Handling: Plenty of Understeer, impressions of my car from Trekkor's AX school Options

[McMark]

After Trekkor's AX school at Infineon I need some confirmation/correction of my assessment. The course included lots of tight 140+ degree turns, two slaloms, and a long left hand sweeper. In all of these elements I experienced oversteer. Braking felt fine, although I'm sure some nice Porterfields would decrease the stopping time.

I'm not interested in upgrading springs or T-Bars because this is mostly a street driving car. But from my 'book learning' of suspension setup, I think tightening the rear would help even out the car. I would like to be able to dial in a bit of oversteer and then ease back off. The only way I can see to do this, with what I have in the car and what I'm willing to do, would be to fabricate an adjustable rear sway bar.

I know many people have their cars set up with no rear bar at all, so am I missing something? I feel like a bigger, adjustable rear bar would also let me run my front bar closer to full hard.

Here's my car setup:
Stock 1.7 (going turbo over the winter)
Stock front T-bars.
19mm front sway bar set at half-stiff.
Unknown age front internally adjustable Konis set on full soft.
Rear bilsteins of unknown age.
Rear springs of unknown rate (but comfortable on street so not HUGE, but not stock either).
Stock rear sway bar.
First generation Falken Azenis (205/55/16) on 6" Boxster 'Snowflake' wheels.
Stock calipers and 'cheap' pads.
19mm Master Cylinder
MC Brace


Also, Trekkor drove my car on a couple runs, so hopefully he'll chime in with an alternate perspective.

EDIT: Original topic erroneously said OVERsteer when I really meant UNDERsteer.

[campbellcj]

Did you try any adjustments to the front swaybar while there? That's the only adjustment you've got besides alignment and tire pressures (which are also significant variables.) You'd probably want to stiffen the front bar and/or bias tire pressure higher towards the front. Or you could try disconnecting the rear swaybar temporarily - pop one or both droplink off and zip-tie it out of the way. Many people are not fans of rear bars at least on stock-ish cars with low power and no limited slip.

Your struts/shocks may also be a factor. If they (or one) is severely worn or broken than all kinds of funky behavior would ensue.

[Trekkor]

I run a HUGE (31mm ) front sway bar set 2/3 to firm and stock rear bar.
No oversteer at all on my car.


I spun your car on my first run at the end of a slalom going into a left hander~ Snap Oversteer.

After that, I drove around the handling.
I don't want to call it an "issue".

It is just different.
My first drive in a stock 914 in maybe 8 years?

I was refreshing, actually.


KT

[Randal]

Did you try any adjustments to the front swaybar while there? That's the only adjustment you've got besides alignment and tire pressures (which are also significant variables.) You'd probably want to stiffen the front bar and/or bias tire pressure higher towards the front. Or you could try disconnecting the rear swaybar temporarily - pop one or both droplink off and zip-tie it out of the way. Many people are not fans of rear bars at least on stock-ish cars with low power and no limited slip.

Your struts/shocks may also be a factor. If they (or one) is severely worn or broken than all kinds of funky behavior would ensue.

+1

What is the old classic saying, i.e., if the rear is loose, then you need to tighten up the front. Do this using whatever you have on board, i.e., combination of sway bar, tire pressures and shocks.

[Trekkor]

This may be helpful:

 Over_Steer_Under_Steer.pdf ( 50.69k ) Number of downloads: 334



KT

[McMark]

I wonder if your rear springs are stiffer than mine Trekkor. (IMG:style_emoticons/default/idea.gif)

[Woody]

Go full stiff on the front bar or get rid of the rear bar.

[Trekkor]

Stock front torsions, 200# rear springs.
So, yes!


KT

[sixnotfour]

Go full stiff on the front bar or get rid of the rear bar.

Ya you should have popped off one link on the rear and tried it agian.

[McMark]

Go full stiff on the front bar or get rid of the rear bar.

Ya you should have popped off one link on the rear and tried it agian.

So these posts totally confuse me. As Randal mentioned, "if the rear is loose, then you need to tighten up the front." But I need the reverse, if the front is loose, then you need to tighten up the rear, don't I? These suggestions would effectively tighten up the front. I thought that would induce more oversteer.

(IMG:style_emoticons/default/confused24.gif)

[sixnotfour]

well then you have Understeer or front push and need to do the opposite .Yup

just going by this in the title "Plenty of Oversteer"

[Trekkor]

(IMG:http://www.914world.com/bbs2/uploads_offsite/sphotos-b.xx.fbcdn.net-1413-1353291407.1.jpg)

(IMG:http://www.914world.com/bbs2/uploads_offsite/sphotos-a.xx.fbcdn.net-1413-1353291407.2.jpg)

(IMG:http://www.914world.com/bbs2/uploads_offsite/sphotos-a.xx.fbcdn.net-1413-1353291407.3.jpg)


Fun car to drive.


KT

[6freak]

Balance sir !! what you do to the front you must do to the back...JMO
(IMG:style_emoticons/default/smile.gif)

[SirAndy]

well then you have Understeer or front push

(IMG:style_emoticons/default/agree.gif)

What you are describing is understeer, oversteer is when the rear is loose ...
(IMG:style_emoticons/default/rolleyes.gif)

[McMark]

Yeah, yeah. I'm an idiot. (IMG:style_emoticons/default/dry.gif) Understeer. I knew that too. (IMG:style_emoticons/default/headbang.gif)

Thanks for posting the pic Trekkor! I was just gonna do the same thing, and you beat me to it. The ass end looks like its sitting up higher in the corners...

[ConeDodger]

The ass-end is normal weight transfer.

I like huge sway bar in the front with stock torsion bars. I think you have a good basic set-up now. Adjust with tire pressure for now.

Also if your rear springs aren't stock, they are at a minimum, 140#.

[Randal]

So is it oversteer or understeer?

Is the front loose or the rear loose?




OK, missed that post, so it's understeer. The front is loose or what some call plowing. If the front is loose tighten up the rear.

Springs, shocks or sway bar, take your pick and/or tighten up what you have. I always go up (spring rate) at least 25 lbs and see how it performs. I'll have to check my spring stash and see what I might have for you. Are you running 8" Eibach

And as a few posters have suggested get a good alighment. Also corner balance the car as you can alter ride height to get it close.

[jhadler]

In a car with relatively stock setup, understeer can be the result of a few things.

Overdriving the corner entry. Plow too hard into the turn, and nearly any car will exhibit understeer. As Trek mentioned, he drove around the car's handling. You're on basically a stock suspension with moderate tires. You will likely find the car exhibiting understeer if you're new to competition driving. It is nearly universal for a new driver to push too hard in the slow parts (resulting in understeer), and not hard enough in the fast parts. Pushing hard in the fast parts, you will find the limits of the car and experience oversteer - guaranteed.

Insufficient camber in the turn will reduce your contact patch to nearly nothing. No contact patch, no grip.

Too soft torsion bars in front will possibly bottom out, and result in instant understeer. The roll center of the car transfers to the outboard contact patch, and grip goes bye-bye.

Looking at the pictures, you've got decent body roll, but not excessive. A little alignment work can help a lot. Get as much -caster- as you can. Caster is effectively dynamic camber. The more you turn the wheel, the more negative camber you gain. With the body roll you've got, I would say this is your first engineering culprit (gotta remember that the steering nut is usually responsible for 90% of a car's ill-handling characteristics).

Get a good alignment into the car before sinking money into springs and bars. If you're gonna run street tires, a degree or so negative camber front and rear. A little toe out in front (unless you plan to play at a track, then neutral toe). Neutral to a tiny bit of toe out in the rear.

Good luck, and have fun! Don't make any big changes 'till you've got a good alignment. And make sure that the bushings are all good. Crappy bushings make for wobbly and unpredictable suspension movement, rendering all my previous discussions moot.

-Josh

[6freak]

Understeer is engineered into the car ...like all cars made for America !...they want you to go off the road strait,not sideways or backwards....seat time will be your best investment,,,really learn the car then change it and most of the time if you slow down you will actually go faster! try it.. ....#1 rule have fun...JMO
(IMG:style_emoticons/default/smile.gif)

[jhadler]

Understeer is engineered into the car ...like all cars made for America !...they want you to go off the road strait,not sideways or backwards....seat time will be your best investment,,,really learn the car then change it and most of the time if you slow down you will actually go faster! try it.. ....#1 rule have fun...JMO
(IMG:style_emoticons/default/smile.gif)

Spot on. The engineered understeer is more of a CYA for the car manufacturers. Go off the road nose first, it's your fault. Go off the road rear first, it's the cars fault. The absurdities of the American legal system hard at work to pull every Porsche 930 off the road... 'Cause when the boost kicked in, and you didn't know what the ^&*% you were doing, you WERE going off the road rear end first.

-Josh