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Author Topic: Rear Shock Conversion to Original  (Read 1263 times)

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september2016

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Rear Shock Conversion to Original
« on: August 21, 2016, 10:50:42 PM »
Thanks Art for all the help you have given me with restoring my recently acquired 1971 MGB back to original condition. I have another question, which may be a little more straight forward than some of my past questions.
A previous owner of my car converted the rear shocks over to the Koni tube-type shocks. Since I know it wasn't the guy I bought the car from, I know the conversion must have been done over 20 years ago, and by the rust on the shocks and mounting plates, it looks it! Anyway, I am going to convert it back to the lever-arm type shocks. It has been quite a while since I have worked on a stock rear suspension, and since I didn't do the conversion originally, I want to make sure I get the new shocks back in as they were originally. The new shocks are on order from Moss, and I expect them any day.

Once I get the new shocks, I think they will be labeled left and right (or I will be able to tell by the part number). It looks like the new shocks will use the same mounting holes as the conversion kit does. Does the shock go on the inside of the frame rail it attaches to (like the conversion kit), or does it go on the outside? Again, I should be able to tell this, once I know left and right. Also, the shock attaches to the frame rail with 2 bolts. On the back of these bolts is a flat washer, a lock washer and a lock nut. Does the flat washer pull up directly against the frame rail, or is there some kind of backing plate through which both of the bolts go, on the opposite side of the frame rail from the shock? The reason I ask is that when I look closely at the frame rail, I can see the outline in the undercoating & road dirt, of where something had pulled up against the frame rail in the past (but is no longer there). Since the rectangular shape of this outline does not appear to be from the shock, I'm thinking they may have used some kind of backing plate on the backside of the frame rail to distribute the load of the 2 bolts coming through the frame rail. Is there anything to this, or am I just seeing things?

I've looked in all of the manuals and I can't find any reference to this kind of part, which leads me to think I may be seeing things. This is pretty hard to explain in a paragraph, so I hope I am making sense. I've seen other cases where a load bearing part is attached to a hollow square tube with more than 1 bolt, where a 'backing plate' is used to help distribute the load across the hollow tube, and away from the bolt holes. Another reason to think there may have been something used in this case.

Thanks in advance for any light you can help shed on this subject.

Jack Wheeler
West End, North Carolina  

Art

  • chfwrench
  • AMGBA Club Tech Staff
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  • MG information: '73 red B roadster
Re: Rear Shock Conversion to Original
« Reply #1 on: August 21, 2016, 10:53:35 PM »
The conversion (either way) is fairly easy. The stock lever shocks mount to the same holes and location (inside the frame) as the upper tube shock conversion mounts.  Arm inboard facing back with the flat side of the shock toward the chassis, so right and left become more obvious if not marked.  Even uses the same bolts.
 
I recently converted my car to rear tube rear shocks (the front were redone stock), which I am enjoying the ride of.  So while very familiar with them, I cannot show you a picture of my car, but see below from a catalog showing the assembly.
 
Most conversion kits reuse the stock lower plate under the leaf spring, but relocate them.  So the biggest thing to note on re-converting to stock is that the lower spring plates were reversed for the tube shocks.  You have to support the car at the body and then remove the nuts from the U-Bolts of both sides and literally exchange and turn the right and left plates so the mounting hole remains on the inside, but facing up on the same (front) side of the axle as in the photo. *
 
With you saying the conversion was done some 20+ years ago, make sure you soak the nuts and thread of the u-bolts in liquid wrench or WD-40 for a while before attempting to remove them.  I'd also plan to have on-hand (or know where to get) replacements in the event they break (Victoria British P/N 18-102, 4 pcs x $4 each, plus nylock nuts, P/N 12-363, 8pc x $0.45 each).  I know most Advance, PEP Boys or NAPA shops have some universal version that may require drilling the holes in the plates a bit larger, but they do fit and work.

Also, in ordering the new lever shocks, did you also order (or already have) the link from he shock to the axle (Victoria British P/N 5-491, 2 pcs x $18 each kit with all mounting hardware)?  

I hope that helps you.  Good luck and let me know how you make out. Safety Fast!
 
Art Isaacs
 
* There are numerous conversion kits out there.  Most reuse the stock lower bracket in some capacity, as described above, which is the most common nd what I have.  Other kits provided specialized brackets for the tube shocks that either merely went below the stock plate, leaving them in place (requiring the brackets only be removed) or eliminated the stock plate entirely for their bracket (requiring replacement stock plates to be obtained).  Make sure of what you have in place, plan the best method of doing the job and parts you will need before you start.
Art Isaacs
AMGBA Tech Staff
chfwrench@aol.com


 

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