BMW BRAKE SHAKES
Is your steering wheel quakin' in its boots? Tie the laces!
The newest BMW E46 is now 10 years old. Many are older. These cars are built to high standards but they're also built as light as possible with light and sometimes thin materials. These can make it easy for slight imperfections to cause strong vibrations. The easy answer is to replace everything. But some are on a budget. So you'll have more work to do. It's important you fully maintain the suspension and verify the maintenance and operation of your vehicle. The basics of this apply to any car.
If your vibrations start around 60mph and get worse as you go faster, this is typically the result of poor balancing. You may say, "But Mango! My wheels ARE balanced." Try another shop. Not all balance jobs are created equal. Some shops do not regularly calibrate their machines. Yes, the machines that balance your wheels need to be "balanced" themselves. Go to a larger tire store for this as their equipment is more likely to be kept-in-check. Don't rely on some small shop all the time. Some people prefer road-force balancing where a load is placed on the wheel to replicate its intended use.
OEM wheels are your best bet as far as avoiding vibration. The reason is OEM wheels are hub-centric from the factory and this makes easy to center correctly prior to applying a clamping force (torque) to the wheels. Also be sure to thoroughly clean, and if necessary lightly sand, all mating surfaces. This includes the wheel mounting face where it touches the hub and the hub surface itself. There should not be any corrosion at this interface. It must be medical-grade clean for full safety and vibration free driving. Check periodically as corrosion can build. The corrosion could crush which would reduce the biting area of the wheel to hub. This can be dangerous. If you have aftermarket wheels, try purchasing the appropriate sized wheel mounting rings (aka hubcentric rings) to assist in centering the wheels. These, as far as I know, are not crucial to the loading of the wheel, but simply to assist in centering the wheel only. If you feel you need them for safety, by all means, buy them. Make sure wheels are true and round with no damage or bumps. Make sure the wheels are evenly torqued down in a star pattern using proper fasteners and torque values. 90 lbs is what I use. Make sure your torque wrench is accurate.
Needless to say, make sure your tires are of high quality and name brand. Make sure there's no bubbles or high or low spots on the sidewall or tread itself. Newer tires are better. Ensure they are inflated to the proper pressure and there's no flat spotting from donuts or track driving.
4) Control Arm Bushings
50k miles or you don't know how old they are, replace them. If visually worn, replace them. If there is movement in them when the wheel is grabbed, replace them. If you get a clunk when you tap the brake sharply, it's the control arm bushings usually. Replace them.
5) Control Arms
These have balljoints. Replace them if damaged or broken or loose.
I don't see these as a common cause for vibrations but I suppose in theory, it could happen. Replace them.
7) Wheel Bearings (at the request of the two posters who mentioned)
A wheel bearing can also cause vibrations. Particularly, you will hear a low rumble get louder as you turn left or right as the bearing is loaded up.
If your wheel shakes as you brake, all the above could contribute, however you might have Bunk Brakes. But Mango, I've replaced my brake pads and rotors! Ohh, did you now? Well I ask this. What brand? If you used low quality aftermarket, or aftermarket products generally perceived as "good" but suck anyway (BammerBrasCo, eBay, Autozone brand, Poodleman Drilled and Spotted and Dotted etc), then yes they can cause your brake shakes. What causes brake shakes, Mango?
Not warping. Not that rotors CAN'T warp, it's just next to virtually impossible. Particularly with our large rotors. The problem is PAD DEPOSITS. With quality brake parts, it's HARD to get pad deposits to the point of causing brake shakes. CrappyBoy pads can overheat QUICKLY causing DEPOSITS to form. This is why your generic BunkBoy pads caused deposits which caused vibration.
QUALITY BRAKE PARTS ONLY, ya hear?
Here are my recommendations for brakes. Check yourself to see what works best for you.
BEST: Genuine BMW Factory Pads and Rotors
Very good: Brembo, ATE, Jurid
Acceptable: Meyle, Stoptech, Zimmerman, BMW Performance rotors
Poor: eBay generic, Autozone, BimmerBro etc. (generic BMW store enthusiast brands), anything non-BMW drilled/slotted
Also if you still get vibrations using QUALITY brake parts, you could also have a stuck caliper which is causing your pad to glaze the rotor. You can also be highlighting any other deficiencies in your suspension as noted above.
By definition, if all the above are checked, verified, and ensured, then you should not have any vibrations.