PUBLISHED : Sunday, 22 March, 1998, 12:00am
UPDATED : Sunday, 22 March, 1998, 12:00am

S.K. Lee (Sunday Morning Post, March 15) repeats a fallacy which I am faintly surprised no one from any of the bus companies has refuted in the past - that squealing brakes are the result and indication of poor maintenance.

I established many years ago, on a very large fleet of 25-ton gross weight trucks, that the squealing, whether from drum or disc brakes, is caused by the composition of the brake lining itself, which differs from one manufacturer to another (Don and Mintex, for example, had different characteristics).

Most linings are a combination of asbestos and other minerals to give longer life and better performance - which they certainly need in Hong Kong - but exemplary maintenance standards, which I had at the time, do not necessarily cure squealing. (It was not unknown for some drivers to prefer squealing brakes because they then knew they were good).

If the brake linings are worn out, and you have a metal-to-metal contact, you will certainly get an awful noise with zero stopping ability, but the fact that buses, in particular, in Hong Kong do stop efficiently, indicates that excessive wear or poor maintenance is not the problem.

Perhaps someone from the bus companies would like to comment further.

H. LLOYD Kowloon