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Rear suspension SPAX conversion


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Had the Armstrong dampers replaced a good few years ago with the Rimmer's type 1 conversion kit (done by a TR specialist in Lincoln) but I have never really been happy with the top shock anchors fitted to the brackets bolted to the rear wheel arch.  My concerns maybe unfounded but I feel that there is strain, if that's the right word, placed on the rear body that may be the cause of an annoying squeak from the rear of simple just stressing the metal around welds etc.  I am thinking of swapping to the type 2 brackets that fit to the chassis.  Anybody done that and what was it like or are my fears unfounded due to Covid-19!!

thanks

Adrian

Screenshot 2020-06-14 at 17.08.22.png

Edited by Adrian Lawton
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28 minutes ago, Adrian Lawton said:

Had the Armstrong dampers replaced a good few years ago with the Rimmer's type 1 conversion kit (done by a TR specialist in Lincoln) but I have never really been happy with the top shock anchors fitted to the brackets bolted to the rear wheel arch.  My concerns maybe unfounded but I feel that there is strain, if that's the right word, placed on the rear body that may be the cause of an annoying squeak from the rear of simple just stressing the metal around welds etc.  I am thinking of swapping to the type 2 brackets that fit to the chassis.  Anybody done that and what was it like or are my fears unfounded due to Covid-19!!

thanks

Adrian

Screenshot 2020-06-14 at 17.08.22.png

Adrian 

About the worst one you can fit, Racetorations is the best imho.

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I'm not happy with the idea of the Type 1 conversion, transferring some suspension loading to body panels that were never intended for the task. I've had Type 2 brackets with Gaz on my '6 for about 15 years and never had a problem, even when touring southwest Ireland fully laden on some appalling road surfaces.

Nigel

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Hi Adrian

I considered converting from lever arms and dismissed type ones as a bad idea, as you say due to the stresses they exert on the bodyshell, which was never designed to cope with direct suspension stresses, but I thought type 2’s were a good idea as they bolted directly to the lever arms chassis mount points, I even bought and fitted a set.

But there is a thread on here showing the result of a chassis failure with a type 2.

https://www.tr-register.co.uk/forums/index.php?/topic/66376-rear-shock-conversion-what-not-to-use/

I suppose the failure is down to the chassis not being designed to take the kind of high vertical loads imposed by telescopic shocks rather than lever arms and or an incorrect or incompatible model of telescope being fitted.

But I don’t suppose it’s an exactly common occurrence and will probably have been contributed to by hard shocks and errr, spirited driving over rough surfaces and even chassis weakness due to age and corrosion, although all TR6 chassis are now old, so there is a a risk.

And I’m sure lots have fitted them with no issues and that they offer benefits over lever arms so each to their own.

Cheers  Keith

 

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In Roger Williams book on the TR250/6, he notes that a common failure point of the trailing arm is the shock mount cup. He even shows a photo. Let's imagine the shock cup fails whilst your are driving. With a lever shock it hangs mostly out of the way. With the Spax, the shock slowly extends to full extension then the cup pendulums about. If it happens to catch the inside rim of your aftermarket aluminum wheels it just might dig in and rotate up and jamb itself between the rim and the extension of the frame for the lever arm bump stop. Thereby bringing your rear wheel to a very sudden complete stop. This is most exciting when you are doing 65 mph. It will break free after you slam into the concrete barrier, but maybe dig in again. Ask me how I know.........

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The failure of the trailing arm at this point with telescopics is usually down to the shocker being at full compression before contacting the bump stop.  The important thing is to remove the spring and make sure that the trailing arm contacts the bump stop before the shocker is fully compressed. if not damage is going to happen.

Are the dealers still selling the type 1 brackets?

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Adrian i have the racetoration ones in a list of parts that i am getting ready to list for sale if you decide to go that route.

Roy

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The other thing with type 2 is to ensure you have the ones that attach to the main chassis rail as well as at the lever shock mount. CTM used to make this type.

But also agree you need to shocks to be matched with the setup so the original bump stop on the trailing arm is in use.

Tim

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17 hours ago, Andy Moltu said:

 

Are the dealers still selling the type 1 brackets?

Unfortunately yes still available.

Stuart.

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On 6/15/2020 at 12:20 AM, Keith66 said:

Hi Adrian

I considered converting from lever arms and dismissed type ones as a bad idea, as you say due to the stresses they exert on the bodyshell, which was never designed to cope with direct suspension stresses, but I thought type 2’s were a good idea as they bolted directly to the lever arms chassis mount points, I even bought and fitted a set.

But there is a thread on here showing the result of a chassis failure with a type 2.

https://www.tr-register.co.uk/forums/index.php?/topic/66376-rear-shock-conversion-what-not-to-use/

I suppose the failure is down to the chassis not being designed to take the kind of high vertical loads imposed by telescopic shocks rather than lever arms and or an incorrect or incompatible model of telescope being fitted.

But I don’t suppose it’s an exactly common occurrence and will probably have been contributed to by hard shocks and errr, spirited driving over rough surfaces and even chassis weakness due to age and corrosion, although all TR6 chassis are now old, so there is a a risk.

And I’m sure lots have fitted them with no issues and that they offer benefits over lever arms so each to their own.

Cheers  Keith

 

I fitted a CTM type 2 over 20 years ago but it has another fixing point to the rubber buffer point. No problems so far!

Bruce.

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Hi Bruce

And i think the vast majority like you won't have any problems at all, esp if the appropriate shock unit is fitted.

But all our cars are old and they fail for many many reasons. Modifying from std spec is one, not modifying is another.

After all i doubt the expected design life expectancy of a not hugely expensive 1970's car was ever going to be 50 years.

They why we kepp having to mess with them.

And to be honest restoring and keeping them going is half the point.

Cheers  Keith

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1 hour ago, Keith66 said:

Hi Bruce

And i think the vast majority like you won't have any problems at all, esp if the appropriate shock unit is fitted.

But all our cars are old and they fail for many many reasons. Modifying from std spec is one, not modifying is another.

After all i doubt the expected design life expectancy of a not hugely expensive 1970's car was ever going to be 50 years.

They why we kepp having to mess with them.

And to be honest restoring and keeping them going is half the point.

Cheers  Keith

Did CTM know something about the type 2 that others do not and that is why they added the extra mounting point ? I used the Spax gas type they lasted over 20 years now replaced with their last type  which I have to say gives a better ride even set on the soft side.

Bruce.

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TR Bitz brackets also have the extra mounting point. I first fitted the TR Bitz brackets along with Spax back in 1997, took them off for a year in 2015 and refitted HD lever arms thinking I could get back to the nose in the air and TR6 squat that I thought I was missing. I hated it and the lever arms which crashed over every pothole so it has been back to the TR Bitz brackets and Spax ever since and I have to say the ride is faultless.

cheers

Derek 

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Hi Adrian,

As always, many view and opinions here.

TR Shop do a Type 2A, heavy duty telescopic rear damper bracket for the TR4A-6.  Choose carefully, as this is typically an area that can receive quite a lot of stress, so you need something fairly substantial. Note: these Type 2A dampers are different to those of MOSS, or mentioned above.  These brackets also pick up the bump stop on the chassis, too. TR Shop will also sell you the appropriate Koni rear dampers, so essentially, complete kit. - £315

 

I have also tried the Racetorations damper brackets - nothing wrong with them, and lightweight.  I would say they are not as substantial as the TR Shop ones IMHO, but will work and give trouble free miles, as they did for me, on track and on the continent.  That was with Spax dampers at the time, again, no complaints with Spax, and easier to adjust damping with them in situ, as opposed to removing like you do with Koni.

 

 

Good luck.

 

Cheers.

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Out of interest has any tried the coil over type, with the damper mounted to the trailing arm? Our group leader sent a link to an american company producing new chassis called Ratco. On their website they also had the tube conversion & coil over types.

Alan 

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8 hours ago, astontr6 said:

Did CTM know something about the type 2 that others do not and that is why they added the extra mounting point ? I used the Spax gas type they lasted over 20 years now replaced with their last type  which I have to say gives a better ride even set on the soft side.

Bruce.

Bruce

To be honest better chance than average that maybe they did, afterall they build new and repair the whole range of TR chassis so i'm sure they've seen pretty much most of the likely problems and would design mods with that in mind.

Alan, now I'm def no chassis or mechanical engineer but my feeling would be that i wouldn't want to put any more forces through the lever arm mounting on the trailing arm. A coilover with that as a bottom mount just seems like it could be too much to me and I'm sure i've read somewhere this is a known failure point. But someone with more knowledge than I maybe able to comment more knowledgably than I can.

Cheers   Keith

 

 

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17 hours ago, super6al said:

Out of interest has any tried the coil over type, with the damper mounted to the trailing arm? Our group leader sent a link to an american company producing new chassis called Ratco. On their website they also had the tube conversion & coil over types.

Alan 

I believe that is a set-up that Revington TR sell.

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1 hour ago, Andy Moltu said:

The coil overs put a lot of load on the top of the chassis mount as quite thin metal in an area that has seen a few split in this area.

This previously badly repaired split wasnt even on one with a coilover setup so be aware that adding additional loads isnt going to help.

Stuart.

 

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