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KOG
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Discussion Starter #1
Both brakes wore inner pads out while showing almost no wear on outer pads, right side got into rotor. I've been monitoring pads at every oil change and the outer, which are visible, didn't indicate any need to change. 60K, front pads are maybe half worn from new which would also indicate that rears should be fine. Three of the eight "abutment shims" are missing which probably explains a "clunk" noticed when applying brakes in reverse. Procedure in shop manual for retracting rear caliper pistons with special tool isn't working either unless it takes a LOT of force to turn the piston back in.

??? Anyone have experience with these things?
 

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I've never had a car with rear discs, but that kind of wear suggests to me that the caliper is binding on the guide pins. I had that happen with my wife's last car - inner pads cut to nothing while the outers were like new. No outward sign other than very gradual loss of effective braking, because those were the front pads. The rears don't act as much, so you would be less likely to notice.

I've read that the retraction method is a bear, they tend to rust up and be difficult to get the pistons in, but I've never done it.
 

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Does your shop manual recommend any special tools for the rear calipers? If they are the "twist in" type they need to be turned while pushing them in. Inner pads wearing excessively sounds like your guide pins are sticking. With the pads removed and the calipers bolted back in place, see if they slide back and forth fairly easily. The proper tool for compressing the calipers can be bought or sometimes rented from most local auto parts stores. DO NOT use the pneumatic caliper compressor on this Mopar, you WILL damage the calipers and ultimately solve you problem by purchasing new ones!!! Good Luck!!
 

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KOG
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Discussion Starter #4
OK, as noted above, I've got the special tool. The pistons aren't moving easily with that. Since I haven't done this before I don't want to damage anything by using excessive force. Unless there's a trick not noted in the FSM it must take a lot of force.

There's no rust, wear or binding on the slides or pins. And the pads actually slide on shims in this application. This is a southern car, it's never seen snow or salt, no rust whatsoever. To illustrate the climate here we've got a '67 Dart with no rust as well.
 

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Virginia Gentleman
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Bob Lincoln said:
I've never had a car with rear discs, but that kind of wear suggests to me that the caliper is binding on the guide pins. I had that happen with my wife's last car - inner pads cut to nothing while the outers were like new. No outward sign other than very gradual loss of effective braking, because those were the front pads. The rears don't act as much, so you would be less likely to notice.

I've read that the retraction method is a bear, they tend to rust up and be difficult to get the pistons in, but I've never done it.
Comment on rear brake wear. The assumption that rear brakes don't wear as fast as the fronts is not a given with vehicles that have traction control. Co-worker of mine has a Pontiac G8 where the rear brakes wore out nearly as fast as the fronts did. Turns out he is somewhat of an aggressive driver and unknowingly his driving habits were activating the traction control (by activating the rear brakes at times).

Our Journey has traction control and at times (especially after cleaning the wheels/tires) that brake dust builds up faster or first on the rear wheels. I try not to drive in such a manner as to activate the TC. but invariably it does happen.

One additional thought. The rear brakes on my Ram had to be serviced at ~90K miles. I had thought I would get closer to 120-130K out of them since the fronts were serviced at 66K. Turns out the pads are not as thick as they use to be. Engineers cuttting weight were ever possible.

The point here is the basic assumption that the rear brakes don't do as much work isn't always true. Especially with vehicles that have traction control.
 

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KOG
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Discussion Starter #6
Somehow I don't think that traction control is an issue with rear brakes on the T$C. We have seen a traction control issue on an 01 T&C - wore out the right front pads much faster than the left front.

The major question remains: how much effort does it take to retract the caliper pistons, and is there any trick other than real force involved?
 

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There was a Chrysler Tech Tip TT9001840 that addressed uneven rear pad wear/noise on the 2009 RT-body. I don't know if this is what is happening here.
The piston should screw in with downward pressure and turning clockwise. Make sure that the rubber boot doesn't twist with the piston turning.
If the new pads have 180 degree locating nubs on the lining backing plate, make sure that they fit in the piston recess slots.

Issue Description:
For uneven pad wear, off-brake noise, or an issue other than piston doesn't screw-in or re-adjust out, do not replace caliper assy. Instead, replace adapter bracket PN 68029886AA, both rear brakes. Add grease PN 04796269 to new adapters in four locations (under pad clips only - not on pad side).
 

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As far as twisting in the rear calipers, are you sure you're twisting in the correct direction? I don't know about yours, but I've seem some that will twist counter-clockwise and IIRC, my old Subaru twisted clockwise. Try it both directions with steady, but not extreme force.
 

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KOG said:
Somehow I don't think that traction control is an issue with rear brakes on the T$C.
I agree. I would blame the ESP (aka stability control) before the traction control.

From the Manual:
Electronic Stability Program (ESP)
The Electronic Stability Program (ESP) enhances directional control and stability of the vehicle under various driving conditions. ESP corrects for over/under steering of the vehicle by applying the brake of the appropriate wheel to assist in counteracting the over/under steer condition. Engine power may also be reduced to help the vehicle maintain the desired path.

ESP uses sensors in the vehicle to determine the vehicle path intended by the driver and compares it to the actual path of the vehicle. When the actual path does not match the intended path, ESP applies the brake of the appropriate wheel to assist in counteracting the oversteer or understeer condition.
George
 

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KOG
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Discussion Starter #10
FSM specifies clockwise rotation on both sides.

ESP is also a highly unlikely cause of pad wear in this case. This thing has never been driven anywhere near its limits so as to engage ESP.

I'm going with Imperial Crown's diagnosis. Is there any possibility that the brackets can be had as a warranty claim?
 

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I would suspect the calipers are at the least going to be a little sticky trying to get the piston back in in the given circumstances. The entire load was being taken by the inner pad on the piston which is going to generate a heck of alot more heat and toque on that piston fully extended than if the caliper was centering properly, especially if you had metal to metal contact.

Id try to be as gental as possible with it and carefully try to get some movement out of the pistons, usually they go in alot easier once you get them started. Getting them started after that much heat might take a little pursuasion but dont break it. Be sure to take a real close look for signs of heat stress. Its not uncommon to see cracking in the rubber sleeve around the piston, and sometimes the metal of the piston can get brittle if overheated too badly.
 

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KOG
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Discussion Starter #12
Rubber boots are not cracked, but there's no doubt been plenty of heat in the area. I'll just start leaning on the pistons until they move. Haven't been rushed on this so far because I'm waiting for the pads to show up. I've gotten good service from Performance
Friction Carbon Metallic pads on other vehicles and those aren't stocked locally here. Also not cheap the first time, but lifetime warranty and outlast, outbrake others from what I've seen in the past so I'll pay.
 
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