Front brakes on a school bus are significantly smaller than the rear drive axle mainly because there is much less weight to handle and you want a balanced stop while braking. Brakes are engineered to even out the stopping accuracy when the brake pedal is applied and give the operator the proper feel when driving in the city and on the highway.
With that being said the linings on this bus were separating from the brake shoe and needed replacement even though there was sufficient material left. The regulations dictate our next step is to replace the drums and shoes. Since the steering axle is much lighter that the rear axle front brakes last much longer but that can cause a problem not getting up to temperature quick enough.
Brake material is engineered to withstand high temperatures and can be specified for certain applications like highway, off road or stop and go driving. The linings are very hard and eventually the brake drum will get a glazed finish which causes brake noise or chatter when applied. We have the tools to machine the drum and linings but extra labor is required. After a brake job the mechanic takes the bus out for a road test to burnish the brake linings into the drum which seats the lining against the drum making a good contact.
If a driver is experiencing brake noise I will advise them to make steady brake applications going down a grade to heat them up. This will help alleviate the noise but it’s usually a temporary fix. Eventually we have to machine the brakes which always works. The driver reports the noise because of the attention they get from the public who think the worst like a metal on metal no brakes situation when really their is nothing to worry about besides the noise.
One thing I’ve learned over the years is never second guess brakes and think they will get better on their own. Once a problem exists it takes a hands on repair to fix it. We don’t need drivers worrying about a brake condition while having to watch the road and supervise school children. For the unforseen problems in a bus fleet we have spare buses to give out so the repair is done properly before releasing it back in to service. Road testing is compulsory with our operation and eliminates break downs out of town or at a school in the middle of a run.