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Old 05-18-2018, 08:36 AM   #15
Norm Peterson
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I'd start by looking at 275/40-19's on 19x10's.

Another vote for Apex.


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Old 05-19-2018, 07:32 PM   #16
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Quote:
Originally Posted by Roostie View Post
I disagree that you fail to get any benefit from wider-than 215 tire on an 8.5" rim. Shops may not even mount a 215 on an 8.5" rim because that rim is wider than the recommended fitment range for a 215. An 8.5" rim is the max width rim for most 245/50 tires. I just bought wheels and 245/50 tires, and had to get the 8.5" rims even though 9" was available, because 9" is outside the range for the 245/50 tire size I wanted.

While it is true that you will get best performance out of a tire by putting it on the widest rim within the manufacturer's fitment range for that tire, it is not true that you gain no benefit from putting more than the narrowest tire that will fit on a given rim. I have studied this issue extensively for competitive autocross.
GRM has published multiple tests showing no performance benefit for section width exceeding wheel width. I'm not proposing a slight tire stretch for a street car, I brought it up to demonstrate the difference. That said, plenty of national level AutoX competitors appear to disagree as evidenced by their setups, so it's entirely possible there is a very small advantage. For a street tire of the class in question, it's not going to matter. I see a lot of people focusing on buying a wide tire, and not focusing on whether it's worthwhile. I also think one is better off buying a better (class) of tire in a narrower size, than shoving a wide tire on a narrow wheel. Wider often costs more.
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Old 05-20-2018, 07:56 AM   #17
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Quote:
Originally Posted by Snrub View Post
... plenty of national level AutoX competitors appear to disagree as evidenced by their setups, so it's entirely possible there is a very small advantage.
Anything a national-level Auto-X competitor does for tires and wheels is an artifact of the class ruleset, and where any benefit no matter how small is sought. Auto-x at that level can be a game where 0.00x seconds matters, and the guys at the top do their own testing.


Quote:
For a street tire of the class in question, it's not going to matter. I see a lot of people focusing on buying a wide tire, and not focusing on whether it's worthwhile. I also think one is better off buying a better (class) of tire in a narrower size, than shoving a wide tire on a narrow wheel. Wider often costs more.
Particularly for street-only duty, people understand the "bigger is better" part without necessarily understanding that everything that supports the function of what you just made bigger needs to be bigger/stiffer/grippier/etc., if you want to make it as good as it could be.


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Old 05-20-2018, 08:07 AM   #18
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Quote:
Originally Posted by Roostie View Post
While it is true that you will get best performance out of a tire by putting it on the widest rim within the manufacturer's fitment range for that tire, it is not true that you gain no benefit from putting more than the narrowest tire that will fit on a given rim. I have studied this issue extensively for competitive autocross.
This ↑↑↑

Maximizing the performance when the tire size is fixed is not the same thing as maximizing the performance when the wheel width is fixed.


In the taller profiles (60 & up, maybe even 55's), even max-recommended width might not maximize cornering. Might take half an inch wider than that.



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Old 05-20-2018, 01:36 PM   #19
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I've gotten a little lost in all of the recommendations. So is there a worthwhile benefit to doing 245/40R20 front with 275/35R20 rear vs 245/40R20 square? Thanks!
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Old 05-20-2018, 06:01 PM   #20
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Originally Posted by Could've_had_a_V8 View Post
I've gotten a little lost in all of the recommendations. So is there a worthwhile benefit to doing 245/40R20 front with 275/35R20 rear vs 245/40R20 square? Thanks!
Thanks for saying so. We got a little bit off-topic there with our tire-nerd discussion. I think (hope) that Norm, Snrub and I all agree that for your car, on which you intend to stick with the non-staggered 20" rims (which I believe are 8.5" wide), and you live in San Jose California, you are better off using a square set of 245/40/20 summer performance tires.

Squeezing 275/35/20 tires on the rear pair of 8.5" rims will give you little or no added grip in the back, it might create more understeer which isn't fun or fast, and you'd lose the ability to rotate tires front to rear. I see no advantages other than cosmetic, and I don't even care for the look of wide tires squeezed on rims.

For a better ride and typically better handling, I recommend non-run-flat tires, but you need to be prepared to deal with a flat. Your car probably came with an inflator and tire slime kit, just be ready to use it. Find the kit in your car and read the manual about the procedures, before trouble strikes.

Looking at TireRack.com and DiscountTire.com (might be called America's Tire in your area), I see these non-run-flat summer performance tires in 245/40/20 which would be good for your plans to drive on street and track:
Firestone Firehawk Indy 500, $151
Michelin Pilot Sport 4S, $349 (!)
Pirelli P Zero PZ4, $269
Pirelli P Zero, $265
Continental Extreme Contact DW, $227
I left out tires from TireRack that are designed for a particular model of vehicle, and I left out tires I think aren't as good as those listed above. Opinions vary greatly about which tire is best... but I think the Firestone is the best pick. TireRack found that it outperformed the BFG sport comp-2 which I've enjoyed, and which may previously have been the top performing tire in the bargain-end of the summer performance tire market.

Consider the treadwear rating of the tires. The manufacturers designate a number that isn't independently verified, but it is supposed to represent how long the tire will last. In theory, a 300 TW rating tire should last 50% longer than a 200 TW rating.
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Old 05-20-2018, 06:30 PM   #21
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The distraction probably started with post #2.

As for 8.5" wide wheels, I agree with Roostie (↑↑↑) about not going wider than 245's.


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Old 05-20-2018, 10:20 PM   #22
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Thanks for the very detailed response. Square Firehawks it is.
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Old 05-21-2018, 06:26 AM   #23
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Quote:
Originally Posted by Roostie View Post
I see these non-run-flat summer performance tires in 245/40/20 which would be good for your plans to drive on street and track:
Firestone Firehawk Indy 500, $151
Michelin Pilot Sport 4S, $349 (!)
Pirelli P Zero PZ4, $269
Pirelli P Zero, $265
Continental Extreme Contact DW, $227
I'd add the Michelin Pilot Super Sport ($305-ish, currently on close-out at Tire Rack) to that list. While the PS4S is the newer and better tire, the PSS can still hold its own out there on the track and in the wet.


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