Jump to content
Forum software update now live Read more... ×
foster461

Rear shock conversion, what not to use

Recommended Posts

If you have this style of shock conversion bracket I would suggest that you remove them, throw them in the bin and refit some proper lever shocks.

 

20180614_083544-X3.jpg

Share this post


Link to post
Share on other sites

Hi foster 461 ~

 

Who the hell supplied this load of dangerous rubbish? You need to name and shame these Cowboys!

 

Tom.

Share this post


Link to post
Share on other sites

I hope that wasnt fitted to your car Stan.Judging by the angle that it works its not that surprising that it has torn out but I wonder what the trailing arm looks like too.

Stuart.

Share this post


Link to post
Share on other sites

Yep, that is off my TR6. These brackets have been on the car for a long time, 10 years or more. I knew they were potentially dangerous and I have a new pair of lever shocks in the basement ready to install but I never got around to it as usual. Frame looks good other than the broken welds from where the bracket tore off. Even though the shock mount is a beefy bit of steel plate it is welded to the thin sheet metal bracket.

 

20180614_084051-X3.jpg

 

This happened last weekend on a club drive. Part of the route was on a very potholed bit of road and that is when the bracket let go. Car drives surprisingly well minus the right rear shock.

 

I'm hoping that I can clean things up and re-attach the bracket. We will see how that goes..

 

Stan

Share this post


Link to post
Share on other sites

Hmm I think if your going to re-attach that section I would be inserting some extra plating across the join to avoid it tearing to the side of the weld. I know if it came in here I would be fitting a complete new bridge from CTM part number CTM 1219 here http://www.ctmengineering.co.uk/tr6.htm

Stuart.

Share this post


Link to post
Share on other sites

Hi foster 461 ~

 

Who the hell supplied this load of dangerous rubbish? You need to name and shame these Cowboys!

 

Tom.

 

You can buy this style of bracket from several suppliers Tom including Moss in the USA. https://mossmotors.com/triumph-tr6-250/suspension-steering/rear-suspension/rear-shock-conversion-bracket-set

 

Mine is not the only catastrophic failure, there are other examples of these brackets causing the shock mount from tearing away from the bridge.

 

Stan

Share this post


Link to post
Share on other sites

Hmm I think if your going to re-attach that section I would be inserting some extra plating across the join to avoid it tearing to the side of the weld. I know if it came in here I would be fitting a complete new bridge from CTM part number CTM 1219 here http://www.ctmengineering.co.uk/tr6.htm

Stuart.

 

Thanks Stuart. Plan A is to go for a quick repair to keep the car roadworthy for this summer. If that doesnt go well I will have to replace the whole of the rear bridge sooner rather than over the winter. It is not that expensive, I just have to verify that the part sold by TRF is complete with the diff and shock mounts or if they need to be purchased, aligned and attached separately.

 

 

 

Stan

Share this post


Link to post
Share on other sites

I have a similar ali version from R******ions that started to tear the bridge. The top of the bracket could move backwards and forwards so putting leverage on the bridge below the two bolt-holes. I cured it by bolting the top of the bracket tight against the inner wing. A proper bracket design would have a strut to prevent fore-aft motion.

Peter

Share this post


Link to post
Share on other sites

Hi Stan,

 

Go with the CTM version as suggested by Stuart.. I've had them fitted for 10+ years. When you look at them they are clearly designed and built by someone who knows what he is doing. Not surprising really Colin's been around TR racing and restoration for many years.

 

Rich

Share this post


Link to post
Share on other sites

If you route through the luggage compartment

and use shocks of proper length nothing will fail.

My set is a modified Rimmer type 3

 

The riding comfort gets better because bigger valves in Bilstein shocks

open on bumps and keep the heavy forces away from the mounting points.

 

All the arms routing outside are a quick and dirty solution in my view.

If you do a conversion do it right and stiffen the whole rear!

 

I have mine for more than 20 years in use and can report better riding comfort

better roadholding and no damage anywhere!

 

post-13092-0-36593400-1529052162_thumb.jpg

Share this post


Link to post
Share on other sites

If you route through the luggage compartment

and use shocks of proper length nothing will fail.

My set is a modified Rimmer type 3

 

The riding comfort gets better because bigger valves in Bilstein shocks

open on bumps and keep the heavy forces away from the mounting points.

 

All the arms routing outside are a quick and dirty solution in my view.

If you do a conversion do it right and stiffen the whole rear!

 

I have mine for more than 20 years in use and can report better riding comfort

better roadholding and no damage anywhere!

 

attachicon.gifBilstein rear.jpg

Very positive experience also on my side w/ the TR6, since the '90 w/ the RB Type 3

Regards

Edited by Marc R

Share this post


Link to post
Share on other sites

Hi Stan,

 

Go with the CTM version as suggested by Stuart.. I've had them fitted for 10+ years. When you look at them they are clearly designed and built by someone who knows what he is doing. Not surprising really Colin's been around TR racing and restoration for many years.

 

Rich

My CTM reference was for the whole shock absorber bridge not for conversion brackets, The three point mounts are a better idea but my personal preference is still for lever arms

Stuart.

Share this post


Link to post
Share on other sites

If you route through the luggage compartment

and use shocks of proper length nothing will fail.

My set is a modified Rimmer type 3

 

The riding comfort gets better because bigger valves in Bilstein shocks

open on bumps and keep the heavy forces away from the mounting points.

 

All the arms routing outside are a quick and dirty solution in my view.

If you do a conversion do it right and stiffen the whole rear!

 

I have mine for more than 20 years in use and can report better riding comfort

better roadholding and no damage anywhere!

 

Bilstein rear.jpg

Do you have a part number for those dampers please?

Share this post


Link to post
Share on other sites

Hi Pete, they are custom made from the

Bilstein Sports Department.

They are the large 50mm tube type for bigger valves inside.

As you can see the rear mounting point is also custom made.

It has a dome 5cm higher.

 

The Bilstein are a bit longer for same working length due to

the gas area and the piston to keep the oil inside pressurized.

 

Mine are 5cm longer than the Spax are what the kit was designed for.

 

This is the original with the lower mounting point for the SPAX

 

post-13092-0-70856100-1529078606_thumb.jpg

Edited by TriumphV8

Share this post


Link to post
Share on other sites

My CTM reference was for the whole shock absorber bridge not for conversion brackets, The three point mounts are a better idea but my personal preference is still for lever arms

Stuart.

For the same reasons, I sourced 2 pairs of original lever arms Amstrong, a 1st one std and a 2nd one reinforced.

 

Regards

Share this post


Link to post
Share on other sites

Hi All

 

I'm kind of with Marc R on this in a couple of ways.

 

I went down the route of getting similar rear damper conversions and they are fitted to my car as we speak.

 

I'm in no danger in the short term as my 72 Pi off the road undergoing a resto.

 

They were aquired from a well known supplier in a large city in the south east and as they attached to the original chassis lever arm mounting points rather than the bodywork seemed a good idea, given all i had read about lever arms being poor old tech the message very much was move forward and get telescopics, yeah.

 

But for a different reasons, more compliance and a smoother ride on the levers and this is what it had in 1972 i've also aquired a pair original Armstrong lever arms which i'll be refurbing and fitting, err soon.

 

But it also highlights another point most graphically.

 

Start making mods, Esp adding modern kit, with out really going into it on a engineering level (and I don't have a mechanical engineering degree and am not a mechanical design engineer) and you can be taking some big risks.

 

And thats for a couple of reasons,

 

Firstly the car was not designed with this mod in mind, so the way a lever arm transfers the forces to the chassis is completly different to the way a telescopic transfers the forces and the chassis (clearly in this case) was not up to the job.

 

Secondly engineering knowledge has progressed massivly in the last 50 years since the TR6 was designed and our cars simply may not be up to using alot of these new developments without exposing weaknesses or problems in other areas that the original designers didn't give a thought to or weren't even aware of.

 

So its very much caveat emptor and simply don't take everything at face value.

 

You might be fitting a seemingly sensible well designed item but some of the unforseen or unexpected consequences might be slightly surprising, as in this case.

 

I really never though my design of telescopic conversion kit could rip the chassis apart.

 

Cheers

 

Keith

Share this post


Link to post
Share on other sites

Any modification usually results in it finding the next weakest mechanical or structural link in the chain from my expience until you reach the end at which point the system of parts can deal with the altered loads. Triumph designed the system with the loads worked around the kit of parts.

 

Bit like upping engine power without improving the suspension and brakes first. they will fail.

Share this post


Link to post
Share on other sites

Well,

The fatigue cracks in the chassis and later improvements of the block casting only show that the original designers also missed certain weak areas here and there.

Even with modern cars and advanced design software, weak designs still exist.

A good example are the VW distribution chain and piston debacles.

 

Sharing experience on this forum of what works (and what does not) can avoid pitfalls.

Waldi

Share this post


Link to post
Share on other sites

Hi All.

 

I have just fitted the very same brackets as the offending item in this post, but the reason I purchased them was that they were supplied complete with KYB shocks and were suitable for the addition of a brace (there was no way I was going to use them without one) down to the redundant lower bump stop mount. It was a relatively straight forward exercise as I've posted before, but after reading this topic I think I'll go one step further and add a bracket back onto the bodywork as per the pic. I was previously of the view that brackets connected to the bodywork weren't a well 'engineered' option and still do, but it may well be the solution to the problem at hand.

 

post-14246-0-01960800-1529191534_thumb.jpg

 

However, there are a couple of observations I'd like to make (possibly relevant to this case). Firstly, and as stated by others, this style of bracket on its own will act as a lever arm on the original Armstrong mounts and over time the resultant flexing will cause stress, fatigue and eventually failure. A brace is essential as noted in the following article. Secondly, the kit must be set up so that when the trailing arm bumpstop is fully compressed tere is still some stroke still left in the shock. If not, the bracket will take a hammering at full compression inevitably leading to total failure. In my opinion (and that's all it is), if the Armstrong lever action dampers were allowed to bottom out in the same way (say if the bumpstops were removed, although not sure that would be the case though), then I'm quite certain that the brackets they are mounted to would break in time in exactly the same way.

 

"Don --- I'm not an advocate of the tube shock kits offered, but I did convert when my second pair of lever shocks gave out the second time (after about 250,000 miles). Thought this would be a good time to see if the 'tubes' were what was claimed. I do believe the reason the frame cracks at the attachment point is because, unless some things are altered, the shock will bottom out when fully compressed. With the road spring removed, it's easy to physically see what hits first. We want the conical bump stop to absorb this full upward movement, not the shock. If it's the shock, it will try pulling loose where attached to the frame.

First, the new, tall, bump rubbers are in order. To give even sooner contact, a 1/8 inch spacer under the bumper 'washer' was added.
Next was moving the shock's rubber donuts around to give more stroke to the upward process. Now the bump stop makes contact at least 1/4 inch before the shock it fully compressed.

 

Can't speak for the path that the trailing arm takes and any negative effect on the shock motion. I'll I can say is that I've had my KYB Silvers in place for maybe 12 years and there's no sign of any frame cracking, and believe me I checked many times after hearing the stories! "

Regards

Gavin

 

 

Share this post


Link to post
Share on other sites

Hi Gavin,

Adding an additional bracket/connection as you indicate is a good idea (to me).

It will reduce any movenents of the top of the bracket, which cause additional stresses on the original bracket.

Use decent bolts for the additional bracket, 3/8 and a firm plate on the inside of the car.

Regards,

Waldi

Share this post


Link to post
Share on other sites

Hi all

 

Reference my previous recommendation re: CTM conversion brackets, I forgot to mention that I also fitted a new/rebuilt CTM chassis, so no 45 year old original chassis stress points to worry about! :rolleyes:

 

Rich

Share this post


Link to post
Share on other sites

I re-attached the ripped off bracket today and reinforced the joints. That should hold it for the summer and I will replace the crossmember after the summer season. I think replacing the crossmember will be easier than re-attaching the bit that was ripped off since all the welding will be where the crossmember meets the chassis and the access is good.

 

I also installed the new lever arm shocks that have been sitting in the basement for the last 10+ years.

 

The left hand side was fine, no sign of anything coming adrift. I imagine that if you have a TR6 with a perfectly welded crossmember it may hold up just fine but if there is one weak weld, the leverage on these cheap brackets will find and exploit it.

Share this post


Link to post
Share on other sites

Also for you lot driving on the wrong side of the road the right hand side bracket takes all the gutter side potholes/drain covers etc.

Stuart.

Share this post


Link to post
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now

×