So I have been fighting to get the evoIX to understeer less, and so far have done the following:

-2.5 camber in front
-1.5 rear
0 toe

Works springs
RRE rear bar on ful stiff
255-40/17 RA-1

The symptoms are that I wear the edge of the front right tire (Pacific Raceways is CCW and hard on the FR). That tire probably wears twice as much on the outside edge as any of the other 3 tires. I took tire temps, though not too diligently, and found, as expected, that that tire was the hottest on that edge. The rear tires were about a 40 degree cooler than the fronts - certainly an indication of Usteer. It happens mid corner and later mostly, less on initial turn-in, though I can get it to happen then as well.

So what is the solution?

1 - Front Sway? Perhaps, might keep the mcpherson strut geometry from going less negative
2 - Stiffer front springs? This, in theory would help as well...
3 - More front camber? Yeah, no, I still have to drive to work, and 2.5 should be plenty.
4 - Could be my driving - I guess I am used to more 50/50 RWD cars...

So how do I get this thing to quit eating front tires like they were STi's?

Marek

 

gsc center diff

 

Stiffer
Lower
More -camber (consider a track setting and a street setting)
Less rear -camber (though breakaway to oversteer will be more abrupt)
narrower rear tire and/or rim (nutty but it works)
Bigger front bar

As Nils recommends the diff will help but just on throttle.

As you have learned the outside fronts are getting cooked so the only real fixes are the stiffer springs, more neg front camber and the bigger front bar (and the diff later in the corner). The others give you the balance you want/crave but by de-gripping the rear ("band-aid" fix).

 

1.)Driver mod
2.)Increase pressure in fronts

 

Increase pressure in fronts?

 

increase pressure in REAR.

 

less pressure in the rear creates more oversteer.EG. 35 fr 32 rear. Or for the track more like 44 front 35 rear.

 

wrong. less pressure in the rear creates more understeer by transferring weight to the front tires during cornering.

 

lol...

 

Combat understeer:
1 Widening the front track(wheels and spacers).
2 If you lowered the front you must raise the roll center back up.
3 Stiffer springs
4 Frt camber, the evo seems to like around -2.7 or more but chalk around sidewall edges and pyrometer are your best friends.
5 Correct tire pressure; nobody can acurately tell you correct pressure unless they know the tires you run, the track, the temps that day, how the car is behaving and your driving habits etc.

 

Wow some crazy advice on here! Be careful who you listen to. Look up a few posts from the people that give you advice and youll know real quick who to take advice from. More importantly, how are those R1s working out for you and have you run Hoosiers or any other R tires in the past to compare them to?

Marty

 

Hi, Marek.

You have two choices: increase front grip or decrease rear grip. In theory, increasing front grip is better (for obvious reasons). In practice, losing a touch of rear grip to neutralize the car doesn't hurt much as long as you don't go overboard.

The thing that really jumps out at me is the zero toe. An easy way to get the rear mobile is to add a tiny bit of rear toe out. That helps tremendously under braking, though it's not particularly effective under power.

Anyway, it's an easy enough tweak to try. No parts to buy. Just need a good alignment shop.

Emre

 

Are you asking about autocross or track driving? In what part of the turn is it understeering? What are your tire pressures?

 

Thanks guys -

This is for a track, not autox.

Tire pressures are about 44 hot front/about 3lbs less in the rear. Now that I read that, I might lower the rear a little more. It your eyes bugged out at the 44, any lower in the front and I am sure I would have corded the new ra1 in about a session and a half.

So, as to the + rear toe, anyone running this?

What about raising the fr roll center? Is this really going to make a difference? Those who have the whiteline kit, can you comment?

Marek

 

I'll offer some input based upon theory alone. Roll-center is going to affect how much of a moment arm the front suspension is fighting against when dealing with weight transfer. This, in theory, is combatted by stiffer anti-roll bars or stiffer springs. Raising the vehicle in a strut-suspension system, or raising the roll-center, may lower the required roll resistance.

With all that said, it could be possible that your roll-center is too low, you are rolling too much, overloading your outside tire and giving you the results you are trying to avoid. That is one theory...

Something that must be asked:
Are you going in too hot and scrubbing speed, holding your maintenance throttle too long, letting the front end settle before entering the corner, or are you stuffing your foot in it at the earliest possible point in the corner?

I will admit that I am inexperienced, but I have seen a lot of little adjustments that make a huge difference in how the car holds the road. All of my track experience is in the Evo on street tires, with almost all of it on completely stock suspension. The fact that you have a rear anti-roll bar, which I don't feel my car needs, and are running race tires, which I haven't driven on yet, could put this far beyond my experience.

-Jon