understeer how do I minimize it?

[325is///M-tech]

I agree With DSP74 From what I have found adding front bar and even adding some bump to the front struts has removed under steer. I would start with adding a set of camber plates and or a larger front sway.

[DCColegrove]

First off the e30 chassis can do some strange things because of the "designed in" suspension characteristics.

The rear camber shifts to negative on the loaded side and positive on the unloaded side (Is this making sense?) and has a tendency to dig the rear of the car in.

The OE (Motorsport) solution was to widen the trac, add additional front caster (to match that digging in action of the rear) with the offset cabs and to increase the rear ASB diameter to 14mm.

Having said that...

I can't remember what we were talking about...

It's weird getting old.

[Fidhle007]

I actually want to jump in here for real too because there's a lot of false info being thrown around. Sway bars are not effectively the same as stiffer springs, because they TRANSFER force, rather than absorb it. When you decelerate into a turn (even just off the throttle, no brakes involved) the weight of the car is transfered forward and to the outside. This puts the more weight on your outside front tire than the others and causes understeer. A stiffer rear sway bar will help transfer some of that weight across the car and keep the inner tire down but a bigger front bar will help to keep the body flatter, allowing that outside front tire to do it's dirty work. The other thing a bigger front bar will help is turn-in, so you'll initiate easier but at the limit, it will lift the inside tire sooner than a smaller bar will. But really, when you're transferring that much weight across the car you should be relying on those outside tires because at the limit they'll be pretty light no matter what your bars are like.

[Fidhle007]

that's weird... the total opposite happens to me... when i have lower front and higher rear, i can oversteer better that's why i set my rears to 45-50 psi and my fronts to 32 psi whenever i drift and when i have higher fronts and lower rears, i understeer..... when i auto-x, i set my tires to 32 psi in front and 36 psi in rear and it works well for me. anyways, that's my experience, who gives?:)

I don't think you've ever actually driven a car...


Or learned to read...

[DSP74]

you are right in that respect, but you have to be *really* low in order to get to that point in the camber curve where you start loosing camber (basically where the angle between the control arm and strut is greater than 90*).

And if you are that low, chances are your car is stiff enough that your suspension isn't compressing appreciably to notice much difference in the camber curve, even if you are passing that point. Essentially, you could simply go with stiffer springs and have the same effect.

Camber control in a dynamic situation. Nothing to do with ride height (although I guess you could hurt the camber CURVE by being VERY, VERY low.....

If a car doesn't have enough negative camber a bigger bar will limit roll making the car gain less positive camber. Making the front end stick more.


Put the books away guys


edit: to clarify ALL cars lose camber during roll

[Jeremiel5]

lower front, or higher rear will help understeer.

lower rear, or higher front will help oversteer.

that's weird... the total opposite happens to me... when i have lower front and higher rear, i can oversteer better that's why i set my rears to 45-50 psi and my fronts to 32 psi whenever i drift and when i have higher fronts and lower rears, i understeer..... when i auto-x, i set my tires to 32 psi in front and 36 psi in rear and it works well for me. anyways, that's my experience, who gives?:)

[AlarmedBread]

Trail brake, feint, handbrake. In order of preference.

[nando]

Camber control

you are right in that respect, but you have to be *really* low in order to get to that point in the camber curve where you start loosing camber (basically where the angle between the control arm and strut is greater than 90*).

And if you are that low, chances are your car is stiff enough that your suspension isn't compressing appreciably to notice much difference in the camber curve, even if you are passing that point. Essentially, you could simply go with stiffer springs and have the same effect.

[whiltebeitel]

iflytii has the right idea. Sways will increase traction to a point, then it will become counterproductive when it prevents all the wheels from contacting the ground. Generally, a bigger bar from stock, coupled with the sticky tires you SHOULD have is quicker.

[DSP74]

Camber control

[Hallen]

DSP74, How do you figure that? An increased roll bar stiffness will act the same as stiffer springs for the purposes of under/over steer.

Stiffer roll bar in the front will increase understeer and decrease oversteer. It will help to reduce body roll so the car will be more responsive, but it will still increase understeer.

Just one reference in the chart on this page

[iflytii]

According to the books people read....

The car right now, needs a bigger front bar.

So your suggesting that a basic understanding of suspension dynamics isn't a prerequisite for giving good suspension advice?

Suspension tuning isn't as simple as "stiffer" here and "softer" there. It requires some understanding, i.e. reading, and a lot of experience tinkering. I'm sure just about everyone here with a good amount of seat time has eventually fallen into the prescribed formula for what works best for our cars. At that point it's easy to simply suggest Y component will fix X problem. My post was an attempt to give some insight to the OP rather than blindly suggesting bolting parts onto his car. Not knowing the usage of the car, the drivers experience level and nothing more than the springs installed there are a lot of solutions possible - many of them are free.

Sway bar settings in relation to understeer/oversteer are heavily dependent on other suspension variables. Camber, tire pressure, spring-rate, rebound all play a major role in how different sway bar settings will affect which end looses traction first.

As I said previously, stiffer swaybars up front will result in less movement of the suspension under cornering load, resulting in understeer. However, combine a stiff swaybar and a lot of negative camber and the result under suspension load is the front outside tire ends up being "square" to the ground creating the maximum contact patch in an optimal setup (i.e. lot's negative camber up front and relatively soft front springs). The key is here is determining the "optimal setup".

Anyway, getting back to the original problem. Assuming the understeer problem is not mostly driver induced then you have to start somewhere with fixing the issue I suppose. DSP74's method is certainly valid - throw a bunch of parts at the problem and eventually the car WILL outperform the driver. Personally my checkbook has taught me to be a little more educated in my decisions.

[DSP74]

pretty sure you've got that wrong, generally a bigger front will increase understeer, and a bigger rear bar will increase oversteer

Nope:D

[Borat]

According to the books people read....

The car right now, needs a bigger front bar.

pretty sure you've got that wrong, generally a bigger front will increase understeer, and a bigger rear bar will increase oversteer

[joshh]

Most importantly slow in fast out.... Stop inducing it.

Took the words out of my mouth.

If you're autocrossing, do not break too hard too late.