Mounting rear telescopic shock absorbers

 In Brakes, Wheels, Suspension And Steering, MGA-MGB, Midget

To get the right position of the bottom mount hole, measure the clearance between the bump stop and where it hits the body at full bounce. Add 1/2″ to allow for bump stop compression. (Some people use more, but 1/2″ has seemed enough even on rough forest roads in my rally MGB and has never been a problem in the Widget)

Mount the shock at the top then fully compress it. Mark off from the bottom eye downwards the (clearance + 1/2″) figure. That’s where the hole in the bottom bracket needs to be if you want to avoid the shock bottoming out before the bump stop is full contacted.

It’s surprising just how many commercially available kits don’t achieve this and have the shock bottom out first.

An example:

On a Midget, the distance between the upper check strap mount (a convenient place to mount telescopic shocks) to existing base plate hole is 325mm. (This with the base plate pointing downwards)

Clearance, bump stop to body is 90mm when the car is sitting normally.

Proposed shock has fully closed length of 267mm eye to eye.

So when the bump stop is just contacting the bodywork, the distance between the upper hole and the base plate hole will be 325-90 = 235mm. This is 32mm less than the 267mm closed length of the shock, so the shock will bottom out 32mm before the bump stop contacts the bodywork.

To avoid this, the plate hole will have to be lowered by 32mm+12mm = 44mm (allowing 12mm bump stop compression). To do this, make a plate with a longer vertical leg to achieve our mounting hole in the right place.

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Paul Walbran Motors