Camber, WTF?

I've been reading old posts re. camber (here and in Racing & DE forum) and it seems to be a contradictory mess. Like a lot of folks, my car is a dual-use DE and street machine. But it lives for the track so if it's streetability suffers, that's ok. But if you read all the camber posts here carefully, you will see some posts that say that the rear should generally have more neg camber and some that say that the front should generally have more neg camber. Usually with -0.3 to -0.5 separation. An example from last Apr: JimB says he runs -3F and -2.5R on his 996 racecar. 02 Carrera recommends to Galun that he should try -1.2F and -1.6 to -1.8R. My perception is that both these guys are very knowledgeable. So why does one seem to subscribe more neg camber in the rear (relative to the front) and the other says less? The above was just one example among many. What am I missing here?

A wide wheel needs less camber so it is normal to have less in back on a 911.

The front should require more camber in a track setting. However there are no inexpensive camber solutions for the 996 at the front so many people often get the most they can in the front and run what's appropriate in the rear ending up with more rear camber than front just becuase it's easy to get camber in the rear and very hard / expensive to find a solution for the front. a .5 degree to .75 degree more in the front (depending on what tire) is the ideal setup IF you've got GT3 control arms or camber plates or both to get those values in the front of the car. Andy

Ok, but let me be a devil's advocate for a moment. There are smart folks here (and RennTech and PCA) saying that you need more neg camber in the rear. Are we going to say that the reason they think that is because rear camber is cheaper? You guys in the "more rear camber" school of thought....... what is your reasoning?

If you want to go fast and have the tires and suspension to support it, your car should have -3 to -3.5 degrees of camber in front with about .5 less in back. So -2.5 to -3. Your front toe should be set at .5 to 1 mm out with your back at about 2 mm in. Having said that, it's not realistic in a street/track car. Especially, as Andy pointed out, with the limitations you have on camber. I would max out your front camber up to around -2.5. I'm guessing your max will be much less. Then subtrack .5 from your front camber. If it's more than -1.5 then use that number. If it's less than one -1.5 then use -1.5. So: Front = -2.5 set rear at -2 Front = 1.8 set rear at -1.5 Front = -.75 set rear at -1.5 Just my 2 cents worth. Jim

There is no 996 racer that will tell you that more rear camber is faster. If you find one I promise you they are not fast. (Oddly, 997 cup cars are running more camber in back but that's a different story) The only reason that you would run more camber in back of a 996 is that you can't get enough front camber to be above the minimum (-1.5) that you need in back. Jim

Interesting enough... This weekend I went to get my 996 aligned and found that it was done totally wrong. I'm running 285 30 18's in the rear. and standard in the front. After they finished with my car, it was lose as a goose and still pulling to the left:-( I'm not driving it again until it fixed correctly. I'm a street driver as well, yet am interested in tracking it maybe 2 or 3 times a year. The problem is, I don't totally understand the whole camber & toe thing (negative in the front & back, etc) Can someone please help me out with that so that I can follow this conversation. thanks in advance. STDFAST

Alignment basics: http://www.familycar.com/Alignment.htm

thanks...

To add to the article, on the street alignment is primarily about making your car stable while minimizing tire wear. On the track, it's all about maximizing your cornering ability without totally destroying your tires on the straights. You don't worry about the car being a little unstable (darty) or about tire wear. That's why it's so hard to come up with a good alignment for both.

That is the real problem. For a dual use car, the original poster is probably best off using mildly aggressive street settings. If he uses the values you used on your 996 race car he will destroy his street tires when he puts them back on.

I agree Ray although he does state he wants more of a track setup. I think if I were in Ranger's shoes I'd put as much camber in front as I could up to about -2 and set the rear at -1.5. I'd set the rear toe at around 2 mm in and leave the front pretty close to zero. The car would wander a bit on the street and wear tires but would do ok on the track. I hate compromises. You missed a good time at the BRIC. What an event.

Bummer, I just didn't have the time. I am going to Gingerman next weekend and then I'll probably look for you at TRAC (Road America). You're making me cry when I think about my Boxster set-up. I could make the car faster, but I don't want to sacrifice the tire wear on the street.

With the stock suspension, even M030 ROW sport suspension, you might get -0.5 camber up front. So, you'll end up with -0.5 front and -1.5 rear.

Good feedback guys, thx. My ROW M030 allowed -1deg F and I put about 20 track days on that. Based on my, apparently wrong, research I was running -1degF, -1.5R. I've just dremeled out the front strut mounts and now can get -2F. But I wanted to keep 0.5deg separation and I couldn't get -2.5R. So I ended up with -1.6F -2.1R. Note that I was still under the impression that more rear camber was desireable. Note Kerry's post above. He is advocating more REAR camber. See how much of a clusterF this issue has become? Are we comfortable that the "school solution" is 0.5deg separation between front and rear? My understeer issues used to be significant, but now they've largely gone away. A little bit of oversteer is occuring tho. One of the things that I want to work on this weekend is to figure out if my oversteer is consistantly "power-on" oversteer or "not-enough power on" oversteer. I need to figure out which is really an issue and which one is just my crappy driving. My point is that I'm in a small struggle with oversteer and the guidance for me seems to be to reduce rear neg camber. That sounds, a, problematic. So given my adjustment range and what you've told me, I should set my camber to -2F, -1.5R. But since I'm working on reducing oversteer, what are your thoughts on -2F, -1.7R instead? I haven't played with toe yet. I'm tempted to go ahead and do that, but I don't want to change too many variables at once. Re. tire wear. I'm on the track 4-6 days/month. Street tires. The tires don't get much chance to wear on the street. 4 months is 20 trackdays and the tires are shot. Re. compromises. Roger that. It kills me that there are so many compromises between track and street. Inevitably, I end up with something that is less-than-ideal for both. I'm thinking about getting into E30 spec. But my credit cards are counseling against it.

It would help to know rear toe as well as it can lead to instability. I usually run just a touch in at the rear (2mm or so) to keep the rear from being too lively on the gas at corner exit. Too much or too little toe can hurt grip as well. Is your oversteer issue on corner entry, mid corner, or on corner exit when throttle is applied. All corners, slow speed corners, high speed corners? Is the M030 the only modification to the car. Sorry for all of the questions...I think it will help show the whole picture and get you more sound advise in the end....as you're correct if you're already dealing with oversteer issues (if they're setup related) you genearlly wouldn't want to increase front negative camber as it's only going to give you more front grip and make an oversteer situation worse. Andy

Ok, thanks to all the input, I had the wheels realigned this afternoon. But the set up is now a little non-standard so this is your opportunity to call me an idiot. Based on the consensus in this thread I went from more neg rear camber, to more neg front camber. That's likely to create a pretty darn significant change in handling characteristics. But I didn't end up with much of a difference F to R. The old set up was -1F, -1.5R. With my new dawning awareness, in a perfect world today I'd a gotten maybe -2.5F and -2 rear. But all I could get was -1.9F. So that left me somewhat conflicted on what to do in the rear. I'm wearing out the outside edge of my rear tires badly. So going from -1.5 deg to -1.4deg (in order to be 0.5deg less then the front) seemed foolish. I badly needed to even out the tire wear on the rear. But at the same time, I wanted to fronts to have more camber. And all the fronts would get is -1.9deg. I was determined to come out of this with more neg rear camber. I just could not leave the garage without having done something about the outside edge of my rear tires wearing out. In the end I went with -1.9F and -1.8R. So I'm now in no mans land, between the "more front camber" crowd and the "more rear camber" crowd. But one whole heck of a lot closer to the "more front camber" crowd than I was before. I'll probably have to leave it there too. I've thrown enough money at the darn thing this year. Toe. I also had toe changed from the OEM setup to 1mmF and -1mmR, per this and other threads. OEM had them both positive, although I've forgotten how much. AudiOn19S: Thanks for jumping in and trying to help, but I'm not ready to ask specific questions on understeer vs. oversteer yet. I need to experiment more around the edge so I can identify what is "consistantly" happening. I've been on different tracks all summer, and that is making it very hard for me to study the impact of changes on the car, and better "hear" what my car is trying to tell me. I'll be at Roebling 7 days in Sep and that will be the perfect opportunity to really make progress. I'm an engineer by training, so I've a pretty good grasp of the physics of racing. It's making it all happen on the track that is going to take lots more practice. I was at CMP for 3 days a couple weeks ago. First time there. Had an instructor on Fri so I could get signed off for Solo for the weekend. I was particularly impressed with how he was able to sense what the car was doing, from the passenger seat, better then I was able to from the driver's seat. I've got 30+ track days, so I'm not a complete newby. But it still brought home the gulf between genuinely experience and relatively new to the passion. Anyways, I'll be back at CMP for 3 days this weekend. And I know CMP so poorly that I'll be removing suckage with a cleaver. At Roebling I can polish. But I'll be "listening" as best I can, wherever I am.

Ranger, I think you'll like what you've done. Your alignment will be a big improvement. As for the oversteer, one of the first things you learn in suspension tuning is not to chase tires. If your tires were shot I suspect that's what causing the oversteer. One of the problems you have is that your suspension is so soft you have all kinds of movement which makes it harder to tune. If you can pull it off, I would add adjustable sway bars. They are a much better tool for controling under/over steer. And, as long as you're under there, throw on some coilovers. Jim

Lol, I love ya Jim. Interesting thought on the impact of worn tires. I'd not considered that. As for sway bars and coilovers on the 911, I think that I'm going to quit with swapping out 911 parts. There has to be less expensive ways to create failure than trying to make a dual purpose DD & competant track 911. I'm thinking of buying a Spec E30, if I can find one that someone else has built.

This thread has been useful for me since I am getting my car aligned this week. I am street driving the car only, for now that is, and so I will be asking for a nice setup to provide as little tyre wear as possible. So thanks for all the good info in this thread especially the link to The Family Guy page that shows Wheel Alignment and what it means. Now I am more educated

I've got a better idea! http://www.jimbreakey.com/welcome.html

Wow Jim, your car's fabulous. I'd buy it in a minute. Unfortunately, you want what it's worth. Addendum to Jim's will: "And Ranger gets the 996 because only he would treat it right." Now who's got that Spec E30 and trailer for $6k?

How do you dial in under/oversteer with the help of adjustable sway bars? How do you adjust if you have oversteer for instance?

What sway bars (actually anti-sway bars) do is to manage the transfer of weight from one side of the car to the other in a corner. In layman�s terms that means they control what you probably think of as body roll although that's really not completely accurate. With adjustable bars you can individually control the "stiffness" of the front versus the rear. The simplistic answer on adjusting is the softer your suspension the more traction you have. So to dial out oversteer you either soften the rear (increase traction) or stiffen the front (reduce traction). Obviously the opposite is true for understeer.