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Rear shock conversion, what not to use


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#1 foster461

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Posted 14 June 2018 - 01:13 PM

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


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#2 Fireman049

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Posted 14 June 2018 - 01:22 PM

Hi foster 461 ~

 

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

 

Tom.


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#3 stuart

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Posted 14 June 2018 - 01:40 PM

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.


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#4 foster461

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Posted 14 June 2018 - 02:16 PM

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


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#5 stuart

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Posted 14 June 2018 - 03:30 PM

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.ctmengine...g.co.uk/tr6.htm

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#6 foster461

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Posted 14 June 2018 - 05:56 PM

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.c...ion-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


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#7 foster461

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Posted 14 June 2018 - 06:00 PM

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.ctmengine...g.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


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#8 poolboy

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Posted 14 June 2018 - 07:03 PM

When something similar happened to my car, the PO (TR6BILL) went this route.

https://www.sites.go...ial-crossmember


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#9 Peter Cobbold

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Posted 14 June 2018 - 08:07 PM

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


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#10 foster461

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Posted 14 June 2018 - 08:42 PM

When something similar happened to my car, the PO (TR6BILL) went this route.

https://www.sites.go...ial-crossmember

 

Excellent, thanks for the link.

 

Stan


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#11 rvwp

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Posted 15 June 2018 - 07:02 AM

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


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#12 TriumphV8

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Posted 15 June 2018 - 08:44 AM

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!

 

Attached File  Bilstein rear.jpg   75.73KB   6 downloads


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Cheers

Andreas


#13 Marc R

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Posted 15 June 2018 - 09:53 AM

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, 15 June 2018 - 10:12 AM.

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Marc R

 

DSC_1843 bis.jpg
 

 


#14 stuart

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Posted 15 June 2018 - 11:27 AM

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.


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#15 peejay4A

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Posted 15 June 2018 - 12:43 PM

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?
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Pete 

#16 TriumphV8

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Posted 15 June 2018 - 04:01 PM

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

 

Attached File  SPAX01.jpg   80.4KB   1 downloads


Edited by TriumphV8, 15 June 2018 - 04:04 PM.

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Cheers

Andreas


#17 Marc R

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Posted 15 June 2018 - 04:04 PM

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
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Marc R

 

DSC_1843 bis.jpg
 

 


#18 Keith66

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Posted 16 June 2018 - 10:14 AM

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


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#19 PodOne

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Posted 16 June 2018 - 11:22 AM

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.


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#20 Waldi

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Posted 16 June 2018 - 11:54 AM

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
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