This article courtesy of lizard@gmx.co.uk 

It's not surprising that this extremely clever design is not usually functioning very well after some 75 years. As a result, the sprung hub has acquired an undeserved, bad reputation. However, when in good condition it makes for a much better ride and can be a joy. Owners do sometimes renew bearings when there are problems, but the springbox itself can often be in trouble. Most common issues are: broken springs, corrosion in moving parts, and grease degrading into almost solid material.

However, the dire warning on the springbox deters all but the prepared, and the stupid. Because the springs inside are under enormous tension and will go straight through anything but a brick wall, which includes your head. Basically a bomb. lizard technicians employ a steel safety cage, as well as the jig and it is vital to remember,  DO NOT OPEN THESE WITHOUT THE SPECIAL TOOLS. Even the prescribed method/instructions are not entirely safe and it has taken extensive research and experimentation to discover an effective and safe method

Reconditioning  a springbox includes:

• Full disassembly using the correct jig

• Cleaning every component, often including ultrasonic cleaning.

• Testing the plunger inside the box without springs to measure play.

• Re-surfacing the internal faces until tolerances are restored.

• Repeating the test-fit, blue-marking, polishing cycle until the plunger glides perfectly.

• Reinstalling slipper pads and shims to exact clearances—1 to 2 thou.

• Using the correct graphite/moly grease during reassembly.

• Replacing the springs and buffers, then fully packing with grease.

Enquiries about reconditioning spring boxes - please use address at top