mwood

Well, I'm finally going to have a chance to try out the RX8 this weekend.

We did the alignment yesterday and will run tomorrow on super grippy concrete at Atwater, just to try it out. I haven't installed the Konis, yet, but will do it before the "real" season starts, for sure. We were able to get -1.6F with caster right at 6...I did throw in a little cross caster, because its a daily driver. Set toe out at 1/16th. In the rear, I went with -1.8 and zero toe. I'll see how this works this weekend. If I need to change it, that's cool, my alignments are free...besides, I for sure will have to realign when I install the shocks.

I'm running 245 Kumhos and am curious about tire pressures. I did a search on this forum, but much of the information wasn't clear, there seemed to be signficant differences in opinion and most posts were pretty old. Given that Atwater has so much traction, I'm thinking, even with -1.6f camber, that I'll need somewhere in the 37-38 psi range in the fronts? I'm also imagining running the rears 2-3 psi lower would be a good idea?

This is a new ball game, for me. On the Z06 we ran very low pressures...not something that will work on the RX8, given the camber curve and tire size.

Cito

38 psi all around worked the best for me with the kumhos, but it would be best to ask the folks at the top to be sure. You are going to miss the horsepower, but I think you are going to love the 8.

mwood

Thanks, Cito. I am enjoying the car, it doesn't have much power, but is deceptively fast and just sooooo smooth. The rotary is a very cool motor, even though it sounds like an Evinrude

The car just feels so much lighter than the Corvette, even though its probably only about 200-250 less. Also, the controls feel better, particularly the steering. I'm really happy with it, so far. We'll see how it goes tomorrow

4D-Sport

We ran 43 fronts/39 rear at the Tour in April. We only had -.9 front and -1.4 rear camber at the time. (I'm jealous that you got as much camber as you did... my sub-frame install wouldn't allow me that much while keeping both sides symmetrical). Given the primary intent for my 8 is training novice drivers I wanted to keep the handling somewhat balanced - left to right / right to left.

I've never had the opportunity to drive a Z06 (sigh) but I believe you when you say the 8 feels a lot lighter. If you see Gary McDaniel tomorrow (either red Z06 or unknown color STi) ask him about me chasing his Z06 with the 8 at Thunderhill. I'd catch him under braking and he pull me on the straights. We pushed each other dropping 3/4 second each lap (without traffic) for twenty minutes. Hope to get some video up as soon as I buy the S/W to edit the MPEG2 of ChaseCam's PDR.

Have fun (wish I could be there but have a soccer game)!

Sparky

42f 39r. At Ft. Myers which was high traction concrete I eventually got up to 45F. I like to run on the high side for response though.

Raptor2k

...I need an autocross dictionary

CosmosMpower

33/33 all 4 bone stock. I tried 42/38 last saturday and the car was ALL OVER the place like I was driving on ice. Even did a run with dsc/tsc on and the car was still sliding. I knew something was wrong so I decided to lower the pressures dramatically down to 35/35 and it seemed to behave much better. Then my last few runs I bled some more air out to around 33 all around and it drove GREAT, the turn in was still quick and steady state cornering was predictable.

Checked the tires at the end of the day and they didn't have any rollover past the shoulder and wear was uniform. I think the stock RE040 bridgestones have a VERY stiff sidewall so you can run them at much lower PSI's without having them roll over. We were running on a very rough concrete surface almost like a cheese grater (it's an airport helipad).

So I think it really depends on the tires, the guys running V710's at the same event were in the 22-25 PSI range with good success.

4D-Sport

Agree, it all depends... I'm not particularly skilled at tuning but here's a link to what measured at the Tour in April. Your mileage may vary.

mwood

So, I got 5 runs in with the RX8 today...dang event ran long, so no fun runs, which is really why I went all the way down there.

Anyhow, I started at 40/37, which seemed to work fine. I did let the fronts get up to 41.5 or so, because it looked like I was getting a little too much roll and the wear pattern was going to the very edge...after letting pressure rise, I had about a 1/8" "chicken strip" which I guess is about right?

The car felt awesome, even with stock shocks. Very easy to drive and able to get it to do what I wanted without any problem. Times were right with the AS winner (off one tenth), a guy who runs National and Pro events with some success, so for an out of the box trial, I felt the pace was ok. I have a bunch to learn about this car, though...and am looking forward to more seat time!

altiain

iTrader: (3)

Where was this? At the S2k event? None of the local guys running V710s (Kenny, Jon, or I) run pressures that low. Concrete starting pressures are usually in the mid-to-high 30s, but Pennington is our only local concrete lot. At Mineral Wells we experimented a bit, and all ended up with pressures in the 31-33psi hot range.

mwood

I can't imagine running low 20's pressure, under any circumstances, with the 245 V710. I do think that on anything other than Atwater type concrete, given at least average front camber of -1.2 to -1.6, mid 30's could be a good starting point.

Another thing I noticed yesterday is that, even with 5 runs and 80 degree plus temperature, I really didn't need to water the tires down...at least not in comparison to the Z06 on 295/315 V710s, which would have been smoking hot by the 3rd run, without water. Except for beating up the outside of the driver's front (predominately right hand turns), the tires heated pretty evenly and didn't look any worse for wear, at all.

How many runs are you guys getting out of the Kumhos on the RX8, anyhow?

clyde

Unless the runs were separated by 30 minutes or more, I can't imagine not needed to spray in 80º weather on asphalt or concrete using 245 Kumhos. 285 A6s, maybe not after the first or second run, but definitely by after the third (assuming a "typical" course)

In our experience...

Good for National level events up to about run 50.

Good for local stuff up to about run 75-80.

Good to sell/trade/give to someone cheaper than you for runs 75/80-120 or more.

mwood

OK, I should have said, "didn't have to water much and only the driver's front really got hot" or something...it's not that I didn't have to spray at all, just not nearly as much as I though I would have to.

The wear sounds about the same as I'm used to. I kind of expected that, since it is a 2900lbs. car on a 245, that the tires might wear quicker.

thanks!

Sparky

Yesterday at our local event I forgot my sprayer and ran a best time of 64.8 seconds for the first set of runs. Wife brought the sprayer at lunch and then in the afternoon I ran 63.9. I was on 245 710s and it was 80 deg. out. I was single driver with 15 minutes between runs. That's quite a difference.

mwood

I'm sure none of the time difference was from driving the course, thinking about it for awhile, and then running again ;-)

JK, there's no doubt in anyone's mind that the Kumhos, once they get above about 130-140 degrees surface temp (not to be confused with a heat soaked, carcass derived temp!) get real greasy. The only point I was making is that on a 2900lbs. car on little 245 section tires, I expected heat management was going to be a bigger issue...with increased wear being a by product!

clyde

I wonder if the difference in power and speeds might have something to do with reality not quite matching your expectations based on a much more powerful car?

For the start of this year, John and I shipped a set of our 710s from the previous year to San Diego to be used on a CTS-V for the SD Tour. I can't remember and would have go look it up, but I think the tires had about 35-40 runs on them when we shipped them. The car did 6 runs on the practice course and 13 runs in the event (John stopped for a downed cone just before the finish on Sunday). The tread grooves were completely gone at the end of the event, but wear continued to be equal across the treadface. LS6 powered, 3900 lb car seemed to more than double the wear rate.

Sparky

There wasn't any learning curve involed. I was the course designer and around here locally it's the designers responsibility to pre-run the course for safety. Just one of the perks of the job. Before any rule book readers start posting, it wasn't an SCCA sanctioned event.

Anyway, first set runs were:

65.769 64.835 64.999 65.197

On each run I felt like I was running faster more agressive lines, yet times were increasing as the tire temps hit 155 deg.

In the afternoon on 115 deg tires the times were:

64.051 64.208 63.908 64.240

As you can see, I'm pretty consistent on both sets and it looks like a .9 sec difference. The whole reason I brought it up was because I'm pretty confident that the difference was tires temps and not other factors.

mwood

^ gotcha...please know, I was just joshing around, meant no flames

When I mean flames, it's pretty obvious...maybe not as obvious as xxxx, but obvious

TeamRX8

iTrader: (25)

still haven't learned to search yet n00b

mwood

What? You mean you didn't bother to read my "search disclaimer" in the original post?

CosmosMpower

Oops, typo. I guess I was thinking 32-35 and typed 22-25. Anyways, I was right around that range on the stock RE040's as well.

c41250n

iTrader: (5)

i must be running a weird setup then, im running -2.2 camber 31psi front and -2.7 camber 27psi rear.

mwood

I don't know, but with that much camber you very well could be right on the pressures, particularly on asphalt...less roll under of the outside sidewall.

MazdaRich

How in the world did you manage to get that much camber?

Sparky

Coilovers maybe. Or aftermarket springs.