Keep the rearend still

[mazspeed]

Originally Posted by fatlife

Okay thats understandable, so the only clue the rearend is moving is from the swaybar and your gut feeling? (the rearend WILL move some, but how much is excessive is the key)

All you have to do too move the rear is take and push back and fourth on the car. You can see it go side to side just a little, now image you driving the car at speed and flicking it though corners. 100 times the force of side to side motion. Yes I can feel it, yes the sway bars movement side to side tells me how far it is moving. An inch side to side is not uncommon. The tires during a hard turn on a dip in the turn hit the side of the body slightly, this too is a problem. It's not bottoming out, it's too much lateral movement. This is far from ideal. When you have this kind of movement, you also get camber shifts, this makes it very twitchy at the limit during these shifts of hard corning. No movement is best.

[fatlife]

Well hopefully someone can chime in with some suspension background and fill us in. Good topic...................although there are still holes in your story

[fatlife]

also I went and did your scientific evaluation of lateral runout on my car, only thing that moved was the sidewall of my tire, while pusing violently on the car? But hey, maybe the watts link will be what your looking for. Not many people are using them so maybe you can be our guinea pig

[mazspeed]

Originally Posted by fatlife

also I went and did your scientific evaluation of lateral runout on my car, only thing that moved was the sidewall of my tire, while pusing violently on the car? But hey, maybe the watts link will be what your looking for. Not many people are using them so maybe you can be our guinea pig

I can get mine to move, but just a wee bit, not a lot. I might have a little more force behind my arms pushing the car.

[fatlife]

These are both quotes from Mean69 from a differnet site, sorta confirms whats already been said, I still say you try out some differnet bushings in the rear shackle but this is what I found;

A Panhard bar, or Watt's link, is very commonly used with the vintage race cars, and is pretty effective, especially if rubber type bushings are used on the leafs. You won't get any cross talk, or not appreciably, between the vertical motion of the leafs with regard to the PHB. There is a very slight lateral motion as a function of bump with the PHB that can be minimized with a suitably long bar (over 36" is probably fine for a limited amount of vertical travel, but make it as long as you can). In addition, the bar should be parallel to the ground at ride height, and most importantly, the roll center of the PHB should be as close as possible to the roll center height as determined by the leaf springs, or you will get some form of battle/bind = not desireable. The roll center height of a leaf setup, I am 95% certain, is defined by drawing a line through the front and rear leaf bushings (side view). Where this line intersects the axle, vertically, is your RRCH from the leaf standpoint.

I have seen a lot of debate over this for the past several years, and the conclusion I have to draw from all that I have seen is that your car will probably run faster using one, than it will without using one. Virtually ALL of the early Trans Am cars, and a darned good amount of the early B Production cars I have seen that use leafs either use a Panhard, or Watt's to futher locate the axle assembly. The A-sedan Camaro in my shop right now has a Watt's/leaf setup. There must be a reason for it!

The biggest debate comes in the form of defining the roll center. The leaf springs have one, and there would be a second one defined by the PHB/Watt's. If the two aren't matched (and this is nearly impossible in bump/droop), there will be some form of associated bind between the two. One of those things that you look at and scratch your head, until you see a car on track with one that performs really well (or in the case of the vintage races down here two weeks ago "dozens" of them working well).

If it is just a street driven car, I wouldn't bother, but I would go with a set of the available delrin type bushings. If the car is going to spend a good amount of time on the road course, I'd recommend looking into it a bit further. Though not offered as a product, it would be pretty easy to adapt the Watt's we are using on our three link kit for leaf's. There is a commercially available PHB, and Watt's for early Mustangs (Maier Racing, and Fays II, respectively).

[fatlife]

SO exactly what is your rear setup? springs? spring rates? single or mutli spring? bushings etc? ALso why did you decide to use a rear roll bar?

[mazspeed]

I have to agree with everything there to a point. Like I said my driving style a properly designed watts link will help with my car. Delrun and no rubber bushings on my leafs doesn't stop the fact that the locating points from each side of both leafs from moving side to side.

[mazspeed]

Originally Posted by fatlife

SO exactly what is your rear setup? springs? spring rates? single or mutli spring? bushings etc? ALso why did you decide to use a rear roll bar?

Global west springs dearched in the back. A goofy rear swaybay being changed to a lighter adjustable, if not elimated altogether bar. Crappy fatman carrera shocks in front with their 500 lb springs in front with another cheap 1 1/8th swaybar up front. All this is being changed to custom koni hydraulic shocks with rebound and compression controls, with 550 pound eibach springs with geo changes up front and adjustable swaybar up front. Rear will have either the same springs or DSE springs with the same style koni's and a watts link with either no sway bar or an adjstable swaybar. I'm going to drive the car and let them know what I need after that. The car is being corner weighed to spec the front and rear shocks.

The rear bar was added to keep the car flat and not twist as much. They work better on quick turns, but for mountain driving it's better not to have one. The stiffer chassis and watts link should more then make up for the use of a rear bar on a short track and should be much better on a long fast section. Again it's one of those trial and error type of things that I will know more when I drive it.
I'm not too sure about spring rates in the rear, but I have heard that DSE's are a tad softer. I would like a little harder suspension car then a softer one.

[fatlife]

Well I hope you run this all by someone a little wiser than both of us. I already see some descrapancies in some of the things that you state. I'm suprised no one else has jumped in this thread, what happened to any of the tech here? Everyones so excited about show cars and sema, no one can help out?

[mazspeed]

I already see some descrapancies in some of the things that you state.

What do you mean?