On my trip this weekend up to Maryland I saw a BMW with rear wheel negative camber at high speeds. I remember my grandmother's 1972 Mercedes 280S having the same thing at high speeds or with much weight in the back. I asked my dad about it 30 years ago and he told me it lowers the center of gravity and provides more balance to the vehicle.
I have noticed this feature only in German-made cars and was wondering why we don't see it more often. Obviously there are advantages and disadvantages to something like this but was wondering what is the opinion of those who know about such things.
It's not really a "feature". It's just inherent in the suspension's design. It can happen when an independently sprung vehicle is usually over loaded with weight. I really doubt that negative rear camber itself (not weight induced) will lower the CG. Perhaps just the amount and the where the weight was placed in your grandmothers car would, and that would not only lower it, but probably move the CG to a rearward station.
The car manufacturers test and publish specs that will allow the car to operate safely under all tested conditions and maintain an acceptable level of normal tire wear.
Unless you have some specific task for the vehicle to do consistently, such as oval track racing, or the such, I don't believe that there are any advantages to custom settings.
There is no real advantage to having negative camber when the vehicle is going in a straight line. Too much camber will cause uneven tire wear and have a negative effect on straight-line traction.
The vehicles you say either were out of adjustment or were heavily laden.
Rear wheel camber only serves to ensure the tyre contact patch on the outside tire (during cornering) increases instead of decreases as the body rolls. This increases grip on the outer wheel but decreases it on the inner, unless the design of the suspension members is such that unloading pushes the camber the other way (which it often does). Suspension design is a very complex subject obviously and full of compromises and individual vehicle/design phenomenon. Its not really possible to say "it makes it grip better" without the car and suspension design first being known down to the detail of how long the wishbones are and where their natural rest position is etc.
"badgolferman" wrote in news: snipped-for-privacy@news.readfreenews.net:
It's my understanding that negative camber at the rear helps induce understeer, always desirable for a road car.
Many cars (notably Hondas) with independent rear suspensions are set up with slight negative camber and positive toe. This can just be detected by squatting down behind the car and visually comparing the rear tires to the fronts.
Excessive negative camber is another story. Either somebody did a half- assed lowering job, thinks he's a racer, or has too much weight in the back.
"Tegger" wrote in message news:Xns9A1F61D8BCE97tegger@207.14.116.130...
I think it would be more correct to say that negative camber increases rear grip, reducing the tendency to oversteer. Most race car suspension includes some negative camber both front and rear. The positive toe is needed to improve straight tracking (with positive camber, you need negative toe, aka toe in). The downside is that this setup can cause excessive rear tire wear, particularly if you spend a lot of time on roads with a lot of crown (like many city streets).
Negative camber can really help with grip. Years ago (early 90's) NASCAR Harry Gant had really good late season performance in NASCAR races. Eventually people figured out he had improved his handling because his car had more negative camber at the rear. This was done by bending the housing of the solid rear axle used by NASCAR "Cup Cars.". The next year everyone was doing it. The downside was that it placed more strain on the rear axle mechanism, and the incidence of burned up differential gears and broken rear axles greatly increased. A couple of years later, when Bill Elliott started driving for Junior Johnson, he had a string of early season victories (4 of the first 5 races as I recall). His car was clearly handling better than everyone else's. Again people were able to determine from observation that he was running a lot more negative camber on the rear tires. BUT, everyone else that tried running as much negative camber at the rear (by bending the housing) had massive problems with rear axles. Elliott was threatening to run away with most races and the overall championship.NASCAR (after a lot of whining from the "Intimidator") couldn't allow this. They went over Elliott's cars with a fine tooth comb and finally found the secret - Junior Johnson had added an extra coupling a the outboard ends of the rear axle that allowed the axle to run at a slight angle at the outside end. This allowed the axle to be bent to provide more rear negative camber without placing as much stress on the axle shafts. Think of it as a sort of constant velocity joint. Naturally NASCAR outlawed this innovation. Fortunately for Elliott, in those days, innovations weren't consider illegal until specifically outlawed, so he did not lose any points. These days, all innovations in NASCAR are illegal unless specifically allowed by NASCAR.
Negative camber and positive toe can help with grip at the front as well. Back when I was young and not so smart I used to autocross a Pinto. Pintos had decent front suspension with a lot of adjustments. I asked a local alignment shop to crank in negative camber and positive toe. As soon as the tech looked at how I wanted the car setup, he came looking for me. He asked me three times if I really wanted it set that way. I said I did. He said I wouldn't like it and that they would not guarantee it. I said fine. At the end of the autocross season I took the car back to the same shop and had it returned to the normal factor specs (positive camber, negative code). The same tech came looking for me again and gave me the big "I told you so." I let it go. Actually the tires had not worn strangely and the car drove just fine. I suspect that if there was a downside, it would have been that the front had so much more grip than the rear, that the car would have oversteered in an emergency situation. The setup definitely worked well for autocrosses.
I dont know if its good or bad for rear wheels to be like that, all I know is that it looks silly Don't we have *active* suspension nowadays and *intelligent* all wheel drive that determines which wheel needs the most traction while driving.
Must admit I've never really seen that as a sensible thing. Ive driven cars with serious understeer problems and by god were they dangerous - roundabout, a little too fast...or a little greasy - thats right, straight on across the roundabout. Fast corner, misjudge it - slide right into oncoming traffic/hedge. At least with oversteer you can generally counter it without crossing lanes. I suppose braking (most peoples natural reaction) transfers weight to the front and aids grip, unlike oversteer, which is the only redeeming feature in my eyes. The only times ive had panics in a car have been understeer - somehow controlling oversteer comes naturally, controlling understeer comes after plenty of ass-puckering experience!?
Yup, I think a normal car, even a BMW, wouldn't have a negative camber integrated in the design. BMW most probably have better power weight in the front and rear. Active suspension, in my understanding, will automatically adjust the stiffness of the suspension depending on the driving condition, harder & lower suspension when cornering. intelligent awd that will distribute the power on the tire which needs it most as well. Now a normal car, lets say a Camry, and you put in active suspension and intelligent awd, that will make it maneuver better. I think this technology is made so that cars would NOT be modified to have negative camber. What I don't know is how quick the system responds to the driving conditions. If its too late, then its useless.
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