How Much to Turn Brake Drums A Comprehensive Guide

Brake drums are essential components of a vehicle's braking system, especially in many older vehicles and some heavier vehicles like trucks. They work in conjunction with brake shoes to create the friction necessary to slow down or stop the vehicle. Over time, however, brake drums can wear down, warp, or become out of specification. This can lead to reduced braking performance and safety issues. One common solution for worn or damaged brake drums is to have them turned. But how much should you turn brake drums? This article will explore the factors that determine the amount of turning required, the process involved, and when it’s necessary to replace the drums instead.

What is Brake Drum Turning?

Turning brake drums refers to the machining process of removing a thin layer of material from the inner surface of the drum. This is done to restore the drum's ideal shape, ensuring that the brake shoes make proper contact. Turning can correct issues like warping, scoring, or surface irregularities that develop over time due to use and heat exposure.

Factors to Consider Before Turning Brake Drums

1. Thickness Specifications Every brake drum comes with a manufacturer’s specification for its minimum thickness. When a brake drum wears down due to repeated use, it can become thinner than these specifications. Turning the drum too much can bring it below this minimum thickness, compromising its structural integrity and performance. Mechanics typically check the dimensions of the drum against the manufacturer's specifications before proceeding to turn it.

2. Existing Damage If the drum has significant wear, cracks, or deep grooves, turning may not suffice. In these cases, replacement is often the better, safer option. Inspecting the drum thoroughly helps mechanics determine if it is suitable for turning.

3. Brake System Type The type of braking system—whether drum or disc—affects how much turning of the brake drum is feasible. Some systems are designed to accommodate more wear than others.

How Much to Turn Brake Drums

In general, a brake drum can be turned anywhere from 0.010 inches to 0.030 inches, depending on the severity of the wear and the drum's current condition. Most manufacturers recommend a maximum of 0.060 inches for drum resurfacing; however, any amount turned should still leave the drum within its minimum thickness specification.

Mechanics usually use a lathe designed for brake drums to ensure a smooth, even surface. This machinery is calibrated to remove only what is necessary, thereby prolonging the life of the drum.

The Turning Process

The turning process typically follows these steps

1. Inspection The mechanic inspects the drum for any excessive wear, cracks, or warping. 2. Measurement Using micrometers, they measure the current thickness of the drum. 3. Setup The drum is mounted on a lathe, which holds it securely while it is being machined. 4. Turning The lathe cuts away the outer surface of the drum, removing material evenly to achieve a smooth finish. 5. Final Measurement After turning, the mechanic re-measures the drum to ensure it meets specifications.

When to Replace Brake Drums

If the brake drums are worn beyond the minimum thickness specifications or if there is extensive damage, replacing them is the safest choice. Using worn drums can lead to brake failure, potentially resulting in severe accidents. Additionally, modern vehicles often come with disc brakes, which may offer better performance and require less maintenance than traditional drum systems.

Conclusion

Understanding how much to turn brake drums is essential for maintaining optimal braking performance and ensuring vehicle safety. Regular inspection and timely maintenance can prevent more extensive repairs down the road. Always consult with a qualified mechanic if you have doubts about the condition of your brake drums or if you're considering turning them. Safety should always be the priority when it comes to your vehicle’s braking system.