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Rotoflex to swing spring conversion


David Kirk
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Hello,

I am a little way of from completing the restoration on my Rotoflex GT6 but I wonder how easy it is to loose the Rotoflex and go back to the swing spring arrangement? 

This may be easier than you think as I have a spare rear axle set up from a Spitfire 1500 (diff, driveshafts, spring etc).

Is it possible? Any advice welcomed.

David

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Just off the top of my head - if the only difference is brackets for the lower wishbones and the shockers in the wheel arches (maybe the handbrake cable as Pete says) then by removing the brackets, and replacing the current shock mounts with the chassis extensions that used to be available, and using the assemblies from a swing-spring Spitfire... possible?

I'd prefer a proper GT6 leaf spring... but if the brake pipes and hoses were as the Spitfire... interesting. Sorry, David, not much help other than musing, but it must be possible.

 

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Why do it?

The Rotoflex rear setup handles better and isn't as difficult to maintain as some say.

Here goes, I'm reaching for my tin hat as I type...

Swing spring rear axles still hop sideways on bumpy corners, but don't let go suddenly like swing axles. And swing axles usually let go when the driver enters a bend too fast then lifts off . Rotoflex tracks true through the bends.

To take a Rotoflex car back to swing axle or swing spring is backward step.

Merely my opinion of course, no doubt serious/heated debate will ensue!

Nigel

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Remove the complete Rotoflex uprights, driveshafts and spring.

You shouldn't need to remove (cut off) lower wishbone mounts from the chassis or the shock absorber mounts from the inner wings.

Swapping the diff is optional - all depends on which ratio you want.

Fit the swing spring and Spitfire uprights and driveshafts.

Work out some suitable arrangement for the brake pipes

Fit a set of Spitfire shock absorbers - as they would be fitted on a Spitfire.

The Rotoflex handbrake cable "should" be the correct length.

You may want to get a swing spring from a late GT6 rather than the Spitfire one as the rear of the tub is heavier on a GT6 so the spring is different.

And its all reversible when you find you want to go back to the Rotoflex

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11 minutes ago, dougbgt6 said:

I've a late GT6 with swing spring, it's just as good as rotoflex and doesn't have the maintenance problems.

Right, we've got a swing spring owner (Doug) and a Rotoflex owner (me) disagreeing about GT6 rear suspension.

No surprise there! How about a swing axle owner to extol the virtues of the Mk1 back end?

Nigel

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Radius arm brackets are in a different place on the heelboard. But the dimples are there, just need to get the 2 brackets and get them welded in place.

Having had a fairly powerful and thrashed spitfire (as inway ahead of a GT6 in terms of power)  which initially used swingspring, but moved to rotoflex,  I would say rotoflex is a little better, but at the expense of complexity and extra weight. However, CV rotoflex helps matters more. 

What would I do? if the car is used as most are, I would happily use swingspring. If doing trackdays etc, rotoflex is handy.

One more thing, spitfire rear brakes are smaller than GT6. However, I used spitfire drums on my 2.5 vitesse, and could still lock the rears up. So adequate!

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Apologies to Nigel, I think Clive has put it more eloquently than me. I don’t race or drive on the limits, so for me they are the same. But I stick by the maintenance thing.

There’s a few threads on here detailing the difficulties of replacing RF leaf springs, spring lifter tool required and still difficult. Swing spring system, you just pull the old one out and slip the new one in.

Rotoflex donuts,  difficult to do and have to be more frequent done because of the quality spares available. Swing spring, we’ll, nothing to do.

Doug

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Yes, the maintenance issue with rotoflex is troubling. However, a springlifter is not a "technically advanced" tool, but a hub puller required for swingspring bearing replacement is.

I am lucky. I use rotoflexwith the "Nick Jones"  CV conversion. It means no setting up of wheel bearing, and being CV's no fighting the donuts to get the shaft in situ. The advantage over a swingspring is that there is no UJ inthe shaft, which is highly stressed and prone to failure. Of course, rotoflex greatly reduces camber changes too, so you can safely use 60 profile tyres if you wish.

But as above, my vitesse was fine on swingspring, and built with simplicity in mind. Never even changed the UJs in my ownership, but they were top quality spicer ones (I don't think those particular ones are still available, it was 26 years ago)

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Thanks all,

A very nice set of thoughts and advice.

 

I conclude that although I can see the benefits of lower maintenace for the swing spring, it will require a bit of engineering work to fit - not impossible, but it would not be a straight swap. Although I will be unlikely to get the benefit from the (arguably) better handling set-up of the Rotoflex and I will be having to suffer higher maintenace effort it would seem, overall, sensible for me to keep the Rotoflex.

All I need to do now is decide if the CV conversion is worth the money. I see Canley don't do it any more but Rimmers still have stock (£ ouch).

Also there is the option to change the rear dampers and mount to the chassis rather than the inner wing. Again Rimmers have that for slightly less £ ouch than above.

David

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On the question of Rotoflex maintenance, though it's a bit more difficult than swing spring, it's really not that bad. My thoughts as follows:

- The spring lifting tool isn't necessary to remove or install the rear spring. I fit two 6" lengths of 3/8" stud in place of the two centre studs on top of the diff. With plain washers and nuts wound down on these longer studs to hold the spring clamp plate, remove the four outer nuts and studs. Carefully wind the nuts up the pair of long studs, slowly releasing the tension on the spring until the spring is almost touching the underside of the body. With the shock absorber lower mountings undone, there is little or no tension on the spring.

- The hub bearing adjustment is tricky the first time you do it, and getting it wrong would lead to disaster. But it very, very rarely needs to be done as genuine Timken bearing will have a long life.

- Rotoflex replacement is a fiddle the first time but get easier with practice. Always fit good quality couplings, never use cheapies. Or better still fit a CV joint conversion then any perceived disadvantage of the Rotoflex setup is history.  I got my CV shafts direct from Classic Driving Development, excellent kit.

- Swing spring cars will need UJ replacement from time to time, it's a had worked component as it has a dual role in Triumph's design, to transmit the drive and to act as a suspension pivot.

One other rear suspension modification I'm considering is fitting the chassis brackets so the upper ends of the shock absorbers will mount on the chassis rather than the body brackets. I suspect - but can't prove - that some of the rear end rattles in my GT6 may be the result of firm dampers feeding road shocks into bodywork that wasn't really designed for such loadings. It's an unproven hypothesis which I must test sometime.

Nigel

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If you don’t drive the car hard, you probably won’t notice much difference. While not a forgiving as Roto, long shaft swing spring is not a “widow maker”.

You can take more liberties with Roto without it trying to kill you and it feels much less fidgety on bumpy roads.

Fitting chassis extensions so you can not use the damper brackets on the wheel tubs is a good mod, but if you convert to CV shafts you don’t need them - just use the chassis brackets. Shorter dampers (the standard swing axle ones) are needed either way.

CV shafts? Try Classic Driving Developments, he doesn’t list them but he does do them. Worthwhile IMO if you intend keeping the car.

If converting to swing spring 
- the radius arm brackets have to be moved/added to the outer positions.
- rear brake pipe layout altered to match the Spit layout.
- I think you’d need to add the chassis guides for the handbrake cables to avoid the handbrake adjustment varying with suspension position (originals could be left in place)
- You need to plug the two middle spring stud holes in the diff.
- You need a proper GT6 spring. Spit one not strong enough.

Nick

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16 hours ago, Nigel Clark said:

Right, we've got a swing spring owner (Doug) and a Rotoflex owner (me) disagreeing about GT6 rear suspension.

No surprise there! How about a swing axle owner to extol the virtues of the Mk1 back end?

Nigel

GT6 MK1 running on GT6 MK3 swing spring; it's been converted since about 2002 and has run very well ever since, but much better with the GT6 spring than the Spitfire spring I originally used.

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1 hour ago, Colin Lindsay said:

GT6 MK1 running on GT6 MK3 swing spring; it's been converted since about 2002 and has run very well ever since, but much better with the GT6 spring than the Spitfire spring I originally used.

Sounds like a useful upgrade for a Mk1. Out of interest, did you also use the thicker anti-roll bar that goes with the swing spring setup?

Nigel

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20 hours ago, Nick Jones said:

 

Fitting chassis extensions so you can not use the damper brackets on the wheel tubs is a good mod, but if you convert to CV shafts you don’t need them - just use the chassis brackets. Shorter dampers (the standard swing axle ones) are needed either way.

 

Nick

Thanks Nick. 

I had not appreciated that the extensions were not needed if the CV conversion was done. Looking at the car now I see that the reason for Triumph moving the top damper mount to the wheel arch is because the rotoflex coupling is so large it obstructs the chasis mounting holes.

Makes a CV conversion slightly more affordable as the extensions are not needed.

David

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Regarding the body brackets for the horizontal links, while they have to be moved for the swing-axle, they are bolted in place not welded. (You add shims for the tracking.) You have to move the holes - location dimples already present. BUT ... the body is a box-section at this point. Can someone tell me (and David) are there crush tubes (to reinforce box section where bolts go through) and are they present in the swing axle locations???

Cheers, Richard

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32 minutes ago, rlubikey said:

Regarding the body brackets for the horizontal links, while they have to be moved for the swing-axle, they are bolted in place not welded.

The actual brackets are bolted but they are bolted to reinforcements on the inside of the floor, which are welded in place. Lift the carpet and you'll see what I mean.

And I don't think they go through the box section bit - that's just above - so it's the crush tubes in the reinforcement that you need.

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3 hours ago, Steve P said:

My twopenneth,

Having been overtaken by my own rear wheel on the RBRR when the shaft snapped at the hub end in my MK 1 Vitesse,i would opt for Roto every time,my Vitesse is now CV shafted roto and i have all the bits to do my 1500 Herald as well.

Steve

Technically then it seems to me that it's no longer roto but CV jointed; you no longer have the problems associated with the rotoflex doughnut and have modernised the setup. 

Having had two GT6 rear halfshafts shear on GT6, admittedly 15 years apart, I thought about it, but the cost- compared to new halfshafts - put me off.

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1 hour ago, Colin Lindsay said:

Technically then it seems to me that it's no longer roto but CV jointed; you no longer have the problems associated with the rotoflex doughnut and have modernised the setup. 

Having had two GT6 rear halfshafts shear on GT6, admittedly 15 years apart, I thought about it, but the cost- compared to new halfshafts - put me off.

I think"rotoflex" suspension refers more to the style rather than the actual components. At least these days. And yes, goodnessknows why Triumph used an "iffy" rubber donutrather than the CV which was used in other Triumph cars. Possibly cost? Or I did hear a whisper it helped diffs to survive.

But  I think the experience of one shaft breaking would make me move to something better. Twice, the cost would appear a bargain. The carnage a broken shaft can cause could hit the wallet far more. Besides strength, you would have the advantage of slightly more refined ride and handling. This is from somebody who is notoriously reluctant to spend unnecessarily on the cars. But the extra costs were justified. Next stop will be Marcus style radius arm delete.

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8 hours ago, Steve P said:

My twopenneth,

Having been overtaken by my own rear wheel on the RBRR when the shaft snapped at the hub end in my MK 1 Vitesse,i would opt for Roto every time,my Vitesse is now CV shafted roto and i have all the bits to do my 1500 Herald as well.

Built our Spit up as roto (with CV shafts) in considerable part due to the number stories of lost rear wheels....... Three wheels on my wagon and no brakes.....  no thanks!

Another angle to that is that all the OE shafts are at least 40 years old now, so fatigue has had time to do it's work.  So you might think that new ones are a wise investment - and on the face of it, you'd be right.  However, having heard a few stories and seen a few pictures of new shaft failures, or near failures in the last couple of years..... perhaps not.  Problems seem to be mainly with the way that the UJ yoke forging is attached to the shaft and being rather less secure than the OE ones - which very rarely fail at that point.

Nick

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