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Pressing them back in on some newer cars can be tricky. Caliper Atv 150
If you haven’t changed rear brake pads on a newer car recently, you might be surprised to find it can’t be done without special tools. It’s been probably 30 years since I replaced rear pads on a car, back when I was working as a mechanic on British cars. These days, I only do my own wrenching when I have time—if it’s something I can knock out quickly. Replacing the pads on my 2015 Ford Transit Connect seemed like a job that should take about 20-30 minutes. And it would have, if I had the right tools.
As it was, I jacked up the car, removed the wheels, disassembled the brakes, then reassembled them, put the wheels back on, and dropped the car on the ground in 30 minutes—no better off for my effort. That half hour included some head scratching over the pistons that I couldn’t retract, preventing me from installing the new, thicker pads. I knew there was something I was missing and a little research revealed what was going on.
Many cars today have disc brakes on the rear, with calipers that have integrated emergency brake functionality. On these calipers, the piston, usually actuated by hydraulic fluid, is also actuated by a cable when you pull the emergency brake lever. In order to keep the emergency brake cable in adjustment, the piston on these calipers ratchet, and spin as they push out. Unlike traditional pistons, which you simply press back into the caliper, these newer types have to be spun as they’re pressed back in. And naturally, that needs to be done with a special tool.
The good news is, that a universal brake caliper piston tool kit can be bought for as little as $25. Yes, there are nicer ones from Snap-On and other professional grade tool manufacturers—I would have bought one of those, if I needed to use it every day. But, I might need to use it once a year, at most, for my family’s two cars. So, I opted for the cheaper tool—the quality of the universal kit was better than I expected, and it enabled me to complete the job just fine.
You’ll change the rear brake pads exactly as you normally would, with the exception of how you retract the piston in the caliper. So, I jacked up my vehicle and removed the wheel in the usual fashion.
Note: The following are the steps I took, for my vehicle with manual emergency brakes. Yours will certainly differ visually, although the process would basically be the same. Some cars have electronically actuated parking brakes. These, like a fellow editor’s 2017 Mazda 3, may have a specific, in-cockpit procedure to put the brakes in “maintenance mode” in order to press the pistons back into the calipers.
First, I removed the retaining spring on the outside of the caliper. Then I located the two caliper pins at the top and the bottom of the brake caliper. These pins perform a couple functions. The first is that they bolt the caliper to its mounting point. The second is that the caliper slides on them to keep it centered over the rotor as the pads wear.
On my vehicle, the hex heads of the caliper pins are covered with a rubber sleeve and cap. I removed the caps to access the pins and remove both top and bottom. I then pulled the caliper away from the rotor. At this point, I could remove the old brake pads.
The kit comes with a hook to hang the caliper from. Using this prevents the caliper from hanging by the flexible brake hose and potentially damaging it. I found a spot where I could use it on my vehicle. Once the caliper was secure, I selected an adapter from the tool kit that matched both the diameter and pin orientation on my piston.
With the right adapter selected, I snapped it on the threaded piston compressor. The parts are magnetized and they easily held the adapter in place.
Note: The kit comes with two threaded piston compressors, labelled "LH" and "RH"—for left hand, and right hand. This indicated the direction each compressor is threaded. The left (LH) works for the right side brake caliper, and the right (RH) for the left side. This is because the pistons get spun in opposite directions, on opposite sides of the vehicle.
Next, I took the brake pad shaped backing plate and slipped it over the piston compressor’s handle, down its threaded shaft, to rest on a shoulder around the tool’s body. With that accomplished, the tool is ready to use.
Now, all I had to do was position the tool in the caliper with the backing plate in the position of the outboard brake pad. This allows the tool to put light pressure on the piston as it spins back into the caliper. It took a lot more turns than I expected to fully retract the piston because the threads it runs on are very shallow. I also noticed that the tool would loosen up as the piston retracted, so I had to re-tighten the tool against the backing plate occasionally.
With the piston fully retracted, I replaced the brake pads and re-installed the caliper. Then, I tightened the top and bottom caliper pins.
All that was left to do was re-install the brake pad retaining spring, put the wheel back on, and drop the car back on the ground—then, do the other side, of course. Overall, the job was relatively easy, the tool worked well, and it took maybe 5-10 minutes longer than it would to do the front brakes, which don’t have ratcheting pistons.
Brad Ford has spent most of his life using tools to fix, build, or make things. Growing up he worked on a farm, where he learned to weld, repair, and paint equipment. From the farm he went to work at a classic car dealer, repairing and servicing Rolls Royces, Bentleys, and Jaguars. Today, when he's not testing tools or writing for Popular Mechanics, he's busy keeping up with the projects at his old farmhouse in eastern Pennsylvania.
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