Curing Understeer In A 924-S
 

From my previous thread, a few people made mention of the understeer problem that the 924-S has.

Without completely ruining day-to-day driveability on this car how do you fix it?

It seems that 16X7.5's on the front back will fit with a nice set of 220/50's on all four corners.

Heavier 220lb springs in the front (but keep the stock height) and Konis (or Bilsteins) front and back.

What about the anti-sway bars?
How thick on the front and rear?

Please, sound off on this and be specific.
I'm trying to lean without making some really costly mistakes. :)
Thanks!

Anybody?*
:)


















*Shameless bump.

I have simple ways of creating oversteer. Run 40psi of tire pressure in the back and run 25 in the front (it'll help a bit). OR use cheap-o crappy tires in the back and sticky ones in the front. If you're wanting to upgrade your suspension get a rear sway bar. Increasing your front spring rate and not doing anything with the back suspension will create more understeer. I would think upgrading to Konis in the back would help with oversteer, but I don't get the whole torsen bar set-up (my jap-loving @$$ likes coil-overs)

Lift the throttle abruptly in the middle of a hard corner. That will definitely reduce the understeer. ;)

Simplest thing to do is to inflate the rear tires to a few PSI more than the fronts. I wouldn't suggest 40 PSI rear and 25 PSI front just because 25 PSI is way too low. Try 30-32 PSI front and 40 PSI to sidewall maximum on the rears.

Aaron

EDIT: 220/50 tires might be a touch wide depending on the car, you might get some rubbing on the fenders. Also, I'm not sure about the rolling radius of those tires, if it's significantly different from the rolling radius of 195/65-R15 or 205/55-R15 tires then your speedometer will be rather severely inaccurate.

Just running some numbers through the calculator though, the new tires would only be about 1/3 of an inch larger in diameter (20.33 inch diameter vs 19.99 inch diameter) so things look OK. But I've not double-checked those numbers.

Sorry, I suck at life

Thanks Aaron!

How about the sway bars?

How big and on what end? :)

And if you happen to know how an anti-sway bar works, that would be cool too.

So I DON'T want to put wider tires on the rear?
Is that right?

If you really want oversteer, you can install a larger rear sway bar. However, Porsche is all about balance, and unless you know what you are doing, your going to mess with that balance. If you want to drive with the tail hanging out all the time, you should have bought a V8. If you just want a better handling car, get some wheels from a 87 or newer 944 Turbo. 16X7 front and 16X8 rear with 205/50 and 225/45 will make your car handle very very well. With these wheels, and Pole Position SO-3's I have to do something very stupid to get this car to loose grip! For hints on suspension mods, read the archives. It has been covered many many times. Good luck.

Never driven a 924S but my 944S seems to be neutral, understeer off throttle, oversteer on throttle. It has stock wheels and tire sizes and 28mm bar in front and 17 rear.

Re: Curing Understeer In A 924-S
 

Stiffer fronts springs will increase understeer. If your car does not have a rear sway bar get one, they can make the car handle more neutral. Weltmeister makes an adjustable rear bar so you can dialin as much oversteer as you want.

Mark
'86 944NA

I made a significant improvement in understeer on my 87 924S with stock suspension by installing an 18mm rear sway bar in combination with a 23.5mm front bar. Also, Koni Sport adjustable shocks help. Mine are set a half turn off full soft in the rear.

The car will still push, but it is much more neutral than before and will transition to mild oversteer on a sweeper. A limited slip would help in the tighter corners.

With a bigger budget, I would install stiffer front springs and bigger torsion bars.

I run 205/50x16 on 16x7 wheels. I think bigger rear tires would tend to increase the push.

My .02.

924SBob (the other one)

Haha, sorry. That came off a bit more abrasive than I meant. :)

I just have a big phobia about under-inflated tires.

Aaron

Get a bigger rear sway bar and keep the front stock, this will make a world of difference. It would also be the most cost effective if you went with a used one.

Front springs will only make understeer worse.

Konis are great if you have the money.

If you want an 18mm turbo bar I've got one for sale.

how much is the bar, and will it help/fit a 924 n/a?

As others have said, upgrading (or installing a new) rear sway bar will give you the best bang for the buck in terms of dialing out understeer.

Also: wider tires in the front will definately help with your understeer issues. My 944S2 came stock with 205/55-16 front, 225-50-16 rear, and for track use, I run with 245/45-16's all around. This made a HUGE difference for the way my car handles! While 245's all around may be a bit too much for a 924S, but you can certainly go with 225's all around. (225's will fit on 7 inch wide rims, BTW).

Another idea is to upgrade your shocks to Koni Yellow adjustables, and set your rears slightly firmer than your fronts.

I do not recommend varying the tire pressures so greatly front to rear. Nor do I recommend getting a 'crappy' set of tires for the rear. Both suggestions are dangerous, and the results are unpredictable. Use the same brand and model of tire at all four corners, and vary the pressures front to rear by not more than 2-5psi. Remember, our cars are well balanced: you shouldn't vary the pressures that much!

What application are you using your car for? Daily driver? Autox? Track? Depending on the application, there are things you can do.

One more very important thing: do only one modification at a time! Don't change everything all at once: otherwise you won't know what changes helped or hurt your handling! Baby steps is the way to go when you start down that slipperly slope of suspension upgrades! :eek:

HTH,
-Z-man.

Totally with Z man on this issue! I run 205fr-245rr on a 924S the 245's will only work on rear. The 205's helped reduce this problem to a degree. BALANCE is the ticket here! Change the rear set up and you will need to change the front too. Alignment is the next issue needing attention. Tires will dictate what camber and toe needed as well as the suspension upgrades. As far as air pressure goes it will vary greatly from track to track and weather conditions. Best to run at temps that give you the best feel in the seat of your pants. Take many readings and set your tire psi cold to achieve the hot temp needed 34 cold to 40 hot for example. Record your temps and handling characteristics at those temps and get the tires at a psi that gives the least understeer. Sman:)

924Sman,
"I run 205fr-245rr on a 924S the 245's will only work on rear. The 205's helped reduce this problem to a degree. "

Are you running 15's or 16's? Care to share your alignment specs?

I run -1.25 degrees camber in front. zero toe. 3 deg caster. Back runs about -1 degree. This is an all purpose street-autoX setup. Tire wear on inside front is noticeable, but not bad.

924SBob (the other one)

Bob, 16" BBS 3 piece.....2.25 neg in fr and rr....zero fr to 1/8 toe in rear
Sman

The 18mm turbo bar will fit any 924/944 that has a stock rear sway bar.