Hello, I would appreciate some advice on tires if anyone has time to help. After driving another RWD Model 3 with upgraded tires on twisty mountain roads I have decided to replace my stock Michelin Primacy all-season tires on my RWD 18s with the Michelin Pilot Sport 4S tire, I live in Los Angeles and I don't drive anywhere cold. My goal is sticking to the road, accelerating quickly after a turn without spinning the rear wheels, and improving safety/stopping distance. If there are any benefits in ride comfort/absorbing bumps then that would be great too. I'm OK with losing some range and I know the tires won't last as long. What size tire should I get? Stock tires are 235/45/18, should I get that? Or should I get a wider tire instead like 245/45/18 or 255/45/18? I don't know much about tires. Thanks very much!
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Buying Performance Tires - Best size for 18-inch wheel?
- Thread starter Sunshine Speed
- Start date
Knightshade
Well-Known Member
265/40-18
They fit fine (according to at least one tire vendor on here) and they're identical in diameter to stock so no worries about the odometer/speedometer or other sensors being off.
Technically you're supposed to run a 9" width rim instead of 8.5, but it works fine and tons of other (non-tesla) folks have been doing that for years.
They fit fine (according to at least one tire vendor on here) and they're identical in diameter to stock so no worries about the odometer/speedometer or other sensors being off.
Technically you're supposed to run a 9" width rim instead of 8.5, but it works fine and tons of other (non-tesla) folks have been doing that for years.
Thanks Knightshade, that's really helpful. For me personally, I want to follow the rim width range as recommended by Michelin for my 8.5 inch aeros, and I want all 4 tires the same (not staggered). I see the stock tire diameter is 26.3 inches. On the Michelin website I see these 3 options for Pilot Sport 4S that are wider than 235:
1) Size 255/40ZR18/XL (99Y), diameter of the tire is 26.0 inch.
2) Size 245/45ZR18/XL (100Y) , diameter of the tire is 26.7 inch.
3) Size 245/40ZR18/XL (97Y) , diameter of the tire is 25.7 inch.
Should I go with #1 because it's the widest tire that is officially inside the rim width range and it's also the closest to the stock tire diameter? Only 0.3 inch difference. Thanks.
1) Size 255/40ZR18/XL (99Y), diameter of the tire is 26.0 inch.
2) Size 245/45ZR18/XL (100Y) , diameter of the tire is 26.7 inch.
3) Size 245/40ZR18/XL (97Y) , diameter of the tire is 25.7 inch.
Should I go with #1 because it's the widest tire that is officially inside the rim width range and it's also the closest to the stock tire diameter? Only 0.3 inch difference. Thanks.
If it fits the rim (I've seen reports that it does), then 265/40/R18 is exactly the same circumference, with plenty of tire choices:
https://www.tirerack.com/tires/tire...R8PS4SXL&vehicleSearch=false&fromCompare1=yes
Wheel and Tire Guide for Tesla Vehicles - Unplugged Performance
Tire Size Comparison
https://www.tirerack.com/tires/tire...R8PS4SXL&vehicleSearch=false&fromCompare1=yes
Wheel and Tire Guide for Tesla Vehicles - Unplugged Performance
Tire Size Comparison
Looks like 255 would be the widest for 8.5" wheels:
Tire Width for a Wheel/Rim Size Chart
This being said, can we not do better than measure tires using milimeters x aspect ratio x inches? Who come up with this stuff?
Tire Width for a Wheel/Rim Size Chart
This being said, can we not do better than measure tires using milimeters x aspect ratio x inches? Who come up with this stuff?
From our experience, for maximum cornering response, the ideal tire width for a 8.5" rim is 225/235. On my SW20 Mr2 track car, for example, I have Front: 215 on 8-inch wheel, Rear: 235 on 9-inch wheel. A good rule of thumb is that when you lay the wheel down on its side, the rim should touch the ground, not the tire.
With a tire wider than the wheel, there is a good deal of deflection when you turn the steering wheel. If you were to run 255's vs the stock size, when wiggling the steering wheel on the highway you will feel the car floating and wiggling on the tires as they deflect.
This is of course for the best cornering performance, if your goal is outright grip in a straight line, accelerating or braking, you will benefit from the widest tire.
There have been some very interesting tests done in the motorsport community, one such test on Miata autocross cars, where they tested one tire size, with increasingly wider wheels. The lap times and response improved with each wider wheel until of course, you end up with some ridiculous stretch and only a postage stamp sized piece of tire is touching the road!
TLDR: Use wider wheels if you want wider tires, if you want to keep the same wheels, look for a better compound in the same size.
With a tire wider than the wheel, there is a good deal of deflection when you turn the steering wheel. If you were to run 255's vs the stock size, when wiggling the steering wheel on the highway you will feel the car floating and wiggling on the tires as they deflect.
This is of course for the best cornering performance, if your goal is outright grip in a straight line, accelerating or braking, you will benefit from the widest tire.
There have been some very interesting tests done in the motorsport community, one such test on Miata autocross cars, where they tested one tire size, with increasingly wider wheels. The lap times and response improved with each wider wheel until of course, you end up with some ridiculous stretch and only a postage stamp sized piece of tire is touching the road!
TLDR: Use wider wheels if you want wider tires, if you want to keep the same wheels, look for a better compound in the same size.
Thanks for that info MountainPass, it's really helpful. I'm definitely staying with stock 18-inch aero wheels for now. I'm surprised to learn that maybe the wider tire won't corner as well, so maybe I won't get 255 width.
Looking at the tirerack size comparison tool, I see there's an option that gives me a wider tire and bigger sidewall:
Stock : 235/45/18
Proposed new tire : 245/45/18
This 245 width tire is 3% wider, 2% more sidewall, and 1.5% more diameter and circumference compared to stock. Sounds like I will have better grip and braking from increased width, and better ride comfort from increased sidewall. I'm not worried about the 1MPH difference on speedometer due to small difference in diameter.
Does anyone know what drawbacks or problems I could have with getting this size tire? Probably reduction of electric range but anything else?
Looking at the tirerack size comparison tool, I see there's an option that gives me a wider tire and bigger sidewall:
Stock : 235/45/18
Proposed new tire : 245/45/18
This 245 width tire is 3% wider, 2% more sidewall, and 1.5% more diameter and circumference compared to stock. Sounds like I will have better grip and braking from increased width, and better ride comfort from increased sidewall. I'm not worried about the 1MPH difference on speedometer due to small difference in diameter.
Does anyone know what drawbacks or problems I could have with getting this size tire? Probably reduction of electric range but anything else?
The only drawback would be a reduction in range just because you have switched away from the stock tires, which have pretty amazing rolling resistance. It will be minimal, 245's aren't wide enough to cause more wind resistance or anything like that! I say go for it!
Interesting, will look for that. The original Continentals do seem to have a narrow tread for the width, making them appear stretched (despite being classified as the proper width for the rim).
What then makes the M3 so understeery? (evident in your track video as well)
Yes the base tires are less grippy and they deflect under cornering but that’s not it. The suspension seems to hold ok until one loads it too much and then it snaps into horrible understeer. Never mind a performance driving situation, it does this even when cornering more vigorously, in tight turns, at street-legal speeds. I felt the same behavior with a Performance Model 3 with the Michelin PS4, albeit at higher grip levels (which I felt, in some ways, made the problem worse).
Is it insufficient camber or does the car need a different type of spring or strut?
In your video, the coilover seemed to cure some of the understeer and you mentioned you’d have wanted a wider front tire. Would a wider tire have sufficed or was the remaining understeer caused by insufficient camber or something else?
TL;DR:
With such a stiff chassis, how can I make my Model 3 handle properly (more like an M2 or such)? I’m not looking for extreme grip or performance, just for a satisfying cornering feel.
More front camber would definitely help with understeer! At our last track day, we tested out 275's on the front of the car. This completely eliminated understeer, it was incredibly balanced. We ordered new 10" wheels immediately after that test, and we are heading to the track on Monday to set a new lap time. Staggered tires make sense on a Porsche, but the M3 with its 48/52 weight distribution needs to have a square setup. Always fit the most tire possible in the front, regardless of the car!
This doesn't mean you need 275s all around, 255s all around would still have the same balance, and be a bit more lively since it would have less grip. Look at the Scion FRS, that car is a hoot because it can slide around on those little OEM tires!
Thank you for your feedback! It's quite nice to have someone respond from actual personal/competent performance driving experience.
I'd like to get a set of wheels to use with summer tires (will keep the OEM 18" for the winter) and I was going to pick whatever looks decent as long as it fits and it does the most to quell the understeer. If 275s on 10" fit the front, then that's what I'll do all around. Once I have the new wheels, I'll move on to figuring out what to do about the suspension.
What offsets will you be using front and back and what would you say is an ideal offset/scrub for poised street driving with good cornering feel (again, a la Cayman/M2)? I'm not planning to lower the car or push the wheels out for better looks or anything of that sort. Should I stick with 40 offset and just go 10" wide or are there any benefits to using some other offset?
TIA!
Also, how are those front brake pads you have for sale? The description indicates that they are formulated for street driving, which would be exactly what I'm looking for.
I feel that the brakes in the Model 3 are quite weak. It's not that they don't stop the car, they just don't do it too convincingly. Unless I'm imagining it, it feels like the colder they are, the worse they feel and grip. I use low regen but I do have some 800 miles on the car already, so the pads should be well worn in, nonetheless they still feel pretty weak. For now, my big fat Q7 (with OEM Brembos) feels more convincing under braking than the Model 3.
I'd guess the rotor does not make that much of a difference and it's probably all down to the pads. Am I correct in this assessment?
Do you have any measurements of how the car performs (in say straight-line 60-0 braking) with those MPP Page Mill brake pads vs the OEMs? Do they feel better?
TIA!
That's a good question!
@MountainPass, what was that TPMS dialog that popped up during your video? Was that to record the new tire pressures or the new tire diameter?
I would guess it could, after running for some distance, compare the GPS-measured distance with the wheel revolutions and determine that the tire circumference has changed. Does anybody know if it does that?
Knightshade
Well-Known Member
Pads and rotors can't reduce stopping distance. The brakes don't stop the car, the tires do.
If you want to change the "feel" of the brakes you can do that with brake upgrades.
If you want to stop the car shorter you can do that with stickier tires.
That’s a very superficial way to look at braking and it’s not accurate except when looking exclusively at the narrow situation where you lock up the wheels.
Assuming unchanged caliper compression forces, different pad materials provide different friction coefficients and different friction coefficient variance with temperature, humidity, pressure etc. These change the brake system engagement curve (and thereby the “feel”), making it more or less effective for a given “normal” pedal application force.
If you’re willing to stand on the brake pedal every time you slow down, then yes, the tires become the weakest link in the chain and the ability to stop is exclusively defined by their static friction limits. In all other cases the pad and rotor materials have a big impact on how well one can modulate the brake pedal to stop effectively and smoothly.
Knightshade
Well-Known Member
No, it's a correct way to look at it based on how physics works.
If you don't believe me check out Brembos FAQ explaining why they don't bother to test 60-0 braking.
Because their brake upgrades don't improve those times. They physically can't. Better tires can.
So what you're saying is changing brake parts can't change stopping distance.
But it can change the "feel" of the system.
Which is what I said in the first place.
"How short I stop when I'm only applying the brakes part way" is a nonsensical measure of...well... anything.
It'd be like measuring 0-60 at 1/4 throttle. If you care about the time 0-60 then you're flooring the car.
Likewise if you care about the time 60-0, you're flooring the brake.
And it's extra weird you're the person who asked for a 60-0 stopping test and now are complaining that's too narrow a case (where you stand on the brake- which is how such tests are done).
We’re hijacking the thread now. I understand your point but it’s not covering my questions to @MountainPass.
Reductio ad absurdum:
Put a dollop of grease on your brake pads, do a 60-0 test and report back if the stopping distance is the same as before.
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