Brake Pad Replacement Gone Wrong?
 

So, I'd noticed that the front brake pads on my 2008 Cooper S hardtop were wearing thin. I'd heard good things about Akebono's EURO pads, so when I saw them show up in the parts finder I decided to give them a try. The part matching the front pads for the '08 Cooper S Hardtop was the EUR1204.

When I went to swap out the pads however, I discovered a bit of a problem. The Akebono pads didn't fit into the calipers if the stock retaining clips were in place. The pads didn't come with any replacement clips.

Now, I had two choices as I saw it, since I wasn't in a position to wait for new pads to arrive (the old ones were even more thin than I'd thought) and I'd already done the teardown:

1. I could have taken a grinder to the pads to shave off just a touch off the tabs to make them fit the retaining clips.

2. I could go without retaining clips, since the pads fit into the calipers fairly well.

I'd never put much thought into it, but I'd once been told that the retaining clips weren't really super important, and that they mostly served to keep the pads from clanking around in the tiny bit of space they had to move within the caliper after each brake release. I chose option 2.

The first couple days went well enough. No clanking. On the third day however, I noticed a rhythmic knocking noise whenever I coasted idle. At first, I thought it was engine knock, but when I paid close attention it seemed clear that it was the pads. Looks like the clips may be more important than I was told.

Time to ask for advice. At the moment the car is parked, but I'll need to make a decision soon. Do I put back the stock clips and modify the pads? Do I leave the clips out and do something else? Do I do nothing at all and expect the knock to disappear after a while? I'm open to comments and suggestions.

I'd try contacting the maker of the pads and ask them about why they sell a product that won't fit

How I ended up solving it
 

So, its been a while since I posted the issue. I solved it, but I thought it might be useful to someone to post an update.

I pulled the wheels back off, freed the calipers and pulled the pads out. I reinstalled the original clips and carefully observed exactly where the pads couldn't fit in them. I took the pads to my workbench and fired up my Dremel tool with a small grinding wheel in it and ground down about half a millimeter at the point of contact, which spanned about a 4 mm stretch on the top and bottom edges of the plate on the back of the pad. That was enough to let the pads slide snuggly into the clips. They had enough play to move with pressure without binding, but almost no wiggle room at all.

My guess is that the manufacturing tolerance was just out of spec enough on either the clips, the pads, or both. That tiny half millimeter on each side was enough to fix the fit.

After the pads were back in place, I compressed the piston just a touch to slip the calipers back in place and put the wheels back on. After a quick test drive, first at slow speeds in a parking lot next door, then at high speeds on the highway, I was convinced that this had one the trick. As I write this, it has been almost a month and the noise has not come back.