast that cranking the wheel scrubs your front tires to a state of understeer (which can be done with just about any car). I have a set of PS2 21's, to try this summer, but am not confident I'll even be able to find "at the limit" characteristics with those, either. So, I sort of expect the exercise might prove the Conti Silents are what to stick with.

    There isn't much point in trying to slide a Tesla around, but it would be great if at some point we could at least use the grip the tires are good for.
     
  5. SDRick

    SDRick Member

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  6. Naonak

    Naonak Member

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    Wait, what? A Model S has massssssssive understeer. On 21s. I don't now about 19's, but I can't imagine the situation is any better, specifically for the reasons you describe. If I go in to a corner hard on my MS, it will push right through that corner without thinking - this is on 21" summers. I take the same corners in my VW, Lotus and Volvo without a problem. I always have attributed it to the weight of the car and didn't really ding the MS for it's lack of steering capabilities at the limits.

    Do you have some sort of different set up than by P85 and P90DL, or made any mods that reduce the understeer?
     
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  7. grahamsimmonds

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    I have a staggered 21" set up on my P85DL and have never had noticeable under steer. I had a P85D loaner with 19"s recently and the main thing I noticed was the softness around corners. The ride is marginally harder on my car but not nearly as bad as the German performance cars. All in all, I notice a more planted experience on all corners and more control even when changing lanes on the motorway.
     
  8. CHG-ON

    CHG-ON Still in love after all these miles

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    I do like the Hankooks. At 1/2 the price, it's hard not to. I have only had them break out when I am too aggressive (read: hammering it) after coming out of a corner. But they recover instantly with a slight lift from the go pedal.
     
  9. StaceyS

    StaceyS Member

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    We've got 21" Turbines with Continentals on them for the summer, and 19" Rial Luganos with Dunlop snow tires on them for winter. On dry pavement, I've noticed less traction on acceleration with the snow tires than the Contis, which I would expect. Particularly, if you give the car a kick while you're in any sort of a curve, the rear end will get waggly very easily (RWD P85). This is partly due to the lesser traction, but also due to the greater flex of the higher sidewall of the 19" tire compared to the 21".

    In adverse conditions (heavy rain, slush, snow, ice), the Dunlops far exceed the performance of our Contis. I recently had the opportunity to drive a loaner 70D over a snowy pass with 21" Contis (just like our car), and drive back the same day in our car with the Dunlops. There was about 4" of packed snow on the road and snow still coming down in both cases. Our car accelerated better, was more planted and had far more lateral stability than the loaner, and this was due primarily to the tires. If the 70D had snow tires on it, it would have been unstoppable!

    I must say that with the 21" Conti summer performance tires, I was very impressed at how well the 70D handled the snow! It was like a hard-core ultra-marathon runner doing a power hike wearing fancy dress shoes!
     
  10. tmyl21

    tmyl21 Member

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    Do you feel a lot of that performance of the 70D with 21" Continentals over a snowy pass was due to the fact that the 70D is all-wheel drive? It would probably be a different experience in your P85 on 21's in any snow.

    Since we're here and on the topic, have you ever driven in snow on the 21" Conti's in your P85? And if so, what was your experience?
     
  11. Edmond

    Edmond Permanon

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    You need an alignment to lolachampcar's specs.

    You need an alignment to lolachampcar's specs.

    I tried to tell people but it does no good. My thread is here somewhere....
     
  12. BriansBucketList

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    I just put a set of Rial Lugano 19s with Hankook Evo 2s on a 70D today replacing the stock 19s (the old ones being delivered in February) and I'm impressed. The tire rack TPMS was detected as a new wheel, and at 45 pounds cold pressure, TPMS was showing between 46-47 pounds when the tires got warm. FYI, they were shipped at about 32lbs pressure. I really, really wanted 20s or 21s, but I don't drive the same route every day. With autopilot, I don't look for potholes.

    I feel like the Hankooks grab a bit more in the turns, but have not pushed them to the limit, and m starting to wonder why I need to be at the limit. I also want to be able to go almost anywhere without worrying about bent rims. The 20/21s look so good, but the use case mostly that they look great, and less sidewall flex, but for a daily driver car, I honk 19s are more practical.

    I live near the Fremont Supercharger / Delivery Area and there are more 19s than anything. There were a few black Model 3s there for testing, and it looked like they had 20/21 on them. Possibly a lighter car. I have a Model 3 deposit, but what I have now, is better than anything I've ever driven before. Of mild interest, the Tesla 19s were made in Mexico, the Rials made in Germany. Also, of interest, is no spare tire, and jacking the car up is probably something you should try, specially if you go lower profile than 45. You may actually have more jack space with 20/21, but my bottle jack was too high.

    Life can be good with 19s.
     
  13. StaceyS

    StaceyS Member

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    I think the 70D did better in the snow than I expected because it was AWD. I was very impressed with how well it handled the conditions. Where safe, I did push it to see how the car behaved, and the traction control nannies definitely chimed in and modulated my ridiculous throttle inputs...

    I have never driven our P85 with the Contis in snow yet, but I'm curious to see the performance. Given the situation, I would expect acceleration to be diminished, and the lateral stability (its ability to hold a straight line in snow, or to corner) to be similar to the 70D.
     
  14. HyperMiler

    HyperMiler Member

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    That is exactly true. Understeer is equal to the rear axle pointing straight overruling the front wheels pointing into the turn.

    Now what could one do to increase understeer in a Model S:

    Run wider tires in the rear - check
    Run significantly more negative camber in the rear - check
    Run significant toe in in the rear - check
    Put more weight on the rear axle - check

    To reduce understeer, listen to Lola!
     
  15. Edmond

    Edmond Permanon

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    There are a number here, who won't listen HM, for emotional reasons.

    But their loss. Who cares? They can't know.
     
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  16. Pale Hearse

    Pale Hearse Member

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    I wouldn't categorize the understeer on the 90D as "massive".
    I just took a very spirited drive yesterday up the back side of Mt. Hamilton to Lick observatory.. one of my favorite driving roads.

    The car loves to be pushed hard.. it's especially good at it going up hill.. but it is a family car designed to keep you safe.
    When you enter a corner, where one might down shift or even heal toe a standard car to keep everything loaded in the right direction, the Tesla responds TOTALLY different. Basically the steering wheel becomes the throttle. Turn in makes the car dumb itself down and respond coming out of the corner more like a high powered front wheel drive car.
    While it is true there is some understeer, it is equally true that the key seems to be modulation of the throttle... and not lifting.

    Someone at Tesla allowed the traction control to basically understand that if the driver turns in but does not completely lift the throttle, that the intent is to make it around the corner without crashing.. so it simply does that.

    Amazing car.. but totally different from any petrol driven 4wd. So with that said, it's up to the driver to decide what is better and in what format.
    In a race up that same road.. if the drivers were equally skilled amateurs.. and one was in a Corvette and one in a Tesla.. the result would be that the Corvette would either make that 40mile journey 2 minutes or so faster than the Tesla.. or.. it would crash trying.

    The Tesla wins.

    Why?

    Simple.. the Tesla will turn that same time.. exciting the driver and treating them to some very Disney Land type fun every single time.. without killing you. Because it was designed to do that.
    I always find it amusing when people try and compare hypercars to the Model S. The MOMENT they do that.. they loose.

    Now that said, if you want a look at how the two seat sport Tesla should, and probably will, look like.. take a look at the Rimac.
    Should Tesla produce such a car, that will be the car to start comparing to the Ferrari's and Lamborghini's... Porches and the like.

    The model S is what it is.. a FANTASTIC handling full size sedan... that pushes just a little.
     
  17. tmyl21

    tmyl21 Member

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    It pushes rather well too !!!

    Nice post P.H.

    I enjoyed every word of it
     
  18. Naonak

    Naonak Member

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    Please correct me if I'm wrong, but doesn't Lola reccommend setting rear camber to -1.0 degree from the stock ~ -1.95 or so? So how do the two statements you just made here jive?

    As a side note, I took one of my cars to the service center today and asked them to align it to Lola specs just so I could see what kind of difference it made ... the car can't be set to -1.0 camber. It's at it's limits for reducing negative camber already and it's not anywhere near -1.0 ... somewhere in the vicinity of -1.85 or maybe -1.7 ... they said it can't be adjusted any further without taking things apart and moving bolts and other internal bits.
     
  19. Edmond

    Edmond Permanon

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    I made a thread explaining everything, but it dropped dead I guess because people didn't understand it.
     
  20. HyperMiler

    HyperMiler Member

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    I apologize for writing it up ironically, stating what to do to increase understeer.

    To decrease understeer, you need to

    Run equally wide (non-staggered) tires in the rear
    Decrease rear negative camber as Lola says
    Reduce toe in at rear to moderate levels as Lola says
    Reduce weight on rear axle

    Lolachampcar, Linkster and Edmond have written this up beautifully in several threads, as you have noticed, e.g.:

    Negative Camber in the Rear and Expensive Tires

    Dear Moderator: That one should become a sticky IMHO
     
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