Since today it was the most asked question and everyone knows the problems with the rear transverse leaf spring - so i decided to republish an old entry
Spitfire Rear Suspension
The spitfire's transvers spring rear axle suspension was a cheap way to realise a independent rear axle, ideal for a low price range, light sportscar, maybe even more revolutionary on the Triumph Herald.
But this transvers spring solution is known for it's bad handling. The rear tyres move to a negative camber and jack in rapidly causing a loss of grip. The Triumph Spitfire and Herald were not unique in there rear axle layout.
If you have got one of those, or something else using the Spitfire/Herald Frame and rear axle, there are solutions - for road and track.
Spitfires and GT6 racing in the US came up with a lot of innovative Ideas, not only to keep the tries on the road, but as well to adjust the rear spring.
The factory addressed the issue by using the so called "Swing Spring", where basically a second spring catches the main spring. Standard on later models, but you have to be careful - Swing Spring from a car using longer driveshafts are therefor longer and will even increase you negative camber.
For every degree of sporting pedegree, lowering the car, from the ridiculously high ride heigh they came from the factory, seems like the only way to go. Especially with today's roads, there is no need for a long way for the spring.
Lowering the Spitfire's front by using shorter than coil-springs is straight foreword, the angle of the steering, and the bonnet's inner wings are the most obvious limitations.
Lowering the rear can be achieved the easiest by adding a spacer between the differential and the transvers spring.
It is as easy as it sounds, wider tyres, more grip will reduce the chance of the rear to jacking in.
GT6 Rotoflex axle
The GT6 rear axle assembly is popular by some as an upgrade to the Spitfire's rear suspension.
Besides the fact, that it isn't a Spitfire part, it wasn't available when early Spitfires were around (a little bit like the swing spring), and requires changes made at the frame.
As well as the weight added to the light, nimble car. With 700kg ever kilo counts, it is always power to weight.
I personally had a red MKII with a swing spring and lowered using a 3cm spacer. It wasn't perfect but it was safe on road and track, but it maybe wouldn't have been enough for a rally stage.
I spun at the track, but as seen on the picture, the camber was still not negative and the tyres were always on the road.
Overall with this little modifications, the car was fully controllable and nice drive. One lap I managed to get control ofer the rear again, chasing a TR4, one lap later I spun - delivering good information for this blog entry today.
But "Swing Spirng" arrangements are not period correct.
Counter - Spring
Period correct, used by group44 and Kas Kastner prepared race cars in the US, later sold in Europe by SAH, a single leaf is bolted as a counterpart to the differential housing...