Street Tire Class 2013

JohnByers · **Posted:** Wed Jul 10, 2013 9:12 am

JamesShort wrote:

If Chuck can tame that M3 with 245s at all 4 corners, I'd say your Mustang should be fine.

This.

fwiw, on my RTR RX8 I run 245/40/18's on the stock 8" wide wheels on Rivals and I love the grip!

Andrew Jonell · **Joined:** Mon Mar 23, 2009 6:43 pm **Posts:** 1350

Tarheel Stance Car Club.

Chuck Branscomb · **Posted:** Wed Jul 10, 2013 9:54 am

Andrew Jonell wrote:

Tarheel Stance Car Club.

Tarheel Stretch Car Club:

DickRasmussen · **Posted:** Wed Jul 10, 2013 12:26 pm

I'm pretty sure that Andy Hollis and others with similar testing knowledge say that for street tires versus R tires the streets generally are better with the proper size rim versus larger tire on "narrow" rim.

Just read a couple of posts on another forum from Andy Hollis (sorry Art :lol:

) and from Woody of Tire Rack. Data that they have supports the theory that "true street tires" such as the Rival work best with a "square" (i.e. Tire width = tread width ) versus the A6 approach of widest possible tire on the stock rim.

Ryan Holton · **Posted:** Wed Jul 10, 2013 12:40 pm

Ohhhh I can play too

That's a 205 Rival vs a 215 Z1

Look at the actual tread width for the Rival, they run BIG.

Chuck Branscomb · **Posted:** Wed Jul 10, 2013 1:21 pm

Art,

I forgot to get back to my point on the Rivals, so I guess the "sec" turned into a few hours. Video link is from a Performance Center CCA "autocross" back in April on the Rivals. Before this event, I had only ever driven the track down there with the M5 and on NT-01s every time. I would say the Rivals are really close to the NT-01s in ultimate stick and better in transients.

Anyway, the point I wanted to make is how forgiving they can be if you go over the top of the tractive force/slip angle curve. They still grip really nicely even when you overcook it and have to use large slip angles, lots of steering angle, to correct.

Click on an HD mode in the video and full screen it. At about the 1:00 mark is the entry into the tightest section of the course, a left followed by the right. Note how in that right turn I overcook the entry just a bit, and you can see from the apex onward that I dial in some lock and then have to dial in a lot more. Note how they just continue to stick and then by the time I'm nearing the track out point I can get back into the throttle hard and get the rear rotating. Stuff like this just makes me love these tires more each time I drive them since an autocross for me is fraught with mistake making all around the course...just try to make them small mistakes, and it's nice to have a tire with such stick that is forgiving.

https://www.youtube.com/watch?v=tFhtzGsXD6M

On an A6 or NT-01, if I had overcooked that entry that much, the corner would have been blown as neither of them grip well past the peak of the slip angle curve but in fact drop sharply off. Not only that, but I doubt I'd be able to get the tail rotating near the track out point with them either.

Arthur McDonald · **Joined:** Fri Aug 29, 2003 1:54 am **Posts:** 2052

Chuck,

Thanks for taking the time to reply in, depth, twice. I don't have the budget (or interest, at this point) to buy multiple sets of tires to do a comparison. So I will probably go with the 245s.

James,

Thank you for pointing out that Mustangs are easy to drive. As I always say: If you can drive a Prius through the Starbucks drive-through, you're ready to drift a GT-500

John,

Your car only weighs 900 lbs (as far as I'm concerned) so not a fair comparison.

Dick,

I'm still steamed that Andy stole a Laurinburg/NCAC ES trophy from me (by about 4 seconds), a few months before he was nailed for you-know-what. He never sent me a note of apology.

Ryan,

Nice to hear from you!

Arthur McDonald · **Joined:** Fri Aug 29, 2003 1:54 am **Posts:** 2052

I ordered 245/40-18 Rivals. The tire rack rep, same guy I talked to Tuesday, challenged my choice, noting that I have a heavy, powerful car. Well, heavy. And so we had the discussion about matching rim width to tire width and sidewall stiffness.. and then he asked if could call me back after he checked with a colleague who had been testing different width Rivals on a Miata.

He called back in 5 and said the 245 was right, that the Rival does not like too-narrow rims. I assume this was a sincere answer, after all, the 245s are $56 less per tire than the 275s. And he threw in a new set of lug nuts for the wheels I bought from them 4 years ago, gratis.

Twenty minutes after I got the email confirmation of my purchase, I got the Tire Rack "The Boys of Summer: Extreme Performance Tire Test" test report in my inbox. http://www.tirerack.com/tires/tests/tes ... p?ttid=172 Based on that, the Direzza ZII might be the faster tire, at least in the hands of a surgeon. Fortunately, I'm a ham-fisted Mustang driver.

Chuck Branscomb · **Posted:** Fri Jul 12, 2013 7:35 am

That's hilarious Art. You will not be unhappy with the Rivals. Interesting they found the II a tad quicker (and expected actually) than the GMR tests which had the Rival clearly out front not only on average lap time but also peak lap time with two different drivers. It would be nice to see how TR tabulates their test data and how many drivers they use, etc.

The second thing is that it would be nice to get *independent* test data somehow, but without an individual forking out the bucks for a comprehensive test, we get what we get.

I say that because I'm thinking about an issue 25 years back when I worked at IBM and was in the Proprinter group (anybody here remember the Proprinter?). It's 1988, HP had just introduced the Deskjet, and we were in the middle of developing a bubble-jet printer also, as the age of impact dot matrix printers, which the Proprinter III excelled at, was coming to a close. Sales rates of the ProIII all of the sudden dropped substantially at Computerland and some other outlets as customers were choosing the Epson competitor printer. One month the PIII is well ahead, then a switch happens in the market. Investigation turned out that Epson was providing a direct to the salesperson incentive of $25 per printer to move their product. Funny how overnight that month the Epson became the "best printer".

Steven Carter · **Posted:** Fri Jul 12, 2013 7:44 am

The only caveats I could see from the TR vs GRM data are the car used (heavy F30 328 for TR vs light CRX/Civic for GRM) and that the TR car was stock set-up vs autocross setup for GRM.

I am also not sure how much weight to place on a 5-second slalom..seems too prone to driver noise for such a short timeframe.

DickRasmussen · **Posted:** Fri Jul 12, 2013 7:56 am

Arthur McDonald wrote:

I ordered 245/40-18 Rivals. The tire rack rep, same guy I talked to Tuesday, challenged my choice, noting that I have a heavy, powerful car. Well, heavy. And so we had the discussion about matching rim width to tire width and sidewall stiffness.. and then he asked if could call me back after he checked with a colleague who had been testing different width Rivals on a Miata.

He called back in 5 and said the 245 was right, that the Rival does not like too-narrow rims. I assume this was a sincere answer, after all, the 245s are $56 less per tire than the 275s. And he threw in a new set of lug nuts for the wheels I bought from them 4 years ago, gratis.

Twenty minutes after I got the email confirmation of my purchase, I got the Tire Rack "The Boys of Summer: Extreme Performance Tire Test" test report in my inbox. http://www.tirerack.com/tires/tests/tes ... p?ttid=172 Based on that, the Direzza ZII might be the faster tire, at least in the hands of a surgeon. Fortunately, I'm a ham-fisted Mustang driver.

FYI one of the lead Tire Rack testers (Woody) posted yesterday afternoon on another forum that their data still supports the idea of keeping the tire width and the rim width similar rather than the A6 approach of squeezing wide tires on relatively narrow rims for Stock. Also note that BFG's intro for the Rival used 245's on Mustangs.

I wonder why they didn't test the R-s3 in this comparison since it is changing to 200 TW with no change to the tire?

Ryan Holton · **Posted:** Fri Jul 12, 2013 8:05 am

Steven Carter wrote:

The only caveats I could see from the TR vs GRM data are the car used (heavy F30 328 for TR vs light CRX/Civic for GRM) and that the TR car was stock set-up vs autocross setup for GRM.

I am also not sure how much weight to place on a 5-second slalom..seems too prone to driver noise for such a short timeframe.

Andy Hollis also chimed in that the TR test only did a standard tire pressure across all 4 tires. They did not test to find the best pressure for the fastest lap times.

I think saying "there are no wrong choices" applies here. All these new tires kick ass.

Chuck Branscomb · **Posted:** Fri Jul 12, 2013 8:32 am

Ryan Holton wrote:

Andy Hollis also chimed in that the TR test only did a standard tire pressure across all 4 tires. They did not test to find the best pressure for the fastest lap times.

I think saying "there are no wrong choices" applies here. All these new tires kick ass.

Good point Ryan. I know on most BMWs they specify lower front pressures to induce understeer even on staggered wheel setups. :shock:

The stock pressure spec on our E90 330i is 32 front and 36 rear after this thing already has 225/40 front and 255/35 rear with a 50/50 weight distribution. The F30 is spec'd at 32/38.

TR should at least even out pressures at something like 35 cold all around for testing tires like these not to mention tuning pressures based on how each tire design is interacting with the car. Sigh.

DickRasmussen · **Posted:** Fri Jul 12, 2013 6:56 pm

Chuck Branscomb wrote:

Ryan Holton wrote:

TR should at least even out pressures at something like 35 cold all around for testing tires like these not to mention tuning pressures based on how each tire design is interacting with the car. Sigh.

I think that is what GRM tests are "for" . . . :lol:

Bill Aycock · **Joined:** Wed Sep 26, 2012 1:55 pm **Posts:** 117

Les Davis wrote:

My advice? Just run your appropriate Street Mod class, screw silly SCCA rules and most importantly PAX (PAX SUX) and enjoy modifying you're car however you like. Boost is fun, more boost is more fun. If you have a turbocharged car and you are running stock boost level you are not having as much fun as you could be with your turbocharged car, run more boost, and have more fun.

Upon further review, Les is correct. More boost is definitely more fun :twisted:

Can we schedule than Non-points event already?

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