I wish I had read this last night when I was installing mine. I test fit pads into the rear st40 caliper just to see how the pads went in, no issue. I wished I had also checked out the st60 caliper beforehand.
The abutment plate on the calipers are the main issue. Add in questionable pad production, too much paint and it's all adds up to a super tight fit. The abutment plates are not perfectly 90 degrees on one of the pad sides, I think it's the bottom. There is a slight pinch making it appear to try to put tension on the pad. But in reality it just makes it a bitch to put the pad on. The top is 90 degrees, if both were 90 degrees them the pads should slide in and out like I'm sure most of us had envisioned.
We had to Dremel down the pads and I had to tap them in with a mallet. It didn't require a lot of aggression but I didn't expect this. In my opinion this bypasses the appeal of the stoptech bbk since it in fact does not allow fast pad changes if you have to grind down sides of pads, and bash them in with a mallet. I was really hoping it was remove the bridge everything slides in and out. Reality is pry out the bridge, rip out the pads, grind down new pads, bash them in, replace the bridge. Now that I've done it and going through this thread I have to modify the caliper a bit if truly quick pad changes is my priority.
Glad that JAJ confirmed my initial suspicions. I will flatten the springy abutment plate for now and order the non springy abutment plates from HP. Track car who gives if the pads rattle slightly?
E92 M3 - Track Rental
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Mclaren MP4-12C - ATS Package
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