Triumph suspension discussion thread
Discussion
This subject arose on another PH forum, so rather than divert the threads there, I suggested we adjourn to the Triumph forum. I'll offer my opinions and I'm glad for others to join in.
There are many myths about the Triumph small-chassis suspension systems, especially that the swing rear axle is a problem exclusive to the marque. In fact the built-in problems of a swing axle were well known then, and shared with any other car that has a swing axle. Examples include Volksvagens up to 1967, Mercedes 300SL (!) Porsche 356, Tatras, Chevrolet Corvair and others. I include this list not to excuse the faults of a swing axle but to show how widely used it has been in car production.
I won't go into the problems, there are plenty of websites that do that, just say that there is an extreme amount of camber change from bump to droop and that this can cause "jacking" under extreme cornering. Triumph were very aware of the problem, and during production brought in an innovative modification that went a long way towards dealing with them. The "swing spring" pivoted the transverse rear spring on the differential, so that the body could roll more than the suspension, without impairing the ride in a straight line. They later produced a fully controlled rear axle, with a lower wishbone (reversed) and a rubber donut (Rotaflex) at the outer end of the drive shaft, but that was no longer a swing axle.
To control the rear axle for competition, it's necessary to control the camber change. Two main ways:
1/ lowering the car by raising the transverse spring. This puts the axle in a different part of its arc, so that it rides on the straight with more negative camber, and for the same side force in cornering moves less far into the positive camber part.
2/ increasing the spring stiffness, so that the axle moves less for the same cornering side force.
I did this for my experimental Silverback, Vitesse Estate race car
which worked very well in that respect. The pic shows it exiting Camp Corner at Castle Combe, and you can see the body roll, with little rear suspension movement. But it then fell foul of the other Triumph design fault, the step in the halfshaft. The end is machined to a small radius for the single hub bearing, and a sharp step left in the shaft, an obvious stress raiser, that makes wheels fall off. Literally.
And the Rotaflex version is today plagued by the single parallel wheel bearing, poor quality donuts and the cast iron wishbone, enormously heavy. My latest, SofS (Son of Silverback), has MGF rear uprights with doubly opposed conical hub bearings and a CV joint, connected to Volvo half shafts that have LoBro joints at the differential. And fabricated, fully spherical jointed wishbones.
Other designs may be found on Triumph websites, such as using double radius arms instead of the wishbone, and full conversions to coil-overs. See Club Triumph and the Sideways Technologies sites.
John
There are many myths about the Triumph small-chassis suspension systems, especially that the swing rear axle is a problem exclusive to the marque. In fact the built-in problems of a swing axle were well known then, and shared with any other car that has a swing axle. Examples include Volksvagens up to 1967, Mercedes 300SL (!) Porsche 356, Tatras, Chevrolet Corvair and others. I include this list not to excuse the faults of a swing axle but to show how widely used it has been in car production.
I won't go into the problems, there are plenty of websites that do that, just say that there is an extreme amount of camber change from bump to droop and that this can cause "jacking" under extreme cornering. Triumph were very aware of the problem, and during production brought in an innovative modification that went a long way towards dealing with them. The "swing spring" pivoted the transverse rear spring on the differential, so that the body could roll more than the suspension, without impairing the ride in a straight line. They later produced a fully controlled rear axle, with a lower wishbone (reversed) and a rubber donut (Rotaflex) at the outer end of the drive shaft, but that was no longer a swing axle.
To control the rear axle for competition, it's necessary to control the camber change. Two main ways:
1/ lowering the car by raising the transverse spring. This puts the axle in a different part of its arc, so that it rides on the straight with more negative camber, and for the same side force in cornering moves less far into the positive camber part.
2/ increasing the spring stiffness, so that the axle moves less for the same cornering side force.
I did this for my experimental Silverback, Vitesse Estate race car
which worked very well in that respect. The pic shows it exiting Camp Corner at Castle Combe, and you can see the body roll, with little rear suspension movement. But it then fell foul of the other Triumph design fault, the step in the halfshaft. The end is machined to a small radius for the single hub bearing, and a sharp step left in the shaft, an obvious stress raiser, that makes wheels fall off. Literally.
And the Rotaflex version is today plagued by the single parallel wheel bearing, poor quality donuts and the cast iron wishbone, enormously heavy. My latest, SofS (Son of Silverback), has MGF rear uprights with doubly opposed conical hub bearings and a CV joint, connected to Volvo half shafts that have LoBro joints at the differential. And fabricated, fully spherical jointed wishbones.
Other designs may be found on Triumph websites, such as using double radius arms instead of the wishbone, and full conversions to coil-overs. See Club Triumph and the Sideways Technologies sites.
John
Edited by tapkaJohnD on Wednesday 20th July 11:34
Thank you RCK!
A popular mod for Heralds etc. is a bracket that does the job you decsribe.
See: https://shop.tssc.org.uk/product/rotoflex-rear-sho...
It's decsribed as for Rotaflex suspension but can be used on any.
John
A popular mod for Heralds etc. is a bracket that does the job you decsribe.
See: https://shop.tssc.org.uk/product/rotoflex-rear-sho...
It's decsribed as for Rotaflex suspension but can be used on any.
John
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