How to Fix Your Muscle Car's Dragging Brakes

'Working to make your car go faster can sometimes involve addressing what is slowing your car down. That's the situation we're facing with our hot street/strip car. The brakes are dragging mercilessly because of mismatched components causing excessive brake-pad wear, overheated rotors and slowing us down at the dragstrip. This situation has been eating through brake pads, ruining rotors, and slowing down the car at the dragstrip. This story is going to help you find out if your car has a brake-system problem and show how to correct this issue.

Brake-System Problem-Solving
Is your car incredibly difficult to push around? Are the brake pads completely worn to the backing plates in less than 1,500 miles? Do your rotors look black and scabby after a few thousand miles? Is your car slower at the dragstrip than it should be? While these symptoms are extreme, any even close indicate a disc-brake system that is holding the pads against the rotors even though the driver is not attempting to slow the vehicle.

To many, the thought of someone having these issues on their car and not knowing it seems surprising. But we know of cars out there that have these problems, and, until now, those owners didn't know why.

Dragging Brakes
In general, dragging brakes usually arise from mismatched components. Like most vehicles with this problem, the vehicle being improved in this story gained rear disc brakes in place of the production drums when an aftermarket rearend was added. This should have helped the vehicle performance, but it actually hurt it. That's because the production front-disc/rear-drum proportioning valve was left on the vehicle. This stock proportioning valve has a residual pressure valve in it that helps to slow the rate at which the brake shoes relax from the drums. Unfortunately, this feature makes the rear-disc brake pads drag on the rotor-causing excessive heat buildup and pad wear, slowing the vehicle.

Figuring out how to go faster sometimes means minimizing the things that slow you down-like a brake system that is dragging!
Figuring out how to go faster sometimes means minimizing the things that slow you down-lik
This is the stock GM proportioning valve that came on many late '60s and early '70s A-body vehicles (Chevelle, Skylark, LeMans, and Cutlass) for a front-disc/rear-drum system. If you install discs at all four corners, this needs to be removed and replaced with a proportioning valve for a disc-brake system (or a manual prop valve-as is being done in this story).
This is the stock GM proportioning valve that came on many late '60s and early '70s A-body

A Wilwood proportioning valve (PN 260-8419) and some 31/416- and 11/44-inch steel brake lines were acquired to make this improvement. The brake line is available at most local auto-parts stores, and the proportioning valve is available from all the large mail-order houses.
A Wilwood proportioning valve (PN 260-8419) and some 31/416- and 11/44-inch steel brake li

Based on our research, there were lots of folks who said, "Oh, yeah, I made that mistake," which means you need to know about this situation.

The photos show the stock proportioning valve being replaced with a manual Wilwood proportioning valve, and the heat-damaged rear Wilwood solid discs and pads being replaced by Wheel to Wheel Powertrain (W2W) in Madison Heights, Michigan.

As a side note, this vehicle went from being almost completely unpushable to totally free, which told us everything we needed to know. It has gone faster than ever before at the dragstrip, and the manual proportioning valve has allowed the owner to tune the brake bias to provide maximum stopping performance.

Though this vehicle was repaired while up on a four-point lift to allow photography, the work can be performed on floor jacks-just be prepared to work in some very tight areas, as the brake system is usually buried under a lot of parts (exhaust, drivetrain, and so on).
Though this vehicle was repaired while up on a four-point lift to allow photography, the w
As a result of the brake system dragging, the rear Wilwood rotors were trashed after just 1,500 miles. They will be replaced in this story along with the brake pads.
As a result of the brake system dragging, the rear Wilwood rotors were trashed after just
This fix was started by unbolting the stock proportioning valve from the frame and hard brake lines. Use flare-nut wrenches on the fittings to minimize the chances of stripping the nuts as you work to loosen them.
This fix was started by unbolting the stock proportioning valve from the frame and hard br

W2W reworked the brake system on this vehicle. The installer positioned the Wilwood manual proportioning valve on the framerail with the adjuster dial just below the framerail and marked the framerail for where to drill the two mounting holes.
W2W reworked the brake system on this vehicle. The installer positioned the Wilwood manual
Two oversized holes were drilled in the framerail so that nutserts (which are similar to rivets) could be installed to allow two bolts to be threaded into them. Installing nutserts requires a special tool, but they are really great for blind installations such as this where you can't reach the backside of the fasteners being used for mounting a component.
Two oversized holes were drilled in the framerail so that nutserts (which are similar to r
Once the Wilwood prop valve was mounted, the techs at W2W got to work creating new hard lines to attach the rear brake line from the master cylinder and the factory line coming from the rear of the vehicle.
Once the Wilwood prop valve was mounted, the techs at W2W got to work creating new hard li

The factory proportioning valve joined the lines that run to the two corners of the front brake system, so we needed a union at this point on top of the driver-side frame rail and plumbed to the front-brake outlet line of the master cylinder.
The factory proportioning valve joined the lines that run to the two corners of the front
Wilwood solid rear rotors and pads are used on many street and racing applications with great stopping and durability-as long as you don't drag the pads!
Wilwood solid rear rotors and pads are used on many street and racing applications with gr
Disc-brake caliper pistons should be spread before removal of the caliper from the rotor as this will make it much easier to reinstall the calipers with the new pads. An open-end wrench is being used as a spacer with a caliper spreader tool to get the pistons to completely back out.
Disc-brake caliper pistons should be spread before removal of the caliper from the rotor a

The rotors are held on brake hats with small bolts that need to be carefully removed before the rotor can be swapped with the new rotor (make sure the hat is clocked the same way as the rotor you removed). Add two drops of red Loctite to each bolt, hand start all the bolts into the rotor, then torque in a radial pattern to Wilwood specs.
The rotors are held on brake hats with small bolts that need to be carefully removed befor
Slide the hat/rotor back onto the wheel studs, clip the pads into the caliper, and put the caliper on the mounts. Bolt the caliper in place. This is a good time to check that the caliper is centered on the rotor by measuring the opening on each side of the rotor face (the measurements should be within 0.05 inch of each other). If the caliper is not centered, use shims to properly position the caliper around the rotor.
Slide the hat/rotor back onto the wheel studs, clip the pads into the caliper, and put the
Two oversized holes were drilled in the framerail so that nutserts (which are similar to rivets) could be installed to allow two bolts to be threaded into them. Installing nutserts requires a special tool, but they are really great for blind installations such as this where you can't reach the backside of the fasteners being used for mounting a component.
Two oversized holes were drilled in the framerail so that nutserts (which are similar to r