Suspension Tuning Question

[gchandler]

How would I have to set up a car in order to make it oversteer off throttle on the breaks and understeer on throttle?

This may seem out of right field, but there is a method behind the madness, any help would be greatly appreciated.

[chicane67]

Put a spool in the differential.....

[sinned]

Put more bias in the rear brakes and run a throttle stop to limit the amount of power to the rear wheels (assuming we are talking about a RWD). That will accomplish your goals without upsetting the the chassis.


edit- maybe back off the front bar as well to add some under steer.

[gchandler]

Another requirement is that the tires need to be spinning.

[zbugger]

Hmmm.... As I think about it, I realize I'm not the most intelligent about this stuff. I did come to this though. What if you ran a bar up front that was bigger than necessary? I think that would accomplish what you want. Too big of a front bar should do very well in that case.

[sinned]

Should we have titled this thread "How to build a drift car"?

[TLWiltman]

The increase in rear brake bias is right... But it'll be pretty hard to get understeer with spinning rear tires. It's a matter of physics. A spinning (or locked) tire has no directional stability (that's why e-brake turns work so well). Now... if you WERE talking about a drift car... I read somewhere that the mod for increasing stability was actually to use smaller front tires and increase available steering lock. A driver, no matter how good, can only "catch" a yaw angle equal to or less than the available steering lock. More steering lock=more yaw angle=more points.

[Norm Peterson]

How would I have to set up a car in order to make it oversteer off throttle on the breaks and understeer on throttle?

You can get some help from working with rear axle roll steer, as long as the rear suspension is soft enough in bump/rebound to have much travel. You might end up with relatively short links at unusual inclinations to go from vehicle roll oversteer with the rear end raised (engine braking or actually on the brakes) to vehicle roll understeer with it squatting under power. You'd probably want the "anti's" to be relatively small as well . . . maybe an adjustable rear sta-bar . . . perhaps even different front end alignment settings . . .

Ditto about wanting/needing more steering lock.

Norm

[Mean 69]

You can get some help from working with rear axle roll steer, as long as the rear suspension is soft enough in bump/rebound to have much travel. You might end up with relatively short links at unusual inclinations to go from vehicle roll oversteer with the rear end raised (engine braking or actually on the brakes) to vehicle roll understeer with it squatting under power.

That's kind of hard to do with a Truck Arm setup. Not stated here, but having read previous posts and seen the cool videos, I know this is what they are running.

Have you guys experiemented with changing the rear roll center height on the PHB? All the other suggestions sound like great things to try too.

Mark

[TLWiltman]

I was just thinking about shock valving. Let me see if I can get this right.

To get oversteer under braking:
-Soften compression in front
-Stiffen rebound in rear
-Increase rear brake bias
-Raise front truck arm mount (like a torque arm, when you increase anti-squat you increase the tendency for brake hop. I think that's how she works)
-Lock the axles together more effectively (posi to locker, locker to spool). A detroit locker seems to be particularly effective.

Understeer on acceleration
-Soften compression in rear
-Stiffen rebound in front

Have you ever thought of incorporating a pinion-mounted e-brake to the design? I think if you were minus the ratchet mechanism, it might work

BTW, you must be the "formula D Camaro" guy, right?

[David Pozzi]

How would I have to set up a car in order to make it oversteer off throttle on the breaks and understeer on throttle?

This may seem out of right field, but there is a method behind the madness, any help would be greatly appreciated.

For oversteer on corner entry:
A light weight flywheel and clutch will help, and if you rev the engine fairly high (in gear) before jerking your foot off the pedal, engine braking will slide the back around, a little jerk with the wheel upon turn-in and some trail-braking will help too.

Some extra rebound damping might help give some corner exit understeer.
I'd try reducing caster too.

[gchandler]

Right on with the drift car thing.

Currently we are adding as much steering angle as possible to the car and Tein is building some shocks for the car later this week. The car is running two sets of wilwood calipers on the rear with one set operated by a hand brake and the other on the foot brake.

Right now I plan to add some sort of adjustable front and rear swaybar to help fine tune the car.

Thanks for all the notes, as with everything, setting up a car takes track time, analysis, shop time, and then back to the track.