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Technical Information (MGB 13F)

SPAX Rear Shock Absorber Kit

Last Updated - 01/31/10

British Automotive’s redesigned rear upper shock absorber mounting bracket kit is suitable for your SPAX (SPG824) telescopic shock absorber kit. While these shocks are fitted with integral bump stops, it is advisable that the OEM rubber bump stop be retained and active under full bump conditions.




Since these SPAX shock absorbers are the early style 19” open & 13” closed, we have provided you with a modified adjustable upper mounting bracket set. See P0002644

This new design features the following:

  1. A new upper shock absorber mounting pin position with a maximum offset of 3.1/4" upwards which, depending upon your vehicle's rear suspension ride height, may not require the change over of the OEM shock absorber lower link mounting plates from side to side.

  2. Multi mounting holes that allows for simple installed height adjustment increments of approximately 1".

  3. Allows for a more efficient shock absorber working angle. Various shock absorber  kits that are available have shock absorber angles of between 20 and 25 degrees, this new upper bracket, depending on the mounting holes used, will reduce this to between 5 and 8 degrees.


Since, the working angle of the shock absorber will vary with it's installed height, the installer should be aware of any shock absorber body interference with the rigid brake lines that run along the axle tubing. If there is any interference, simply bend the offending brake line to clear the shock absorber body.


NOTE: In the past, we have provided instructions requiring that the vehicle jack stands be placed, depending upon which operation is being carried out, either under the body, or either under the rear axle tubing. We have reviewed these prior instructions, and concluded that it is more convenient to have the vehicle on car ramps, or a hoist, with the wheels making contact in such a way that the full vehicle weight is exerted over the road wheels.

Remove the shock absorber links from the lower plates.

Remove shock absorbers complete with links.

Using the lower of the 4 mounting holes, install new upper mounting bracket. There is no need to install the lockwashers at this stage, simply hand tighten nuts.

(1)…. Measure the distance from the upper bracket shock absorber mounting stud to the center of the OEM shock absorber link mounting plate hole.


Compressed Length 13.0"
Extended Length 19.0"
Working Length
Ideal Fitted Length
Ideal "Bump" Travel 3.0" *
Ideal "Rebound" Travel 3.0"

(2)… Rotate the adjustable upper bracket to the ideal fitted length of 16” or as near as possible to this length as in (1) above.

(3)… Measure the distance between the bump stop pedestal and the progressive bump stop rubber. This measurement now represents the suspension travel that the rear axle goes through before actual bump stop contact is made.

Hopefully, the amount of distance in (1) would be slightly less than 3.0”. Normally, we would like to see 2.5”, therefore allowing ½” of bump stop compression. If this measurement is abnormally low, your rear ride height is probably low also.

Since, your Spax shock as a built-in bump stop, you could remove the OEM bump stop rubber. However, this is not advisable. Look at reestablishing your ride height with the fitting on new road springs, or simply have your original springs re-arched. 

(4)… Install all remaining hardware.

NOTE: For ride and comfort, your shock absorbers have been set on the softest setting.