Doing some "work" to get more negative camber up front ...but now trying to decide entirre set up....Been so long since had this done I am forgetting.
RA1, 16 X 225 50 w/ 7.5" wheels front
Ditto 16 x 225 45 w/ 8.5 rear
Shooting for 2 1/2 negative up front
What should I do @ the rear.
Mainly DE/track but some autocrossing.
Prefer to compromise ax set-up as opposed to track. 2.7 at this time if it matters.
Thank for the help
Terry

There is really no simple answer to the question.
I have no experience with RA1s other than they are radials and like more camber that bias plies.

This thread and associated links will give you an idea about where to start and how to test to determine what your particular set-up likes best.

I will ad that my MR2 set-up for AX has a pee pot full of negative camber and 0 toe front & rear. Driving it on the street is a PITA.....it wants to follow every seam & undulation on the road.....turns good tho.


http://forums.pelicanparts.com/porsche-aut...od-thought.html

With my RA1s I had a little over -2 in the rear and it felt great.

neg camber in that range will make RA1 work well under the foot of a very agressive driver. if you do not jamb it into the sidewalls you will just get too much inside wear needlessly.
neg 2.5 in the front may req mods to the shock top plates and elongation of eh 3 plate mount holes....or tarret chamber plates

Negative camber settings are a function of driver aggression, tire construction, and the rest of the suspension set up. When I was running my relatively softly sprung 914-4 on Hoosiers, I had -4 degrees of front camber and tire temps said I needed more. Keeping the car flatter would have reduced the need for more camber.

For the rear, I pulled all the shims out and ran it. At the ride height I was at, that was 2.5 degrees in the rear and tire temps indicated that was about right.

My car was stock front T-bars, 22mm front sway bar set most of the way stiff, 200lb/in rear springs and 225/45/15s all the way around.

I detect some B Roberts BS here.

Testing by GRM some years back showed that camber in excess of -3.5 degrees resulted in loss of braking performance to the detriment of AX times.... In other words, the test drivers started going slower. Those drivers were no slouches.

On our 914 racer we noticed the loss of brake ability way before -3.5
we did a test at -3.0 and could tell the increased brake zones over -2.5

but couldn't really detect any better cornering performance.

so we never run -3.0 anymore
always stay between =2.5 to -2.8
test was run on hoosier R6

we actually have run a set of RA1's, but never dial the car in for them
just dial in for the hoosiers as the toyo's are for warm up, enduro's, and rain
brant

Good stuff...Hate to say it but I heard exactly what I was hoping for ...Past experience seened to be -2 in the rear...but someone was telling me -1....Was not so sure about that >Thanks
Terry

I would say depends upon the car, track, and the tires. The article that I remember from GRM about camber testing was in a Mini Cooper S around Streets of Willow which isn't really a fair comparison to a 914 at AX. Braking does suffer at much over -2.5 in my experience but because I ran 4 front calipers and an ajustable pressure limiting valve I could still set it up to lock the rears at the same time as the front or a little before and trail brake heavily to help scrub a little more speed. Anyone who has driven a GoKart knows you can get by with out front brakes if you don't mind sliding a bit and understand the limitations.

Also to support my point, the 2009 GT3 Cup Service Manuel I have suggests starting at -4 degrees of camber in the front and they are neither softly sprung or have a worse camber curve than a 914. A 2009 Cup isn't a great comparison but probably is about as good a data point as a Mini Cooper is.

There are few absolutes in racing as every car and driving style are all a little different so none of us can really say anything more than what we have found on our cars. On my current 911 I have -2.8 in the front and that seems to be enough as I don't lean on the front tires with it quite as much as I do in a mid engined car.

how did you get neg 4 in teh front of a 914?

Nothing special just de-cambered ball joints, undercoating removal and a little tweaking to get the top hat all the way over with no dust shield and a low ride height. Quite possible that both my spindles were bent though. The decambered ball joints are good for ~0.75 so it really wasn't that much more than most.

I know they make them but I have never seen one. is teh pin off set?

Yes. The actual ball portion of the joint is much smaller and pushed to the out side ~1/4" over stock. They also allow for a greater degree of articulation which I wanted as when I took a part the old ones that came out of the 914, there was a groove worn in the inside keeper of the ball joint from over articulation. I liked them so much that they were the first mod I did when I bought my current 911 from my Dad after the 993 RSR sold.

Interesting thread - I should be able to add my data point tomorrow as I will be running SOW with very similar conditions, tires and setup to this time last year, except more aggressive alignment...