Which rear springs for a Mopar ?

[AlexP]

I need to put a set of springs on the back of my mopar. I have a 15/16" sway bar up front with 350#/in torsion bars (Mopar 1.22" bars) with Koni Reds, and currently stock HD leafs with a 7/8" sway bar and another pair of Koni Reds.

What spring rate would you use in the rear to balance the roll couple ?

[G_T]

Alex,
First - I am *NOT* an expert on this - just going to relate what I have experienced searching for the same answer.

This is nearly an impossible question to answer - i searched for the answer for months. Sophisticated software and, more importantly, spring rates/characteristics for the rear leafs is needed. It is nearly impossible to find vendors who know or state what the rates are.

You are also going to need know the weight bias of your car. What I found is that vendors talk in terms of wheel rate and roll resistance of your sway bar/spring combinations.

Is your car being built for drag or road course?

One of the autocross guys told me his barracuda with .99 Bars had a wheel rate of 200lbs. He also said that Top competitive Autocross Mopars run about 350 lbs wheel rates.

I am running an Alterkation on the front of my Charger with 550lb coilovers and the 1.25" sway bar. Bill Reilly told me:

There's a spring that seems to be quite popular - Eaton/Detroit Spring makes a leaf spring with a 50lb higher than stock rate with, I think, 1.5" drop.The wheel rate from spring only is going to be right about 293lbs. - I can't remember what brakes you have, so it may vary a hair depending on the hub position(track width will change the wheel rate slightly)The front frequency is 2.0cps - thats with the 550 springs.With the sway bar and springs you have, roll resistance of the front is 1298lbs per degree of roll. To give you a comparison, the stock front suspension with a 1" sway bar provides 880lbs of resistance, so this system is quite a bit higher.I'd love to figure out some rear springs for you, but there's an issue - first, my software doesn't support leafs, and second(and more importantly), myself and a road racer buddy of mine have been trying without luck to get inch-pounds info from spring makers. Apparently they have no inch-pound info to compare various off-the-shelf springs, and we're just supposed to trust them.But the Eaton spring I mentioned above seems to be liked by alot of guys I talk to....

So, what did I end up doing? I bought some 225lb composite leaf springs for the rear. I will modify the front coil overs and add a rear sway bar after I can drive it. I am consistently told that you need track time to really dial it in. Also, that the rear needs small (if at all) rear sway bar.

Finally, the different leafs (HD, XHD, SS, oval track, etc.) behave differently and you can't just go by the spring "rate". The HD, XHD, SS have progressively more arch and/or shorter front segment for a good launch. Whereas, the oval track type of spring tend to be much flatter so that there is less side-to-side flex in the corners.

This probably didn't help - so good luck and be sure to post what you end up going with. Your best bet is to talk to the expert vendors in this area (speedwaymotors.com, afcoracing.com or landrumsprings.com for detailed info on springs, rates, set ups, handling, etc.).

[AlexP]

I've already talked to speedway, and their Chrysler style 200in/# seem to be the ticket. Near zero arch and easy installation.

I think I'm going to step up to a Hotchkis fron 1 3/8" hollow bar when they finally revamp their product line from mopars in the coming months.