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
tapkaJohnD said:
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.
Interesting thread! 
Just with ref the above, I thought the swing-spring came after the rotaflex set-up? Ie fixed transverse spring (bolted to diff) > rotaflex > swing spring (able to pivot on diff). My late GT6 had swing-spring and never landed me in trouble, but maybe I didn't try hard enough.
Impressive work you've done to cure the camber change though.
One reason the Triumph's swing axle was more problematic than the other cars the OP mentioned is the relative lack of weight on the rear, and the high-ish pivot for the arm (wheel centreline).
VWs, Corvairs and Tatras were rear engined, so the weight transfer on throttle lift-off was less, and IIRC the Mercedes had a low-pivot swing axle in an attempt to limit the jacking effect.
I have driven a fair few miles in old VW beetles, and owned a (modified) '62 Herald - the Herald was definitely more twitchy on a trailing throttle.
When I replaced the cast-iron boat anchor under the bonnet with a significantly lighter (and more powerful) 1.2 litre engine from my wrecked '67 Corolla, the handling felt more stable.
VWs, Corvairs and Tatras were rear engined, so the weight transfer on throttle lift-off was less, and IIRC the Mercedes had a low-pivot swing axle in an attempt to limit the jacking effect.
I have driven a fair few miles in old VW beetles, and owned a (modified) '62 Herald - the Herald was definitely more twitchy on a trailing throttle.
When I replaced the cast-iron boat anchor under the bonnet with a significantly lighter (and more powerful) 1.2 litre engine from my wrecked '67 Corolla, the handling felt more stable.
I saw a modification on a Herald used for Autocross (or similar), it consisted of a Bowden cable-based ststem to tie together the upper ends of the hub carriers. This was supposed to limit the extent to which the outside rear wheel could tuck under, not sure how successful it was.
I had a Mk4 Spitfire that was supposed to be better than the Mk3 and earlier. All I can say is that if the Mk4 was better then I'm glad I never drove an earlier model. I suspect the main benefit of a swing axle is that it was cheap; I know it was a very common arrangement but not one I want to experience again. The "jacking" effect does describe it very well, it feels most odd when the back of the car sits up and the thing starts to pivot on its axis.
I had a Mk4 Spitfire that was supposed to be better than the Mk3 and earlier. All I can say is that if the Mk4 was better then I'm glad I never drove an earlier model. I suspect the main benefit of a swing axle is that it was cheap; I know it was a very common arrangement but not one I want to experience again. The "jacking" effect does describe it very well, it feels most odd when the back of the car sits up and the thing starts to pivot on its axis.
The rear set-up was fine at the time it was designed, but then it was designed for a 948cc/34.5BHP Herald. Sure the tuck-in issue was there but you didn't have enough power to induce it.
Of course when you start upping the power to 95BHP in a GT6 that's no longer quite so true. Even then things weren't as bad as they were made out, a bit like the Merc A class and the Elk test. Yes, drive it like a t
t/race it and it can bite you but I bet even most GT6 drivers never experienced a tuck-in in real life.
The Rotoflex set-up fixed the problem but cost a bomb to manufacture so the swing spring was developed as a cheaper, but almost as effective alternative.
There was also a live axle Spitfire built by the experimental department than one of the engineering bosses took for an evaluation drive and ordered to be scrapped right away on his return. It was much better than a standard Spitfire and would have embarrassed senior management had they found out as they were the ones responsible for the TLS set-up (by demanding all Triumph cars had IRS so they could say so in their marketing - but also demanding the cheapest possible solution).
Of course when you start upping the power to 95BHP in a GT6 that's no longer quite so true. Even then things weren't as bad as they were made out, a bit like the Merc A class and the Elk test. Yes, drive it like a t
t/race it and it can bite you but I bet even most GT6 drivers never experienced a tuck-in in real life.The Rotoflex set-up fixed the problem but cost a bomb to manufacture so the swing spring was developed as a cheaper, but almost as effective alternative.
There was also a live axle Spitfire built by the experimental department than one of the engineering bosses took for an evaluation drive and ordered to be scrapped right away on his return. It was much better than a standard Spitfire and would have embarrassed senior management had they found out as they were the ones responsible for the TLS set-up (by demanding all Triumph cars had IRS so they could say so in their marketing - but also demanding the cheapest possible solution).
//j17 said:
The rear set-up was fine at the time it was designed, but then it was designed for a 948cc/34.5BHP Herald. Sure the tuck-in issue was there but you didn't have enough power to induce it.
You don't need power to get it to tuck under, you only need a wet roundabout and 25mph. I dread to think what Heralds were like on crossplies.My comments on another forum was the reason for John to start this thread.
I had a Vitesse in the very early 1970's before I could legally drive and it was ragged around a farm. Lots of tuck under oversteer in safety.
In the late 1970's I had 2 GT6's. Both Mk3's but with different rear suspension setup.
The standard tyres were 145/70x13 (if I recall correctly) and I swapped the rears for 185/70x13 on wider wheels. The tyres were Avons with a very square edge and flat tread. This change drastically improved the handling and reduced the tuck under to almost nil.
The changes made to John's race cars makes a great deal of sense based on my memory of the issues that the transverse leaf spring created.
Realistically Triumph just got the rear axle/suspension wrong. But they never had solid rear axles to use AFASIK (Dolomite?).
I swapped the last GT6 for a new Golf GTi 1.6 Mk1 which was light years better in every way really.
When ever I see a GT6 I wonder how I managed to get in one let alone do all the things a young chap does........
Paul
I had a Vitesse in the very early 1970's before I could legally drive and it was ragged around a farm. Lots of tuck under oversteer in safety.
In the late 1970's I had 2 GT6's. Both Mk3's but with different rear suspension setup.
The standard tyres were 145/70x13 (if I recall correctly) and I swapped the rears for 185/70x13 on wider wheels. The tyres were Avons with a very square edge and flat tread. This change drastically improved the handling and reduced the tuck under to almost nil.
The changes made to John's race cars makes a great deal of sense based on my memory of the issues that the transverse leaf spring created.
Realistically Triumph just got the rear axle/suspension wrong. But they never had solid rear axles to use AFASIK (Dolomite?).
I swapped the last GT6 for a new Golf GTi 1.6 Mk1 which was light years better in every way really.
When ever I see a GT6 I wonder how I managed to get in one let alone do all the things a young chap does........
Paul
Interesting snippet from one of the owners of the company that originally made the rear leaf springs for Heralds etc.
He had a drawing of a swing spring dated probably late fifties - ie for the original Heralds. I suspect it wasn't actually made to save some cost.
The British Spring Company of Bridgnorth once made a batch of "original" swing springs for later Spitfires - they were awful - used to sag to one side soon after fitting.
He had a drawing of a swing spring dated probably late fifties - ie for the original Heralds. I suspect it wasn't actually made to save some cost.
The British Spring Company of Bridgnorth once made a batch of "original" swing springs for later Spitfires - they were awful - used to sag to one side soon after fitting.
caziques said:
Interesting snippet from one of the owners of the company that originally made the rear leaf springs for Heralds etc.
He had a drawing of a swing spring dated probably late fifties - ie for the original Heralds. I suspect it wasn't actually made to save some cost.
The British Spring Company of Bridgnorth once made a batch of "original" swing springs for later Spitfires - they were awful - used to sag to one side soon after fitting.
Let's be honest the rear suspension on these cars was always bloody useless. The front end was great but the back was light years behind contemporary Midgets and the like. When part of the damping comes from the fact that the leaf spring has rubber buttons separating the leaves and that after a few thousand miles they are worn out, you are onto a loser.He had a drawing of a swing spring dated probably late fifties - ie for the original Heralds. I suspect it wasn't actually made to save some cost.
The British Spring Company of Bridgnorth once made a batch of "original" swing springs for later Spitfires - they were awful - used to sag to one side soon after fitting.
battered said:
Let's be honest the rear suspension on these cars was always bloody useless. The front end was great but the back was light years behind contemporary Midgets and the like. When part of the damping comes from the fact that the leaf spring has rubber buttons separating the leaves and that after a few thousand miles they are worn out, you are onto a loser.
This isn't honesty, it's just misinformed regurgitated pub talk. Without getting into the relative merits of MGs v Triumphs, a rudimentary cart axle can hardly be described as light years ahead of anything, even during the 60's or 70's. It was certainly effective and Triumph's decision to use the flawed irs was unquestionably driven by their wanting to offer a USP rather than any credible belief that it offered any great advantages over a cart axle.Nonetheless, huge success in racing in the States testifies the fact that they weren't overly difficult to sort out effectively. When I first started running the 160 bhp K series engine in my car it had the swing spring rear end with the late longer half shafts and worked well enough - albeit not as well as the twin wishbone set up I have now put on there.
Essentially, the Triumph system has its limits and weakness, but it was a long way from "bloody useless".
Just a wild note here - have a look at the back of an early Triumph based Marlin kit - what the designer Paul Moorhouse did, was simple and straightforward - he moved the shockers to be almost VERTICAL - over the hubs.
This resulted in the rear end being limited from 'jacking up' by the shockers hitting their bump stops, and also giving better damping.
I owned a Marlin, fitted with Vitesse Mk1 suspension (later moved to wider Spitfire shafts), GT6 3.27 diff, and a tuned 2500 (175 Strombergs) with saloon box and odrive. I got it to 'hop' quite a few times, but it was always well behaved.
True though, you were sat nearer rear axle in the Marlin, so that also helps quite a lot too ...
This resulted in the rear end being limited from 'jacking up' by the shockers hitting their bump stops, and also giving better damping.
I owned a Marlin, fitted with Vitesse Mk1 suspension (later moved to wider Spitfire shafts), GT6 3.27 diff, and a tuned 2500 (175 Strombergs) with saloon box and odrive. I got it to 'hop' quite a few times, but it was always well behaved.
True though, you were sat nearer rear axle in the Marlin, so that also helps quite a lot too ...
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
I had not seen that before. The Marlin used the original shocks if that makes any difference. I ended up breaking the diff with the 2500 engine !
You could have a HUGE discussion thread about relative merits and drawbacks of certain designs, fact is, there isn't anything which is perfect.
There's whole BOOKS on this sort of stuff !
The nearest you will get to perfect is a carefully set up double wishbone for each wheel, and even then there can be issues with driveshafts etc.
And what about the chassis flex ? Yeah, it goes on and on....
For kits and swops, A standard cart axle is fine, but only if located properly, which does NOT mean just via the springs, and is probably better for tarmac (by a little bit) than a classic swing axle. But not a lot....
And you already have the twin wishbone front, pity about the trunnions, but hey... it's better than struts....
You could have a HUGE discussion thread about relative merits and drawbacks of certain designs, fact is, there isn't anything which is perfect.
There's whole BOOKS on this sort of stuff !
The nearest you will get to perfect is a carefully set up double wishbone for each wheel, and even then there can be issues with driveshafts etc.
And what about the chassis flex ? Yeah, it goes on and on....
For kits and swops, A standard cart axle is fine, but only if located properly, which does NOT mean just via the springs, and is probably better for tarmac (by a little bit) than a classic swing axle. But not a lot....
And you already have the twin wishbone front, pity about the trunnions, but hey... it's better than struts....
RCK974X said:
And you already have the twin wishbone front, pity about the trunnions, but hey... it's better than struts....
I dunno, trunnions are no real problem as long as they are lubricated. The usual is that you buy a car that's seen no lubrication for years, you oil it up, next MoT it needs one trunnion, the year after it needs the other, then it goes about 4 or 5 years provided you keep the oil up. My top tip was to pump in oil one month and grease the next, you get an evil mixture that won't leak out like oil and that won't gum everything up like grease. Every few weeks you slop in a bit more of one or the other, then the things last for years.The problem with the extension bracket is that the shock length and hence the suspension travel is very short. There are a few trick brackets that push the top mount further up the wheel arch but there is not much space. A few years ago I spent quite a bit of time trying to remodel the GT6 suspension without ever finding a practical solution.
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