sYnth.

So I headed down to Boundary Bay today for the Velocity program and wow I'm definitely hooked. Only problem is I need new tires now... I know people on S2Ki recommend goin 225/50/16 & 245/45/16 for non-OEM tires but this really just limits me to the Hankook R-S2 (in terms of value, price, etc.), and honestly I won't be able to afford SO2s at this rate. Is it really that bad to go with the standard sizes with the Kumho tires? (SPT & MX) I know this has been beat to death on the S2Ki forums but I just wanted the opinions of local Auto-X regulars.

Also, my car seems to understeer quite a bit at times (X-Brace & Strut w/ ok tire pressures). Would this be normal for a car with a stiffened front end or did my worn tires attribute to this in a big way??? Both of my instructors seemed to get caught off-guard by the understeer as well.

SumAznGuy

Who was your instructor's? Not all instructors have experience driving rwd, especially an S2000. I have autoX'd for many years in a fwd car and making the switch to rwd has taken a lot of adjusting.

To be honest, the S-02's do not give you the bang for the buck compared to the RS-2 or Kumho MX's.
I recommend getting the 245's for the rears and 225's for the front.

Race Miata

Drivers not familiar with the S2k handling can quite easily get into understeer especially on tight turns.

Chassis stiffening up front theoretically increases front-end grip. Don't mix up with suspension stiffening up front which increases understeer.

What wheels/tires and wheel alignment are you running?

sYnth.

I had Yarko and Igor. Igor was pretty honest about being a FWD driver but I thought Yarko would be able to handle it a bit better. He was really suprised by the understeer.

I'm running stock wheels and SO-2s. Fronts were a bit low on tread but in no danger of failing tech. The tech even joked about them being perfect for AutoX. 38PSI in the fronts and 41PSI in the rears.

Umm.. not too sure how to write out alignment settings in the easiest way but here they are..

Primary
------------------------------
Front: (Left, Right)
-Caster 6.2, 5.9
-Camber -0.4, -0.4
-Toe 0", 0" (Total 0")

Rear: (Left Right)
-Camber -1.5, -1.6
-Toe 7/32", 7/32" (Total 7/16")
-Thrust Angle 0.0


Secondary
------------------------------
SAI L9.6, R7.5
Included Angle L9.2. R7.1
Setback F0.1", R-0.2"
Track Width Diff -2.2"
Wheel Base Diff 0.3"

Race Miata

1). -0.4 front camber is too little up front. You want at least -1.0. I run MAX front camber, about -1.5 and I can still use more. Keep around 0.5-1.0 degree camber stagger (i.e. rear should run ~0.5-1.0 MORE -ve camber than the front).

2). 7/16" total rear toe is too much. Aim for 1/4" total rear toe.

3). You want higher pressure up front, about 2psi higher than rear for the stock tire stagger.

All these contribute to your understeer, listed in the order of significance.

sebmour

i ran the RS2 at my local autox. 205 f and 245 rear on stock 16'' rims.
They ran great love them....pressure was at 33 f and 35 rear...
2 other S2K that day, both with coilovers, saner front swaybar, r compounds. One with header also ran 65.2 the other ran 62.8.

I am completely stock and ran 66.7.
I think these Rs2 are great daily rubber and some great street auto-x rubber too.

i do not know about my alignment specs should be factory settings from 1 month ago.

sYnth.

Race Miata
Awesome, thanks for all the insight.
Could you possibly post up your alignment settings? I bought the car about a year ago and these are the settings he had. Since I'm planning on AutoXing as much as possible I'd like something more aggressive.

EDIT: Doesn't adding more pressure in the front reduce grip? What pressures are generally okay for fronts and backs???

sebmour
Why did you run 205's in the front? I thought the compensated size was supposed to be 225? Just wondering because I think these are the wheels I'm going for within the next month or so.

Race Miata

You're welcome.

I'm still in the process of finding good alignment setup so don't take my exact numbers as bible. Plus I'm running 17x7.5/8.5" wheels with 215/45 and 245/40 and my setup is more towards track lapping so my best numbers may not work best for you for autoX. As of today my rough numbers are:

front camber: -1.5
front toe-in: 0.0
front castor: 5-ish (not max)
rear camber: -2.1
rear toe-in: ~3/16" total

Regarding tire pressure, adding more doesn't always mean losing grip. It's only true if you're increasing pressure from the optimum. Think about this. The car is ~50:50 weight distribution. The front tires are narrower. In order to keep similar contact patch shape, a narrower tire for the same load requires more pressure.

As the faq mentioned, stock rear S02 is underrated and is more like 245 but stock front S02 is not as underrated. You *might* get too much oversteer going with 225/245 if you don't go with FSB as well.

SumAznGuy

My alignment is basically taken from the autoX faq. I am running 1.8 degrees negative camber in the front, max castor 5.67, and 1/8 toe out 1/4 total toe out.
Rear is 2.0 negative camber, 1/8 toe in 1/4 total toe in.
I like this setting a lot. Perhaps a little more toe in in the rear could be better. I am running Toyo RA1's 245 in the rear and 205 in the front.
I think the car would do better with a wider front tire as I find that when I really push the car, there just isn't enough front tire with the 205.