ron mcatee

First of all, you stated your car is a narrow body. Looks like a 911SC or Carrera to me (no year stated) which is not a narrow body. With the turbo tail , you'll get more down force in the rear. With a whale tail and the front spoiler, i think you get a better drivable car at speed.

Steve Weiner-Rennsport Systems

FWIW,...

None of these tails: ducktail, Carrera, or Turbo make any downforce, they simply cancel varying degrees of lift.

With the proper front spoiler, the car remains pretty well balanced at speed as long as it has a one degree, nose-down rake.

theiceman

Ron when he said narrow body i think he meant non turbo

race911

I was reading through just waiting to drop this comment............

What about damper valving? Were these RSR's off the shelf? Steve has a gajillion times more experience than me, but I've never seen a coil over setup on a torsion bar car that was just bolted on and worked right.

Steve Weiner-Rennsport Systems

Good point, Ken,...

Stock RSR shock valving is just awful. It was terrible back in '73 and its still bad.

JMHO, but anyone using RSR struts & shocks needs to have them revalved to make the suspension work properly. Bilstein's compression valving is FAR too stiff, is just one example,....

pete917

Yes, my mistake. I meant non-turbo body....

pete917

Thanks Steve. I bought the RSR shocks and springs off the shelf.

Have I made a mistake? How do I go about putting it right.......Is this my high speed instability problem? It sounds like it might be more likely to be the angle of attack of the car.

whalebird

I think steve has this one pegged. As far as front/rear rake, We always set the 911 up with 1 degree of rake taken at the middle of the door sill. Ride height measure from anywere on the body can be totally misleading. A proper corner balance and alignment will probably get you where you want to be once you address the shock valving.
Oh, I got an earfull from on old racer once concerning the differance between downforce and negetive lift.

pete917

this is all really helpful - thank you guys.

To see if I have the problem that Steve has identified, could I measure the angle by measuring the distance from the floor of the sideill at front and back and thenn calculating the angle. I dont have the necessary equipment to measure at a single point.....

If this is good enough to pin point the problem I can then at least take the car someowhere to get measure accurately....

Steve Weiner-Rennsport Systems

I use a digital protractor placed on the doorsills as accuracy is critical. This works on cars that have not been damaged

Naturally, these measurements are made on our alignment rack which is absolutely dead level so you need such a surface for these exercises to be meaningful.

theiceman

While I am sure the rack is by far the best mehod , fairly cheap digital protractors are eadily available that will give you som eidea. Mine for example will provide a delta difference . placed on the ground, zro it and then put it on the sill and will provide the difference between ground reference and sill ..

pete917

Thanks Guys. A digital protractor it is then. Any thoughts on which one, otherwise I'll just do a general search.

Im pretty sure my garage floor isnt level. So I can either get the type like yours iceman when it takes the floor into account, or maybe put packing pieces under each wheel until its level and true.

Either way, I think this is my first piece of investigation

g-50cab

I phone has free bubble level applications - They work well on the springplate angle.

What tires are you running? One of my DE buddies had a set of kuhmos street tires that where really squirrley at high speed (over 110).

He changed them out - and his issues went away.

theiceman

i got mine from harbour fright, it is actually a magnetic saw balde angle calulator. I put it on a 4ft pice of flat stock i had and put it on the floor underneath the sill , zroed it , then put it on the sill . not an exact science but gives you an idea. did the same to measure my camber

Tango635

To quote Steve.."absolutely dead level so you need such a surface for these exercises to be meaningful."

So if you want to get it to the 1 degree spec, you're not going to get there with a garage floor, IMHO. On the other hand, if garage floor is the only method available to you, then you could error to have a little excess rake.

Also, once you have put your suspension to the correct specs, if that still doesn't get you the stability you are looking for, the next step I would try would be to lower the car. In my experience, a 1 inch drop makes a huge difference.