There is a tool available for the purpose. The tool fits into the caliper piston head notches, and has a turnscrew which rotates the caliper piston head while compressing it. Watch the caliper piston boot while turning, as it can catch and tear. It helps to use a small screwdriver to push the seal of the boot back slightly before compressing the piston; less likely to catch and tear that way. If you notice the boot pulling, back up on the turnscrew to relieve tension on the boot, and use the small screwdriver. I 'rented' the tool at Autozone; they put the cost of the tool on your credit card, then refund it when you return the tool.
Most likely the piston will need to be turned not compressed
Rewind it with a piston rewind tool or, at a pinch, use needle nose pliers.
I have a 2004 TSX and learned the hard way how to change the rear brakes and had to buy a rebuilt caliper for my mistake. Most brake calipers compress with a simple C-clamp to make room for the larger/newer brake pads. The rear brakes on a TSX are different and you'll notice they have a couple of grooves on the caliper piston. They make a tool that is sold at AutoZone that allows you to compress the caliper piston by rotating it clockwise back into the piston. (It looks like a metal cube with metal prongs sticking out) I also recommend using brake grease on the exposed caliper piston boot prior to compressing it as this will allow the piston to rotate without damaging the boot. Don't forget to bleed the brakes afterward since rotating the piston will likely allow some air into the brake caliper.
If parking brake uses these calipers - they are threaded special tool (not expensive) is required, availlable at Sears or auto parts to thread piston fully into caliper body
take the tire off, remove the caliper, remove and replace brake pads, compress piston, slide caliper over the roter, tighten up the bolts on the back of the caliper, do one side at a time, open up the master cylinder before messing with it, its pretty easy.
Remove the rear wheels. Remove the Caliper off the Rotor by removing the two (top and bottom) bolts that hold it on. (14mm i think) Remove the old pads. Compress the piston all the way back into the caliper to provide space for the new pads. (Checker/O'Reilly Auto sells a cube like tool that fits onto a 1/2" ratchet to compress the piston) Put the tabs and new pads in. Replace the caliper mounting bolts and attach the caliper back onto the rotor. After you're done make sure you press the brake padel in all the way and Slowly let it out. You're making sure the caliper piston is correctly seated against the pads and they'll self adjust.
Use a "c" clamp (front) to slide piston into caliper body Rear piston is threaded and requires a special tool to screw piston into caliper body Tool not expensive and available at Sears or auto parts
There is a tool used to twist the piston back into the caliper I bought mine from Canadian Tire.
Extremely simple with simple tools, lift and support the vehicle safely on flat land, after breaking the lug nuts of the wheel loose. Take the lugnuts and wheel off use a c clamp to compress the caliper, when calipers removed do not let hang. Take off rotor and put new one on. C clamp must be used to compress the piston of the caliper in order to fit new rotor on
screw it in turn the piston clockwise and screw it in , only for rear brakes
---- You have to turn it (caliper piston) as you are depressing the piston back into the caliper. You can't just "jam" it in. I used a caliper tool (for depressing the caliper) and turned the piston with large jaw pliers. This gives both inward pressure and the turning motion. I turned it clockwise and that seemed to work. There is a special tool you can buy to turn the piston as you push it back into the body of the caliper but if you work carefully and you are VERY aware of the rubber boot (don't rip it) then pliers are ok (don't tell the Ford dealer). Cover the pliers with something so you don't scratch/ruin the piston. The front brakes are just a standard push - don't need to turn them. Why do the back brakes work this way? Has to do with the parking brake. If you look you can see that it is attached to the caliper on the rear.
front pushes in with a bar, rear screws in...