Why Did 2021 M3P go with 9" wide 20" rims instead of 8.5"?

[Alan2000]

Anyone know the reason for going 1/2" wider on 2021 rims and using the same size tire? Seems to me that's adding more aerodynamic drag without any additional contact area of the tire with the road. I never cared for the stretched look on tires vs a more square sidewall look.

 

[Dallas J]

There's probably no way to know why they made that internal decision, but its appreciated from a performance tire perspective.

 

[Gauss Guzzler]

Yeah it's a good question. They planned to offer a Ludicrous version of the Model 3 and they opted for the extra weight and complexity of a divorced spring rear suspension in order to provide crazy-deep wheel wells for the 20" x 10" wheels that were planned so clearly they have wanted wider wheels since the start.

And curiously the Zero-G track wheels are 9" wide but include better fitting 245mm Sport 4S tires instead of the 235mm Sport 4S they've paired with the standard 8.5" wheels since 2018.

One theory is that they wanted stretched sidewalls. Not only do they look, uh, dope? But it's easy to see how the rounded shape presents a more aerodynamic profile. More importantly, the angled sidewalls are much more bump-compliant than vertical walls without sacrificing any cornering stiffness or feel.

The other theory is vendor supply chain dynamics. The fact that they somehow ended up with Pirellis out of the blue seems to suggest that something was going on in the contracts department. Maybe they planned to put the 245 4S's on there but Pirelli had a great last-minute sale they couldn't resist? Or maybe they wanted to switch to Pirelli anyway (they are quite good) but forgot to let them know that the design changed from 8.5" to 9" until it was too late?

 

[MaskedRacerX]

Maybe they planned to put the 245 4S's on there but Pirelli had a great last-minute sale they couldn't resist? Or maybe they wanted to switch to Pirelli anyway (they are quite good) but forgot to let them know that the design changed from 8.5" to 9" until it was too late?

Great post, good info regarding the rear suspension (vs. wheel size) design.

I'm not in the loop, but I do get supply chains, cost management, etc., and if I were to place a bet, it would be on the quoted above - i.e., there was every intent to move to a 245/35, use the same tire sizing / wheel width for the two performance oriented wheel/tire packages.

I would not be surprised, if they quietly just start using 245s on the M3P in the next several months.

 

[Sam1]

Great post, good info regarding the rear suspension (vs. wheel size) design.

I'm not in the loop, but I do get supply chains, cost management, etc., and if I were to place a bet, it would be on the quoted above - i.e., there was every intent to move to a 245/35, use the same tire sizing / wheel width for the two performance oriented wheel/tire packages.

I would not be surprised, if they quietly just start using 245s on the M3P in the next several months.

The Tesla spec 235/35/20 PS4S has more tread width than the non-T0 spec 245/35/20 PS4S. They would have to redesign a completely new 245 width tire for Tesla to even get more tread on the pavement.

Either way the Pirellis suck that come on the factory, those things are almost a full inch thinner on tread width than the T0 PS4S...Just got my new car in yesterday and having the pirellis removed this afternoon. Going to run a 0-60 right before and right after the swap to get some data. I could tell just driving the car yesterday it launches softer than my 2019 performance, and it felt almost like the front axle was spinning a lot more once the car started moving. Assuming that's just a traction issue.

 

[MaskedRacerX]

The Tesla spec 235/35/20 PS4S has more tread width than the non-T0 spec 245/35/20 PS4S. They would have to redesign a completely new 245 width tire for Tesla to even get more tread on the pavement.

Either way the Pirellis suck that come on the factory, those things are almost a full inch thinner on tread width than the T0 PS4S...Just got my new car in yesterday and having the pirellis removed this afternoon. Going to run a 0-60 right before and right after the swap to get some data. I could tell just driving the car yesterday it launches softer than my 2019 performance, and it felt almost like the front axle was spinning a lot more once the car started moving. Assuming that's just a traction issue.

Good info, it'll be interesting to hear about your results.

Yeah, I know Pirelli has some brand equity, including being used in motorsports/ on some exotics, but they had the same bad rep with Mustang folks , they were the tire included with the Performance Package, and they were mediocre at __best__. Almost everyone swapped them out for a Firehawk Indy or MPS4S.

I might do a wheel swap, in which case I'll just leave the wheels/tires all mounted up, and then I'll just bolt them back on ~34 months from now when I return the car

 

[Sam1]

Good info, it'll be interesting to hear about your results.

Yeah, I know Pirelli has some brand equity, including being used in motorsports/ on some exotics, but they had the same bad rep with Mustang folks , they were the tire included with the Performance Package, and they were mediocre at __best__. Almost everyone swapped them out for a Firehawk Indy or MPS4S.

I might do a wheel swap, in which case I'll just leave the wheels/tires all mounted up, and then I'll just bolt them back on ~34 months from now when I return the car

I put a set of the 18" 235 PZ4 porsche spec pirellis on my other car and took them off a few days later. It felt like you were driving on dough compared to the PS4S. Unless they change something drastically, I wouldn't consider using pirelli on a heavy car any time in the future.

 

[Kvitravn]

I think the 9x20 + 10x20 package would be great for performance but of course cost some range.

They probably felt longer range was more important than laptimes os went wioth the super narrow 235s to distance themselves from competition.

 

[Sam1]

Good info, it'll be interesting to hear about your results.

Yeah, I know Pirelli has some brand equity, including being used in motorsports/ on some exotics, but they had the same bad rep with Mustang folks , they were the tire included with the Performance Package, and they were mediocre at __best__. Almost everyone swapped them out for a Firehawk Indy or MPS4S.

I might do a wheel swap, in which case I'll just leave the wheels/tires all mounted up, and then I'll just bolt them back on ~34 months from now when I return the car

Forgot to go get times on the new ones, will in a day or two...have to do it in the same location because the city used Grade-A asphalt as a test in this area and a section of it is as good as an unprepped track surface.

As far as everything else, handling is much better, there's almost no spin from either axle now, cornering is much more predictable and the tire actually fills out the wheel and looks normal instead of looking like the tire is too small like the pirelli

 

[MaskedRacerX]

Forgot to go get times on the new ones, will in a day or two...have to do it in the same location because the city used Grade-A asphalt as a test in this area and a section of it is as good as an unprepped track surface.

As far as everything else, handling is much better, there's almost no spin from either axle now, cornering is much more predictable and the tire actually fills out the wheel and looks normal instead of looking like the tire is too small like the pirelli

And what tire spec/brand did you swap to? I retraced your posts, and wasn't 100% sure (MPS4S in a 235/35 T-spec?)

 

[Sam1]

And what tire spec/brand did you swap to? I retraced your posts, and wasn't 100% sure (MPS4S in a 235/35 T-spec?)

It was the PS4S Tesla spec 235/35/20 - same tire that was on the m3p prior to pirelli