We just got the new JCW, with the Brembo brakes. I took a quick look at the brakes and didn't see any obvious way to measure the brake pad thickness using the BMW brake thickness tool. Am I missing something?

My best idea currently is as you can see the edge of the backing plate, you could use the tool to measure the thickness of the pad and backing plate, then subtract the backing plate thickness. How thick is the backing plate?

 

For a quick and dirty method, I used the BMW brake tool against the backing plate. The top corner of the pad sticks out from the caliper and you can use the tool to measure from the backing plate to the rotor. It turns out that under estimates the pad thickness by about 1.5mm. So if the tool reads 7mm like that the pad is about 8.5mm actually.

Then I discovered that doesn't tell you the whole story. The pads may wear unevenly with the top of the pad wearing more than the bottom of the pad. This seems to be particularly true under heavy brake use, like at the track. So this method may over estimate the actual pad wear.

The pads also wear unevenly inside pad vs outside pad, so the only sure way to check your pads is to take the wheels off and pull the pads. I use my calipers to do this, zero out the backing plate thickness, so I can directly measure the pad thickness at both ends of the pad. So now I'm keeping track of 8 different pad thicknesses.

I'm being especially paranoid after a friend (not one with a MINI) tells how he trashed a rotor not measuring the inside pad thickness and wearing a pad down to the metal.