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Old 29th March 2022, 14:51   #11
Dashnine
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Originally Posted by xsport View Post
the springs are quite capable of pushing back a piston. provided of course it moves freely and is not sticking or seized. sometimes , as i have said in a previous post they can take quite a bit of forcing into the piston, no matter how square you try to offer them in....
The springs mentioned (I assume are rivetted to the back of the pads?) hold the pad to the piston. The piston itself is retracted away from the disc by the flex in the hydraulic seal when the brake fluid pressure is released - i.e. rollback. All the springs do is to make sure the pads move away from the disc with the piston.

Or at least that's how it was done on Girling sliding caliper brakes (the Colette) on which all sliding calipers are based.

Still have no explanation about how pads can wear at the top and bottom unless the pad backplate is bent.
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Old 29th March 2022, 15:51   #12
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Cheep discs can cause this hard /soft spots ,then you get uneven wear in the pads which accelerate the wear in the discs then you fit new pads and they ride on the high spots and the low spots get rusty because the pads aren't touching the low spots and so it continues until you fit new discs and pads and it all starts over again
When I was spannering back in the 80s you could buy abrasive pads which cleaned the discs up a treat don't seem to be able to buy them now
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Old 29th March 2022, 15:53   #13
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spot on.100 % correct. provided the springs sit correctly within the piston and do not exit partially , or try to , once pressure is released. ...
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Old 29th March 2022, 18:28   #14
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When I was spannering back in the 80s you could buy abrasive pads which cleaned the discs up a treat don't seem to be able to buy them now
Abrasive pads were a consequence of asbestos being removed from brake pads. While not great for ones lungs, asbestos was a fantastic material for friction materials, conducting heat away from the disc.

When the various materials initially used as asbestos substitutes worked from a friction point of view, they weren’t great at heat transfer so discs warped, brake judder ensued and so abrasive pads were introduced to machine the disc true again. And discs lasted about as quarter as long as before.

Friction materials evolved to be less abrasive, but there’s still an element of machining going on with associated shortened disc lives.
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Old 30th March 2022, 21:22   #15
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Quote:
Originally Posted by Dashnine View Post
The springs mentioned (I assume are rivetted to the back of the pads?) hold the pad to the piston. The piston itself is retracted away from the disc by the flex in the hydraulic seal when the brake fluid pressure is released - i.e. rollback. All the springs do is to make sure the pads move away from the disc with the piston.

Or at least that's how it was done on Girling sliding caliper brakes (the Colette) on which all sliding calipers are based.

Still have no explanation about how pads can wear at the top and bottom unless the pad back plate is bent.
Mostly the pads move back a very small amount by disc wobble caused by a very minute fraction of movement in the wheel bearings. There are no return springs and as you say those short flat springs rivetted to the pad are simply to locate the pad.

Most of the folk in this thread are talking about rubbish and badly made pad assemblies. These anomalies cause problems that never occurred with the original pads supplied by Rover.-----
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Old 30th March 2022, 22:05   #16
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Never had the problem myself, but, when the V6 stood out on the front drive for twelve months, the disc’s rusted slightly. I took the wheels off, and ran some brake cleaner on a piece of rag around each side of the disc’s first, after removing the whole calliper. I then got some emery cloth and cleaned up the disks in turn. I gentle used another piece of emery cloth to rub the brake pads on to remove any rust that was on the disc that had transferred to the pads. They have performed very well ever since. . Now the diesel which has been in the garage for the last one year nine months, there was a leak in the rook, caused by a stupid neighbour poking a piece of piping through the rear of the roof letting the rain in. The three disc’s are still shiny, good air flow in the garage, but the one where the leak was is a little rusty. I have had the car up and down the drive to the garage to get rid of the rust. It is not perfect, but will get the same treatment as the KV6. By the way, the disc’s are Pagid all round. I recommend them.
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Old 1st April 2022, 11:18   #17
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Quote:
Originally Posted by xsport View Post
if you look at alot of these pads , and pay careful attention to the spring clips that hold them inside the piston, more often than not , they are either not positioned centrally or equal. i have noticed this times on different makes. i had one set that would go in reluctantly , and pop back out at the slightest tap on the calliper. sometimes the springs were twisted at an angle or not even the same sizes . i wonder if the clips push out the pads at an angle whilst driving and then re seat when the pedal is applied. some of the new ones are a pain to fit inside the piston and must distort once inside , to an aukward angle and then not give a square initial contact at all. you can try to adjust them equally with the help of some moles but never get them equal as the spring material is very tough. the rear brakes never get much pressure on them as most of the braking is done on the fronts. sometimes the central rivets are not even central to the pad, and vary even on expensive pads. this would also give you problems on the pad carriers with the pads sticking. things aint what they use to be is an understatement...
Perhaps this explains the poor quality. https://www.youtube.com/watch?v=IL031aSTSuI&t=16s
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