Rear brakes dragging

First I have limited experience with Audi, as this is a friends car. I have Audi A4 and went through the experience of trying to replace the rear brake pads. I know that the pistons have to be rotated back into
the calipers and I was (I think!) successful at that. Prior to replacing the pads, the brakes worked fine.
So here's the problem. On the drivers' rear wheel, I back off the piston just enough to get the new pads into the caliper, around the disk. I made no attempt to back the piston all the way into the caliper ( was that a mistake?). I did the same on the passenger side, but probably backed the piston further into the caliper on this one.
Got everything back together, pumped the brake pedal a few times ( rather hard to insure that the pads were somewhat settled ). I then backed the car down the driveway, which is VERY steep and at the bottom of the driveway applied the brakes quickly and hard, hoping to: 1) insure they were working, and 2) to adjust them ( in the same manner as american cars in the past - which may again be another error ).
At that point the car was driven about 7 miles (by the friend) and at the end of the trip, which was stop and go on california freeway, the rear brake - particularly on the driver's side, was smoking. Also noted when the car was returned, that parking brake had very limited travel ( sounds like it was overadjusted??).
I have since disassembled both rear side, backed the piston all the way in and 'gently' backed out of garage. All seems better, although there is still a slight 'burned pad smell' but that is declining with time. I think the smell is left over glazing, although braking is fine at this point. Parking brake adjustment is now okay.
I have reread the service manual ( which I have and used! ) and I see nothing about backing all the way in, nor any comment on adjusting the pads themselves. I have verified the the parking brake adjustment.
Comments - Suggestions? Does anyone know what I did wrong? ( I know I am probably asking for a large 'ration' here but other's opinions are useful!)
Steve
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stvnjns wrote:

It is in error. This applied to self-adjusting *drum* brakes. It does nothing at all on a disk brake.

What you did wrong was not pay someone to do this *shit job*. I am not criticizing you. It sounds as if you pretty much know what you're doing. I, too, am a reasonably competent amateur mechanic, but this is one job I *will not do*. These brakes suck out loud. It is a stupid design in a number of ways and the only way to be sure they're properly installed is to have someone with the expertise - and the responsibility to redo it if they screw it up - do the job. When I discovered that my Jaguar X-Type shares the same design, I ponied up the obscene number of US dollars it took to have the dealership change the rear pads. Then I went home and changed the pads on my Jeep - just like I do on my BMW - and just as I plan to do on the front end of the Jaguar. Some things just aren't worth the aggravation. Working on Audi rear disks is one of those things. -- C.R. Krieger (Been there; done that.)
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C.R. Krieger wrote:

Weird. I found it to be fun and easy.

Heh.
Not necessarily true. The *proper tools* to do the job are required.
Expertise - that's also necessary, but it can be passed along via written instructions (with pictures is nice, but without works.)

I've never once had a problem after doing this job, but I'm careful, do a thorough job, and don't scrimp in any area. The cam for the handbrake actuator can stick if not properly cleaned and lubed. The guide pins can stick if not properly cleaned and lubed.
I've found what happens is that folks just don't clean this stuff when they are doing a caliper rebuild. It takes me about a half hour to disassemble, clean, lube and reassemble a pair of rear calipers. Screwing the piston all the way back in, with the proper tool, helps make sure all goes well.
While I would prefer that the rears have the same design as BMW or Porsche, I've never had any trouble with calipers that I've rebuilt and installed, and I'm no pro mechanic.
E.P.
1995 UrS6
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Well Thanks to you both - I have noticed that many people have had issues with these calipers, whether as a result of their own inexperience or due to the calipers. The service manual was limited help ( A standard Audi manual, not after market )
In response to 'cleaning', I did clean and lube.
Although it says nothing about it in the Audi service manual, there seems to be (based on web pages and responses elsewhere) an implied requirement to retract the pistons COMPLETELY back into the caliper. It is not clear how this is determined nor is there any real comment on having to do this. In past experience, with non-Audi brakes, simply retracting the piston far enough to allow the new pads to clear the disk was sufficient. I really think that not fully retracting the piston was the error that I made, so if anyone else can think of anything else that I may have done wrong, I will assume that was my fault and move on.
Thanks for the responses - didn't think I would get any for a while there! Steve
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OK, I'll add my two (British) pence worth - about 3.9 US cents today, that's a v.good exchange rate!
Anyhow, whilst I haven't actually done the rears on my B6 S4 yet - I am familiar with similar rear callipers.
There are a number of important "tips", which the manuals often don't cover. Firstly, disconnect the handbrake cable from the calliper arm. Secondly, wind the caliper pistons back in fully (observing usual cautions re: master cylinder level & piston boots). After fitting new pads and re-assembling caliper - do NOT re-attach handbrake cable yet. Pump the brake pedal, slowly, but hard, reaching maximum travel on each pump. Continue pumping until pedal reaches normal pedal travel. Start engine & allow to idle, then press brake pedal v.hard again a couple more times - this allows the benefit of servo assistance to apply max pressure to brake pedal.
Now, this next part is not critical, and it can be omitted if you are not comfortable with driving without a handbrake. It does help to get the correct rear caliper piston adjustment, but, and it's a big but - there is a WARNING. Read it properly and understand that by following this particular point, you will NOT have a working parking/emergency/hand brake, and any relevant safety and legal requirements are your own responsibility. OK - warning fully understood and responsibility for you own actions accepted - with the handbrake cables still disconnected, drive the car to bed-in the new rear brake pads - this can take upto about 150miles (but the first 20 or so miles removes the biggest of "high spots").
After this initial bedding-in, you can re-connect the handbrake cables to the rear calipers. Before you do re-connect them, two more good tips. With the rear wheels raised (and the car properly supported on stands), spin both rear wheels to make sure they spin freely, to check for no obvious binding from a stuck piston. Next, re-connect the handbrake cables - making sure there is enough free play in the handbrake cable, and with the handbrake in the OFF position, the actuating arms in the calipers are resting against the caliper stops. (Some service manuals on different cars state a specification of upto 2-3mm between the arm and the stop, but I personally try to aim for zero clearance - however, this depends on the strength of the return springs, and also the travel on the handbrake lever.)
With the cables re-attached, work the handbrake fully on and off a few times, then fully release (in the off position) the handbrake. Re-check that the rear wheels spin freely - hopefully exactly the same as before refitting the h.brake cables. If there is obvious binding of the rear wheels - two things can be wrong. Look at the caliper levers to see if they are resting against the stops (or within the appropriate tolerance). If they are not, use a lever on one side, then the other, to pry the caliper lever back to its stop. If both the caliper levers can be helped to the stops, then you may either have weak return springs, or a stiff handbrake cable. If, however, you can get one caliper lever to rest against the stop, but the opposite side then moves away from the stop, and vice-versa for the opposite side, then you need to add more free play in your handbrake cable itself.
Rgds
Sean B6 S4, A5 GTI
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Thanks for the VERY informative description. It confirmed and added to much of what I found. I hope this also helps others.
Steve
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You're welcome. It's always good to hear some feedback, whether good OR bad.
Keep the shiny side up, rgds
Sean
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