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Tires sizing for 3P+

Discussion in 'Model 3' started by JADCa, Dec 4, 2018.

  1. JADCa

    JADCa Member

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    After a few very fun track days, my front tires have chunked and need replacing. I think I have decided to just replace the front tires by moving the back tires which are still ok to the front and trying to go a bit wider in the rear with the same 4S tires to get a bit more grip in the rear. And better looks.....

    Anyone have any experience/thoughts on what is best with the 8.5" rims? 245/30, 245/35, or 255/30?

    Also, what pressure have people found works best for the track? I started at 37 cold which was way too high and lowered to 36 hot for my best time, but that is in the 20's cold which is pretty low for such a low profile street tire. Also, there is still a lot of variation in my driving of this car, so it may have just been better driving and not optimum pressure.

    Randy Pobst used 245's when tuning the car, but that is all they provided for sizing as far as I can tell.

    Any help would be great.
     
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  2. kbecks13

    kbecks13 Active Member

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    Going with wider tires on the same width wheels isn't going to gain you a whole lot (and costs more!) but i'd suggest 245's if you want something fatter. Also keep in mind that going to a staggered set-up with wider rear tires means you will likely develop some understeer.

    I'm personally running 19x9.5" wheels with 265 tires (square) as a performance set-up and it works great, but is much noisier on the road (RE-71 tires).

    I think higher pressure actually works better for the Pilot Sport 4S since the Model 3 is such a heavy car and the outer shoulder on that tire uses a softer compound. When i was on the track i ran them at 35 PSI cold and 40 PSI hot and had a good bit of tire wear. A friend ran his at 40 PSI cold and his tires looked much better at the end of the day (and our times were basically the same).

    Check out this other thread as well: Best Tires/Wheels for Tracking Model 3
     
  3. JADCa

    JADCa Member

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    Thanks for the link. Good info, but more about new rims and non-P+

    I found the 4S got very slippery for me about 45 hot and seemed to keep getting better the lower I went, but limited data and lots of variables.

    Running with track mode, the car felt like it needed a bit more grip in back, though the front sidewalls were the area that overheated. I think a lot of the damage may have been done at a previous event before track mode were understeer was the issue.

    In sizes, the 235/35 stock tires have 786 rev per mile, the 245/30 have 805, the 245/35 have 777 and the 255/30 have 798 so the 245/35's are the closest but will be slightly smaller lowering the back which is not optimal. The 255/30's are the next closest and seem to make the most sense, but does anyone know how the computer will handle the slight variation? Anyone not running square?
     
  4. kbecks13

    kbecks13 Active Member

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    I think Track Mode just errs on the oversteer side of things, i felt the same. Very curious to hear if anyone has run track mode with a staggered set-up!
     
  5. JADCa

    JADCa Member

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    I had a hard time balancing right at the limit with track mode. Going 90% was fast and stable, but getting exactly on the edge seemed to put the car into a drift, which is fun, but not fast. Not sure if it was me learning a new car and software or the programming to make it drift easily.

    That is why I came here hoping for some insight on staggered options and how the car behaved before committing to new tires.

    Any help would be great as we explore new territory with this car. I did beat ALL of the Porsches at the Porsche Club event, so even the 4S tires are not that bad.... This car is an AX monster.
     
  6. bradhs

    bradhs Member

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    Great thread... Glad you started it OP.

    The 245/30 is likely out because max load is not there...

    The 245/35 seems to be the best fit but barely wider. Would it really matter much to gain 10mm? Plus you're dealing with a tire that can handle more load, maybe that will reduce ride comfort or you can run them at lower pressure?

    The 255/30 would be awesome, Rim Width Range is within spec, and you'd gain .79 inches per tire. Not bad. The tire is slightly lower, that might not look as good to fill that empty wheel well.

    Whichever way you go, I definitely want pictures.
    '
    2018-12-04_21-38-04.png
     
  7. JPUConn

    JPUConn Active Member

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  8. bradhs

    bradhs Member

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    But on the stock performance 20's?
     
  9. EVTuning

    EVTuning Vendor

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    No I run 10 in the rear and 8.5 in the front. 255’s would fit all around on the stock wheels no problem. So long as outside diameter is similar to stock and the same front to rear you’ll be fined
     
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  10. kbecks13

    kbecks13 Active Member

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    Sure it will fit, but the tires will be pretty darn big for an 8.5" wheel and having all that extra rubber will hurt turn-in response plus results in the edges of the tires lifting under cornering. If you want the best response, put skinnier tires on a wider wheel or at least stay on the lower end of the tire width recommendation spectrum for a given wheel.

    Dont just take it from me, listen to Mike Kojima!
    The Ultimate Guide to Suspension and Handling Part 1, Wheels and Tires - Page 3 of 5 - MotoIQ

    Wheel/Tire Fitment guide:
    Tire Width for a Wheel/Rim Size Chart
     
  11. bradhs

    bradhs Member

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    Thanks for the info. Based on what I've read we should only consider the 245/35ZR20XL (95Y) tire.

     
  12. bradhs

    bradhs Member

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    Thinking this further ....

    My P85D had ...
    Front 245/35R21 Rear 265/35R21
    Wheel Front 8.5J x 21 Rear 9.0J x 21 Offset 40mm


    And according to that website:
    Size..min..ideal..max
    8,5 225 235 or 245 255
    9,0 235 245 or 255 265

    Tesla used the ideal size on the front rim and the max size on the rear wheel.

    Don't you think it would be safe to use the 255 size which is labeled max?
     
  13. kbecks13

    kbecks13 Active Member

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    Yes it's safe. I am just saying that a fatter tire on the same size wheel will change some of how the car handles since you have more flexible sidewall rubber and might change your steering feel. For example i currently have 19x9.5 with 265 on my Model 3 and am planning to go down to 255 on my next set of tires.

    That means i would have the same width rubber on a wheel that is 1 inch wider than the stock 8.5" wheel. Think about all that rubber sitting on the 8.5" wheel, it's gotta go somewhere and it will be very flexible!
     
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  14. EVTuning

    EVTuning Vendor

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    Stretching the tire on a wider rim also will have negative effects on handling and turn in feel. You also won’t have any sidewall of the tire to protect the face of the wheel.
     
  15. JADCa

    JADCa Member

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    Stretching the tire to extremes is bad, but none of these sizes I am considering do that. Going with a wider rim gives you a bit more tire on the road for a given tire width, but with modern tires, it is a very small improvement and mostly done to avoid point penalties in classification. The 8.5 rims will safely and properly handle a 255 tire.

    Thanks for all the input, I think I am going to go with 245/35/20's on the rear mostly because that size fits well, ads a bit of rubber, and has just a very slightly larger diameter, but within wear variations of the 235/35 so the computer should be happy. The 255 is just a bit too short and the 275 too much for the rim.

    Also, if it doesn't work well, i can just buy matching front tires and have the setup Tesla used for final tuning of the track mode.
     
  16. bradhs

    bradhs Member

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    What did Tesla use for final tuning? Was it the 245/35R20's? What about the 255/35R20? Too tall? May fill in the gab between the top of the tire and the fender.
     
  17. JADCa

    JADCa Member

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    Tesla used 245/35/20 Cup 2 tires. The 255/35 is too tall, the 255/30 is close, but slightly smaller diameter, usable, but not good for looks. 255 square would work well.
     
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  18. 4hs93lsi2

    4hs93lsi2 Member

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    Can you elaborate on your source please? I’m definitely getting 245, but there’s very few reports of 245s (245/35/20) on the car (P3D) in general. The guy who got 255/35/20s on reddit said he was so close to rubbing that he’d go with 245 next time. I would have less buyer’s remorse if your source was verifiable. Thanks.
     
  19. bradhs

    bradhs Member

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    This is exactly what I wanted to know, thank you!
     
  20. bradhs

    bradhs Member

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    Do you know where his comment was about 255 not being a good size? Personally I think it might be perfect. See this link: UPDATE: 255/35/20 Michelin Pilot A/S 3+ fitment on Performance Model 3 - And first use of the parts catalogue! : teslamotors

    Here's one of the OP's comments/reply: "It’s the upper limit of acceptable. People do put 265s on 8.5 inch wheels, but its not ideal and starts to get pretty risky imo. Honestly I think 255s are great on these particular wheels - theres a lot less sidewall sticking out past the lip than I would have expected based on the 255s (also AS 3+) I ran on my STi with the 18x8.5 inch oem BBS"
     

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