Its time to change the rear brake pads - I seem to remember some discussion on this awhile back - something about either requiring a special tool and/or being difficult without experience - anyway, I have looked in the archives and do not see anything - so my question is do I need to know anything special to change the rear pads on an 85 SE or is it generally like changing disk brake pads on other cars?

Thanks

 

You need the caliper toold that pushes and spins the piston at the same time.

 

Yea if you take a look at your calipers, you'll see they have the parking brake assy attatched to them surrounded by a rubber boot. This ingenious design makes them expensive as hell. We're talking like $100 a caliper fully loaded. They work by, when you pull on your parking brake, a level attatched to the caliper housing takes the piston and spins it out putting pressure on the rotor. The piston in our style of caliper requires essentially a clamp like lovintha7 said above to spin it back into the bore. Not a normal style "C" clamp, i would think that if your local auto parts store rents out tools that they would have that in their arsenal. If not, then you might be forced to pull it off and have someone do if for you. It also might be a good time to rebuild them, or if you can't, buy new ones. Remember, if one caliper is stuck, then most likely the other is also if not on its way.

 

just buy it at your local NAPA or something ... it's called a psiton rotation tool. a universal one should have the pattern that fits the Rx-7, but take a measurement and/or pencil copy of the piston with you. it's worth the $12 or whatever they charge.

 

Just a quick tip, but get the right tool for the job.

I've heard of others using 2 screwdrivers to fit into the 'cutouts' at 180 degrees from each other, but if you slip just once, you're going to cut through the rubber piston seal and risk damaging your piston and brake caliper. During a recent rebuild, there is only a simple rubber ring on the inside of the piston bore to hold pressure other than the 'dust-seal' on the outside. Two types of grease are used between the rubber ring and the dust seal because it helps to prevent hydraulic fluid blowby under pressure.

The correct tool is a metal cube that has all sides cut open with a 1/2" drive socket opening. On each of the 6 sides are manufacturer specific spacing and shapes of the piston depressions used to rotate the pistons as you apply pressure.

Other than this step for compression of the brake pistons, the rest is just like the front. Remove the parking brake cables with the calipers still mounted to save some hassle - if you remove the caliper first, you take out the slack in the parking brake cable that allows you to remove it from the slot in the actuator. HTH,

 

is this for all models with rear discs?

or just the -se's?

 

All models...

When I did rear pads on my GSL, it was my first time with disc parking brakes, so I didn't have the tool.

I used a pair of needle nose pliers and put an adjustable wrench on the pivot point of the pliers... Worked well, no ripping of the boot when I slipped.

But yeah. I've since bought the cube. Get the cube. The cube owns. I think my cube cost me $15 or $20...

 

Pele, Are you still in Alexandria? Where did you buy your "cube"? and does it do the job?

 

Thanks guys, Good information .....
I need to change my brake fluid at the same time, so question is if I open the bleed valve will that let me turn/push the piston back in without a special tool, e.g. by hand?

Also, I see Mazda recommends a "Disc Brake Piston Wrench" (#49 FA18 602) in the shop manual. Do any of you have one of these/used one of these? I suppose Mazda wants the cost of a new car for one?

 

I've moved to my own place in Lorton.

The Cube, AKA: A Disc Brake Piston Wrench is available at PepBoys or Advance Auto parts... Hell. You can get em anywhere.

The cube defenately does the job. Otherwise I wouldn't praise it so much.

You MUST get the Cube.

 

^ yep ... that's it. i think i paid $12 at a local NAPA.

 

I had to change rear pads at the race track unexpectedly. It was a bitch! I used a large C-clamp to compress the piston, but it was only marginally effective. I ended up going through the painstaking process of:

1) Open bleed valve
2) Compress with C clamp
3) Release and turn piston with needle nose vice grips
4) Repeat 2 and 3 until fully compressed
5) Install pads and bleed brakes

If the Cube makes it easier, I am all for it!

It was a painful experience.

 

I have not yet changed the rear pads on my RX, but I have changed them on a wRX. I just used an adjustable wrench to push the piston back in.

BUT, do be careful if you use this method. My friend was chaning the front pads, and ripped the rubber boot around the piston. That renders the caliper almost useless. I have not ever heard of "the cube".

HTH!

 

Well, why would you have to compress them? if you just pull the caliper off, and dont touch the brakes, the piston should stay completely in, so when u go to put it back on it should go on with a little effort, because the new pads will be thicker, but essentially it shouldnt come out much at all if any.right?my fronts i could just take off, put on new pads, and slide back on, the piston didnt move at all.

 

The rears are a different design because of the Parking brake hardware added to the calipers. The front calipers are free floating design, release the pressure the piston retracts. But the rear piston has a threaded rod attached to it to move the piston in and out, when the parking brake handle is used.

The rear caliper design really hurts the braking performace of any sports car, because it limits the amount of travel of the brake caliper piston. A rear sports car will have a seperate small caliper just for the parking brake.


John

 

im starting to feel i missed something, i changed rear pads last week just before this 2500Km trip, all i did was remove the hand brake cable, compress the piston with a universal tool (just a plate with a long bolt through it) dropped the new pads in, all done! no need to bleed, or even adjust the hand brake!

am i missing something here??