What will reduce understeer

Since the search is not working...... what can be done to reduce understeer ? I am not looking to make big changes, just looking to make the car more neutral.

lots of stuff: Higher front tire pressure Lower rear tire pressure Larger front tire section Smaller rear tire section More negative front camber More positive rear camber Softer front springs Stiffer rear springs Thinner (weaker) front sway bar Thicker (stronger) rear sway bar Weight distribuation more rearward

Me behind the wheel :edit But the question is pretty vague. The better input you give the better answers you'll get.

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What kind of gas do you use? 93 octane? -td

sandbags.......

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wait a minute redridge.... those dont sound correct... (though I admit I have no experience or real knowledge) those sound like fixes for "oversteer" How can I be so wrong?

Not driving a car with the engine all the way in the back... AKA no fun.

thanks for all the help, you may now return to polishing your..........

What's already done to the car? Adjusting your driving style can help out alot too. Trailbrake helps alot. Bigger rear bar is a goos start and it's cheap however it's a band-aid fix as you generally want to fix the end that's not working well (front) first but that's more money to fix.

trailbraking

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this sh**... can be debatable, but increasing oversteer (more rear traction), reduces understeer... no?

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technically yes (sometimes).....but increasing rear grip doesn't necessarily reduce understeer. You can still push like a dump truck. You are looking for more FRONT grip which isn't a 1 to 1 relationship by increasing REAR grip. You could also illustrate that reducing REAR grip would increase FRONT grip thereby reducing understeer. The two easiest ways (in real time) I get rid of understeer is trailbraking and trailing throttle oversteer with trailbraking being the preferred method (increased cornering speed) and the later being the one when I have screwed up the corner.

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well since you put it that way... it makes sense.... thanks for the clarification. This always spins my head... especially in the early morn.

welcome FYI....it helps that I drink most of my coffee intake for the day well before most are even up (comes with having a one year old) and I spend a considerable amount of time on track so feeling these characteristics continually sure helps speak from real world experience.

start with 0 toe and max camber at the front (assuming stock suspension should be around -0.5 Deg)

It should also be noted that Trailbraking shouldn't really be practiced on the street either. You could practice pedal feel if you wanted to on the street but to really get it to work right you need to be way beyond the level you should be driving at on the street. That's why for street driving throw a big rear bar on the car and take away some grip at the rear and you'll move balance to the front that way for better "general" feel. Doesn't necessarily mean you'll be any faster at the track but it'll feel better on the street. When I had just H&R springs on my car I ran a M030 front sway with a GT3 rear sway and I really liked the way the car drove.

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Gawd I am lost... isn't oversteer the *** coming around...in otherwords LESS rear traction? Sorry to keep this up, but for me its an area I dont know much about and this is great info (not that it will change my driving to and fro work )

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Not necessarily always. Oversteer can happen when you have too much FRONT grip, too little REAR grip, or any combination of several factors but yes the quick and dirty definition is when the rear runs out of traction before the front does in a corner. ....and just the opposite for understeer. The reason it is not a 1 to 1 scenario and not a "when increasing one the other decreases" is because there are more variables involved with trying to achieve "balance" between the two when taking corners.

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I was reffering to the lowering rear tire pressure to increase oversteer thus reducing understeer.... Dell stating that it was not a 1-1 relationship... so the argument was not complete.... Like what was previously mention, the dynamics of trail braking, momentum and throttle control around cornering better explains over/understeer relationship... more so than my traction explanation

Oversteer is when you hit the wall with the back end! Understeer is when you hit the wall with the front end! Unknown author

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All true. Sometimes a heavy throttle foot also helps!

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Again, sorry for my ignorance, but if hit hit the gas harder, aren't you transfering the weight to the rear of the car, thus reducing the front traction and actually increasing undesteer? Boy, I have this ALL wrong

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To the OP, where are you experiencing understeer? At corner entry? Midcorner? Exit? All through the corner? Despite the street tendency towards understeer, I would first look at your driving technique before fiddling too much with the setup. It is possible that you are exacerbating the inherent understeer by abrupt release of the brakes or a heavy right foot. Depends on a number of factors, including the car, what gear you are in, and the corner. But in a 996, a heavy foot too early in the corner can result in corner entry understeer because of decreased front tire patch due to rearward weight transfer. This coupled with poor braking technique can wreak havoc on your corner entries. In other instances, a heavy throttle can result in throttle oversteer - which completely eliminates understeer In general, if you balance the car correctly with a smooth release of the brakes and transfer to power smoothly, the car will take a set nicely. Once the car is set and turn-in is complete, a hefty but smooth application of gas by/around apex is recommended to keep the car set. [This does not take into consideration trailbraking or trailing throttle to rotate the car.] -td

with zero suspension changes. Wider front tires help reduce the understeer.

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I've never understood this reasoning. But, I admit I've never spent much time on it. I'd like to hear technical reasons why wider tires are better in the context of tire patch. My (simple mind) reasoning is: contact patch is directly related to vehicle weight. You might have a wider contact patch with wider tires, but it will be the same area as a narrower tire, since you haven't changed the car's weight. With the same area in contact with the road, you will have the same traction. I.e., no reduction in understeer. -td

I agree with you (himself) but what I read was increase throttle equals decreased understeer. I see where placement of the throttle is important and I supose with the *** coming slightly off track (sliding out) understeer can be achieved. The OP did not mention where understeer occurred, so in a sence the reply is correct and incorrect dependant on when in the turn it is used. Thanks, fun info

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True, but if you go really heavy and break the rear tires loose, "voila", instant oversteer.......

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Ed, if you are interested, I highly recommend the book "Going Faster - Mastering the Art of Race Driving" from the Skip Barber Racing School. It's a great book, and does a very good job of explaining technical information.

are there pictures or do I have to read ?

Lot's of pics

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What's odd is how Porsche would go to such great lengths to design such well-balanced cars... then spec out stock wheels and tires that make 'em plow like a FWD. Probably just trying to keep people out of the ditch, while still allowing enthusiasts an easy upgrade path to the true design performance. We recently had a big discussion about this over at autocross.us that's worth a read if you're interested in this sort of thing: http://www.autocross.us/forums/index...topic=4410&hl= Short answer is that when you're cornering, you're never really going in a straight line, the rubber is bending and stretching, and you crab sideways a little, kinda like a sailboat or an airplane in a cross-wind. This is called "slip angle." Wider tires (due to the wide thin contact patch) allow grip at a greater slip angle than narrow tires before the rubber stretches too far and lets go of the pavement with the audible squeak/squealing you're no doubt familiar with. This gives you better overall cornering force. In theory, you can run wider tires at lower pressures, as well, which increases the size of the contact patch (at decreased pressure and thus increased coefficient of friction), and increases overall traction. FYI, I ran last autocross season OEM stock, but for this season, I'm putting bigger tires up front and increasing front negative camber to reduce understeer. I don't want to increase oversteer, as that would mean less overall traction. But I would like to decrease understeer. I'll let you know in a few weeks how well it worked

If we're speaking just on technique and not just setup changes, Keith Code's "Twist of the wrist" series is an outstanding read. Yes, they're geared towards motorcycles but the constant focus on contact patch management which is critical on a bike directly applies to our cars to a fair extent as well. They're some of my favorite books and I read them once a year as a refresher.

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I'm speaking from my actual experience with zero suspension changes in an AX envrionment. The wider front tire reduces understeer and allows for more effective braking. 8.5"/10.5" rims 225/295 huge understeer. PS2 235/295 understeer. PS2 255/295 almost neutral. PS2 255/295 w GT3 bars. neutral PS2, R888 This is not even talking about overtiring a 255 tire on a 7.5" rim which I think you are referring to. My effective contact patch is much wider on a 8.5" rim from 225 to 255 tire. sjfehr has it on the mark. BTW I am trying out a 265/285 combo TY which I expect to be loose (R1 size/diameter limitation). I still have my 255/295 r888 mounted if you local, you can slap it on and run some skidpad test to realize the huge difference what a 'little' the extra front width can do to balance the 996.

Just lift off the throttle.

This is way too complicated a topic to make much headway in a discussion thread but I will say the 996 comes nicely set up from the factory. Let's face it, a neutral car is really an unpredicable car. You never know if it will understeer or oversteer. A car set up to oversteer is a handful. I'm sure we all think loose is fast and we're all fast but let's get real. Very few can drive a loose car fast. A car with nice controllable understeer is a joy to drive fast. Just my 2 cents. Jim p.s. if your 996 pushes like a pig, it ain't the car!

I have never liked understeer. To me it is an uncontrolled slide. Now a car that tends to oversteer is a slide that can be controlled. As the rear steps out you can lift off the throttle leaving the car pointed at the apex, in effect tightening up the corner. Where as an understeer that is headed for disaster leaves one choice, get the tail out . If there wasn't room or time it can be ugly. That is why I prefer a set up that induces oversteer rather than understeer. So to be more specific, what sway bar change is needed to reduce understeer, making the car more neutral with a tendency towards oversteer ?

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I haven't put a calculator or serious brain power to this, but my first thought responses are below. My two premises are: contact patch is dependent only on weight and pressure. Friction is [mostly] dependent on tire compound and surface conditions. There may be significant differences in handling due to sidewall thickness alone. Changing sidewall ratio can change the center of gravity (ride height), rake, and turn-in responsiveness. Regarding slip angle and the crabbing tire: different compounds behave differently. I would guess that some manufacturers design tires to operate with particular dimensions contact patches such that the generalized concept may not apply. Further, for hard tires, like the PS2, I am not convinced that the "crabbing" theory holds up. With racing slicks, I'm fairly sure there is something going on requiring wider tires - perhaps to ensure integrity of the tire, but I haven't seen data or been convinced that it affects contact patch, slip angle, or friction characteristics. Some people say yes, other peole say no. Despite both "people" being educated they still disagree. I'm on the fence. What is "effective tire patch"? And, the actual patch should be WIDER, since it has 30mm more width to start with. But that doesn't mean it has more contact patch area for the same car weight and air pressure. I appreciate the offer, but I've actually driven your tire combination, and a *few* others. And I'm not convinced that (for my car) wider fronts descrease understeer. [In the last few months alone I have driven: Yokohama A005 slicks; Hoosier Slicks; Dunlop Slicks; Hoosier R6; Michelin Pilot Sport Cups; Toyo RA1; and Toyo R888]. I have both 8" and 8.5" fronts, with 10" rears. In my experience the REAL different is setup, not tire width. I do recognize that for some cars all there is to adjust is tire width and pressure. Like I said, I haven't studied this at all, so I may be way off - but I can't believe the answer is as simple as "wider is better." -td FWIW, my car has been through 3 full suspensions, 4 different types of sway bars (adjustable and not), adjustable and non-adjustable drop links, different alignments, ride heights, track widths (spacers), etc etc, so I really haven't been paying attention to tire width and handling.

The OP simply asked what minor change can be made to dial out some understeer. To me it all starts with tires assuming all other variables being fixed. I am speaking what works for me, with your car do with whatever you want. No point quoting and being somewhat critical on what works for me. I only upgrade one area at a time to note the results before making further changes which has worked out nicely for me. Neutral/tight/loose is relative on speed/driver anyways. Loose for one driver, might be tight for another. For AX I like it neutral (controlled slip angle for all 4 wheels), which of course in a real slow hairpin there is still understeer but in general neutral handling throughout most of the course at 45-55 mph. For DEs, I loosen the rear sway bar a notch to have a bit of understeer to minimize the 'pucker' effect. There is a diminishing return going with a wider front tire past a certain point. I do not know what that threshold is currently. Hoosier is making a 255 a6, how many AX drivers in Stock classes will be upgrading from their 245s front tires?

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To use oversteer to rotate your car prior to the apex you turn in early and trail brake hard. The heavy braking while turning shifts your weight forward reducing traction in the rear which induces oversteer. You better not plan on lifting to catch the car though or you will be in the weeds. The right thing to do is to transition from trail braking to fairly heavy throttle (depending on the corner) to shift the weight back to the rear taking the car from oversteer to neutral at the apex. Because you come into the corner early and fast and brake very late this can be very fast but it's not for beginners. One false move and you are in a world of hurt. If you really feel the need to change your car to help with this the best way to help the weight transfer. If you have 2 way adjustable shocks increase rebound in back allowing the rear to lift more under braking or decrease compression in front allowing the it to dip more or both. If you don't have adjustable shocks do something to increase turn in like softening the front bar or stiffening the rear. The downside is that this will also increase oversteer under acceleration at and after the apex. You can also play with toe. A little toe out in front and toe in in the rear will help. Or pressures, or.........

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My only concern with putting really wide tires on front is getting them warm enough to stick. On the track or AX this might work but on the street too wide a front tire could actually increase understeer. FWIW, when I raced a 996 I tried every possible tire combination and found a 245-315 R6 combo to work best. I had lots of suspension changes though.

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Grip is almost entirely a function of the adhesion properties of the tire, the adhesion properties of the road or track surface, the size and shape of the contact patch and the amount of pressure (weight) between the tire and the track. Almost all changes to the car and all driving techniques affect one of these properties. No matter what car you get in the one thing under your control is weight transfer. Some racer (whose name I can't remember at 2:43 am) said learning to drive fast is all about learning to move your car's weight to where it's needed. I'm going to bed.

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Does PSM come into play at all here as an electronic means to limit rotation? I've been leaving it on, as it doesn't seem to get in the way at all, and generally keeps me pointed in a straight line if I screw up.

apart from car setup and a good corner balance/alignment, you could practise trailbraking (and early turn-in), it deals with the understeer by keeping the front wheels planted hence giving you traction in front and lets you rotate the rear end around the turn letting you brake later, even finishing your braking at the apex if you can get the timing right. some understeer isn't a bad thing cuz it lets you play with the oversteer inducing techniques

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I'm certain it would but to be honest I've carefully avoided PSM in my cars and I would never drive a students car hard enough to find out. Jim

Jim, Good to see you back here in the "regular" 996 board. This is one of the best threads in weeks over here. Andy

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+1 good info

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I was curious about that also and measured the tempersture (infrared) of my r888 after a long cruising trip back home from AX. The front and rear tire temp differential was close to the FR temp differential I get on the track. One thing to note (AX) is a wider front tire (~same diameter) allowed me to brake a bit deeper without ABS kicking in when I swappped wheels. Does it mean a actual shorter stopping distance, dunno.

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Hey Andy, I stop by from time to time but seldom post. You guys know a lot more about 996s than I do and frankly I don't care what oil people use. I teach our region's racing physics class so I couldn't keep myself from jumping in. There's a bunch of mis-information out there. I'm going to look for Twist of the Wrist. If you are bored sometime Google "The Physics of Racing". It's a series of articles that are dry but have a lot of good info. I think they are all on one of the Miata racing sites. Later, Jim

I think is sould be low front and higner rear.

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That surprises me a little bit but it's good news for you. My only real experience with wide fronts was when I tried to run 265 MPSCs on the front of my 996 race car. The track I was on (Brainerd) is very fast with long sweeping turns. I had a heck of a time getting the fronts as hot as the rears and the car pushed like a pig for the first two laps. If you can stay out of the ABS you will stop faster so that's more good news.

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+1 - great book Honestly, this thread is a little confusing, and I "think" I understand this stuff pretty well. Read the book, you'll get a much better explanation. amazon...

Hmm, I took the OP to be in jest mocking the search function being broken. But, then the thread actually took off, lol Sorry if my post came across as critical, as this wasn't my intent. I was only quoting you top give context for my replies. Please don't take it personal. And although loose/tight is driver dependent, there are universal changes that should affect the car's behavior on an objective level. However, as JimB noted, without actually saying it, the tire patch/friction/grip/etc issue is much more complicated than we can probably every discuss or understand. -td

Oh hell - I was going to pass this up - but I'll respond mainly because I used to think my car was an understeering pig. I went to my first DE last year, full of myself, saying how bad the car plowed. Of course, track junkies and other knowledgeable folk let me spout off - I guess out of kindness, or not wanting to get into a debate. So, from my perspective, I USED to think my car was push-happy and I appreciate some folks' tolerance. I solved this, as many in this thread suggested, by trail braking at the track my first time out. It actually worked quite brilliantly. My instructor was reasonably impressed, I think. He too was driving a 996 and felt that it's basic setup was to push in the front. But I also agree with a previous post that you shouldn't be practicing trail braking on the street - it's really more for driving at the limit. Then I started reading more, driving more, listening more to the track folk and to my mechanic. By the time I went to VIR last Fall - I had slotted the strut towers in the front just to get another 1/2 degree of negative camber in the front. But I was still running the stock US suspension. Let me tell you, hitting triple digits on the climbing esses at VIR was a bit of a roller coaster in the middle - car was floating enough to "almost" set sail off the track. However, the front end, just with an extra 1/2 degree of negative camber made a huge difference in my cornering and my cornering technique. I was doing very little trail braking - car was rotating better, even with some very light throttle at apex. Now, I installed PSS9s this week and dropped the car 30mm from the stock US ride height - looks better, and now I have over 1.5 degrees negative camber in the front. I added a bit more rear to compensate too - so the car is still reasonably neutral. So - once you get the car handling somewhat neutral (to perference), then it's all driver controlled and it's up to you whether you want to set the car up to have a bit more oversteer/understeer at the limits. The power in the 996 is plentiful enough that you can push (understeer) the car under hard acceleration, you can break the rear wheels loose (maybe) and generate oversteer, you can use braking/trail braking to generate more front grip to rotate the car, or you can use trailing throttle oversteer to lift the weight off the rear wheels, causing more oversteer. So - in addition to lot's of replies here that are technically correct. My point is that you can drive the car well however it's set up - it's up to the driver and the driver's skill. But then again, you probably have a preference as to how it's set up. If you feel the car is not gripping enough "naturally" in the front, you can add wider tires up front, adjust suspension, or use driving methods like trail braking. In short, there's no "right" answer - too many options. But it's good you're learning (I know I'm learning) and I don't think you could have a more fun car to learn with. Cheers and good luck.

none taken, it's the internet. I was just sharing my experience from a AX perspective. Everyone's driving style is different. My driving bud's 911 rear end is loose (midturn/exit) IMO but he comments it is balanced. It is very complicated since every factor is interrelated and comes into play.

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I ran Pss9 with slotted towers also on all my tire combo. -1.8 f -2.0 r Wife doesn't have an interest driving the 996 so now it will sport some 700/900 JIC setup. Make sure you check your strut top, upon disinstall I found one of my rubber strut top was torn.