Handling problem?

[RallySnake]

I enjoy the technical problems posted here. You have a chance to learn something and share experience. I just installed my new Holley Avenger carburetor on my Arntz and am really happy with the added power over my old Quadrajet smog carburetor. To test for fuel supply in severe conditions, I took it out to the local skid pad (mall parking lot) and made some fresh skid marks. I am pleased that the carb supplies power under all conditions but a little worried about the handling. When I push it past the tire's adheasion limits in a right hand turn, it breaks loose evenly and is balanced in a nice four wheel drift. I can easliy control it and straighten the car out when I like. In a left hand turn, however, the rear end is loose and comes around too fast. If I am not quick with opposite steering, the car will spin out.

This testing is done with 28 pounds of pressure in the front tires and 30 in the rears and two people in the car. My car has MG front and Jaguar rear suspension. It has 4 KYB coilovers in the rear and KYB tubes in the front on custom brackets. It has a 1" front swaybar and a 3/4" rear swaybar. The battery in mounted in the right side of the trunk behind the right rear tire. I am thinking that the spring rate in the right rear needs to be softened up, either with the Jaguar upper spring mount or the rear swaybar. OR The right front spring rate needs to be stiffened up. The tires are all the same size Toyo 275/60/15s. I selected these tires in hopes of achieving perfect four wheel drifts. I'm halfway there.

I would appreciate any other ideas or input (other than driver weight adjustments).

Paul

[Roscoe]

The best way to test for ideal pressure is to get hold of one of those hand held pyrometers. Take the car around and get the tires nice and hot and have a friend immediately check the tire tread outside inside and center.

I think you are running a bit too much pressure.

Roscoe

[Bob Putnam]

Paul,

I suspect that you're right about the diagonal spring loading (although this could be a tire problem too). The effect would show itself with too much preload in the left front and right rear. If the springs are not easily adjustable, try making some adjustable links for the sway bars and diagonally load them. If it fixes the problem, you'll at least have some procedural direction.

[niles]

Your symptom is consistant with an out of balanced footprint.
Imagine a four legged table; If the front left and right rear suspension was "longer", ie had more weight on them. The "long" diagonal carries more then 50% of the weight. Accordingly the right front/ left rear carries less. This makes the car handle very assymetrically.
Solution: find someone with a set of scales and get a even weight footprint on all four corners. Don't think you can do it with ride height, that sometime compounds the problem. My recent example I measured, plubbobed, etc and thought it was perfect. Set it on a set of portable race scales corners were off over 200 lbs.
The first setup is set the corners and then realeign. Then experiment with pressures, etc before messing with springs. Springs will not cause that unless you have a "flat/weak" springs which exaserbates the footprint problem.

gn

[xlr8or]

Interesting point Niles. I was thinking maybe a thrust alignment issue. If the thrust line is out of whack you can see the same type of issue. I have seen it when racing off road. You get good drifts going one way and jumpy rear going the other.

Saw this happen on a car with a custom rear suspension setup that was misaligned on the chassis to the point where one wheel stuck out about a 1/4 inch more than the other. Not real noticable when sitting but at speed the car looked like it was pointed left but going straight.
It was much more willing to slide one way than the other.


Scott

[Jamo]

Paul--I noticed the same thing when I first got the Butler (same setup on everything you listed) during autocrossing--though in that venue I tend to run about four pounds more in the front compared to the rear, and it was on Hoosiers bias ply tires (32/28 usually).

I got a four wheel alignment with the rear slightly (very slightly) toed in and it disappeared. Very linear tracking after that at the limits and beyond.

[RallySnake]

Thanks for all the input guys,

You've given me some good ideas to work on.

Jamo,

Did you ever find Hardknott Pass during your trip to England? I read that they used it during a recent RAC Rally.

Paul

[Jamo]

Paul
I don't know--maybe--what area of England? We were in the south, most of Wales and its mountains (mostly Snowdonia) and the middle--including the Cotswolds (they call them mountains--more like speedbumps to us).

[wilf leek]

Actually Jamo, the Cotswolds are known as "Hills". We try not to call geographical features "speed bumps" if we can avoid it. It's just too nouveau. LOL

Paul - I agree with the above - get the corner weights set (with driver in situ) before you go looking for other problems. Made a big difference to my own car.

[RallySnake]

Thanks Wilf and everyone,

If I remember right, Hardknott Pass was in the Lakes District, one of the most beautiful places in the world, on a sunny day (a rare occurance). Hardknott leads north to Wrynose Pass. They comprise an assortment of twists and turns in uphill and downhill combinations that will try the most sophisticated suspension.

Now where did I put those bathroom scales?

Paul

[Fred Douglass]

....am I glad to hear that you got that remedied!!!!....