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Rear Disk Brake Question #4104950 05/24/16 05:58 AM
Joined: May 2016
Posts: 301
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NibbanaBanana Offline OP
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Joined: May 2016
Posts: 301
Greetings BTOG Mechanics,

My first post here. I posted this same question about six months ago on the Kia forums but didn't get any responses.

I had to replace the rear brake pads and rotors on my wife's 2013 Kia Rio. This is the first time I worked on a rear disk brake system. I don't completely understand the internal workings of the calipers but figured out that the pistons screw in and out like some other rear disk designs I've read about on the internet. Different from the standard front disk design. I'm guessing that the screw mechanism operates the parking brake and acts as an adjuster. Then the hydraulics kick in for normal braking. Not at all sure though.

The backing plate on the original inside brake pad (against the piston) had a dimple that sits in a groove on the piston face. I'm guessing that this is to keep the piston from turning while the parking brake screw forces it out. I'm not sure about this though. There's a lot of resistance to keep the piston from turning just in the mechanism without the dimple though. But, like I say, I'm not completely sure I understand the construction of these things.

The backing plates on the pads I got from NAPA didn't have a dimple. I went to Advance and 4 out of 6 of the pads that they sold, including the super premium ceramic pads, didn't have a dimple. I put everything back together with the NAPA pads and it seems to be working as it should for about six months now. The brakes are solid and the parking brake holds.

Does anybody have any knowledge of the details of how these work? What is the purpose of the dimple? And why do some pads have it and some don't?

Thanks.
Nibbana


1993 Ford E350 5.8L, 68K
2002 Ford E150 4.2L, 85K
2006 Chevy Aveo 1.6L 215K
2013 Kia Reo 1.4L, 101K
7500 OCI, M1 5-30 winter, M1 10-30 summer
Re: Rear Disk Brake Question [Re: NibbanaBanana] #4105112 05/24/16 09:08 AM
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Kira Offline
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This is a guess so don't yell at me.

I just did a neighbor's rears and I saw alignment dimples on the old pads and none on the new. There is NO WHERE for the parts to go so maybe the dimples are for a pre-assembly step.

A human or robot can grasp the entire, assembled caliper and put it into position.

Also, the pads in my case were original to the car and the pads seemed solidly glued (with dried, anti-squeal compound) into position. Perhaps that compound is glue-like from day 1? Kira

Re: Rear Disk Brake Question [Re: NibbanaBanana] #4105219 05/24/16 11:01 AM
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supton Offline
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Are you sure the pistons screw in/out? On my Toyota's they do not--instead a separate drum brake is used (inside the rotor) for the parking brake.

Are there any DIY guides on Kia/Hyundai forums? I'd think someone somewhere has done this, and taken pics of it.


2011 Toyota Camry, base, 2.5L/6MT, 200k, hers
2010 Toyota Tundra DC, 4.6L/6AT, 157k, ours
1999 Toyota Camry LE, 2.2L/4AT, 220k, his
Re: Rear Disk Brake Question [Re: NibbanaBanana] #4105401 05/24/16 02:07 PM
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NibbanaBanana Offline OP
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Maybe it does have something to do with automated assembly.

I haven't been able to find anything on Kia's, but I saw an "Eric the Car Guy" vid on youtube where he was working on a Honda that also had the slotted piston and dimple on the brake pad. And the pistons screwed in and out as I remember.

The pistons do screw in and out on the Kia. There is no separate parking brake. It uses the regular caliper. But the screw mechanism is turned when the parking brake is applied. So instead of hydraulic pressure, it's a mechanical action to squeeze the caliper.


1993 Ford E350 5.8L, 68K
2002 Ford E150 4.2L, 85K
2006 Chevy Aveo 1.6L 215K
2013 Kia Reo 1.4L, 101K
7500 OCI, M1 5-30 winter, M1 10-30 summer
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