D2 Preload questions..

[Gamble97]

I installed some D2 suspension on my 2g awd car. When I got them they said not to change where the springs were set so I just made sure that everything was tight and I installed them.
I currently have my car on jacks and I can turn the springs by hand and lift them up and down.

Should I tighten them so there is some stress on them while the car is on the stands?

What is the preload as far as how many inces the spring should be compressed?

 

[jtmcinder]

Whether or not you want some preload depends on the spring-rates. The higher the rates, the less likely you are to need some preload (... on the main springs and, therefore, the more likely you are to need helper springs, at least, in the rear). Conversely, with very low rates, such as stock, you will definitely need some preload, as in true stock.

There is nothing magical about preload. All you are doing is getting the static position to be in the right place between full compression and full extension.

- Jtoby

 

[Gamble97]

So should I just tighten them until the springs won't move then reinstall them?

 

[jtmcinder]

That ... depends ... on ... the ... spring ... rates.

- Jtoby

 

[Gamble97]

Oh, haha sorry. I will look up the spring rates, then is there a chart that I follow? I just want to make sure that I am getting the full use out of my coilovers and the most travel as possible

 

[jtmcinder]

Is the length of the shock-body adjustable? In other words: can you move the lower mounting point up and down? If so, then you can optimize for travel, which usually means about twice as much bounce/compression (up) than jounce/extension (down). If not, then you can't set the travel separately from the static ride height, as the height of the perch sets both of these at the same time.

- Jtoby

 

[unclesam099]

The D2s should be adjustable. I know that the KSports are, and the D2s are very similar.

I'd like to know as well because I'm looking at getting one of the two setups.

 

[jtmcinder]

D2s and K-Sports are totally different! One is orange and the other is purple. Jeesh!

OK, so if these Taiwanese wonders have adjustable lower mounts, as well as adjustable perches, then you have either some trial and error or some calculations ahead of you. You need to know the rates and your corner-weights. This allows you to calculate how much the spring will compress when you set the car back down. Then you take the free length of the spring, minus the expected amount of compression, and set the perch such that you are about 1/3 compressed (in terms of shock travel) when sitting still. Finally, you set ride height using the lower mounts.

Note: if you autocross on R-compounds (especially if you trail-brake), then you might want the rears in the middle, instead of 1/3 compressed. Why? Because this will help prevent 3-legging it at corner-entry due to full extension. Plus, most set-ups have oodles of rear travel, so you don't need to have 2/3 of it available for bump.

- Jtoby

 

[Rx3]

Is the length of the shock-body adjustable? In other words: can you move the lower mounting point up and down?

Yes, you can move the mount point. You have as much travel as the threaded column that the lower mounting point screws on to. As for spring rates on the D2s, unless you requested something specific, I believe they default to 11Kg front / 9 Kg rear.

I don't think you will need any pre-load unless you are doing something extreme with the car.

 

[SAKONE]

I just adjust 5mm at a time, but like what was said it all depends. Get your car on some corner weights. So many adjustments, so many ways to screw up the handling.

 

[wret]

I believe they default to 11Kg front / 9 Kg rear.

If those rates are correct, they are on the stiff side. With my limited experience, you would be best advised to use zero preload. This means just snugging them up so the springs don't rattle around. This will maximize extension, of which you will find there is little. This is what I have found to work best with Tein Flex and it sounds like your springs are a bit stiffer (Teins come with 10/6 kg).

If you are autocrossing you may want to rethink this, as Jtoby mentioned. And as SAKONE stated, if you want to maximize handling for either track or street, you should get them corner weighted when you are done playing around with the height.