275/30R20's on a M3P?

[Lindenwood]

I am really curious as well. Once I decided to keep the Uberturbines, I knew I wanted to get rid of the stretch (and by Fall I’d need to swap for all seasons anyways).

I wanted to add a bit more cushion and rim protection. I went back and forth between 275/30R20 and the 255/35R20, and I ended up actually getting the latter because I knew they would fit up front with my existing spacers, and I was a little worried about what others described as wandering steering with wider tires in narrower wheels.

Still, in hindsight, I probably would go 275 or even 265/30R20. I didn’t get as much rim protection as I was hoping, and I think a little bulge would actually do more to cushion the ride than a slightly taller but more stretched sidewall.

 

[dfwatt]

I am really curious as well. Once I decided to keep the Uberturbines, I knew I wanted to get rid of the stretch (and by Fall I’d need to swap for all seasons anyways).

I wanted to add a bit more cushion and rim protection. I went back and forth between 275/30R20 and the 255/35R20, and I ended up actually getting the latter because I knew they would fit up front with my existing spacers, and I was a little worried about what others described as wandering steering with wider tires in narrower wheels.

Still, in hindsight, I probably would go 275 or even 265/30R20. I didn’t get as much rim protection as I was hoping, and I think a little bulge would actually do more to cushion the ride than a slightly taller but more stretched sidewall.

Wouldn't ever recommend a 275 / 30 on a 9 inch rim. Not nearly enough rim and significantly compressed is actually worse than very slightly stretched, especially on such a radical low profile Tire. Indeed on a 9 inch rim the 235/35 Michelin Pilot Sport in the Tesla spec is technically not even stretched as section width is 9.5 in. The problem with that kind of compression of a 275/30 is that you actually bow up the edge of the tire and lose the functional benefits of all the tire width. We have the 275/30 Michelin Pilot Sport 4S again in a Tesla spec on the rear of both of our performance Model 3s. It's a fantastic tire but it ideally needs a 10.5 inch rim.

 

[Lindenwood]

Wouldn't ever recommend a 275 / 30 on a 9 inch rim. Not nearly enough rim and significantly compressed is actually worse than very slightly stretched, especially on such a radical low profile Tire. Indeed on a 9 inch rim the 235/35 Michelin Pilot Sport in the Tesla spec is technically not even stretched as section width is 9.5 in. The problem with that kind of compression of a 275/30 is that you actually bow up the edge of the tire and lose the functional benefits of all the tire width. We have the 275/30 Michelin Pilot Sport 4S again in a Tesla spec on the rear of both of our performance Model 3s. It's a fantastic tire but it ideally needs a 10.5 inch rim.

While I fully understand why they aren’t ideal for precise handling, I am not sure it is quite this bad. Attached is a 275 spec sheet indicating it is clearly designed for 9-10” wheel widths (most are designed for 9-10.5” that I’ve seen), plus a sample pic of a 275/30R20 mounted on a 9” wheel.

 

[CorneliusRox]

I went with these. Couldn't be happier. Slightly more grip than the OEM PZero's (due to width I'm sure), they look better, cheaper, and they're great in the snow/ice!
I have no rubbing or anything, but I think a 275 would be really tight.
Also, I told the car I have the race tires on there and my speedo is pretty dead on now.

G-FORCE COMP-2 A/S PLUS - 255/35R20
https://www.tirerack.com/tires/tire...Tire=535WR0GFC2ASPXL&rearTire=735WR0GFC2ASPXL

 

[Lindenwood]

I went with these. Couldn't be happier. Slightly more grip than the OEM PZero's (due to width I'm sure), they look better, cheaper, and they're great in the snow/ice!
I have no rubbing or anything, but I think a 275 would be really tight.
Also, I told the car I have the race tires on there and my speedo is pretty dead on now.

G-FORCE COMP-2 A/S PLUS - 255/35R20
https://www.tirerack.com/tires/tires.jsp?tireMake=BFGoodrich&tireModel=g-Force+COMP-2+A/S+PLUS&frontTire=535WR0GFC2ASPXL&rearTire=735WR0GFC2ASPXL

View attachment 814147
View attachment 814148

I had that top pic saved in my phone for a couple weeks as I went back and forth on the sizes .

 

[CorneliusRox]

I had that top pic saved in my phone for a couple weeks as I went back and forth on the sizes .

ha ha thanks for the compliment.
Honestly, if you wanted to do a staggered setup, 275's would probably fit on the rear, but... the wheels are 9" (228.6mm) wheels. 10" (254mm) or 10.5" (266.7mm) wheels would work better.
I'm pretty happy with the results.

I will say, I went with a very toe neutral alignment for tire wear mostly. It's not as stable at high speed cornering as I'd like. I will likely bring it back in a tiny bit and deal with the slightly higher wear at this slightly higher negative camber from the trim height drop. I'm really trying not to go crazy with this car like I have in the past! ha ha I don't want adjustable control arms, coilovers, swaybars, etc... I just want it to look good and feel solid with low maintenance.

 

[tm1v2]

ha ha thanks for the compliment.
Honestly, if you wanted to do a staggered setup, 275's would probably fit on the rear, but... the wheels are 9" (228.6mm) wheels. 10" (254mm) or 10.5" (266.7mm) wheels would work better.
I'm pretty happy with the results.

I will say, I went with a very toe neutral alignment for tire wear mostly. It's not as stable at high speed cornering as I'd like. I will likely bring it back in a tiny bit and deal with the slightly higher wear at this slightly higher negative camber from the trim height drop. I'm really trying not to go crazy with this car like I have in the past! ha ha I don't want adjustable control arms, coilovers, swaybars, etc... I just want it to look good and feel solid with low maintenance.

@CorneliusRox When you add some toe back let us know if it helped.

I went for coilovers and some bushing upgrades on my car, cornering stability is worlds better now, but I hear you on all the potential downsides and I'm definitely interested to know if just some alignment changes could improve cornering stability with the stock suspension, which felt very unsettled to me. (I'm not going back to stock suspension, but e.g. if a friend wants some improvement without going to an aftermarket suspension, would be good if I could give some suggestions.)

 

[dfwatt]

While I fully understand why they aren’t ideal for precise handling, I am not sure it is quite this bad. Attached is a 275 spec sheet indicating it is clearly designed for 9-10” wheel widths (most are designed for 9-10.5” that I’ve seen), plus a sample pic of a 275/30R20 mounted on a 9” wheel.
View attachment 813815
View attachment 813816

Even with your graphic for that particular Tire the section with is 10.9 in. So you're talking about 2in of compression of the section width relative to the rim mounting surface. You can go that way, but almost nobody recommends it, and Michelin specifically does not allow or recommend their tesla spec 275/30 x 20in Tire to be mounted on a 9 inch rim. Indeed our local installer would not Mount such a combo. You do this at your own risk, and you're spending a boatload of extra money to get an oversized Tire to get better traction and you are degrading that asset with this mount. It's your money and your car and obviously you can do what you want but I strongly urge you to spend the extra money to get a proper rim for that tire. There are no good shortcuts in this business and I think you're trying to take one. I don't know if you're planning to do this in a staggered or Square setup but you will need to run a lot of negative camber in the front just to get this combination to clear the fender, and additionally without significant change in offset it will definitely not clear the front steering knuckle. I have a 9.5 inch rim with aftermarket rotors with a 40 mm offset that just clears the front steering knuckle with a 265 / 30 Pilot Sport 4S. I've got only a few mm of clearance and that tire of yours is significantly wider.

 

[Lindenwood]

I wanted to add a bit more cushion and rim protection.

Even with your graphic for that particular Tire the section with is 10.9 in. So you're talking about 2in of compression of the section width relative to the rim mounting surface. You can go that way, but almost nobody recommends it, and Michelin specifically does not allow or recommend their tesla spec 275/30 x 20in Tire to be mounted on a 9 inch rim. Indeed our local installer would not Mount such a combo. You do this at your own risk, and you're spending a boatload of extra money to get an oversized Tire to get better traction and you are degrading that asset with this mount. It's your money and your car and obviously you can do what you want but I strongly urge you to spend the extra money to get a proper rim for that tire. There are no good shortcuts in this business and I think you're trying to take one. I don't know if you're planning to do this in a staggered or Square setup but you will need to run a lot of negative camber in the front just to get this combination to clear the fender, and additionally without significant change in offset it will definitely not clear the front steering knuckle. I have a 9.5 inch rim with aftermarket rotors with a 40 mm offset that just clears the front steering knuckle with a 265 / 30 Pilot Sport 4S. I've got only a few mm of clearance and that tire of yours is significantly wider.

First, I already said I went with 255/35R20 for all the concerns that we have both stated or implied (I.e handling precision and tire fitment in the wheel well / against the knuckle).

Secondly, I specifically mentioned 275/30R20 on factory rims as a means of increasing cushion and rim protection on factory wheels, not as a means to increase traction or performance against any timer. Everything you said is spot-on for performance, but does not apply to the hypothetical goal I mentioned of getting more rubber over the wheel and a little less sidewall stiffness. If someone wants 10mm more rubber past the wheel lip for more curb protection (and FWIW the middle of my 255’s sidewall is definitely inboard of my 9” rim’s outer lip), and a little cushier ride, and perhaps likes the aesthetics of a little more meat, then a 275/30R20 would surely be a reasonable option as long as they are willing to accept some modest sacrifices.

 

[Lindenwood]

Even with your graphic for that particular Tire the section with is 10.9 in. So you're talking about 2in of compression of the section width relative to the rim mounting surface. You can go that way, but almost nobody recommends it, and Michelin specifically does not allow or recommend their tesla spec 275/30 x 20in Tire to be mounted on a 9 inch rim. Indeed our local installer would not Mount such a combo. You do this at your own risk, and you're spending a boatload of extra money to get an oversized Tire to get better traction and you are degrading that asset with this mount. It's your money and your car and obviously you can do what you want but I strongly urge you to spend the extra money to get a proper rim for that tire. There are no good shortcuts in this business and I think you're trying to take one. I don't know if you're planning to do this in a staggered or Square setup but you will need to run a lot of negative camber in the front just to get this combination to clear the fender, and additionally without significant change in offset it will definitely not clear the front steering knuckle. I have a 9.5 inch rim with aftermarket rotors with a 40 mm offset that just clears the front steering knuckle with a 265 / 30 Pilot Sport 4S. I've got only a few mm of clearance and that tire of yours is significantly wider.

Legit question:

Reading through some of the AutoX threads, it seems 265s on 8.5” wheels (22% wider than the wheel) is fairly common. I noticed a surprising number of folks at my AutoX event running pretty bulgy tires. I spoke to a Vette driver who said he moved up from 285s to 305s on 20x10” wheels (20% wider than the wheel) this season and saw a definite improvement. I understand why those width ratios aren’t ideal, but the reported success doesn’t seem to align with being so unsafe or ineffective that a tire shop would refuse to install them for a paying customer.

Am I grossly missing something about running 275s on 9” wheels (also 20% wider)?

 

[Firemansim]

So, has anyone actually run 275/30/20 on the front with the Uberturbines??? I keep waiting for the answer on if they'll fit. ANYONE?

 

[tm1v2]

@Lindenwood I think there's two aspects at play there when you see people racing on bulgy tires. One, the rules for their class or series might restrict wheel width but not tire width (or have mismatched restrictions possibly). In that case maybe bulgy tires on restricted width wheels could give a bit more grip, even if it probably doesn't provide the best handling response. If you're in it to win it then numbers win, no matter if the car might feel a bit more awkward.

Two, it could be a simple cost thing, not wanting to spend the $$$$ on even wider 20" wheels just yet, or scoring a great deal on good tires in a size they wouldn't otherwise choose but could plausibly mount to try.

You used the word "unsafe" but I don't think anyone here suggested such tire-wheel pairings would be unsafe. (Well at some extreme point sure, but not the pairings brought up here.) Just not optimal - better to use an appropriately wide wheel if possible.


@Firemansim I think most people who buy a sporty car like the M3P don't do balloon tire sizing on their wheels unless forced into it for reasons mentioned above. Plus anyone actually wanting balloon tire sizing for real offroad-y use, e.g. dirt trails, will probably downsize from the huge fragile Uberturbines, because they make no sense for such driving. (Not that the Uberturbines really make sense on pavement either, if your roads are as poorly maintained as mine.)

So...I'm going to say very unlikely anyone who will read this has tried 275/30R20 on Uberturbines. If you try it, report back how it goes! I do get liking the bulky tire look, heck I'd prefer it over stretched tire sizing that's so common these days, but it's basically non-existent among TMC M3P owners from what I've seen.

 

[tm1v2]

@Lindenwood Also I'm guessing many/most Corvettes are traction-limited for putting power down in autox courses. (Just a guess, feel free to correct me if that's wrong!) It seems possible most of that Vette driver's gains from the fat tire pairing are from putting more power down, rather than improving cornering grip.

If that's the case I would not expect the same benefit in an M3P...

I'm completely armchairing this of course.

 

[colindo1990]

I've ran 275/30/20 on 20x9 for my bmw before, they look fine

20x9 et 35 should clear inner and outer

if I were u, I would run 245/35/20 in fronts and 275/30/20 in the rears


my current set up is 20x9 245/35/20, 20x10 295/30/20

 

[Lindenwood]

@Lindenwood I think there's two aspects at play there when you see people racing on bulgy tires. One, the rules for their class or series might restrict wheel width but not tire width (or have mismatched restrictions possibly). In that case maybe bulgy tires on restricted width wheels could give a bit more grip, even if it probably doesn't provide the best handling response. If you're in it to win it then numbers win, no matter if the car might feel a bit more awkward.

Two, it could be a simple cost thing, not wanting to spend the $$$$ on even wider 20" wheels just yet, or scoring a great deal on good tires in a size they wouldn't otherwise choose but could plausibly mount to try.

You used the word "unsafe" but I don't think anyone here suggested such tire-wheel pairings would be unsafe. (Well at some extreme point sure, but not the pairings brought up here.) Just not optimal - better to use an appropriately wide wheel if possible.


@Firemansim I think most people who buy a sporty car like the M3P don't do balloon tire sizing on their wheels unless forced into it for reasons mentioned above. Plus anyone actually wanting balloon tire sizing for real offroad-y use, e.g. dirt trails, will probably downsize from the huge fragile Uberturbines, because they make no sense for such driving. (Not that the Uberturbines really make sense on pavement either, if your roads are as poorly maintained as mine.)

So...I'm going to say very unlikely anyone who will read this has tried 275/30R20 on Uberturbines. If you try it, report back how it goes! I do get liking the bulky tire look, heck I'd prefer it over stretched tire sizing that's so common these days, but it's basically non-existent among TMC M3P owners from what I've seen.

From my mentioning of it being “unsafe,” I mean to say I am skeptical that a certified and insured tire shop wouldn’t take my $80 to mount tires on wheels perfectly within their specified limits. Sure, I have had to sign waivers for mounting oversized (or undersized) tires, but an outright refusal seems a little silly to me without being way outside of bounds.

 

[dfwatt]

So, has anyone actually run 275/30/20 on the front with the Uberturbines??? I keep waiting for the answer on if they'll fit. ANYONE?

You might be able to get a shop to mount them but it would not be recommended and the stock wheel would not clear the front steering knuckle with those tires. The section width is almost 11 in so you're talking about 2 in of compression of the section width in a very low profile tire. And you have to have a big change in offset to have it clear the front steering knuckle. So that would rule out the OEM stock wheels. Even with lots of negative camber I think you'd need something like at least 1 cm of additional offset. So short answer is no.

 

[Lindenwood]

You might be able to get a shop to mount them but it would not be recommended and the stock wheel would not clear the front steering knuckle with those tires. The section width is almost 11 in so you're talking about 2 in of compression of the section width in a very low profile tire. And you have to have a big change in offset to have it clear the front steering knuckle. So that would rule out the OEM stock wheels. Even with lots of negative camber I think you'd need something like at least 1 cm of additional offset. So short answer is no.

I think we’ll just have to agree to disagree on this one.

*edit*

Actually, I don’t think we really even disagree, but we both seem determined to be right so that’ll be enough for me.

 

[dfwatt]

I think we’ll just have to agree to disagree on this one.

*edit*

Actually, I don’t think we really even disagree, but we both seem determined to be right so that’ll be enough for me.

I'm not sure how you can have a disagreement about something that is so clearly established and has been reported on by other members of the form. A 275/30 will not fit underneath the front steering knuckle on a Model 3 unless there is a change in offset. This means the stock 20 in uberturbine wheel will not work. This is not complicated. So in the interest of scientific and empirical process, please by all means do try this and report back to us what you find . No need to even debate the viability of the 255/30. That's been tested and proven to work and sits pretty well on a 9 in wheel.

 

[Lindenwood]

I'm not sure how you can have a disagreement about something that is so clearly established and has been reported on by other members of the form. A 275/30 will not fit underneath the front steering knuckle on a Model 3 unless there is a change in offset. This means the stock 20 in uberturbine wheel will not work. This is not complicated. So in the interest of scientific and empirical process, please by all means do try this and report back to us what you find . No need to even debate the viability of the 255/30. That's been tested and proven to work and sits pretty well on a 9 in wheel.

Good God.

In my post I EXPLICITLY addressed the concern about fitment of a 275/30R20 on stock 20x9s without careful spacer selection.

Like I said, at this point this exchange is more about winning an internet argument than adding meaningful insight for the OP.

 

[dfwatt]

Good God.

In my post I EXPLICITLY addressed the concern about fitment of a 275/30R20 on stock 20x9s without careful spacer selection.

Like I said, at this point this exchange is more about winning an internet argument than adding meaningful insight for the OP.

Sorry I'm not sure how you can get a 1 centimeter spacer onto that wheel? Again you keep trying to salvage a bad idea. Get a proper wheel with the proper offset. This is more than about who's right. This is also about safety. You are recommending things that are problematic from a safety standpoint. You do not have enough lug nut grab to run a spacer that will get that wheel and tire outboard of the front steering knuckle. Sorry. Or as you would say Good God!