Inside brake pads wearing 75 % in less than 5000 miles

Could be your rear brake cable is bad,causing your brakes to wear more,

The brake pads are well within a good long life. Brake wear life depends on a number of factors, the most significant is the driver. Most people feel that they are easy on brakes and that is usually not true...

Rotors are damaged by: normal wear; waiting too long for pads and damage from metal to metal contact; and HEAT. Heat damages rotors and causes them to warp. Cars now days have less material on the rotors and therefore they have shorter life.

On some vehicles it is only slightly more to replace rotors, versus resurfacing them. A resurfaced rotor has less material, so warping happens faster.....Some shops just routinely replace rotors, rather than resurface for just this reason.

Other shops routinely replace calipers, which can be agrued either way, but a caliper that hangs slightly will cause rotor warp. My preference is to replace calipers when they need it, by leaking or binding....

you can't estimate brake wear with mileage, dirver style, conditions such as highway, city, hilly country, all have a different effect on brake wear, i have seen some drivers only get 15,000 miles and others over 100,000, best to get them inspected once a year and replaced when 60 to 70% worn

When they wear out. There is no recommended mileage for brake replacement, like there is for timing belts, fluid changes, etc. This is because grandma driving slowly down the street, lightly touching the brakes to slow and stop might go 100k miles before her brakes wear out, and her grandson driving the exact same vehicle and pounding on the brakes to stop quickly for traffic, stop signs, etc. may get 18k miles on his brakes. So, the brakes have to be checked for wear occasionally to determine when brake replacement is needed. You must be careful though, as some repair shops will tell you to replace the brakes when you could drive the car for another year w/out worrying about the brakes. Vehicles are equipped with 'wear indicators.' which will make a lot of noise when the brakes pad linings wear down. The wear indicator makes contact with the brake rotor when this happens. This is the signal that you will soon need to replace the brake pads. You can actually still drive the car safely for some time after this, but the noise is annoying! When you do have the brakes replaced, make sure the shop bleeds the brake lines thoroughly to flush them out, and replace the fluid. This is overlooked by many people, and can lead to problems later (brake fluid absorbs moisture, which will corrode components (calipers, brake cylinders) and cause them to fail. So, if you don't hear anything, don't worry about the brakes. If you are still concerned, have a shop that you trust inspect the pads for wear. If you don't know of a reputable shop, ask friends and family who they would trust. Good luck!

Yes, your vehicle needs to use the semi-metal brake pads.

Asbestos has been the best brakepad material; however, asbestos was outlawed last decade. Currently, the best is brakepad is semi-metal. The brakepad is impregnated with brass filings.

All semi-metal brakepads carry a limited lifetime warranty against wear. Purchase a set and compare to the ones on your vehicle.
-Gort.

Most of the stopping power goes to the front of the car. You usually go thru two sets or sometimes three sets of front pads before you need to change the rear brakes. It sounds odd the rear brakes need to be replaced at 22,000. havee the front brakes been replaced before?

I would take it to the dealer because of unusual brake pad wear.brake pads under normal wear are not covered usually.But if the outside pad wore down to metal and the inside is ok that is a caliper sticking causing a drag of the outer pad to the rotor.

I would replace the MASTER CYLINDER. BLEED AIR from master cylinder BEFORE INSTALLATION. Hope this helps

BMW rotors are not known for lasting very much more than 30-45k miles. When the brakes are inspected, they measure the pads using a special tool threw the outer brake pad. Min spec is 3mm. When the pads are replaced, they measure the thickness of the rotors. The rotor spec is stamped on the rotor. if they are under that spec, they recommend replacing them as well. Next time you bring it in for service, just ask them to measure the rotor thinkness, (its not a huge task, all they have to do is take the wheels off). But more often than not, the rotors wear just as fast as the pads.

You need to get the rotors turned and get new brake pads.