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Changed the front brake pads for the first time on Saturday - thanks to all for your earlier suggestions. I'm a reasonably experienced mechanic but I've had bad experiences working on ABS systems on cars in the past, so I was a little hesitant. But it worked out fine. A few Lessons Learned:
1. I was originally going to pull the front wheel and remove the calipers to replace the pads, but upon reflection (and consulting the RepRom) decided to do it with everything mounted. That was the right decision. This is a ridiculously easy job. If you have half a bit of mechanical ability, and a T-30 male wrench, you can do it. There's virtually no way to screw up and not be able to back out and recover. Took me about a half hour, with most of that time washing parts, drinking coffee, and enjoying the morning sunshine.
2. Lots of choices of front brake pads out there. I decided to use OEM on the recommendation of the dealer based upon suggested life of the pads. I got 44k off the first set. A bit pricy, though - $89/side (not much less at MaxBMW). I'm sure others have different opinions.
3. To remove the pads, you have to back out a screw that holds them in place. The screw (called a "grub" screw) in turn has a little clip that keeps it from backing out accidentally. Be sure to remove this clip before you try to back the screw out! Once you get the grub screw out you remove a spring steel retainer plate. Simple Green and a bit of elbow grease worked fine to clean these up before replacement.
4. The torque for this "grub screw" is not listed in the normal table of torques. I found it finally in the RepRom - 7 Nm. This is probably not a critical torque item as it doesn't hold two things together, it just holds the screw against its stop. So "Gut Enuf" is probably good enough.
5. Good idea to clean around the pistons before pushing them back into the caliper to make room for the thicker new pads. Also, check the reservoir to make sure that when you push the pistons back you don't overflow. Brake fluid + paint is a BAD combination.
6. Most logical way to replace the pads is one pad at a time, one caliper at a time. (If you remove both pads first, when you push the pistons back on one side you'll push them out on the other side). I found that two old plastic toothbrush handles (I don't throw away old toothbrushes - they're amazingly handy things to have around, and if they get dirty in their second life, you can toss them then) were just the right size to cram between the pistons and the rotor to push the pistons back to get space for the new pads. And being somewhat soft plastic they didn't score anything up.
7. First little bit the pads rubbed against the disc and heated it up. After a few miles and a few service actuations of the brake lever they settled in. I don't know if there was some residual pressure in the line or what. In hindsight I think next time I'd install the pads, squeeze the brake handle to fill the pistons, then open up the bleed valve to get rid of any residual pressure. (This latter step isn't covered in the RepRom, but clearly something was going on until the pads seated).
Onwards.
JayJay
1. I was originally going to pull the front wheel and remove the calipers to replace the pads, but upon reflection (and consulting the RepRom) decided to do it with everything mounted. That was the right decision. This is a ridiculously easy job. If you have half a bit of mechanical ability, and a T-30 male wrench, you can do it. There's virtually no way to screw up and not be able to back out and recover. Took me about a half hour, with most of that time washing parts, drinking coffee, and enjoying the morning sunshine.
2. Lots of choices of front brake pads out there. I decided to use OEM on the recommendation of the dealer based upon suggested life of the pads. I got 44k off the first set. A bit pricy, though - $89/side (not much less at MaxBMW). I'm sure others have different opinions.
3. To remove the pads, you have to back out a screw that holds them in place. The screw (called a "grub" screw) in turn has a little clip that keeps it from backing out accidentally. Be sure to remove this clip before you try to back the screw out! Once you get the grub screw out you remove a spring steel retainer plate. Simple Green and a bit of elbow grease worked fine to clean these up before replacement.
4. The torque for this "grub screw" is not listed in the normal table of torques. I found it finally in the RepRom - 7 Nm. This is probably not a critical torque item as it doesn't hold two things together, it just holds the screw against its stop. So "Gut Enuf" is probably good enough.
5. Good idea to clean around the pistons before pushing them back into the caliper to make room for the thicker new pads. Also, check the reservoir to make sure that when you push the pistons back you don't overflow. Brake fluid + paint is a BAD combination.
6. Most logical way to replace the pads is one pad at a time, one caliper at a time. (If you remove both pads first, when you push the pistons back on one side you'll push them out on the other side). I found that two old plastic toothbrush handles (I don't throw away old toothbrushes - they're amazingly handy things to have around, and if they get dirty in their second life, you can toss them then) were just the right size to cram between the pistons and the rotor to push the pistons back to get space for the new pads. And being somewhat soft plastic they didn't score anything up.
7. First little bit the pads rubbed against the disc and heated it up. After a few miles and a few service actuations of the brake lever they settled in. I don't know if there was some residual pressure in the line or what. In hindsight I think next time I'd install the pads, squeeze the brake handle to fill the pistons, then open up the bleed valve to get rid of any residual pressure. (This latter step isn't covered in the RepRom, but clearly something was going on until the pads seated).
Onwards.
JayJay