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comments and questions from old guy
Hi guys and girls. Just did the front brake maintenance on my 2012 135i.
When I got the car in'16 I removed all the rotors and lubricated all the contact points on the hubs etc. with antiseize compound. I do my brakes regularly and I almost never have to replace pads or rotors. (On one of my vehicles I did 225,000 km on the original rotors and on another I did 300,000 km.) I have been doing brakes for 35 years and was a licensed mechanic for a while when I was younger. THANKS to the OP and all of the other contributions here!!
1. When you have a bolt or nut which is difficult to turn, always work it back and forth until it breaks "free". That is loosen and tighten a bit, loosen and tighten a bit less, etc. It is surprisingly easy to break even a big bolt if you do not do this.
2. I totally understand the two methods for front caliper removal - allen head bolts versus the two hex head bolts "at the back" on the torque plate. I have only used the allen head bolt removal method (on this car). After the first time, they are easy to remove and replace and I doubt there is any risk in this. The reason I like this method is that replacement of the caliper onto the rotor is very very easy this way.
3. I had a tough time getting the pads in (front caliper) because the pad would not go past the spring clip, kept catching on it. It was much easier when I backed out the torx screws. I'm curious how you get the pads in place if you don't back out the screws? Maybe I'm just clumsy.
4. One theory I have about the shims on the back of brake pads is that the shim are made of a "stainless" or rust resistant material and this prevents the pistons from rusting to the back of the pads. On the 135i they also take up some space at the ends of the pads where they slide "in and out" as the brakes are applied or released. If the pads shims are not used, the pads will be looser in the caliper and may tend to rattle (?)
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