wrx guide

Changing springs

So I used to have a set of King Springs superlows on the standard GC8 struts. They were fine for looks but handling was actually a little worse than standard (the piston was no longer at it’s ideal working height/range plus king springs aren’t great in terms of spring rate either). The main problem however was when I upgraded my rims and tyres, the offset and larger width meant that my tyres were rubbing (mostly at the rear but also at the front sometimes). I had the rear guards rolled and although it was much better, the tyres would still rub on most corners/bumps.

Fig 1.1 - 2nd hand STi v5 struts

I figured I needed to get a little bit of ride height back for more clearance and also get a spring and shock absorber combination that could handle the bumps much better. I saw a set of STi version 5 struts and springs for sale on the local forum and snapped them up. The springs were standard STi so still too high for my liking. I decided on a set of new Eibach springs that were slightly lowered (about 30-35 mm from standard) and set about swapping them over before installing the struts.

What I noticed when I had a closer look at the struts was that the standard shock absorbers had been replaced with Koni yellow adjustable inserts. Score! These are much firmer than even the STi absorbers and also the are adjustable in terms of rebound from about 25-50% firmer than standard up to around roughly 200% firmer.

Anyway, getting on with swapping the springs. You’ll need a pair of spring compressors (which you can see in the later pics below) and if you’ve got access to a compressed air rattle gun, that comes in really handy. The top nut is usually the main issue if you don’t have a rattle gun as sometimes the piston likes to turn with the nut, making it hard to undo the bolt. It’s easier if you loosen the top bolt while the struts are still on the car, I didn’t have that luxury unfortunately as I bought the set already off that sti.

So go ahead and loosen that top bolt a little (not much though because you don’t want that top hat to get shot out doing damage to your car or you!). At this point, or even before you’ll want to mark on the top hat how it’s positioned. A couple of marks that line up with the bottom of the strut worked for me. Next you can go ahead and attach the spring compressors opposite each other to distribute the force evenly. You may need to put one part of the compressor in at a time (at least where the spring gets tight) and wind it up the spring a little. Now start compressing the spring a little at a time on each side. You don’t want a bulge on either side which tells you the force isn’t being distributed evenly.

Fig 1.2 - sti/koni strut disassembled

You shouldn’t need to compress the springs too much, just enough to undo the top bolt without any force pushing out still. Once this bolt is undone then you can pull all the parts out as shown in fig 1.2. This is a front strut. It’s a good time to give the strut a clean in those hard to reach areas if that’s your thing (might as well make it look new).

The old spring needs to be decompressed following the same process (slowly unwinding each side a little at a time). Then the new replacement spring needs to be compressed and installed. I’ve read about some people also modifying or replacing the bump stops for lowered struts (the yellow thing on the end of the piston) but I wasn’t too sure about this so I left it as is.

Reassemble the strut in the same manner and make sure the top hat is in the right position that you marked earlier. Put the spring into roughly the right grooves (it will settle in properly after some driving) and pull the piston out to full length so you can get the top bits on. I found that the piston keeps falling down if you stand the strut up so I assembled them laying flat. Get the top bolt on and tighten it up (not too much as it’s probably best to torque it to the right settings when on the car).

Now you can undo the spring compressors as you’ve been doing and once you’ve done the whole process another few times, you’re ready to put your struts back into the car. I’ll be writing another guide on removing/installing the struts themselves so check back later for that guide. Once the struts are all on the car, make sure you torque up all the bolts to the correct values (don’t forget that top bolt). If you’ve got anything to add, please leave a comment.

Completed strut with Eibach spring.

Tags: Springs

This entry was posted on Sunday, April 4th, 2010 at 1:51 pm and is filed under Mechanical. You can follow any responses to this entry through the RSS 2.0 feed. You can leave a response, or trackback from your own site.