The brakes rank as perhaps the most important safety feature on any vehicle. For heavy-duty trucks, the value of reliable brakes goes up even higher, given the massive amounts of momentum that such trucks generate. For that reason, truck operators should have their brake systems inspected and maintained on a regular basis.
Yet getting the most from your brakes takes more than just regular servicing from a trained professional. You should also understand as much as possible about the factors that lead to excessive wear. This article outlines three key conditions that lead to premature brake drum wear.
1. Brake Drag
A drum brake system operates on fairly simple principles. When you depress your brake pedal, pneumatic power causes the brake shoes to expand outward against the inner wall of the brake drum. The resulting friction causes the drum - and hence the wheel - to lose rotational force. The more forceful the contact, the more quickly your truck slows.
When you release your foot from the brake pedal, the brake shoes should retract enough to no longer have any contact with the drum. Brake drag occurs when the brake shoes don't move away completely. Instead, the shoe remains in partial contact with the drum surface. The resulting friction often leads to overheating, which in turn may cause cracking, scoring, or hot spots.
Brake drag may occur as the result of either mechanical problems with your brake shoes, or as the result of problems with the air system that powers your brakes. In either case, seek professional assistance as soon as possible. Not only does brake drag damage your drums, but it also causes the brake shoes to wear out prematurely.
2. Loose Wheel Bearings
A truck's wheels rotate through the action of heavy-duty bearings, which require careful tuning. If too tight, the bearings constrict motion and create damaging friction. If too loose, the bearings allow the wheel to wobble in place, which leads to negative camber alignment. At first, such alignment problems don't pose any huge threat to your brake drum.
Yet as bearing play grows greater, and alignment issues grow more pronounced, your brake shoes have a harder time contacting the brake drum completely. You may notice that your brakes seem less efficient than usual. As the problem worsens still, brake drag may ensue.
In that case, the brake drum inside of the tilting wheel sits at such an extreme angle that it presses into the brake shoes even when they retract correctly. To resolve the issue, have a technician inspect and adjust the amount of play in your bearings. If the problem has gone on too long, you may need to replace your bearings replaced.
3. Damaged Brake Spider
Like the brake pads in passenger vehicles, a truck's brake shoes wear down over time and eventually require replacement. A brake shoe mounts to a component known as the brake spider. Although made to survive for far longer than the brake shoe it supports, a spider may suffer damage as the result of wear and tear.
Cracks may form around either the cam and anchor pin sites or around the bolt holes. Likewise, the spider may become bent. Brake spiders often become bent as the result of improper servicing. Either type of damage affects the angle of the brake shoes, which potentially leads to brake drag and a damaged drum.
Truck owners must take their brake systems seriously to ensure optimal safety. Brake drag contributes to decreased safety, as well as to premature failure of brake components. For more information on how to keep brake drag at bay, contact the truck experts at Clutch & Brake Xchange Inc.