IRS Coil over shock spring weight...?

[4agedub]

Does anyone know the weight springs that the guys normally use with a uniball system when the torsion bars are eliminated? I just need a guide of where to start when I buy the springs.

The application is circuit racing with quite a heavy setup on the rear due to the turbo manifold etc.

[volksbugly]

I have the same question. I just got myself the entire rear suspension for a porsche 944. I started looking into what the aftermarket porsche are using, but haven't found any really good info yet.

[FJCamper]

Gentlemen,

Try 250 pounds per inch springs to start. Going up or down from there depends on the vehicle, tires, and driving style.

With all other things being equal, you can "balance" the weight side to side by increasing/decreasing the adjuster turns. That means each side will have a different adjustment, but the weight per tire will be the same.

To add roll stiffness, you tighten the adjusters so the spring resistance on both sides is equally increased, which might require rebalancing. Of course, too much stiffness brings on bouncing, so you have to reduce the temptation to continually adjust.

Round track racers sometimes "stagger" adjustment to stiffen up the outer suspension, and even road racers might slightly stagger the suspension to favor the fastest exit to the longest straight.

First time I ever saw this, knowing it would make some of the other turns problematic, I asked the crew chief how did you compensate for that?

"Well son," he said. "That's what the driver is for."

FJC

[4agedub]

Thanks FJC

[buildabiggerboxer]

Hi 4agedub, I've run 250lb X 2-1/4" springs but it was in a Rallycross Beetle, I would say it's too soft a spring for circuit racing with all your rear extra turbo hardware and heaver ally cased motor, there's a lot of leverage on the spring in the stock position, when I moved the shock outboard and on top of the a arm to almost inside the wheel, I reduced poundage to 200lb and was still able to remove the rear ARB with the handling I wanted, lots less leverage on the Spring, I would guess you will need 400 or 450lb for what you are doing, assuming the stock shock location, but that will really tax the stock upper shock mounting towers, plating and boxing them in with extra tags off the upper bolts to the body is a good move, the towers are cast steel and weld well, there are also clearance problems to the Spring and a slim coil over is required, a 2-1/4" should be ok, a 1.9" would be best for clearance, but then the biggest Spring poundage available for that size is 'only' 400lb. Inverted or 'upside down' coil overs are available but move the Spring clearance problem to the upper mounting,, the bigger 2-1/2" springs will foul the a arm without a new lower mounting and the arm modified and channelled for Spring clearance, nothing comes easy m8.

[buildabiggerboxer]

Some more discussion on rear coil overs here, not much content on Spring poundage tho'. Regards BBB.
http://www.germanlook.net/forums/showthread.php?t=11821

[buildabiggerboxer]

Yet More, includes some chat on Spring rates and Spring clearance problems.... BBB
http://www.germanlook.net/forums/showth ... 413&page=5

[4agedub]

Thank you for all the info, I'll check it out.