2007 BMW E90 N46B20
Mileage: 67k km
Early January, OBC said my front brake linings can last another 2.5k km.. 2 weeks later or 1k km later, I’m at –500km !! 
Hence, the following DIY.. 
Been changing brake pad since I first own cars.. and still doing it to my other higher mileage Toyota mini MPV.. refer to my archive.
Here goes:
1) Use a brick to block the rear wheel to secure the car preventing it from slipping of the jack.
2) Turn the steering to the right for a left wheel job so the brake caliper is exposed.
3) Loosen the wheel lugs before jacking the car.
4) Jack the car.
5) Unscrew the lugs and remove the wheel. The wheel tend to seize at the rusty wheel hub and require some effort to knock the wheel out. I used a rubber mallet. So worry the jack slips while I hammered it. Check out the rusty wheel hub.
6) Unplug the plastic protective plugs, item 7 below so we can reach and unscrew both the upper and lower guiding bolts using size 7mm Allen key wrench, item 6.
7) Use a sharp plier to slide the guiding bolt out so we can lift up the caliper housing.
8) Carefully remove the brake wear sensor. It can be recycle depending on the condition of the sensor. I’m not so lucky because I broke mine. I pulled/forced it out before opening the caliper housing, hence snapped into 2 pieces..
9) Slot in a metal bar or wrench handle into “X” below and use it as a pivot to push the caliper piston back into it’s camber, to make room for the new lining. Make sure you apply force to the center of the piston surface so even pressure is applied. Uneven pressure make damage the piston seal in the long run.
Make sure you monitor the brake fluid reservoir so it does spill/overflow. Remove any excess brake fluid carefully because the corrosive fluid can damage our car’s paint. If contacted with the car’s body, immediately rinse off with water, wash with soap and wax it.
Also please note that the 2 guiding bolts need not be taken out entirely.
10) Clean the slots where the lining seated, it’s filled with brake dust. The clean seat allow the lining to slide in and out during operation, prevent sticky pads. The lining over the caliper piston is plug into the piston cavity, so need to apply some force to unplug it.
11) I prefer to install the brake sensor before returning the caliper housing into place because I can see how the sensor is seated without the brake disc rotor blocking my view. You may do it later.
More photos:
Pad/lining that I use. TRW brand.
Close-up on the sensor
Old vs new
The bill, yup! I bought both front and back, same price. For E90, only the front left and rear right has sensor.
Notice how I use the wheel to support the rotor, just in case the jack slipped.. Also notice the L-shape bar on the lower right corner? I used that to push the caliper piston returning it back into the piston camber.
By the way, have fun figuring out how to reset the OBC counter.. haha! 
Thank you for reading!
