Under steer

[MarkR171]

Reading this thread has been a good help, but I'm still stuck on the decision of to sway or not to sway. From what I gather, people are having both positive and negative effects when changing the front sway bar and its benefit differs on a case by case basis.

What would people recommend for D-Stock class autocross on a tight, technical course? D-Stock = Tires, Catback, Shocks, Front Sway legal only. I don't leave 2nd gear and slaloms, hairpins and tight 90 degree turns are common. The surface is at an angle, but relatively flat. Would a stiffer front sway help me under these conditions?

I have in car video of the layouts of the events I run in if it helps get an idea of the layout. Youtube link in my sig.

I know the D-Stock nationals winner in '08 ran a Hotchkiss bar (32mm) front + alignment pin removal + 275 hoosiers f/r. Maybe the non-staggered hoosiers helped alleviate some understeer so the stiffer bar didn't have as much of a negative effect?

[Evice]

Originally Posted by JimD

You have lost adhesion at the rear and the back of your car is starting to do it's own thing. You have to point the front where the back is headed and reduce throttle so the rear can hook up. It is especially important to not make violent changes in anything, throttle, brakes, steering when in oversteer. Mild oversteer may be corrected through a little less throttle and steering into it. Hard oversteer requires steering into it, significantly less throttle, and then recovery of the steering angle back where you really want to go when the rear end hooks up.

Sorry JimD. I am really not agreeing with you here on your recommendation how to correct oversteer. Lifting off or reducing throttle doesn't always work, on the contrary you may increase the oversteer. There are way more variables to consider on how to correct the oversteer. Don't wanna get into that discussion here, may be different topic.

I reduced understeer in my car, and gained more balance and predictability with very simple mods. I got TCKline D/As, changed the springs and their rates, got TCKline camber plates and got wider front tires. All the mods, have future use, and helped the understeer.

[Kcc]

Over steering = front tire lost traction?

Under steering = rear wheel spin?

Please correct me!

Kcc

[Thaddy]

Originally Posted by Kcc

Over steering = front tire lost traction?

Under steering = rear wheel spin?

Please correct me!

Kcc

http://en.wikipedia.org/wiki/Oversteer

http://en.wikipedia.org/wiki/Understeer

[Evice]

Originally Posted by Kcc

Over steering = front tire lost traction?

Under steering = rear wheel spin?

Please correct me!

Kcc

Understeer is traction lost in front tires where the front wants to go straight.
Oversteer is where the backend moves out of line.

Understeer pushes you out of the turn, oversteer initially make you look more into.

Also check the links given.

[130i-ftw]

better oversteer that understeer, I had the occasion to experience for the first time understeer in wet conditions and it's clearly not funny, I lifted my foot from the throttle and hopefully I was able to regain control ...

[sodara]

under-steer = hitting tree with front end
over-steer = hitting tree with rear end

clarkson said it something like that on topgear

[Yogijet]

Originally Posted by bradford

People are doing the front bar only because it's cheap.

You can do the rear bar (within reason - bigger is not always better) too but you need to drop the subframe. = big labor $$$ or big PITA if you're doing it yourself. And if you're in there you're nuts if you don't do the subframe bushings = additional $ and PITA.

So faced with the above, most people just spend a couple hundo on the front bar and call the job done. YMMV.

Tell me something. Anyone see any issues (performance negatives) with doing the BMW Performance Suspension and the M3 front sway bard and control arms in the first instance, then doing the M3 rear sway, rear subframe bushings, and LSD afterwards but all at once? I'm outside the US, and my BMW German-trained mechanic is a star and not particularly expensive so the cost is secondary to desired result. I'm looking for reduced understeer and sharper more focused and balanced handling.

[Evice]

Originally Posted by 130i-ftw

better oversteer that understeer, I had the occasion to experience for the first time understeer in wet conditions and it's clearly not funny, I lifted my foot from the throttle and hopefully I was able to regain control ...

This is completely unacceptable, you must be CRAZY to even suggest that!

Understeer is ALWAYS safer, and it has been accepted like that by almost all Auto Manufacturers as well. The reason is any inexperienced regular driver will LIFT-OFF in an unexpected situation due to panic. And that is THE remedy for understeer. And this is why almost all road cars have built in understeer tendencies out from the factory.

However on Oversteer, it requires more complicated solution, depending on the car's behavior at that point in time, which a 'regular' driver lacks off. Sometimes you lift, sometimes you full throttle, it all depends.

[130i-ftw]

I don't know I feel more a passenger of my car when it understeers than oversteers of course within a certain limit ...

[Evice]

Originally Posted by 130i-ftw

I don't know I feel more a passenger of my car when it understeers than oversteers of course within a certain limit ...

Then don't be a passenger! Be pro-active and straighten your wheel split second to grab traction quicker, then steer again.. and do this multiple times before you head on the curb or tree. Waiting for the car to slow down enough due to lift off might just not be enough, you can still end up in the curb.

[130i-ftw]

Originally Posted by Evice

Then don't be a passenger! Be pro-active and straighten your wheel split second to grab traction quicker, then steer again.. and do this multiple times before you head on the curb or tree. Waiting for the car to slow down enough due to lift off might just not be enough, you can still end up in the curb.

I had runflats at that time and I could feel the tyres sort of boucing and massive vibrations on the steering wheel, very disturbing ... but when you're headed to the curb I don't think most people will have the reflex of steering again towards the curb

[Evice]

Originally Posted by 130i-ftw

I had runflats at that time and I could feel the tyres sort of boucing and massive vibrations on the steering wheel, very disturbing ... but when you're headed to the curb I don't think most people will have the reflex of steering again towards the curb

Of course, simple signs of understeer is the massive vibration. and yes regular driver won't steer into curb again, they will be simple passengers..

[The1]

if you're getting the major vibration, you've gone well beyond the limit of under-steer. you need to learn to feel for the under-steer before it gets to that point.

this should just start to feel a big vague and your steering input will not change much of the direction your going, that should be the first indicator, so don't fully lift off throttle ( could cause you to spin if you get too much grip on the front too fast) and back off the steering a little, then re-apply as mentioned above.