Dubonnet - Knee action Suspension and Repairs
This design of this type of independent suspension was developed by Andre Dubonnet of the aperitif firm.
The American GM corporation purchased the invention from Dubonnet in the early 30s.
Gm further developed the design over a three year period thereafter being the main car manufacturer who used them for a short period.
This in turn had an influence on the Vauxhall car company of UK (GM purchased Vauxhall in 1925) who further developed and fitted the units to their cars from the 30s to 50s.
There are quite a few models of this suspension type (with and without torsion bars), mainly being within Vauxhall cars, but the idea was also applied to BMW, Alfa Romeo and Fiat to name but a few.
The main problems encounterd with this type of suspension - the basics:
The oil seals were the main fault.
Leaking after a very short period due to their construction and material of that day.
The general recommendation for oil checks was every 1000 miles, this rarely happened.
Subsequently the loss of oil had a detrimental affect on the needle bearings and shock absorber assemblies.
Apart from the oil puddle on the floor.
First indication on some designs of low oil was shock absorbers not working (soft ride).
Others indicated a lot of steering play plus shock absorbers not working.
Some owners thought because the oil leak had reduced or stopped (due to low oil) everything was alright, far from it!
Usually the shock absorber was the first to suffer, with valves getting corroded and pistons being scoured.
Then the bearings started to wear allowing what was left of the oil to escape. Needles start to break up, and depending on the construction design, started the damage process to both the main housing and spindle.
A thicker oil was sometimes used to combat the leak but this only made matters worse. The ride became extremely hard if valves were still working thereby putting a strain on all moving parts - and the still leaked out anyway.
Units are stripped, cleaned and assessed.
Housing and Carrier arm alignments are checked using special equipment.
Housing and arm spindle is then checked as to which bearing configuration is to be used.
All internal parts checked for wear and assessed as to degree of repair or replacement.
Housing and spindle are machined together with new seal carrier as required.
Repairs to internal parts such as control levers, spring seats etc. are carried out using specialist materials to the surfaces and then ground to original specs.
Shock absorbers are refurbished using original components if possible, or remanufactured parts from the workshop, including valves, springs and pistons.
All bearings, rings and seals are new.
Rebuilt units for Vauxhall G25