Changing Lever Arm Shock Absorbers on MGB

Armstrong lever arm shocks are available in a variety of damping grades. The variations are made primarily in the valving.  The way these devices work is that there are two pistons pushing oil back and forth through an orifice.  This orifice is small, so there is resistance to flow due to the viscosity of the oil in the piston chambers.  If the size of the connecting hole was not allowed to vary, the damping would be VERY strong for sudden jolts. It would be so strongly damped that it would be rigid for all practical purposes. In order to accomodate sudden jolts, the oil is allowed to force its way past the small orifice through a larger spring-loaded valve.  There are actually two separate valves in the valve assembly.  One to control the upward jolts (bounce) and another to control the downward return of the suspension to its rest position

The drivers side on my MGB was becoming a bit bouncy and just say passed it's MOT last year so with the MOT coming up in a few months I though it would be a good idea to change the lever arm shock absorbers.



How to change the lever arm shock absorbers

MGB jacked up on chassis rails and trolley jack under spring pan1. The Car was jacked up and axle stands placed under the chassis rails. A trolley jack was placed under the spring pan to take the weight of the hub when the pin is removed.





Split pin removed and undoing nut2. The split pin is removed from the fulcrum pin and the castle nut removed. A punch was used to tap out the fulcrum pin. Care must be taken when the pin comes out so that the hub does not drop out and the full weight of the hub will be taken on the brake hose.





undoing the 4 bolts holding the shock absorbers3. The four bolts are easy to remove if you use a long reach socket and a standard ratchet. The bolts should have a split washer as well so be careful that the washers don't drop off while removing the bolts.





Hub assembly tied up 4. This is what the cross member looks like when the shock absorber is removed. It is cheaper to get an exchange shock absorber so the old ones must be handed back to the supplier. I did not what to make two trips so I removed the old ones first. As can be seen I have tied the hub with so cable to take the weight so that the brake hose does not get stressed.




New shock absorber in place5. Here is the new shock absorber in place about to be bolted in place. The bushes in vertical link were changed as well as using a new pin and nut. To get the suspension into position the trolley jack was placed under the spring pan and used to lift into position. It was necessary to undo the nut and bolt which clamp the 2 arms of the shock absorber and wedge the arms slightly apart to get over the new bushes. Once in position the pin can be tapped in and then nut tightened up. The split pin was then put in place and bent up.




Completed job 6. The completed job, while I was on I Wax oiled the inner wings as I could get access to the areas with the shock absorbers off.
With the wheels back on I did the bounce test and everything felt good so I went for a test drive. What a difference, the front of the car did not dive, pitch and roll like it used to so I thing the passenger side shock absorber was going as well.




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| Updated 09-Aug-2008 |