[TR] TR6 rear shock mount break

[Tim Gaines]

I've been doing a lot of web surfing for videos and info on my problem 
of the cracked rear cross member caused by replacing the original lever 
shocks with a tube shock mount. I now see that the problem has been 
widely discussed, probably here on Triumphs as well as on various 
forums. I wish I had paid attention earlier. Inasmuch as both shock 
setups bolt to the same mounting plate on the cross member, I had 
difficulty understanding why the tube setup should do so much damage 
compared to the stock lever shocks. Well, I just found an old thread 
(Ken D, 2018) where one contributer (Walt P) explained a lot with 
reference to Ken D's photo.

"Ken was concerned about the angle of his lever shock link and wondered 
if something was wrong. The consensus was that it was probably normal 
unless the rear spring wasn't seated properly. Walt P offered this great 
explanation.

Notice the angles in the two lever-shock link-arm photos.
Now, imagine that a standard Fixed Mounting of a shock absorber/damper 
was used (between the frame & the TA) to replace the lever-shock & 
link-arm.
As the Trailing Arm pivoted through its full movement, would the Fixed 
Mounted Shock Absorber be able to move- as the Link-Arm did?
Or, would the Fixed Shock Absorber remain in place and rip apart the 
relatively fragile frame that it was mounted on?
Because that is exactly what happens when a Fixed Shock Absorber is used 
to replace the Lever-Shock.

Something to consider if the idea of a rear shock appeals to you.

Some venders DO sell a replacement shock system that pivots with the TA 
movement,
but Others do not.
Be aware of what you are seeing in the their ads."

Well, I had already installed the tube shocks long before this 
explanation came out, so I won't kick myself in the ass too hard. Some 
of you may be interested in another aspect of the "fix" for the cracking 
problem, namely putting lever shocks back on a new or repaired cross 
member. I found a great "Elin Yakov's Rusty Beauties" Youtube video that 
showed how to service the original lever shocks.
https://www.youtube.com/watch?v=AxrBaaLEHpw
I got out my own old pair, opened them up for the first time, and did 
what the video showed. It turned out that Yakov's shocks were pretty 
clean and in good shape. Mine looked bad inside, but I plowed ahead. 
First, I noticed that each of mine had a grease zerk installed in the 
cover, but Yakov's had a bolt (as do the new ones I have seen at Moss). 
Even worse, mine had a load of grease in them and not much else. Who 
knows who put those on! So maybe that is why my ride was so bad, and 
that in turn was why I replaced them with the tubes. I wish I had looked 
inside, but the idea of the tube conversion looked so inviting back 
then. I soaked the units in degreaser overnight, after drying filled the 
first one with motorcycle fork oil as per the video, and it now offers 
great resistance to movement, just as Yakov's did. In a few minutes I 
head to the garage to do the other one. I think I am going to have two 
good lever shocks. Now I need to see if my cross member can be removed 
without too much trouble (the left side is actually unattached to the 
rail now) and repaired with some welded braces.

Tim

------ Original Message ------
>From "Tim Gaines" <mtgaines at presby.edu>
To "Triumphs" <triumphs at autox.team.net>
Date 10/8/2025 4:37:00 PM
Subject TR6 rear shock mount break

>I have been hearing a slapping sound either under or behind me in the 
>1974 TR6 when I encounter even slightly rough pavement, so today I 
>decided to sort it out. I thought I had found the problem quickly when 
>I saw that the spare tire securing hook bolt had come loose, but no 
>such luck. When I finally gave up on simple fixes and jacked up the 
>left rear end and removed the tire, I saw that the cross member had 
>cracked near where the after market shock mount adaptor bolts on. I did 
>a quick check with the Moss parts catalog and that cross member is not 
>available with them. So, I'm wondering if this shock mount replacement 
>for the old lever shock (I installed a couple of decades ago) was a bad 
>idea and put too much pressure on that frame member. It occurs to me 
>that there may be some folks out there who have gone through this and 
>can tell me just how a fix should be attempted.
>
>That crack shown in the photo seems to be only on the back side of the 
>cross member. I have learned some welding skills in the last few years, 
>and I have a mig welder, but I have never done anything under a car. I 
>really don't like the proximity of the gas tank either. I am thinking 
>that my local pro welder would be the guy to call on, but is this 
>really something that can be fixed that way?
>
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