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72 gt6 rear suspension question???

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Hey guys.. 

I have a 72 triumph gt6. I was wondering if anyone has added lower a arms to the OEM rear uprights? Want to add adjustable ones, weld the perch to the frame, etc.. is there any way to add them to the upright I have??? 

There a long story with the rear of this car. But the end is that I have a swing spring out of a 72 spit setup. Spring was weak so I swapped it out for the solid roto spring I had. 

So now I'm thinking i want to add lower arms to help with some positive camber issues. I'm going g to add a lowering block aswell. But want to get the wheel end to hold. It works well just a bit squarely in a corner also when high rev shift. 

Any info will be appreciated!!! 

I need more negative camber in the rear.  Etc.. 

Pic of the upright and the car.. :)

Thanks

Cheers.

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You can't add lower arms to the swing axle suspension because the driveshaft acts as the lower arm already, with the spring being the top link.  A third link will just lock everything solid.

What you are describing as your wish is the rotoflex system used on the GT6+ (mk2 ) and early Mk3.  As a '72 your car would have had that from the factory - as I guess you know.....

With the swing axle the only way to adjust camber is with ride height, so fitting a lowering block will help.  The swing spring definitely helps the handling "on the limit" and makes it less likely to try to kill you but they are fairly notorious for going soft and being too low.  Worth noting that if the spring isn't too far gone, replacing the nylon button that go between the leaves (and quite often wear down and fall out altogether), this can be enough to make the spring acceptable again.

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Thanks. Good to know. Ya it did have one but p.o did some stuff that shouldn't have been done. Unfortunately, but that's what I was dealt with. 

I'm going to get a lowering block, I will prob get a new swing spring for gt6. The one on the car was a spitfire one. 

I think it will work with those. As well I was thinking about the vette air shocks?? Or maybe a coil over shock??

Front wise?? A better shock? Stiffer spring?? 

I want to get it to some sort of auto cross setup. Stiff. Less squarely!! 

With a block etc.. I'll need to flare the fenders with the 205/40/17 frt and 205/45/17 rear the frts hit on a weird road like a parking lot lean etc. Rears dont right now. But lowered it will. 

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You won'tlike this, but 40 profile tyres are just too "thin" to allow good handling. With a rotoflex rear I would hesitate to use anything less than 60 profile, with a swing-spring they would be marginal. 

Reason is you get a lot of camber change, and a wide/low profile tyre means you will just run on the edge of have to run such low pressures the tyre will deform, neither good news. 

For autocross, get a set of 175/70 13 tyres, it will drive better and times will be improved. 

As to springs, a set of 400lb plus fronts, you want the thin front ARB with your current sprint to improve turn-in and reduce understeer. But if you fit a swingspring then the std thicker matching ARB is best. As to shocks, not sure what you have available. The std black cheap shocks are not terribly good when brand new. But I very much like my Koni's

Afraid I have no experience of air shocks or coil-overs. 

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Agree with Clive on the wheels/tyres and for the same reasons. You need the taller sidewall to allow enough flex to get a decent tread foot print on the road.

Given the auto X requirement I would suggest that you do want a swing spring to tame “tuck-under”. Either a new GT6 one or your old Spitty one with some assistance. I have seen people do this with  airshocks or with low-rate coil-overs (adjustable spring seats) but no personal experience.

I suppose the other option is to stick with the fixed spring, use a lowering block to drop it enough to give 1 - 2 deg negative camber and fit a camber compensator. I would think a swing spring would give more traction out of tight turns but I’m guessing.

Fronts, agree with Clive, but to add that once you get beyond about 350lbs you will have to use spacers on fixed perch dampers, so adjustable ones are an advantage. Avoid AVO. You may be able to adapt locally available coil-overs.

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All good advice above, although 400lbs/inch is a minimum, but see how you get on with them.   Coil springs easy to chnage and not that costly!   Larger wheels have been tried in competition and do not work!    TRiumph suspension has too much camber change, as said above, unlike moderns with trailing and multipoint suspensions.

Do not forget the front antiroll bar!    11/16 then 7/8" from the factory, for competition a 1" one is a good idea.   1500 Spitfire had a 7/8th for goodness sake, and you have that great lump of an engine over it.

John

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Thanks!!! 

Ya I have a spit swing spring setup in the car. I put the solid spring in place from a roto as the swing spring was not able to hold the weight. Also had a bit of a lean to the right. The solid one lifted the car up and is more stiff. But with that I got positive camber issues now with it. 

Other then that the car works great with the 17s. No issues. Front I'd like to stiffen up, so maybe heavier springs and koni shocks. Koni shocks out back. 

But still have that camber issue. I measured the springs. The swing eye to eye was the same distance as the solid one. So ultimately I should have the same negative camber as the swing. But not the case. I think I'll get a new gt6 swing spring, it will be stiffer then the spit one. Maybe? 

Maybe the swing spring is a bit shorter eye to eye o  the flex points?? As to the solid one I put in. Both worked very well, just one had a lean and was a bit weak. Other gives me positive camber. Lol...

Other then that the car works great!!! With the 17s and all. Drives and runs great!! 

Wheres a good place to get springs and shocks?? I'm in canada so would rather stay in canada if at all possible?? 

Cheers.

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All the standard new leaf springs seem to have too much arch, from what I've seen, read and purchased. So if you buy a new one, you'll most likely still want a lowering block. Maybe the GT6 won't be as bad as my Spitfire but the 3/4 inch lowering block isn't enough. I can't really be bothered to fit longer studs and another 1/2" block but do need to address the positive camber.

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29 minutes ago, PeteStupps said:

All the standard new leaf springs seem to have too much arch, from what I've seen, read and purchased. So if you buy a new one, you'll most likely still want a lowering block. Maybe the GT6 won't be as bad as my Spitfire but the 3/4 inch lowering block isn't enough. I can't really be bothered to fit longer studs and another 1/2" block but do need to address the positive camber.

Need more sacks of sand in the boot.... that’ll settle it!

Canada..... I’m afraid I know nothing about Triumph parts suppliers......

I have the opposite problem ..... my GT6 (Roto) is too low at the back... wearing away the exhaust bracket on the road.....

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Ya. I've been reading that most have issues with newer springs and a much higher arch to them. 

I think I'll see about getting a helper spring maybe on the spit swing spring I have, that was originally with the rear setup of this section I put in, from a spit.

Add some better rear shocks and a block. I will have to either cut and flare the fenders, or go back to the 13s and just get new tires. We will see about all that once I figure out the suspension.

I'd love to grab a set of good used g.a.s shocks with some springs for the frt. Gas shocks for the rear. 

I've done all new bushings, brakes, lines, masters, rear oem shocks, ball joints. Etc... lots of work!!! That's just the tip of the ice burg. Lol.

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Ok. Been reading...

I've read that some race setups either drill and move the rear spring bolt down the vertical link. Or others have bought a kit and welded in adjustable hyhm joints to the ends. 

So??? In doing this does it lower the suspension/car causing more negative camber??. Seems reading on it it does..

I've seen pics of guys moving the spring down about an inch give or take, and said it lowers it and adds negative camber in doing so. Plus they add a 1/2 block under the diff to help. 

Anyone know any info on this?????

I've tried to find out more. But I'm not the best at going through the net. Lol...

It's an interesting add to the rear, easy enough for me to do if this is an option. Which it looks like it is. I just need more info on it and opinions???

Thanks

Cheers.

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If re-drilling the uprights you need to be aware of brake pipes etc, over the full range of suspension. It is a simple option, and does exactly the same as a lowering block.

You will need to weld washers to the upright to reinforce the new holes, but simple enough.  Not many people go this route, I guess as a block is the easier option. And as mentioned, possible brake pipe issues.

Whatever you do, don't forget to re-set the rear tacking!

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Thanks.

I am going to do the block. But was wondering about this option. As it does look easy enough to do. I've read people have done both. Block and vertical mod.

They said it works well for them. I dont want to lower the car to much. So with a 1/2 or 3/4 block that about 3/4 drop. With moving the spring down 1 inch on the vertical that 1 3/4 drop in the rear. I think that's to much. I maybe wrong but almost a 2 inch drop just in the rear. ??

But would the vertical drop give me more negative camber???? That's what I need, reason for the block and possible this??? 

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Hi,

Well that's me fucked then.
Adjustable AVO's on the front. Spherical lower bush still good after nearly ten years. Early poly's were shite. 15".
Rear 215 wide & 16" No uneven wear that I can see. Plenty of space for 225 & maybe 235.
Front springs. I've tried a few. Too many to mention. I am removing the 330# as way to hard for me. Fitting 220#.
It's just a car I enjoy.
Cheers,
Iain. 
PS. Skinny ARB & solid drop-links.

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8 hours ago, spitfire6 said:

Hi,

Well that's me fucked then.
Adjustable AVO's on the front. Spherical lower bush still good after nearly ten years. Early poly's were shite. 15".
Rear 215 wide & 16" No uneven wear that I can see. Plenty of space for 225 & maybe 235.
Front springs. I've tried a few. Too many to mention. I am removing the 330# as way to hard for me. Fitting 220#.
It's just a car I enjoy.
Cheers,
Iain. 
PS. Skinny ARB & solid drop-links.

Iain, the early AVO's with the sphericals lasted OK I think, but they changed to poly but kept the narrow eye, causing all the bush failures.

As to wheels, yours has rotoflex, so you don't see the massive camber changes. I tried MGF wheels on my first zetec spit, 205/50 15, and it ran on the inside edges, the outsides only just made contact with the road. Made for "entertaining" handling on an autosolo, so were ditched in favour of 13" wheels which worked much better. 

Interesting about your 330lb springs. I expect you have tried various damper settings already. But the 480lb on my spit are indeed firm, yet not uncomfortable. Even the wife, and daughters have no complaints. 

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On 8/3/2020 at 4:43 AM, zetecspit said:

Interesting about your 330lb springs. I expect you have tried various damper settings already. But the 480lb on my spit are indeed firm, yet not uncomfortable. Even the wife, and daughters have no complaints. 

It is interesting - I'm amazed at how stiff some people have their front ends (I've only just gone from standard to 200lb in my spit). But I presume the fact you're basically sat on the rear wheel arch means a rock hard front end doesn't translate into harsh ride. 

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