Preloading Springs On Coilovers

[morlock]

Hey guys,

I have done a search and read a bunch of very helpful posts (thanks SK!)

First a bit of background. I have bought and installed a set of HSD HR coilovers for my R33 GTST. The spring rates are roughly 430 pounds in the fronts and 350 in the rears (i do have the actual rates written down somewhere)...so not too hard but a bit harder than the rates SK uses on his R32 race car.

I recently lowered the spring seat and reduced the preloading on the spring to next to nothing....just enough to hold the spring in place. I had an improvement in the ride comfort for small to medium differences in the road surface....however going over deep potholes and speed humps the ride is terrible....i attribute this from what i've read on here to be the car hitting the bump stops.

So I guess from this i have to preload the spring more. I thought about starting with 4mm extra height on the spring seat as a starting point.

Anyway my questions are:

1) Is it normal to set coilovers up with a degree of preload on the springs for an R33 GTST? (I know this is a very loose question)

2) The rebound is adjustable on the top of the struts and indicates an L for adusting the knob left and an H for adjusting the knob to the right....now i didn't receive any documentation on adjusting the coilovers when i received them....so I thought L would make it softer and H would make it harder....have i got this right?

3) do you think the 4mm of extra spring seat height is a good place to start?

Cheers for your advice

Morlock

[xr8eater]

good question i would also like to know what the brains trust has to say

[Sydneykid]

My 22 cents (that 20 cents plus GST) worth........

1. Preload has zero effect on the spring rate, it doesn't matter how much preload you add the spring rate is still 430 lbs per inch in the front and 350 lbs per inch in the rear.

When you put the weight of the car on the springs, they have preload anyway. So the little bit that you add by adjusting the lower spring seat is irrelevant.

Some simple numbers;

R33GTST weighs say 1400 kgs

65% front = ~900 kgs (1980 lbs)

The front spring rate is 430 lbs per inch

So 1980 / 2 / 430 = 2.3" (58.5 mm) of spring compression to hold up the front

35% rear = ~500 kgs (1100 lbs)

The rear spring rate is 350 lbs per inch

So 1100 / 2 / 350 = 1.6" (40 mm) of spring compression to hold up the rear

2. Clockwise is usually high damping level. Give it try, you should be able to pick the difference beween full soft and full hard pretty easily.

3. Preload affects the ride height, so you set the lower spring seat position to achieve the desired height.

Cheers

Edited May 6, 2006 by Sydneykid

[morlock]

Thanks SK

Will having more preload on the spring cause the shock to be overworked? I only ask this because i was advised by the vendor that "too much" preload on the spring would make the damper work harder.

Cheers

[Sydneykid]

Thanks SK

Will having more preload on the spring cause the shock to be overworked? I only ask this because i was advised by the vendor that "too much" preload on the spring would make the damper work harder.

Cheers

Rubbish

cheers

Edited May 8, 2006 by Sydneykid