Lowering Torsion Rear Supension
             
First of all a warning and a disclaimer. This is how we adjust the back suspension on our Citroen Saxo Kit Car, whilst the basic principle is the same as a standard road car there may be some minor differences. As such it is not intended as a 'how to guide' to enable you to modify your own car but for information only on how we modify our car. If you choose to use this information to modify your road car, good luck but don't hold me responsible if it all goes wrong and your car is damaged, you injure yourself, innocent third parties or their property.
             
All of the images are Thumbnails and clicking on the will download a full size image. Even so it may take a while to download all of the thiumbnails, especially on a dial up connection.
             
   

The tools required:

  • Slide hammer with 8 mm bolt attachement.
  • Ratchet sockets and spannersto remove shock absorber.
  • Hex head sockets (or Torx bits and 13mm socket for a standard car) to remove anti-roll bar plate and torsion bar end plate.
  • Dummy shock absorber ( you can manage without this).
  • Tape Measure ( but not without this if you want the car level).
  • A Hammer

 
Before starting make sure that the car is securely supported on axle stands, butdon't put them under the suspension arms as they will be in the way in a moment. Our car has tubes welded into the rear chassis rail that accept steel rods to make the job easier.  
             
    Remove the rubber bung from the end of the anti-roll bar plate. On our car this is a metal bolt but standard cars have a rubber bung that is SCREWED into the same place. You will need an Allen key to unscrew it, don't just lever it out with a screwdriver as it won't seal properly when you put it back and water will get in.
Next remove the bolt that holds the anti-roll bar plate to the suspension arm. We use hex head bolts but the standard car is a normal 13mm bolt.  
  We use a slide hammer with an 8mm bolt on the end and hammer the anti-roll bar out but some screw a 12mm (I think) bolt into the endplate and push the anti roll bar out the other end. You do need to remove the plate on this side to get at the torsion bar underneath. Given that you need the slide hammer and 8mm bolt to remove the torsion bars we use this as it's already out of the tool box.
The anti roll bar usually comes out easily and we remove it completely so that it doesn't get in the way.  
We also remove the plate from the opposite side mainly because we find it makes putting it all back together easier.
This is the view after the anti roll bar and it's end plate have been removed. Check the condition of the seal in the middle and replace it if it's damaged in any way. They only cost a few £ from Citroen and are essential in keeping water and dirt out of the rear arm bearings. If these are damaged and water gets in it can result in the bearing seizing and damaging the rear beam resulting in a very big bill.  
  Undo the bolt that holds the torsion bar in. Again on our car the standard Torx bolts have been replaced with hex heads. Mainly because hex heads are bit more robust and stand up to being undone and done up often, as they are on our car.
After removing the bolt you need to remove the washer that holds the tosrion bar in. These are fiddly little b*ggers and if you think getting them out is awkward just wait until you try and put them back in later.  
As we use a dummy shock absorber (more later) to set the ride height we remove the shock absorber completely. If you are simply measuring the ride height and supporting the suspension arm on a jack you can get away with just undoing the top bolt and letting the shock absorber hang down on it's remaining bolt.
Undo the bolt in the other end of the torsion bar - You can leave the washer in place. This one is a bit awkward to get at and we use a short hex (or torx) bit and a 10 mm spanner to turn it.  
  Use the slide hammer (with 8 mm bolt attatchment) to pull the torsion bar out.
They can be very stubborn and you need to hit the suspension arm with a hammer at the same time as pulling with the slide hammer to prevent the torsion bar and suspension arm coming off together. You don't want to pull the suspension arm off the beam as this can give you bearing problems later on.  
  There's no need to remove the torsion bar completely, this is plenty far enough.
We use a dummy shock absorber to determine the new ride height. It varies from car to car and does involve a fair bit of trial and error but on this occasion we changed the dummy shock absorber length from 292 mm to 289mm to lower the car by (hopefully) about 10 mm.    
  The other way to set the ride height is to measure the distance from arch to disk before you remove the torsion bar and the use a jack to hold the suspension arm at this measurement less the amount you want to lower the car by, plus about 5 mm. If the initial measurement is 300mm and you want to lower the car by 45 mm, move the suspension arm on the jack until the arch to disk measuement is 250 mm ( 300 - [45 +5] ). The plus 5mm is because when you remove the jack at the end the suspension arm will drop slightly as they tension the torsion bars. Again it's not an exact science and if you get it spot on 1st time, it's as much down to good luck as good judgement.
The dummy shock absorber in use. As long as you don't change it's length from side to side you can pretty much guarantee that you will get the suspension level - which always helps.    
             
  If you turn the torsion bar around one spline at a time you will find 1 position where it will go back in.
Repeat the process on the other side    
  And reassemble everything.
Put the anti-roll bar back in  
  We find that the bolts holding the rear anti-roll bar plate on tend to come loose, so we use loctite to prevent this.

Ready for wheels and putting back on the ground.