Hi there,
Well, my cousin and i ran my car for teh 3rd time this weekend at a two day event in teh philly region. We jsut got a set of 245/35/18 Kumho v710s on it, and we had some trouble.

First Day:

-The first day was on stock alignment. The car is brand new (2k miles on it).

-We had bad understeer issues. No matter what we did with tire pressures we could not get it to swing aroudn the turns teh way we wanted.

Saturday night we decided to go get an alignement to help the car out.... we madea big mistake i think...

Here are teh approx. specs we used.



FRONT:
-1.5 Camber
Toe Out 0.1
Caster (Here's Where we F'ed Up by going the wrogn direction i think): +5 Deg

REAR:
we pulled some camber out to help swign the rear around. I'm not sure if this was teh right thing to do or not.
-.5 camber
0 toe

SECOND DAY:
the car seemed to cut ntot eh turns much faster, but still wanted to push really bad

SCREW UP:

ANyway like i said, i think we went the wrong direction with the caster. From what i understand the caster adjustment doesn't really give u any more camber through turns on teh RX-8. Is this true? Should i just put the caster back to factory?

Anyy suggestions are greatly appreciated. I want to get this car dialed in.

Tire Pressure: What do you guys think for tire pressure on these tires? I think today we started with 38 front 36 rear cold and worked from tehre. We are just trying to ge things firgured out.

thanks,
Jordan

 

Given the alignment, particularly only -.5 rear camber with zero toe, I'm going to have to say that any push experienced was driver induced...no flames intended!

The front isn't really out of the ball park, at all. Yes, you could sacrifice some caster and get a little more front camber, but most cars (without degassing shocks or other tweaks) are going to end up in the -1.5 to -1.8 front camber range, so you're there already. The rear, however, is way light on static camber, again compared to what we've run and others say they run. I was at -1.6 last year, with -1.8 front camber. Zero toe in the rear is also a good place to be.

So, putting it together, with pretty common type front camber values and very minimal rear camber, the car should not have been tight, as far as I can tell.

btw, the tire pressures are also right in the ball park, for asphalt.

 

When is the understeer occuring? Corner-entry, mid-corner, corner-exit? I tend to agree that it sounds driver induced. Maybe you're coming from something like a powerful f stock car and expect more power on oversteer? Maybe you're expecting too much rotation? If you really want to get sideways you could start resorting to scandi-flicks although that would belong in drift competitons not autox

Given that the car is brand new I don't suspect that the rear shocks are blown or anything but you could check?

 

thanks for the replies. It probably is driver error. I'm very new to autocross. I guess i was expecting more grip and just overdriving the car.

Well i'm glad to hear this is an ok setup. I still need to get a better feel for the car, then start making adjustments again i suppose. thanks for the help.

-Jordan

 

No, it isn't an ok set up, imho. I believe you will end up wanting more rear camber...with -1.5 front, at least -1.2 rear. If you are going to do another four wheel alignment, take the caster out of the front, see what your max front camber value is and then start the rear a couple of tenths more vertical, would be my suggestion.

 

all bets are off until you replace the OE shocks with Koni shocks ...

your pressures need to come up about 5 psig

 

I missed the part about oe shocks...but, I don't think, on asphalt, there's any reason to run 40psi + on the V710, at all...maybe on Atwater quality concrete.

 

it's always better for autox n00bs to be on the high side than the low side, but some asphalt can be as grippy as good concrete and OE shocks allow a lot of instantaneous body roll which means camber loss/tire rollover especially if it's being overdriven

 

For reference, here's what I was running.

Front:
Camber: -1.7
toe: 0
caster +6.7

Rear:
camber -2.2
toe: 0

On day one, I started out with 42psi front and rear on the 285 hoosiers. The Tokicos were set to 1/2 turn from full stiff. First two runs were crazy loose.

I backed the pressures down to 39 front, 37 rear and took 1/4 turn out of the rear shocks. It was much more stable, but did have some push.

On day 2, I went to 41psi front, 39 rear and left the front shocks at 1/2 turn, rear at 5/8ths turn. That seemed pretty balanced, but its hard to say as the rain came.

Definately look into getting a set of shocks if you can. I think the Koni SAs are a slightly better shock in terms of valving, but I switched to the tokicos because I had problems with the front Konis blowing (even though I didn't over-turn the adjusters) and I like the external rear adjustability of the toks.

I think higher rear pressure is the key to getting the car to rotate (unless you want to go with a little toe out in the rear - but a bad idea for a street driven car). Like I said, even with a bunch of camber, it was rotating like crazy.

I was great finally having another R-comp RX-8 in the philly region this year. Hopefully you can make it out to a bunch more events!

 

Kurt,
I'l be at every event hopefully. I think we are taking the car to Blackwood NJ this sunday for a Sotuh Jersey Solo event.

Thanks for the help. I'm probably goign to get it re-aligned at some point this week. Shocks may have to wait, as i just spent 1800 on wheels/tires and 600 on exhaust and 120 on brake pads lol

I also want to do that novice driving course on teh 23rd, just to get some seat time in the car.

thanks,
Jordan