The collapsible steering column fitted to later MGB models (but not the earliest MGBs), MGBGTV8s and on to the RV8 (and many other cars) is a carefully designed and manufactured assembly that is intended to deform and collapse in a controlled fashion in the event of a frontal impact. In simpler terms it means the difference between the steering wheel crushing your chest or just bruising it.

How does a collapsible steering column do this?
The outer shell of the column assembly is made of expanded metal or similarly manipulated sheet metal that is easily crushed. Inside the outer shell there is a more complicated assembly that enables the lower shaft, the part that carries the universal joint to slide axially outside the shaft attached to the steering wheel, enabling steering inputs to be transmitted to the steering rack. The column itself is mounted to the body by means of 3 diecast assemblies that also contain a shear pin mechanism that will allow the column assembly to move downward in the event the driver is thrown against the steering wheel.

It would seem a simple device, but to allow the necessary clearance for the two shafts to slide inside one another means it will probably rattle, so the designers came up with simple solution - the space between the hollow and the solid shaft is injected with a resin based material through two holes in the hollow shaft, these forming a small cylindrical piece that acts as a “shear pin”. It is this that keeps the two inner shafts in their correct position when assembled into the outer column.

These steering columns can easily be damaged
From an investigation carried out on a selection of used steering columns from MGBs of various vintages by the V8 Register with the help of two former Rover employees, it is quite clear that most if not all the columns examined were damaged internally. The resin shear pins have been "popped" (sheared), meaning that the column must now be considered outside the OEM’s specifications.

It seems that there are two major reasons for the damage, the first occurs when refitting the column or steering rack, when excessive force is applied to the lower shaft to get the universal joint correctly positioned and second results from the incorrect removal method of the steering wheel. The correct method, described in the workshop manual, is to use a puller, but many people simply loosen the nut and then, while holding the steering wheel, and use a hammer to hit the nut to force the column down out of the steering wheel boss. This immediately pops the resin shear pins. There is also a need to be aware that this type of damage could occur during transportation of a steering column, if the courier dropped the column end, then it’s probably a dud!