Torsion Bars

by Richard Dobson
GMC Motorsport
www.gmcmotorsport.co.uk

I will use the AX, Saxo, ZX, 106, 206, and 306 in this section as examples. Most aftermarket suspension kits available don't take the factors described in the spring section into account, the kits supplied usually have a star beside them, which when you investigate it, inform you that, only the front springs are included in the kit. This would leave one to believe that the rear suspension is OK as standard. Wrong.

The reason is that all these vehicles don't have coil springs on the rear suspension but torsion bars, which are very difficult and expensive to make in comparison to coil springs.

For those who don't know what torsion bars are, they are sprung steel bars with splines on both ends, one end fits in the radius arm which goes up and down with wheel travel and other end is fixed in the rear cross member. As the wheel goes up and down due to bumps the bar twists against the spring tension.

The problems that this lack of stiffer torsion bars create is that like a lot of front wheel drive cars and especially French cars, the rear suspension is set too high and too soft as standard. When you lower and stiffen the front, this unbalanced situation is made worse. Sadly, many suppliers of these kits and supported by articles in motor magazines say the answer is to lower the rear suspension to make the car level again by just turning the torsion bars around on their splines. This is definitely not a solution, but merely way of getting around a problem. Not many people understand the reason why it is not a proper fix.

The reason it isn't a fix is that to make the cars sit lower you have to take tension off the bar, which exactly the opposite of what is necessary. Yes, it will lower the suspension to get it looking good and level with the front but that's all. If you put on some lowered uprated front springs you will make the handling worse unless you can fit uprated rear torsion bars. If you are more concerned with appearance then this modification is OK but if improved handling is required it is definitely not.

The only solution is to fit uprated torsion bars on the rear. The amount of up rating will depend upon whether they are for road, rally or race specification vehicles. Some of the more specialized fitments are Citroen Sports or Peugeot Competitions Department only, which means they are quite expensive but prices similar to the standard unit are possible. Thus if you are doing any serious competition you need these specialized units as the money not spent here, could negate £500 spent on the power of the engine.