Handling Problem Options

[ClayPerrine]

I got to run my /6 conversion on the AX course yesterday after the Maverick Region AX102 school. Well, I learned a LOT about the car in just 2 runs.


It understeers......BADLY. I can't keep the front end planted to get it to turn. We had a skid pad circle in the course and all I did was plow my way wider on the circle.

What I am looking for are suggestions to fix it.


Front has 23mm torsion bars, delrin bushings, turbo tie rods, and a stock front sway bar (left stock deliberately to allow me to tune the suspension before replacing the bars)

Rear has 165 progressive springs, delrin bushings, and a stock rear sway bar.


I know everyone says to disconnect the rear bar, but IIRC that will just make the problem worse.


My choices.

1. Install adjustable sway bars front and rear.
2. Up the rear spring rate to 180.


Changing the springs is probably the first choice, but I am a bit worried about making the ride to stiff to drive on the street.


So... let's hear the suggestions........

[ken914]

http://www.wtrscca.org/tech.htm#suspension

The link above has set up information that may be helpful. Check tires (age, condition, pressure, etc.) first. Good luck!

[ArtechnikA]

23mm front torsions is HUGE...

so -

these are all possibilities, can be used in various combinations...

smaller front torsions.
disconnect the FRONT bar.
much bigger rear bar, especially if you have LSD.
stiffer rear springs.

trivial to disconnect the front bar and you may discover the VERY still torsion bars are giving you all the antiroll you need.

(and yes, i am still working on your project.)

[eeyore]

In almost all the perpetually recurring understeer threads, the 23mm torsion bar + stock anti-rollbar combination seems to be a central feature.

[Trekkor]

Clay, I like 200#'s in the rear with the rear bar *always" connected.

I run stock front torsions.
With the Konis set full soft it is a nice ride.
On full firm... (IMG:http://www.914world.com/bbs2/html/emoticons/unsure.gif)
Handle's good, though. ( see video )

Don't forget the 31mm front sway bar (IMG:http://www.914world.com/bbs2/html/emoticons/mueba.gif)


KT

[john rogers]

Several things need to be know before we all can start throwing suggestions your way.
1. What tires are you using?
2. What are the pressures, front and rear?
3. What are the current alignment specs, front and rear?
4. What are the corner balance weights?
5. Was the gas tank full, partial, etc?
6. Do you have a limited slip?

[Eric_Shea]

QUOTE

23mm front torsions is HUGE...

(IMG:http://www.914world.com/bbs2/html/emoticons/agree.gif)

Throw some stockers in there for the next race. I wouldn't use 'anything' near that for AX. Those are serious road racing bars in my book.

[brant]

I agree also..
23 front torsions are WAY to BIG.

I have a set of 23's that were too big to run with my 250# rear springs... (on a track only car)

your going to need to put 300's in the rear if you insist on using those 23's.

I down graded mine to 22's in order to match my 250's
In fact I know colorado GT cars that run front and rear aero, and can't use 23's.

(aero devices require a car to be set up ultra stiff to keep the aero down force from being wasted on simply compressing the spring... )

So I know a 914 that runs front splitters and rear wings at: 160+ mph and he only uses 22 torsion bars on it

I would suggest 19's or 20's for your street car with some autox useage.

(I'll bet the 19's are about 150 foot lbs less spring rate than 23's)

brant

[Dr. Roger]

Solutions for...... borrowed from a local SCCA text online. =-)

Understeer Corrections Oversteer Corrections.

Push, plowing, front tires slide out first. Loose, rear tires slide out first.

Usually slight understeer is safer. Oversteer can be dangerous, especially at high speeds.

Raise front tire pressure. Lower front tire pressure.

Lower rear tire pressure. Raise rear tire pressure.

Soften front shocks. Stiffen Bump. Stiffen front shocks.

Stiffen rear shocks. Soften rear shocks.

Lower front end. Raise front end.

Raise rear end. Lower rear end.

Widen front track. Reduce rear track.

Install shorter front tires. Install taller front tires.

Install taller rear tires. Install shorter rear tires.

Install wider front tires. Install narrower front tires.

Install narrower rear tires. Install wider rear tires.

Soften front sway bar. Stiffen front sway bar.

Stiffen rear sway bar. Soften rear sway bar.

More front toe out. More front toe in.

Reduce rear toe in slightly. Increase rear toe in.

Increase front negative camber. Reduce front negative camber.

Increase positive caster. Reduce positive caster.

Soften front springs. Stiffen front springs.

Stiffen rear springs. Soften rear springs.

May need more front suspension travel. May need more rear suspension travel.

Install wider front wheels. Install wider rear wheels.

Use softer front compound if possible. Use harder front compound if possible.

Use harder rear compound if possible. Use softer rear compound if possible.

Remove weight from front of vehicle. Add weight to front of vehicle.

Add weight to rear of vehicle. Remove weight from rear of vehicle.

Drive a different line. Driver may be going in too deep.

Use weight transfer to your advantage. Driver may be getting on the throttle to early.

High Speed. Increase front wing downforce. High Speed. Increase rear wing downforce.

Too much front brake. Too much rear brake.

Vehicle is TWITCHY at limit and hard to keep Vehicle slides and is easy to drive
ahead of in the steering department. at limit but does not corner to full potential.

Lower front and rear tire pressures slightly. Raise front and rear tire pressures slightly.

Suspension may be too stiff. Suspension may be too soft.

Shocks may be set too firm. Shocks may be too soft.

Tires may be old or hard. Roll centers may be too high.

Vehicle may not have enough suspension travel. Lower vehicle.

Vehicle may have a toe problem front or rear. Tires may be too hard.

Increase negative camber front and rear if possible. Widen track front & rear.



A properly set up vehicle will usually push slightly on corner entry, be fairly neutral at the apex (STEADY STATE) and exhibit slight power oversteer on corner exit. Tight courses may require more oversteer, fast tracks understeer.

Items needed: Accurate tire pyrometer, tire gauge, notebook and tape measure. Suspension information books.

Note: This is a sample of the methods used to correct various handling problems. Books have been written on this subject. Not every correction will always work as expected. Stiffer front sway bars will, in many cases, decrease understeer because of reduced body roll and better camber control. The best rule is to change only one thing at a time and keep notes.

Follow these suggestions at your own risk, we listed them to make your racing safer.

[Joe Ricard]

If you need some stock torsion bars I got a set.
I agree way too big for the rear spring you are running.
and the whimpy stock sway bar surely can't be doing much except lifting the inside rear wheel when cornering under power.

[brant]

I'm guessing (but could be wrong) that clay is using 911 front A-arms.

if thats accurate then stock bars are going to be 19mm
which is probably a really good match for the rest of the set up.

of course it means another trip to the alignment shop, but at least only for front....

and if you VERY carefully and VERY accurately measure your ride height before and match it after, you could skip the alignment shop....

(but Clay, knows this... and knows more about wrenching than I ever will)

brant

[ClayPerrine]

QUOTE (brant @ Mar 6 2006, 11:38 AM)

I'm guessing (but could be wrong) that clay is using 911 front A-arms. if thats accurate then stock bars are going to be 19mm which is probably a really good match for the rest of the set up. of course it means another trip to the alignment shop, but at least only for front.... and if you VERY carefully and VERY accurately measure your ride height before and match it after, you could skip the alignment shop.... (but Clay, knows this... and knows more about wrenching than I ever will) brant

Actually, no, I am running 914 front control arms. I bought just the 911 struts. I am a cheap SOB at times. (IMG:http://www.914world.com/bbs2/html/emoticons/biggrin.gif)


And I do my own alignments (With the proper tools.)


But I will take the suggestions of lowering the front torsion bar rate. It's a cheap fix.

[r_towle]

I have 23mm bars, and the 21 mm welt front sway...180lb rears/

It took me a few years of tweeking both me and the car to get it right.

Get the right tires, and lower the front pressure...try a few pounds per run...
It makes a huge difference.
Also, learn to brake HARD before a turn, then stomp on the gas to reset the car...

You can drive the setup you have really hard and do well, once you learn how.

With the front end very stiff, I find that the tire pressure is the key.
It does make the car alot less likely to spin, and that is a good thing, but you need to approach tight corners a bit differently..

Rich

[Mueller]

for the tires, how much wider are the rear tires than the front?

could you possibly have too much rear tire??

do you have spacers up front to move the wheels further outboard to match the the track of the rears?

[Joseph Mills]

QUOTE (ClayPerrine @ Mar 6 2006, 11:55 AM)

But I will take the suggestions of lowering the front torsion bar rate. It's a cheap fix.

(IMG:http://www.914world.com/bbs2/html/emoticons/agree.gif)

23s are way too big. I run 19s on mine with a 22weltmeister bar set on full soft. Even with 180# springs it was still exhibiting moderate speed push. I had to go to 250#s to get the rotation I wanted. I'd suggest you try the stock 17s and see how that works for you.

We'll compare our cars at TALIMENA 1.

..