Importance of rear camber?

[rponfick]

I have a late Mk 4, with the FFR Mustang IRS. I notice the FFR rear camber specs are -1 degrees, and a lot of comments on the Forum running -.5 degrees. With a solid axle, you would have 0 degrees. The car is strictly street with no track use.
I suspect the negative numbers for the IRS rear are to accommodate driver/passenger weight and road spring compression. With my 400# rear springs, I see little settling with two people and fairly stiff driving.
So, what would be the effect of -1, -.5, or zero?
If I change my current -1 degree to a lesser reading, I understand it affects toe. How much is the effect on toe, significant or minor? The front camber is -.5.

Just trying to understand what rear camber has to do with anything.

Thanks, Ralph

[RoadRacer]

Camber on an irs functions the same as at the front.. in simple terms it makes the tires more efficient when cornering. You should follow the factory guidelines.

You also mention rear caster but unless your car rear steers (which few do) there is no rear caster - probably a typo though.

[JohnK]

When I was going over alignment settings with the shop that did my alignment, they explained that camber on the front wheels helps with turn in, while camber on the rear wheels helps put down power in the middle of a turn. He looked at me and said, "but then again, nobody is trying to put down power in the middle of a turn in a cobra, so...." We landed on 0.75 deg. camber on the front and 0.5 deg camber on the rear. This is a race shop that fields a very successful Porsche cup team so they know a thing or two about setting cars up for performance.

[CraigS]

For street driving I like zero to -.5 deg. Especially w/ -.5deg in front. Negative camber up to somewhere around 4 deg increases cornering power. But it also wears out the inside of the tire all the time you are not cornering. Also, on the street the only time you would feel an actual cornering power increase would be driving way, way too fast for the street. I run -3.5 front and -1.5 rear because I autocross a lot. I put up w/ the inside tire wear on my street tires which about every 3-4 years I question myself about.

[Kbl7td]

I experienced this real world the other day. My wife’s 2021 992, developed excessive rear shake that seemed like a huge rock or nail in the tire. Looked at the tires from the outside and all seemed well, plenty of tread left. Finally lifted the car and took the rear tires off. The damn things were worn down to the belts on the inside. My understanding is they have a tremendous amount of negative camber. Handles like it’s on rails, but a pain in the *** to swap tires every 30k.

[rponfick]

James, thanks for catching my typo. Yes, there is no rear caster.
Ralph

[CraigS]

Back around 2000-2005 the Lexus es330 (Camry) had a stock front camber setting of -.75deg. Admittedly this was a front wheel drive car, but I can tell you that many, many owners were pi$$ed when they happened to park their car w/ the wheels turned and saw the inside worn down to nothing while the outside still had 4-5/32 tread depth. There was usually enough slop in the front strut to spindle bolts that I could get rid of .2 to .4deg camber when I did an alignment and no one ever complained that their es didn't corner so well afterwards.