"Tegger" <tegger DeleteThis @tegger.c0m> wrote in message
news:Xns9A1F61D8BCE97tegger@207.14.116.130...
> It's my understanding that negative camber at the rear helps induce
> understeer, always desirable for a road car.
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.
> 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.
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.
Ed
>> Stay informed about: rear wheel camber 
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