from my own experince on a 3 series....the flex lines should be changed with new calipers at around 150,000km. grabbing front brakes is a sign that one side isnt working, i replaced my calipers as one was seized up and had to replace 2 flex lines as they had collassped inside of itself over time. after 2 flex lines and bleeding all the air out of the front brakes my problem was solved. this is from my own personall experince and may or may not be the problem you are chasing but something to concider.
without a little more information, it's hard to be specific, but it kind of sounds like the brakes are grabbing at the front of the car before they grab in the rear. Or, they're grabbing harder in the front than in the rear. This could be because the rear brakes are shot, because the brakes are mal-adjusted or because the brake system proportioning valve is faulty. In any case, I'd take the car to a brake professional to have it checked.
Can be low tire pressure in left front tire, brake rotor sticking, or front end out of alignment causing it to veer left. Shaking can be bent wheel, defective tire, or brakes grabbing. Have the brakes, tires, and suspension inspected.
it means you need new brakes. about 600 bucks for front brakes done at dealer.
Front pads (disc brakes) Rear shoes (drum brakes)
One wheel of the brakes may be "grabbing" because of cracked brake linings or broken hardware. Have the brakes safety inspected soon!
The neighbors I am working on does have an ABS light that is on. So I am assuming yes. But double-check your model. Reason I am working on his is due to the pulsating grabbing the brake pads have on the rotors when applying the brakes. Also another reason the ABS light may be on is due to the warped rotors are fowling what the ABS should be doing.
Sounds like the brakes need servicing.
Brakes work by applying pressure on the brake drum and gradually slowing down your car. This should be a smooth, gradual process. If your brakes are grabbing, the process is anything but smooth - you'll feel an abruptness in the way your car stops, a sort of jerkiness.
You didn't even post which BMW you are working on. It is hard to know your level of mechanical competence, but from the way you asked the question the best thing is to take the car to a mechanic and pay them to do it. If you insist on doing it yourself, buy the correct Bentley manual for your BMW. You can see the list of books here: http://www.bentleypublishers.com/bmw Buy it from Amazon or your local bookstore. BMW brakes are much like the disc brakes on any modern car. The biggest difference is the parking brakes are inside the rear disks.
Is your car equipped with an ABS system? That keeps the vehicle from locking the brakes to prevent skidding. The brakes automatically "GRAB" on and off to slow without skidding
front front - rear rear.
The front brakes on any vehicle do most of the stopping. When you apply the brakes the weight shifts to the front of the vehicle. For this reason the front brakes are needed more than the rear. Try stopping a vehicle with just the hand brake which applies only the rear brakes.