Foam

[Brian Walton]

The annoying thing about applying urathane foam is that unless it is
applied in a very controlled situation you waste 50% of what you put on.
Somebody at the factory just may have done some maths on the time
to apply and the cost involved. If it came to more than a need to have
amount it may have been dropped. After all, its not the foam that
makes the bumper "bump" but the GRP. I would imagine anything over
a 3mph bump and you have forced the bumper into the bodywork.
Mine had certainly done this many times causing a mass of stress
cracks all over the front of the car.

As a side issue urathane foam is a A and B pack combination. Some
modern bumpers are 3 pack combinations which give that extra spring
to the finished foam.

Brian