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Old 08-06-2000, 11:05 AM
Join Date: Mar 2000
Location: Gainesville FL
Posts: 6,844
Lots of good advise here but let me add something to explain what actually happens during caliper application that explains why you get dissimilar wear.

When you apply the brakes, what causes them to unapply???? Its not the spring clips. They are there to keep the pads from rattling and to dampen vibrations...........

The answer is the resilience of the square cut piston rubber seal. When the brakes are pushed the seal FLEXES to allow the pad to come in contact. Overall the piston eventually slips through the seal(with pad wear) but not with each braking. During normal operation the seal flexes out with the pad and something like a rubber band it springs back pulling the piston back also, after the event. Over the years the seals get hard and the piston moves through the seal (eventually leaking) and in this case they aren't pulled back properly. This causes the pad to stay partially engaged with the disc and accelerates wear. Any dirt or corrosion that holds the piston of course causes the brake pads to stick also, but this is usually much worse than just differences in pad wear.

We charge an hour labor to rebuild a caliper. With rebuild kit this is much cheaper than rebuilts and I am sure of the quality.

PS: My father was an administrator for United Air Lines for 40 years before his retirement. He lets me (my shop) do all his work now, but during my childhood he did almost all his own car repairs. Some of my most memerable moments as a child were hanging around the one gas station that he would go to when things were beyond his capabilities.

Steve Brotherton
Owner 24 bay BSC
Bosch Master, ASE master L1
26 years MB technician

[This message has been edited by stevebfl (edited 08-06-2000).]
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Old 08-06-2000, 11:19 AM
Posts: n/a

Thanks for your explanation. I thought it was just me, doing my own work as economically as possible, that saw rebuilding calipers as preferrable. However, when I think about it, if I were trying to turn some profit AND see that the customer didn't have to bring the car back, rebuilding them myself would provide much better quality control. If you see that a caliper is not rebuildable, then you get what you need. I guess it gets back to the old "if you want something done right, do it yourself" motto.

Thanks again for the insight,
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Old 08-06-2000, 03:27 PM
Registered User
Join Date: Apr 2000
Posts: 166

Thanks for the input about riding the brake pedal. That is one habit I have assiduously avoided. Can't speak for my wife, however; anyhow, I do better than 90% of our driving and as stated earlier, neither of us drives hard. Perhaps Steve's point about the difference in wear patterns holds here. I discovered my caliper problem while driving between Baton Rouge and Houston. The car was pulling severely to the right. When I checked, I found the outside brake pad was tightly locked against the disc


Thanks for the clarification. In a previous post I referred to a "rib" on the seal that pulled back the piston. I didn't realize that it was only the basic seal itself.

As to ease of rebuilding calipers, it has been a long time, but I seem to recall that the exterior of the piston has a cutout that has to be installed at a specific angle in order to prevent squeal. I believe my biggest problem was that I could not get the precise angle. I made a template to be used to check the angle. Once the piston was installed, it could not be turned and had to be extracted, repositioned and reinstalled. I don't know how many of these cycles I went through before giving up and just saying, "That's going to have to be close enough." It has worked all right, so I guess it was "close enough".

Thanks to all for the input.

1979 240D
160,000 miles
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Old 08-08-2000, 12:54 AM
Harvey Sutlive
Posts: n/a
Sometimes those rubber sealing rings in the caliper body get put in the wrong way. They've got a bevel that's not particularly noticeable.
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