Brakes & Suspension / Q&A

Ask Away! with Jeff Smith: Are Drum Brakes Good Enough for a Classic Car That’s Not Driven Hard?

My son and I just bought a ’66 Buick Skylark in pretty good condition. The front suspension needs a lot of work and the original drum brakes will also need a complete rebuild. We thought about converting to disc brakes up front but maybe we don’t need to do this because this is such a simple car that we don’t race or drive hard. Would just rebuilding the stock front and rear drum brakes be okay?  We thought this way we could save money to invest in adding better tires and wheels.

D.S.

The answer to your question is a resounding yes. There’s nothing wrong with a properly executed drum brake rebuild in terms of creating a car that’s safe to drive. The biggest detraction from drum brakes is their tendency to fade from repeated hard stops.

I lived in Southern California for over 40 years and freeway driving is often treacherous. On several occasions we had to perform aggressive panic stops from 60-70 mph down to zero in a very short distance. On a couple of occasions in my drum brake-equipped Chevelle this happened on the freeway twice in less than three or four minutes. On the second hard stop, I could feel the brakes beginning to fade but I was able to stop the car in a safe distance. However, if there had been a third instance before the brakes had a chance to cool down, that might have been troublesome.

But these situations occur rather rarely and only in congested freeway driving like in Los Angeles, California. Anywhere else, you might drive 300 miles on the highway and never touch your brakes. So yes, it is safe to consider rebuilding the existing drum brakes, but there are a few important details to remember when performing a drum brake rebuild.

A common mistake that I see very often is not paying attention to the actual brake shoes. Drum brakes use a primary shoe and a secondary shoe. The primary shoe employs a shorter length of friction material than the secondary shoe. The primary shoe is placed on the leading or forward end of the two brake shoes with the secondary shoe on the trailing side.

When the wheel cylinder pushes outward the counter-clockwise rotation of the brake drum creates what is called a self-energizing action that applies more force into the larger secondary shoe through the solid link that connects the shoes at the bottom. This works only when the car is moving forward but this is when full brake torque is required.

It’s very easy to mistakenly place the larger secondary shoe on the leading or primary side of the brake assembly with the primary on the trailing side. If this mistake is made on the left front brakes (for example), the car will exhibit serious pull to left.

Another version of this mistake is placing both primary shoes on one side of the vehicle and the secondary shoes on the opposite side. In the front, this will cause the car to pull to the side with the two secondary shoes. Luckily, no damage is done with this situation and it can be easily rectified by disassembling the brakes and installing the shoes in the correct fashion.

We’d recommend replacing all the components in all four corners to ensure that the system will perform as expected. This is not costly since these parts are very affordable. Assume that you should purchase new brake wheel cylinders, all new springs and hardware, new shoes, and drums. Even with all these new parts, the cost will be less than half of what it would cost to convert to front disc brakes. We would also recommend adding a new or rebuilt master cylinder.

Here is where it might be a good idea to upgrade to a later model, dual reservoir master cylinder. Your 1966 Buick was the last year that GM used a single reservoir master cylinder. Beginning in 1967, all new cars were equipped with dual reservoir master cylinders. The concept is that if your rear brakes developed a leak, the rear reservoir would lose all its fluid but the front brakes would still work because there is a separate reservoir for the front brake fluid.

You can learn more on that topic here: What’s the Difference Between Single- & Dual-Circuit Brake Systems? (And Why You Need to Know the Distinction!)

Adding this dual reservoir master will require re-routing the hydraulic brake lines to separate them front to rear, but this is a simple job that can be easily accomplished.

This is the proper orientation for the primary and secondary drum brake shoes. In this illustration, the primary is on the leading (left) side with the secondary shoe on the right side. (Image/Jeff Smith)
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One Comment

  1. Brake shoe orientation – big shoe to the back.

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