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Tire/Rim size recommendation for new m3 owner

Discussion in 'Model 3: Driving Dynamics' started by bondo, Dec 29, 2019.

  1. bondo

    bondo Member

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    New owner here m3 stealth looking for summer/autox/track day recommendations. I come from the old days when we drove on 185/60 13r so all this 20" R stuff is new. My stock 18's do seem to fold when im thrashing about.

    Looking for Rim/tire combo recommendations for mostly play, once race season is over i'd remove them so mileage and noise aren't a concern.

    Do 19 or 20's offer any real advantages?
    How real is the threat of busted rims and flats on these larger rims? The bay area is full of potholes.
    Do i need 19's or greater with a bbk?
    What offset would i need with a bbk?
    Any "cheap" forged options out there?

    Planning on BBK upgrade in a couple of months (MPP or UPP) but probably not coilovers.

    Thx
    kevin
     
  2. UWGorilla

    UWGorilla Member

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    Can’t speak for 19s but my 20s were doing just fine after 40k miles of service and two days ago I got two sidewall blowouts on a pothole right after leaving the lynnwood, wa supercharger. I run 235/35 on that AS3+. Titan7, VSforged and Martian are the cheapest forged options it seems.
     
  3. al503

    al503 Member

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    #3 al503, Dec 30, 2019
    Last edited: Dec 30, 2019
    I would go with 19"s:
    1. Much greater chance that they will clear a BBK than an 18",
    2. Much more protection against potholes compared to a 20"
    3. Little more quiet than 20" wheels/tires.

    The only downside in not going with the 20's is that they are noticeably more responsive. I went from the Performance 20's to 19's. I could tell right away. The 20's feel more telepathic. Almost twitchy because they react so quickly. It's also feels like you have a bit of down force (about the best way I can describe it.) The 19's are good (I got the PS4S tires) but you will lose some responsiveness.

    Stock offset with the 18's are +40. It would depend on how thick the hats were on the BBK rotors but I would think you would want to lean more towards +30.

    I went with VS forged. My only concern for your application is the load rating. They are a little low (IMHO) for track/autocross at 1500 lbs. I don't plan on tracking the car with these wheels and there are Hellcat owners running VS Forged without issue. But. For track/autox, I'd try to find something closer to 1800-2000 for a little more piece of mind.
     
  4. Ryephile

    Ryephile Member

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    I think it would be a good idea to browse the wheel gallery thread to get some ideas, and also there are some good recommendations in the Comprehensive Road-Course modification thread in driving dynamics sub-forum. Basically, a good track-day setup would be 18x9.5 et35 with 265/40-18 for small brakes or 19x9.5 et35 with 265/35-19 for bigger brakes. You can fit 275 wide up front but it gets really snug with specific model tire profiles and you'll need a bit less offset and a bit more camber to both clear the knuckle and the fender simultaneously. See Rexpelagi's thread. There's no need to do staggered tire sizes with the fairly even weight distribution.

    I can't comment on your roads, but I'm able to drive on my stock 20"s here in Detroit without incident. Basically, the more you hit (or fail to avoid), the more likely you are to damage *any* wheel. Choosing a wheel that has SAE, VIA, JWL, and/or TUV certification greatly improves the probability of it being a quality wheel. I don't see many Model 3 track-setups using 20" wheels, mainly because the tire selection is very limited, and having that short of a sidewall leaves very little margin for error on apex curbing. There are options in the 245/35-20 size, but that's IMO too narrow for track work given the car weight. Of course, the wider tires will increase power consumption on the road, this can't be avoided in the quest for high grip on the track.

    For my track-day setup I chose the 19x9.5 et35 route, as I prefer shorter sidewalls for good transitional quickness and tire carcass communication, I also want to retain clearance in case I go with a bigger brake setup. I chose Konig Freeform's, which are a flow-formed wheel having SAE J2530 and VIA certifications.

    A few questions:
    *Why did you go with a Stealth if you have track-day aspirations??
    *What car runs a 185/60-13? That's even shorter than an NA Miata.
     
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  5. clockwrkz

    clockwrkz Member

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    Thanks for writing this up - very informative! Timely post as I was just starting down the road of new summer wheels. You’d recommend 19x9.5 (45 offset) over 19x8.5 (38 offset) even for road only? Been looking at Asanti ABL-14’s in 19” for my AWD non P and those are my 2 options for sizes.

    What’s the best choice for tire size on that 19”?
     
  6. kbecks13

    kbecks13 Active Member

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    Stealth is a fantastic option for tracking, you save a good chunk of money that you can spend on coilovers, brakes and wheels/tires :)

    +45 is a little high as stock is +40 on an AWD. So you are shifting the wheel/tire centerline inboard by about 5mm and with a 9.5" wheel (and likely large tire) that means close to rubbing. Could always use some spacers to shift it back out though.

    Are you planning on tracking the car? If not, you could get the 19x8.5 and use the 235/40/R19 tires but they won't be super wide if you want that look.

    Flow formed is your friend, it's much cheaper than forged but 80% of the weight savings. Titan 7 also makes some pretty sweet stuff if you really want fully forged.
     
    • Like x 1
  7. bondo

    bondo Member

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    Thank you all for the input I think that helps me out alot. I was leaning toward the 19 9.5's but really didnt want to have to "buy it twice" if i wasnt considering all the angles. Also i wasnt sure the big rim tiny tire thing wasn't some kids wet dream and i'd start driving while reclining all the way back.

    *Why did you go with a Stealth if you have track-day aspirations?? I wasnt even supposed to get the awd and the additional 8K on top of that for the full performance was just too much. When i was told about the stealth it had all i wanted and none of the stuff i didnt care about. (rims , tail , lowered - 8K???) Now I could upgrade the tires and brakes when $$ allows.

    *What car runs a 185/60-13? That's even shorter than an NA Miata.
    In the old days i drove a 510 SCCA IT class and the tires were about a 205/60 r13

    Thx again
    Kevin
     
  8. clockwrkz

    clockwrkz Member

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    Nope - it won’t see a track I don’t think so I’ll go 19x8.5. And I’m assuming it’s best to run both the front and the rear the same? Have read a bit about using different widths I believe but that doesn’t seem like the best idea as the centreline would be off, no?

    Appreciate your help, thanks!
     
  9. kbecks13

    kbecks13 Active Member

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    Yup, since the car has such even weight distribution it does well with a 'square' setup with equal tire sizes on all 4 corners. Another benefit of this is you can rotate your tires properly which isn't possible when you put wider tires on the rear (like you might do on a Corvette or something).
     
  10. clockwrkz

    clockwrkz Member

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    That’s a big help. Thanks for taking the time to respond again.
     
  11. Ryephile

    Ryephile Member

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    Buying it twice would only happen if you weren't sure what you wanted to begin with. The Datsun 510 was a very long time ago, take a moment to bring yourself up to speed on all the current performance cars and what tires they use. 305/30-20 has become a remarkably common supercar tire size. Compared to your 510, the sidewall height has gone from from 111mm to 91.5mm, noticeable but not dramatically different. Since cars are so heavy compared to back then, or even "just" 15 years ago, tire footprints have gone up proportionally. Porsche 911 Turbo, McLaren P1, C8 Corvette, Camaro ZL1, M-B AMG GT, and Audi R8 all use that 305/30-20 rear tire size, for example, with [very] roughly 1,000 pounds static weight per rear tire. The Model 3 dual motor is about the same axle weight front and rear, but there's not a chance in hell fitting that much tire under the front fenders, unfortunately relegating the Model 3 to under-tired status with stock fenders.

    Tesla chose the 235 width primarily for it's low aero drag and low rolling resistance. It's painfully under-tired on the track with that width, on top the stock suspension lacking front camber. 275 width is [AFAIK] as wide as you can get with stock-ish overall height and stock front fenders. The rear fenders can fit more, but there's no reason to make it staggered with a roughly 50/50 weight distribution, you'll just end up with a colder rear tire and lose trail braking adjustability. You can't go much shorter or taller due to the suspension knuckle shape. That, unfortunately, puts the car at a disadvantage from the industry benchmarks. Of course, if track days are aren't your primary interest, then it's merely an inconvenience.

    I hope you can see that even very briefly, tire size isn't "some kids wet dream" nor does it force a specific driving seat inclination. Ultimately you need to match a tire to the suspension tuning and the given dynamic loads to put the tire's hot temp within its functional window for good lap times.
     

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