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Shocks for a GT6. It doesn't sound as simple as I thought

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JohnW63 John Williamson
Apple Valley, CA, USA   USA
In reply to a post by we really need a picture of the rear area of your car, that will give us a what is what on that top shock mount.

The car is currently just a frame on a rotisserie, I'll see if any of my pictures might have a shot of the back end, or a quick web search shows one...



That looks like it, with the conversion kit mentioned before added to the car. Would the shocks just hook where the conversion goes ? At least I thought it would. This next picture makes me think so...





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clshore Carter Shore
Beverly Hills, FL, USA   USA
Yes, your first pic shows the conversion brackets.
Note that the brackets in the pic are not shown in the normal as-installed position.
When the body is bolted to the frame, the tops of the brackets get clamped flat and horizontal between the body and frame.
That oblong hole in the top of the brackets is where the chassis attachment bolt passes through

The second picture is a swing axle car (with a swing spring), and has nothing to do with your GT6+ rotoflex setup.

BTW, the shocks in the first pic look brand new.
Is there some reason you are seeking to replace them?

JohnW63 John Williamson
Apple Valley, CA, USA   USA
None of these shots are my car, just ones found in a quick web search. I was thinking the second shot may have been a swing axel version, but I wasn't sure if the mouting spots changed for them. Here is another chassis with rotoflex:



Do the top of the shocks not attach to the outboard holes on the end of the frame, or is that fore the body to attach ? I was thinking the body attached to the oval hole facing upward.



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clshore Carter Shore
Beverly Hills, FL, USA   USA
You are correct, on swing axle cars the shocks do attach to those brackets.
On rotoflex cars, the shocks would foul the rotoflex hardware, that is why the adaptor brackets are used,
to push the shock mount out for clearance.
If using CV axles, you may be able to use the stock chassis horn upper shock mounts.

A problem with all the pictures, it is difficult to tell if they are original GT6 rotoflex chassis, or Spitfire chassis
that have been modified for rotoflex.
The mods would be addition of the lower wishbone pivot mounts, and parking brake cable guides.

claytoncnc Avatar
claytoncnc Gold Member Marcus Clayton
Melbourne, Ivanhoe, Australia   AUS
You can clearly see in the pictures the amount of distortion in the rubber donuts when shocks are not fitted.
This lends credence to my theory that the shocks are used to limit travel, (presumably to help donut life).

It is this lack of travel that I found to be problematic.

Angle shocks with CV axle will enable the same suspension travel as swing axle, and a much more satisfactory result.

spitfire50 Avatar
spitfire50 Paul Mugford
Rochester, N.H., USA   USA
In reply to # 1502189 by claytoncnc You can clearly see in the pictures the amount of distortion in the rubber donuts when shocks are not fitted.
This lends credence to my theory that the shocks are used to limit travel, (presumably to help donut life).

It is this lack of travel that I found to be problematic.

Angle shocks with CV axle will enable the same suspension travel as swing axle, and a much more satisfactory result.
Marcus,
When your chassis was in full droop how much room was there between the axle shaft and the frame rail? In the last pic there seems to be almost none. Even a small amount there would translate into a lot of wheel travel.
Maybe someone with Rotoflex can measure and tell us.
All the best,
Paul

JohnW63 John Williamson
Apple Valley, CA, USA   USA
Here is a shot om MY chassis, but it's not the best photo.





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JohnW63 John Williamson
Apple Valley, CA, USA   USA
OK, I think I get the rotoflex clearance issue, as I look at some of these pictures. If you attached a shock to the top mount of the chassis, it would lean so far inward, that the doughnut of the rotoflex would hit it. If you run them upward to the bottom of the body, you don't have the same issue. If you use the adapter in the conversion kit, it moves the attach point a bit more outward so things clear.

Alright, here is another question. Does the shock work BETTER if it's direction of travel is more upright, like the conversion kit or mounting to the body ? I'm trying to picture how the suspension moves in it's arc of travel. The more it is laid over, the less the forces upward, when you hit a bump, would be at an angle to the shock and straight up at the leaf spring. The shock would pivot as much as be compressed. The more upright, the more it compresses rather than pivot.

Now, for the big question, to bring this all back to the beginning. Based on my chassis and axles, what shocks do you recommend for just basic driving ? If I get the conversion kit for the shock mounts, what shocks should I get. I now understand the need to make sure the travel of the shocks should be taken into account.



Home of the 1969 GT6+ MK II resurrection project
and a sorry looking 1968 GT6+ parts car trying to stay whole.

claytoncnc Avatar
claytoncnc Gold Member Marcus Clayton
Melbourne, Ivanhoe, Australia   AUS
Paul,
I think that there was at least 2cm between the axle and chassis with the rotoflex.
With the swing spring, the axle almost touches. More importantly, when the suspension was jacked without the shock attached, there was at least 5cm extra of bump available.

With the angled shock, the total extra travel is about 8cm extra, about 5 in bump and 3 in rebound.(See photos, cornering on the limit vs hard compression through the dip)

John,
It is very true that an upright shock with a 1:1 ratio to wheel movement has the potential to achieve better suspension control, than one that is angled.
Indeed, that is the basis behind the very successful "turret" conversions that were sold by Ford for rally applications in their Ford Escort.

If you were to rally a GT6, you would be well advised to install a turret system, with the top of the shocks protruding through the top of the suitably strengthened wheel wells. That would give great control, and sufficient travel to be fit for purpose. (see photo. Standard angled shock also visible)

However, I think you want a road car, where a compromise is necessary.
A set of standard Spitfire/Herald/GT6 Koni rear shocks, mounted to the chassis brackets will give you all the wheel control needed for a road car (even a very fast one), combined with sufficient wheel travel to enable a comfortable ride, and able to tackle any road surface with confidence.
I suspect you may even be able to use a softer Spitfire rear spring if you feel the need, given the extra travel available, which would enhance your traction capability, and open a path way to further handling development at the front end.

Be aware that the rotoflex uprights and wishbones are quite weighty, and real benefits can be achieved by carefully choosing a lightweight wheel/tyre combination, which will give a better overall result than a wider, but heavier tyre.

I would suggest a quality tyre not bigger than a 175/70, or a 185/60 on the lightest set of wheels you can find.
The lighter the unsprung weight, the easier it is for the shocks to control suspension travel.

There are alloy uprights and wishbones available to tackle the weight compromise, but I could not recommend them, because of some unresolved engineering questions that have to the best of my knowledge, not yet been satisfactorily addressed by the vendors or manufacturers. (but they may be OK)



Edited 2 time(s). Last edit at 2017-12-11 05:27 AM by claytoncnc.

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trrdster Avatar
trrdster Wayne Tate
Spencer, NC, USA   USA
Marcus is exactly right and that's that.

Buy the Kit from Rimmer and the right shocks are included.
We have them on a Convertible GT6 and the ride and control are fine..
Unless you have them in a box, the picture does not show you have this kit or part of it on the frame.



Wayne
1970 TR6
2000 Jaguar XK8
1949 Triumph Roadster 2000
1978 Spitfire (rust victim)
1971 GT6 (tarp covered for 12 years, rusted inside out)
1980 Spitfire (getting all the good GT6 parts, all poly suspension and Spax shocks)

JohnW63 John Williamson
Apple Valley, CA, USA   USA
Nope. No kit or shocks worth trusting on the car. We found a single pair in the boxes of stuff. Not sure if they came off the back or front.



Home of the 1969 GT6+ MK II resurrection project
and a sorry looking 1968 GT6+ parts car trying to stay whole.

dherr2 Avatar
dherr2 David Herr
Adamstown, MD, USA   USA
1972 Triumph Spitfire MkIV "Rat Rod"
I just finished installing my rear Rotoflex suspension on my Spitfire (with an R160 differential) and the original Koni Shocks that were on the Spitfire.

When mounted on the Rotoflex uprights and the Spitfire Frame chassis mounts, the suspension does need to be compressed slightly to install shocks as they do not reach completely to the total length of droop of the Rotoflex at it's lowest point unloaded. I don't think this will be a problem when the car is sitting on the ground as the suspension will likely never be fully extended, but the shocks do appear to be the limiting factor for the range or motion of the rear suspension.





Edited 1 time(s). Last edit at 2017-12-11 01:34 PM by dherr2.

claytoncnc Avatar
claytoncnc Gold Member Marcus Clayton
Melbourne, Ivanhoe, Australia   AUS
In reply to # 1502293 by dherr2 I just finished installing my rear Rotoflex suspension on my Spitfire (with an R160 differential) and the original Koni Shocks that were on the Spitfire.

When mounted on the Rotoflex uprights and the Spitfire Frame chassis mounts, the suspension does need to be compressed slightly to install shocks as they do not reach completely to the total length of droop of the Rotoflex at it's lowest point unloaded. I don't think this will be a problem when the car is sitting on the ground as the suspension will likely never be fully extended, but the shocks do appear to be the limiting factor for the range or motion of the rear suspension.


Very Slick, David.

You are right, I did not mention that the Konis have a rubber stop to cushion full extension, and a progressive bump stop at full compression.
The bump stop can be tailored for an application, but I have found the one supplied, with the shock adjusted to full soft is a good all round combination.

The leaf spring itself is self damping to some extent, due to the sliding action of the individual elements.

When thinking about suspension, it can be useful to remember that springs are to keep the vehicle off the ground, and shocks are to keep the wheels on the ground.

JohnW63 John Williamson
Apple Valley, CA, USA   USA
David,

Is that something extra you have surrounding your diff ? Things look a bit more beefy than my setup.



Home of the 1969 GT6+ MK II resurrection project
and a sorry looking 1968 GT6+ parts car trying to stay whole.

dherr2 Avatar
dherr2 David Herr
Adamstown, MD, USA   USA
1972 Triumph Spitfire MkIV "Rat Rod"
The front mount was just made from 1/4 plate, and a stock mount cut down. I had the "unobtainium" aluminum rear casting and had it machined flat and tapped for the fill and drain plugs, but made my top spring mount and front diff mount. They are overkill but probably much stronger than necessary. The other thread shows more of the details here R160 install with a picture from the front that shows the diff and mounts better.

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