Emanuel373

This has been interesting to read. I just bought a 2005 base RX8 as well and reading this I got some inspiration.




The car is stock except Tokico D series shocks and 245/40 18 RE11 tires. I plan to autox it on street tires and will probably be back for more questions and sharing experiences if the OP doesn't mind.

TeamRX8

iTrader: (25)

I doubt he minds, but he's probably wishing he had been on a set of shaved Dunlops instead

marka

Howdy,

No, I don't mind at all. And Mark's right, at least as far as "I wish I could run these and the 225/40 Dunlop back to back".

In the end, for us at nationals we could never dial out enough of the oversteer, particularly on turn in. We got it ok on the practice course, but it was worse on the actual nationals courses. I'm not happy about not being able to adjust the rear rebound, and will be making some changes to be able to do that over the off season.

Mark

TeamRX8

iTrader: (25)

It was well over a second on a 30 sec course that I tested them back-back on, they also were likely impacting your issue as well

PedalFaster

I tested the Michelins and Dunlops back-to-back for a total of fourteen runs at different pressures. My average and median times were both a tiny bit better with the Michelins, but my best time was with the Dunlops. I ended up running the Dunlops because they're the safe choice, but if someone had switched me to the Michelins at the last second, I wouldn't have freaked.

Others' results may vary due to car choice, driving style, surface, etc.

marka

Howdy,

What sizes & what was the surface? Do you tend to have a 'different' driving style?

Probably all moot anyway, if all the "new tires next year!" stuff is going to happen.

One of the things that's nice with the Michelin is that you can get a 245/35-18 size that the others don't make. Shortens up the tire a lot and helps the gearing. The much more common 225/40-18 is similar though, and if the "don't overtire with streets" stuff is right, perhaps that's an equivalent choice anyway.

Mark

TeamRX8

iTrader: (25)

I was testing on concrete at College Station, which imo has more grip than Lincoln

The Michelins have huge voids for water evacuation and were full tread. Unlike some of the other tires, the voids are straight cut so they don't decrease and add contact patch area as the tire wears or is shaved.

The Dunlops were shaved. Full tread Dunlops need at least 30 runs or a lot of street time before they come in. Shaving them minimizes this down to several runs. It also increases the contact patch area as the voids are angled or otherwise have a variable depth. Both were 245 width on 9" wheels, so well supported. The Michelins appear to have a small tread width relative to their sidewall width.

I have previously been running Toyo R1Rs for a long time, and Hankook R-S3s for a long time before that, so I don't claim to be an expert on those other two. It could be that the Michelins need more run time as I was only trying to get them scrubbed for wet course use if needed. The end results were the same for two different drivers, different air pressures. The Michelins communicated their grip level well, but it definitely was less overall for my limited time on them. I wasn't that impressed with them.

New tires are coming next year, but pending those results I intend to go back to Toyo.

PedalFaster

245/40R17 for both makes, on narrow stock rims (7" F, 8.5" R). Asphalt. Hot (sunny with air temperatures in the 90s). My driving style is aggressive but I wouldn't say it's "different". Both sets of tires had a few thousand street miles on them and were thus scrubbed in; Dunlops had maybe thirty runs on them, whereas the Michelins had never been run in anger.

Emanuel373

Sorry, I got a little lost in the last few posts. After all his thread is about CS, so only 18x8 wheels should be thrown in the mix of experiences, everything else seems irrelevant, or not? Correct me if I'm wrong.

I would guess the RX8's behavior changes quite a bit with STX legal wheels and tires.

I'm interested to learn how much tire is reasonable on a stock wheel size, as RTA proved Andy Hollis theory wrong. Looks like you certainly can over tire street tires and it will be significantly faster. They ran 265's on 8" wheels and Andy finished at 221 on the 0.975 corrected overall final PAX index, with the fastest RTR RX8's way behind in the 400+. Yes you may loose feel and transition speed, but in high G sweeping corners, you just have so much more rubber on the ground.

FWIW, I drove a friends 2006 WRX on OEM size wheels and tires (215s on 7") and we didn't really had a chance. The 3-4-Three Challenge

TeamRX8

iTrader: (25)

winning only proves you were faster, the reasons why are not always so clear particularly once you add in 4wd vs 2wd. Awd is superior in low traction scenarios and running on street tires is an equivalent to this. It's the reason that RT was split up into R, A, and F

I already knew PedalFaster is stuffing his wheels, but that he didn't win RTR doesn't necessarily have anything to do with it though using your logic I could counter argue that it did


.

Emanuel373

The Genesis with the GS index is a real tough nut to crack in RTR, next are the various Miatas and S2000, you also can't count the Bimmers out and we don't yet know the real performance potential of the FRS/BRZ, there is also a local 350z that does extremely well on street tires, which also means the 370z is probably even better.

I'm aware that the answer isn't easy and that's why I'm here to learn. I already know Lincoln is different, from almost anything else. Locally I beat myself driving the RX8 (roughly 1 second faster so far) vs the WRX on street tires. So if that doesn't translate to nationals, how would you gauge your performance? What are the things that do matter? Is the answer just to try to get as fast as possible and see how far one get in September? Or are there any clear indications that one is on the right track? How does one know if the car was actually better and one didn't just had a lucky day?

I believe to be a fairly good driver, but autox is just a hobby for me. I just don't have the time and money to do extensive testing. My testing will be done only by attending events.
I'm aware that this lack of of dedication will most likely mean to finish midfield at best, but I'm hoping to find enough information to make a good decision on what tire to bring next year to not be completely out gunned. Any help would be very much appreciated.

PedalFaster

Relatively few people have the time, money, and dedication required to do meaningful tire testing. Fewer still of those people are willing to share their results since they potentially constitute a competitive advantage. Given that, if you're not willing or able to test yourself, you can either wait patiently for someone with the exact same setup and driving style that you have to test tires on your lot and publicize their results, or you can read all of the feedback online from people who have tested tires on different setups and make the best decision you can based on imperfect data.

If you opt to go the former route, expect to wait a long, long time.

Emanuel373

You're right of course imperfect data goes a long way, silly me to expect more specific data about RX8's on an RX8 forum in a stock class thread.

PedalFaster

Feel free to ignore what Mark and I wrote, then. Shame on us for failing to meet your exacting standards while trying to be helpful.

TeamRX8

iTrader: (25)

there are no absolutes, not even in testing

I can appreciate that simpletons require simple answers though ...

MikeTyson8MyKids

iTrader: (1)

Oh Ooo. Zing.

TeamRX8

iTrader: (25)

where were the front Konis adjusted?

godesshunter

I assume a good performing tire is just that, no matter what car you have it on.

If you've had good luck in the past with a certain tire on a previous car, why switch it up?

marka

Howdy,

We had them at ~ 2/3's stiff at first, then moved them to full still (minus 1/8 turn). At full stiff it was a bit better, but only just a bit.

We were also playing with tire pressures a little and for the 2nd day added some rear toe in (previously at zero).

It wasn't scientific, but the car kept getting a little better. Only a little though... It was still loose enough on turn in that it was hard to drive aggressively.

Mark

TeamRX8

iTrader: (25)

you likely don't have enough rear camber and/or toe then, those settings will work OK for R tires because of the grip difference. Street tires changes the game slightly.

marka

Howdy,

Recommendations for alignment for me? Today I'm at:

Front: -1.6 deg, 7 deg caster, -0.2 deg toe

Rear: -1.1 deg, somewhere between 1/8" and 1/4" toe in (haven't measure it with real tools, outside of a half assed string alignment in the wind at nationals. We were at zero toe prior to that).

I'd be interested in knowing when you want add camber and when you want to add toe as well. The car is loose on turn in primarily. Mid corner and corner exit its nowhere near as bad.

Mark

TeamRX8

iTrader: (25)

The rear Koni Sport rebound range is not that aggressive. 1.1 degcamber is really low for the rear. I was probably one of the few people to run it that low, but this was with fat Hoosiers. I also wasn't sure how much toe you added. It was really too low previously.

On corner entry with OE springs the nose is going down and the tail is coming up. It is losing both rear toe and rear camber at the same time during this transition. Once you correct for it you will likely need to make other changes to address middle and exit balance.

Orthonormal

Mark A.: Bryan and Zach ran slightly more camber in the rear than in the front (about -0.2 degrees more) when Bryan won Nationals. Zero toe front and rear, off the shelf Konis and stock swaybars. I've been running -1.1 front / -1.8 rear (zero toe) with the stock 2010 shocks, and it was push city even with the R3 rear bar (which doesn't really make the rear that much stiffer anyway). I'm now at -1.2 / -1.4 with the Konis installed, I'll see tomorrow if that helps.

If you've managed to get oversteer with a big front bar, all I have to say is "that's awesome" because I wish I had that problem.

Orthonormal

So yeah, the car is much better with the new shocks and the new rear camber setting.

TeamRX8

iTrader: (25)

They were on 285 Hoosiers. Big difference.