My 996 understeers like a Buick

Maybe that is a little harsh,however, it pushes much more than my BMWs. I tracked the car for the first time last weekend and unless I braked hard after turn in, I could not get the rear to rotate. I tried lowering the rear tire pressure and running higher in the front. Not much help. Has anyone tried a stiffer rear anti-sway bar? Who makes them? Also, has anyone tried running wider front tires. Thanks.

Try 235 or 245 wide tires on the front - with a wider rim 8", 8.5" or 9". You did not mention your rear tire size but going from 265 to 285s will increase understeer unless you use a wider rim/tire in front.

Wouldn't increasing front tire pressure result in less grip in front, causing the front to break free sooner, causing more understeer? Likewise, lowering rear pressures would make the back stick more, decreasing oversteer. Or do I have this backwards?

You've got it right, Ed. The recommended pressures are on the high side. Increasing the pressures will bow out the tread more, less contact patch, more slip. Try reversing what you did, Salazar, and see if it helps. As Loren has said, it may also be due to your tire sizes. I have a C4S, at that is supposed to have more oversteer, but I do fine with cold pressures of 32F/38R on the std C4S tires. I regularly run with an M3 whose driver and I are at about the same skill level, and I can rotate the C4S around a tight hairpin better than he can with his M3.

I've heard it both ways, but my experience with the rears at least is lower pressure, less oversteer. My car pushes badly with street tires, difficult to rotate. With the Khumo Ecsta V700's, no push at all and actually it's a little loose in back now.

Are you running the 030 sport suspension? If not, you might want to try the swaybar set from this suspension. If you're willing, your best bet might be to make the move to the 030 completely...

Lower the front pressures. You probably made your problem worse. I have a C2 with Conti SportContact2's. I run 30.5 (front), 35 (rear) now. It solved a lot of the understeer. The only thing left to do now is get the ROW 030 suspension or maybe even just put some negative camber in my alignment.

</font><blockquote><font size="1" face="Verdana,Tahoma,Helvetica">quote:</font><hr /><font size="2" face="Verdana,Tahoma,Helvetica">Originally posted by Salazar: <strong>Maybe that is a little harsh,however, it pushes much more than my BMWs. I tracked the car for the first time last weekend and unless I braked hard after turn in, I could not get the rear to rotate. I tried lowering the rear tire pressure and running higher in the front. Not much help. Has anyone tried a stiffer rear anti-sway bar? Who makes them? Also, has anyone tried running wider front tires. Thanks.</strong></font><hr /></blockquote><font size="2" face="Verdana,Tahoma,Helvetica">Camber is factory set at 0 degrees, try realigning it to neg. 1 degrees. The rears could be between neg. 1 and 1.5 degrees, I think the factory alignment is something like neg. 2.5! The RoW M030 is not the best solution for tracked cars. Adjustable anti-roll bars a la GT3 would allow finer adjustment of the handling balance. The Bilstein or H&R coilovers is a better solution than the M030. Also remember you have 60/40 weight distribution. Driving technique involed in getting 996s to 'rotate' is different than most cars--even mid-engined ones. Read Elfords book on 911 driving, good info which translates well 996s.

Palting and Scott in Huston; I think that you have it backward on the pressures. Go to kormanfastbmw.com and search under tec info. They have a HandlingAdjustment Chart. Also, i had a tire tread separation case several years ago and hired an engineer who had developed the first super high perf tires for Goodyear. He told me that tire tread bow is no more. With new high perf tires the belts that are so strong that the sidewalls will bow out under very high psi while the contact patch will stay flat. Anybody have a part # for the sport rear sway bar?

I have mine set at negative 0.5 degrees up front and negative 1.5 degrees for the rear. This helped quit a bit on the auto-x events. But I was told to increase the tire pressure for the front tires by 2-3 psi over the rear. At first I didn't think this would work since I've heard the opposite (lower psi for the front then the rear) but it did help rotate the rear-end around.

Generally, increasing tire pressure increases grip in that tire. In a corner the sidewalls don't deform as much and more tread stays on the ground. However with increasing pressures you reach a point where the contact patch becomes smaller and grip decreases. This occurs more in wide tires with short stiff sidewalls. While with a 30 series tire maximum grip might occur at about 35 psi, a 60 series tire may need 55psi. You might get better lap times running all pressure above the ideal cornering grip pressure, because you scrub of less speed.

safety worker: I too am running the same alignment specs and I could imagine running anything less, maybe a bit more camber but anymore than this will accelerate tire wear too much for my street driving tastes. Salazar - damn u! get your alignment set to -.5f and -1.4 rear and you should like it just fine. Loren is definitely right that the best way to dial out the understeer is to increase the width in the front rim and that's why they did that from 02 up. I think you would be pleasantly surpirised at what it will be like afterwards. Also if you decrease the toe splitting it from factory and zero it will make the car turn in better.

Salazar, Interesting, but my experience in the field has lead me to believe otherwise at least as far as 'my' car and 'my' tires.

</font><blockquote><font size="1" face="Verdana,Tahoma,Helvetica">quote:</font><hr /><font size="2" face="Verdana,Tahoma,Helvetica">Originally posted by Salazar: <strong>Palting and Scott in Huston; I think that you have it backward on the pressures. Go to kormanfastbmw.com and search under tec info. They have a HandlingAdjustment Chart. Also, i had a tire tread separation case several years ago and hired an engineer who had developed the first super high perf tires for Goodyear. He told me that tire tread bow is no more. With new high perf tires the belts that are so strong that the sidewalls will bow out under very high psi while the contact patch will stay flat. </strong></font><hr /></blockquote><font size="2" face="Verdana,Tahoma,Helvetica"> Very interesting. There is also a Goodyear tech who is a member of our PCA region, and he gives tech talks all over the country. In fact, it was through him that my car got to be a "test mule" free track tires! With the curent crop of low profile radial tires, the sidewalls by necessity have to be, and are, very stiff and almost have no flex. What we now need is an umpire tech . Regardless, real world experience is the most believable. I don't know about kormanfastbmw.com, but Rennlist is a Porsche dedicated site, and we are talking about a Porsche 996. Do a search on tire pressures, and you will receive a flood of information. It is a consensus, as far as the 996's go, that the factory tire presssures are too high, and less pressure is more traction. What tires do you have, what rims, and what pressures? There is also a difference in driving technique between a butt heavy 911 and your old car, a nose heavy BMW. If, despite all the well meaning responses here, you insist on larger rear sway bars, check out carnewal.com, one of the Rennlist sponsors. Talk to Gert. He sells all sorts of suspensions as a package, but I'm sure he can accomodate your purchase of just a larger sway bar. Good luck, have fun!!

Salazar, what type of corners are we talking about here? Slow corners? How does the car handle in the high speed turns? Also, where in the corner does the car understeer? Apex to track out? There really is a great deal that needs to be thought though in these scenarios. Changing the rear roll rate may help the handling in one type of corner, but could easily have a negative effect on the handling in another type of corner.

Thanks everyone for the suggestions. What I am going to do is take an hour or so this weekend and set the car up to GT3 specs. Does anyone care to know how it is done? If so I can take pics as I work through it and post a "how to". After driving the car on the street and track I will make a decision about tires. However, I am leaning toward larger fronts. If that is still not enough, I will go with the Gt3 bars.

SPR, looks like you've setup your car exactly like mine! My toe is also setup the way you've done it. After this setup, I have to admit I was very surprised at how the car now handles on the auto-cross courses. It darts a little on the highway but I don't mind it. Still handles less nervous then my '78 SC coupe.

Rememeber that all tires have an "ideal" pressure where they make the most grip. That pressure is dependant on the size of the tire & wheel, type of tire, and weight that the tire must support. Tire pressure are odd because you can be too high or too low and the grip will suck. So it is not as simple as increasing or decreasing pressures. In my 944 race car I run equal pressures at all 4 wheels. This works in my car because I have the same tire sizes and all weights are very close. It took me some time to find the tire "ideal pressure zone". I don't use tire pressure to balance the car. I use my sway bars for that. Obviously equal pressure will not work for 911's, but before you worry about changeing the factorty tire pressure differental you need to find your ideal hot pressures. Sounds like the 996 guys feel that is lower than factory recommended. More Negative camber in front and less in rear will also reduce the understeer. It seems to me the the Stock factorty setting are designed to make the cars "safe" and understeer, but with a little knowledge you can correct that!

safety worker. I hear that on the freeway it is sort of nervious a bit but I am used to it. Over 130 though it really smooths out hehe. At 160 it was pretty docile. What tires are you running? I have the pirelli p zero yellows with 140 or lower (I forget) tread rating pretty sticky. The only thing is that I am running 295's in the rear with a 7.5" front so it's all about throttle steer. The alignment sure helped. I do remmeber the 265's and it was sooo easy to just toss it around all day and was really fun. Now it is more of a challenge but I take turbo's down pretty well so I guess I am doing something right.

Mine smoothes out at 130. Only been a little higher for any distance though. The car seems stable as can be, but the steering does seem squirely.

Nice pics SPR.

heheh Thanks Doug.

SPR, I'm running standard sizes for a '99. 225's up front and 265's in the rear with SO3s on 18' sport classics. I wanted to up a size in the rear to 285's but decided against it since I was already complaining about understeer. I've also lightened the rear (somewhat - don't know how much) with the Fabspeed Maxflow exhausts. That seemed to help a little. But I love the music coming out the back.....

My simple thought was that carreras were meant to be first understeered by throttle decelaration to shake that a** off-track; then throttle back to keep the belly dance.. sorry, living here for more than two months is making my imagination run wild! Waz!

My street wheel/tire set up is 18/8 front with 225/40 and 18/10 rear with 285/30. However, I am getting ready to set the car up for a DE and after reading this forum it appears to me that the 225 front and 265 rear may be preferable to reduce understeer. Also, I hear the the Michelin Pilot Sport Cup is an excellent tire for both adhesion and wear. Any input is appreciated. Robert

</font><blockquote><font size="1" face="Verdana,Tahoma,Helvetica">quote:</font><hr /><font size="2" face="Verdana,Tahoma,Helvetica">Originally posted by roblin: <strong>My street wheel/tire set up is 18/8 front with 225/40 and 18/10 rear with 285/30. However, I am getting ready to set the car up for a DE and after reading this forum it appears to me that the 225 front and 265 rear may be preferable to reduce understeer. Also, I hear the the Michelin Pilot Sport Cup is an excellent tire for both adhesion and wear. Any input is appreciated. Robert</strong></font><hr /></blockquote><font size="2" face="Verdana,Tahoma,Helvetica">I realized a substantial increase in grip by switching rear meats to 285/30s. I added the RoW M030 before changing wheels and tires, so i've driven it both ways. Going from 265/35s to 285/30s is a step in the right direction, but this in itself had little effect on understeer (good or bad). I believe the RoW M030 is a good starting point provided you realign the front camber by as much as 1 negative degree. This will raise the roll center, which transfers weight under cornering in a manner which reduces understeer (substatially). Beware that less adjustability is available on US cars with the stock ride height.