Can anyone explain how the emergency brake auto adjustors, of the type built into the piston of rear disk brakes, work? (As fitted on the Mazda 626 in particular.)
Emergency brake auto adjustment
- Thread starter carmarthen
- Start date
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emergency brake?
Must be the parking brake adjusters.........
Basically, the piston works as a normal piston, but also has a screwthread on the inside of it. The idea is as the pads wear down, when you use the brake the piston will screw out taking up any slack on the pads. When you change the pads for new ones, you need to screw the piston back into the caliper with a 'speacial tool' (usually a pair of swan neck pliers if you havent got the right bit of kit!) so the new pads will fit in
Must be the parking brake adjusters.........
Basically, the piston works as a normal piston, but also has a screwthread on the inside of it. The idea is as the pads wear down, when you use the brake the piston will screw out taking up any slack on the pads. When you change the pads for new ones, you need to screw the piston back into the caliper with a 'speacial tool' (usually a pair of swan neck pliers if you havent got the right bit of kit!) so the new pads will fit in
Neo – many thanks for the explanation.
Sorry about the “Emergency Brake” description – I had lapsed into American terminology. Yep, it’s the parking brake auto adjusters. (Or hand brake auto adjusters.)
I have stripped down the piston as far as I can. The internals of the piston consist of at least an internally threaded sleeve, an eight lobed disk, a smaller disk with a very limited arc of rotation relative to the sleeve, a light torsion spring, and a couple of “C” clips to hold it all together. It is more complex than being a simple threaded piston, and I would like to understand how these internals are meant to work.
Any further information?
On a Mazda 626 there is no provision for using any “special tool” to wind the pistons back in, (The pistons are purely cylindrical, with no notches or lobes.) but a pair of normal pliers do the job easily
Incidentally, it’s a pity all these components are nicely protected by the brake fluid, but then the handbrake linkage (Cam) is exposed to the atmosphere, seizes up regularly, and cannot be removed to clean it up! Then it is about £150 for each new calliper, all for the sake of a 10p rubber boot. I’ve now gone through three seized callipers in 120,000 miles.
Sorry about the “Emergency Brake” description – I had lapsed into American terminology. Yep, it’s the parking brake auto adjusters. (Or hand brake auto adjusters.)
I have stripped down the piston as far as I can. The internals of the piston consist of at least an internally threaded sleeve, an eight lobed disk, a smaller disk with a very limited arc of rotation relative to the sleeve, a light torsion spring, and a couple of “C” clips to hold it all together. It is more complex than being a simple threaded piston, and I would like to understand how these internals are meant to work.
Any further information?
On a Mazda 626 there is no provision for using any “special tool” to wind the pistons back in, (The pistons are purely cylindrical, with no notches or lobes.) but a pair of normal pliers do the job easily
Incidentally, it’s a pity all these components are nicely protected by the brake fluid, but then the handbrake linkage (Cam) is exposed to the atmosphere, seizes up regularly, and cannot be removed to clean it up! Then it is about £150 for each new calliper, all for the sake of a 10p rubber boot. I’ve now gone through three seized callipers in 120,000 miles.
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