Mix n Match autox suspension help please!
 

My car is frustrating me. Im contimplating a total makeover of the suspension setup, just looking for some suggestions from you guys.

for tires I'm running P245/40ZR17 hoosier a3so4's

dampners are kyb agx's front and rear

here is what I have to choose from

bars: stock turbo front and rear
racing beat front and rear

front spring rates: 300 and 450

rear spring rates: 150 and 325

I've been suggested to go softer and that's where the 300 and 150's came from, but I don't like the way the car is rotating. I mean I can force it, with trail braking and such, but the car just doesn't dance like I want it too. I tried removing the racing beat front and using the stock turbo, and that made the car feel like it was more willing to rotate, but didn't help my times at all. So just ignoring all if that's all you had to work with, what would you use for autox???

as a follow up, dampening suggestions?

bump for suggestions please.

The 450/325 combo will probably make the car rotate pretty well, but I dont know how well the AGX will be able to damp it.
I hope you don't have to drive the car on the street. :)
You never said what car this is for. FB/FC/FD?

By rotate do you mean understeer or you can't get your backend around coming out of some of the tight corners?

The 450/325 combo should serve you better for autox. The thing with suspension setting is you have a complex multi-variable equation...

Spring rate
Rebound
Damper
Sway bar rigidity
Alignment
Tire pressure
Brake bias

Personally I set the front sway bar very tight (and it is an upgraded strong bar). I have a stock rear bar and it is set in a moderate to high range (I don't like chassis flex). On the Tokico Illumnia 5 way the fronts are set at 4.5 and the rears at 3. The current springs on the car are H&R sport springs (which are progressive, stiffer than stock, and around 1-1.5" lower, I didn't buy them, rumor is about 30% stiffer but progressive so not ideal). For tires I'm running 245/45/R17 A032R (Soft) and I run them at anywhere from 33 cold to 39 warm depending on the track. I most often try and run even front/rear tire pressures to eliminate that variable from the equation, depending on if I feel the car doing something that day I may adjust tire pressure some since that is the easiest thing to do at the event.

If you're having understeer problems you may want to try braking earlier and then as you start the turnin just tap the throttle to get some of the weight off of the front if you are still understeering (if you can manage to left foot brake you can brake later and still use throttle to balance the car at corner entry -- good luck ;) ). If you aren't able to get the rear end to rotate when you want, you can: raise rear tire pressure, stiffen sway bar, raise damper. Then when applying some throttle in combination with those adjustments you should be able to get the back end around.

This is why a lot of people drag race, there you have horsepower, traction, and gear ratios (of which are all still a concern in autox/road racing too :D ) ;)

I'd say that you need to upgrade the dampers. I don't think the AGXs are designed to handle the stiffer springs. A set of Konis or something similar could do wonders.

yeah the car get's driven on the street, but is not a daily driver so I'm not too concerned with ride.

I was thinking just going full stiff 450's front 325 rear, both rb bars, just beause the car will be a little more manigable and will stay a little more stable in cornering. The only thing I'm worried about is not being able to transfer weight to the rears to put down power under acceleration.

Also would it be accurate to assume that with more bar, and stiffer springs, you wouldn't have to run as much camber? I think I remember reading that somewhere.

My real problem right now is the fact that my tires are shot, and I don't have as much time as I'd like to mess with pressures because of the way our local autox does their runs.

and it's an fc

With those spring rates you will need very little sway bar. I would start with the stock bars for now. And yes, you will probably not need as much camber.
The amount of weight transfered to the rear doesn't change with spring rate. So you should be able to put down the same amount of power as before, under acceleration.
Good luck

Well for the next event, I'm going with a bigger bar in the rear, as the racing beat bar, is only a 15.5 mm one. The one I'm getting is a 19 mm

So with the 300 lb fronts and 150 lb rears, would you guys reccomend go full stiff with the kyb's or a happy medium? Things happen so quick in autox, it's a little hard to tell if dampening is having any effect.

If you doubt the effect of the dampening try full soft front, full hard rear one run and then on the next run swap it to full hard front, full soft rear :D Then for your third run set them at something realistic and hope in tha run or the next (depending how many runs your region gives) you get a good time ;) A lot also depends on your driving style.

That's possibly why you have a push problem...

There's nothing at all wrong with running different tire pressures front to rear if that is what the car likes.

Transfering weight off the front is going to make the understeer worse unless you actually break the rear tires loose and swing the rear of the car around. Also realize that braking harder in a straight line will get more weight off the rear and onto the front, possibly helping the car turn in.

Left foot braking does not allow you to brake later. It takes the car a given distance to slow down regardless of which foot you press the pedal with. Left foot braking merely allows you to more effectively control weight transfer front to rear as well as hold the throttle open while braking. Your braking distance will be the same.

Agreed as long as all those adjustments are on the rear only. Personally if the car is not turning then that is a problem with the front of the car so that is the end I would "fix". Only after exhausting all possibilities of making the front better would I then remove grip from the rear to make the car turn.

Why does the car like it? Because the rest of the setup doesn't balance the car out. The only reason you would need to run uneven tire pressures is if you can't set the rest of the suspension on the car up to eliminate that need. The only reason you may -need- to do this that you can't really control with the suspension settings very well is tire temp and for autocross on the FD I've found they heat up pretty evenly front/rear and sometimes depending on the course you'll get a 'hot tire' due to repeated loading in that direction due to design.

Lets look at the traction circle for a moment and the weight transfer of the car, we can hopefully agree that the more the weight is shifted forward the less total traction the car has, the more you are braking the less traction the front tires have left for turning without ending up in a pushing slip angle resulting in understeer. There is a fine line between too much on the front and too much on the rear for the appropriate amount of turnin steering.

Actually your braking can be later because you don't have to spend time after you finish braking balancing the car again. The overall distance may actually be less as well due to the traction circle again, if you can maintain weight balance on all four wheels evenly the car will have more grip for braking.

It really depends on the car and regardless of the car on a slow speed "tight" hairpin if you aren't concerned with tire wear it is almost always faster to throw the car around the corner and drive out of it (provided we are speaking race cars that all have a good or great weight/hp ratio).

Understeer felt by most autocrossers in a balanced car like FC/FD is usually braking too late and having to break too hard upsetting the balance and traction circle since if the tires are 100% braking they can't be turning at all. Usually driving the car a bit more smooth and a bit less hard will make the car faster and make it feel easier to drive.

That's WAY too much tire for a non-turbo FC...


-Ted

Tire pressure has everything to do with the tire size and the camber settings. Having different pressures front to rear is not somehow a mistake or a shortcoming in the car's setup. Tire pressure and alignment are based on one thing: getting the tire temps up and even while balancing the car.

Circle speak. You said earlier about curing a push problem:

Braking earlier will help the push because you brake earlier and slow down more therefore giving the front tires greater ability to turn since they are not still braking into the corner. But tapping the throttle and "getting some weight off the front" will absolutely not add grip to the front, it will do exactly the opposite. Tires make more grip with additional load, not less. That's the reason people started bolting wings to cars...

I don't care how you choose to apply the brakes you'll transfer the same amount of weight forward everytime. Weight transfer is strictly a function of CG height, wheelbase and track width. Nothing else will change weight transfer.

Agreed.

What tires are you running? Let us know and post up a set of tire temps for them please.

I'm running A032R soft which means unless I have a small run group or get to rerun they don't really get up to temp :( I'm happy if they heat up at all. I've tried dropping the pressure way down for an early run to heat them up and then raising it but all I get on the early run is a sloppy run and by the time the next run starts I'm down to almost no heat gain and more sloppy tires. If I ran a more temp sensitive tire I might have to adjust my suspension settings or tire pressures more. Maybe next season after I have what I consider a class competitive car to support dumping more money into AS03s (or 04s if the 03s are gone by then).

it's a cosmo 2 rotor w/ a to4r, walks the ass around everytime it hits 6 lbs of boost.

and I know a "r" isn't an autocross turbo, im finding ways to work with it.