Quote:
Originally Posted by kevmk81
Taking a local on-ramp in my '16 340i I'm hearing what sounds to me like brake rub. It's repeatable - but - it's only on this single specific on-ramp. I'm assuming the camber and angle of the ramp is just right to get the brakes to do this. Once I'm on the interstate all seems well. I'm not entirely sure which wheel it's coming from - too dang cold to drive with windows down right now - I wouldn't be able to focus on the sound. One thing to mention - when I use the e-brake when I park - when I start driving again there is brake rub until I use the brakes again, say at the next stop sign/street light. Once I drive off - the brake noise is gone. I found my 340i in January at a BMW dealership. The car fax report indicates that all the work the previous owner had done was at their local dealership, so I'm thinking, according to the report, that the only brake work that has been done has been a brake fluid flush/change. So at this point I believe the pads and rotors are original. Car has 36k miles. Any thoughts on what the rub is all about? I'm not really concerned right now but I can imagine it'll get worse. My gut feeling is the brake shield maybe, but that wouldn't affect the ebrake from fully releasing right? I'm brake mechanics ignorant.
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Hard to tell what the problem could be but if you believe the pads are sticking under certain conditions, you'll need to check the calipers.
On M Sport, 2 piston calipers (grey, blue, yellow, red), there are two thin push pins, which, according to RealOEM, require a change every 4 years. There is also an anti-rattle clip, which also requires a change every 4 years. These are relatively cheap parts so you may want to swap them anyway. They act as springs that are constantly under load regardless of whether the car is moving or not, the brake is used or not.
For single piston calipers, check where the 'ears' of the pad rest on the caliper carrier. Over time, dirt builds up on the caliper carrier and can cause the pads to stick. Clean the carrier where the pads sit with a wire brush and manually move the pad on the carrier to check for binding. The single piston caliper also has two pins, shorter but much thicker than the front calipers which can also get dirty which can contribute to binding. I use Nevr-Dull Wadding Metal Polish with success in cleaning these pins. You could replace them but they are relatively expensive and I’ve never run into an issue where they needed replacement. Part of the issue with the thicker caliper pins is over greasing. BMW, and other makers, say no grease, but most shops, and many DIYers will use at least a little. This aids in preventing binding but does attract dirt, which contributes to binding.
Good luck in tracking down the problem. My guess is your problem sounds minor but checking won't hurt and a new set of pins and clips for a 2-piston caliper won't hurt either.