How do you retract the front caliper pistons when trying to install new pads? Thanks in advance.

-Chris Chung

 

jam a large screw driver in between the pads, and pry.

 

Get a huge C-clamp (I think mine is 10"), and with the old pads in place, clamp over the outside pad and the back of the caliper. With the brake reservoir cap open, you should be able to squeeze it open. Watch the brake fluid doesn't overflow. Then install the new pads.

Dave

 

take a piece of wood or something flat and hard and place it against the piston, take a C-clamp and tighten till the piston retracts enough.

 

I would NOT recommend this.

 

Ahhh you beat me to it.

 

Thanks to everyone. I really mean it. When inexperience s#!ts on you it's nice to know that theirs always someone you can turn to. Thanks for all the help and for putting up with my robotic questions that my brother's been typing for me.

 

FWIW, Mazda makes a front brake tool that consists of 2 threaded plates with a threaded rod with a 1/2" square end (to fit your ratchet). You insert the tool in the space between the brake pads and turn the rod, forcing the pistons back in the cylinders.

 

If you have a large wrench, you can wrap it with a workshop cloth and push them in (make sure you have the bleeder open). 24mm works for me.

 

That would be this thing:




Frankly, the screwdriver idea works better. You do one side of the caliper at a time. Take out one brake pad and leave the other behind. Then use TWO screwdrivers. One holds the first piston in place and the other is used to retract the other piston without allowing the first piston to extend more. Pry against the rotor. After you get one piston all the way in, hold it in place with a screwdriver and pry the other.

Next step is to replace that pad and pull the other pad. Then repeat the process for the other pair of pistons.

It takes longer to describe than it does to do it. Just be careful not to damage the dust boots with the screwdriver. In other words, watch what you are doing.

While the tool is slick looking, I've found, after doing this many dozens of times, that the screwdriver method is faster and better.

Also, it's a good idea to open up the bleed screw and attach a catch bottle to it before retracting any pistons. This allows the crappy old, heat cycled brake fluid to go into the catch bottle instead of back in to the master cylinder AND it makes it much easier to retract the pistons. Of course, you should follow this up by bleeding the brakes. I suggest following my instructions on bleeding in order to extract the most air: http://www.zeckhausen.com/bleeding_brakes.htm

 

hahaha, my screw driver coment was based on what i do to work on bikes. i spaced out on the fact that a cars brake rotor doesnt come off with the wheel.

 

Rent a caliper compressor toolkit from autozone, $5.00. Screwing up your brake calipers with a screw driver, priceless.

 

Explain how you'll "screw up" your caliper with a screwdriver? As long as you use a pair of large flat blade screwdrivers or a pair of stubby pry bars and push against the rotor to retract the pistons WITHOUT digging into the dust boot, you'll be fine. The key is only taking out one pad at a time. You just need to look where you are pushing so you don't dig into the dust boot surrounding each piston. Also, with the bleed screw open, it doesn't take very much pressure at all to get the pistons back in.

 

1. In most cases, especially on older cars, the pistons will not move as easily as you discribe. (I know because I have used the "big screw driver method before and learned the hard way", I was lazy that day, what can I say)
2. Unless you plan on resurfacing or replacing the rotors at the same time, putting anything against them could very well damage them. If you have slotted or x-drilled rotors it's even worse.
3. Because you are not going to be able to apply even pressure to retract the pistons you WILL damage them. In most cases the damage are small and go un-noticed. In worst case you can break the piston, now you are faced with caliper rebuild or replacement.
You can always use some kind of work around, you don't always screw up but one thing is for sure, using the correct tool will always save time, energy and regrets. Why take the chance when it takes so little effort to do it correctly.

 

That's true, these cars tend to be much older than the ones I work on regularly. Mine was Lemon Lawed back in 1994! (I still miss it.) I'm used to pistons that glide in almost effortlessly, as long as the bleed screw is open. If you have to apply enough force that you would damage an iron rotor, then certainly a screwdriver is not the right tool. But at that point, it's probably time to rebuild the caliper with new pistons, seals, and dust boots anyway.

The key is to use common sense and that comes, usually, from experience. If the stock RX-7 caliper pistons are indeed delicate and the calipers easily damaged, then you should probably spring for the Mazda tool. It is an attractive addition to any tool box.

 

What the hell?! How can you confuse bikes with cars? One has a big motor and the other has.....pedals........

 

Here's one way:


The new Formula BMW cars use a stock 1.2 liter motorcycle engine from the BMW K 1200 RS and they were lapping Lime Rock Park on Memorial Day weekend at 52 seconds/lap!

 

Not really. Even Ray Charles (RIP) wouldn't confuse that for a bike.


Use c-clamps.

 

Thank you PVerdieck. I don't think many people would confuse a bike with a car. And even bike guys would probably burn him for giving that advise too. Screwdriver and pry is never really something I want to hear on a nice car or bike part that is used to slow me down and stop me. Anyways, at first I actually thought he was talking about a pedal bicycle.

 

Several have mentioned that you should open the bleeder valve. This is important. Shoving the brake fluid back into the master cylinder can cause problems. Be sure to open the bleeder valve.

 

I'm sorry, but I categorically disqualify any method that involves using a screwdriver as a pry bar.

You should have used the word pry bar, IMHO. Snapping a screwdriver is dangerous.

Dave

 

it would probaly suck to get your fingle stuck in one

 

Dave you are obviously not an "OLD SCHOOL" guy. My old '72 RX3 repair manual (translated in Japan I guess) had this to say. ..."make sure the screwdriver is of heavy construction so it will take the abuse when you misuse it as a chisel". Do they know Americans or what!