Getting ready for DIY brake job

I am preparing for my first brake job for my 04 330ci (43,450mi ) no brake issues. I know that I will replace with factory front rotors when I do this job. Should I also replace rear rotors at this time also? What about pad sensors? Thanks

The front brakes do the bulk of your stopping, but you should measure the run-out on your rotors to determine if they have any life left. New wear sensors are advisable as the old ones become brittle and may be difficult to remove & reuse.
If you do plan to replace rear rotors, pads and sensor it's a great time to bleed the braking system.

There. Fixed.

Thank You for your input

I did the complete job even though oddly it was the rear rotors which arrived at the min thickness first.

I just concluded that I wanted all new rotors and pads for all four wheels so I would not have to worry about brakes for another 35K miles or so.

I re-used the sensors and haven't had a problem.

Thanks to all of your responces, this has assisted me in making my plans

I thought the same thing when I did brakes on my wife's Jaguar. Then it dawned on me: traction control. At least on that car, the system brakes the inside rear wheel whenever you're starting to understeer. Like when I'd punch it out onto the street in the snow.

I know this sounds crazy.

I have done the brakes on my 330ci a couple of times and I never replaced the sensor; and by that I mean I tied the old one back up into the wiring loom with tie wraps. It's still in the brake control wiring circuit, it's just not in the brake pads anymore. So as a result, it's not able to tell me when my brakes are close to being shot. Big deal!!

I inspect my car at every oil change, bottom to top; in other words the brakes are inspected every 5k miles. When they are close, it's replacement time. Even if I decided to let them go all the way to the rotors, metal to metal contact, it's not like I'm losing a perfectly good rotor - if I replace pads, the rotor is automatically replaced with them. In actuality, my brakes get serviced long before the sensor would get to get into the picture (2/3s gone is about as far as I'll let them go).

I didn't know what a brake pad sensor was until I started driving BMWs; literally every car I have owned has not had them and I got along just fine. I just like to keep things simple and eliminating the pad sensor from the pads is one of the ways I do it.

Mike Miller would probably want to kill me......

Mike might love it - old school...

I thought I'd get flamed for doing away with the sensors

Good to know I'm not the only one who takes them off the job - really not necessary if you're a car enthusiast.
Cheers all!

Aww come on; those things are cool. Yeah, I usually check my brakes frequently enough to not really need them, but the sensors are only $5 each and it's nice to know they are there for surprises. I recently burned through my front brake pads on a 2,200 mile mountain road trip. Never expected it. Nice to have warnings. Most other brands just have those mechanical scraper thingies to warn when pads are getting thin.

If you push an E30 hard enough at the track, the brakes get hot enough to melt them, triggering the sensor light - I would use them if they could survive the brake temps I see, but they won't so I keep them tied out of the way. I would keep them in play for street driving, however.

I hope this comes across as constructive criticism and not a dig, but I hope those of you who tie the sensors out of the way restore the car to factory spec before you sell it or trade it in?

I would have thought if the car was owned by a subsequent owner, he/she would not want to learn his brakes are squeeling on the steel pad backing as the first warning of service needed.

Just sayin'...

my thoughts exactly....

Let's face it; if your BMW has over 200k miles, we're talking a scrap value car here (excepting some collectable model which my 330ci certainly is not). I have only 120k on the car and have no intentions of selling it ever. There will come the day when something really expensive (like the engine) gives up the ghost and I will either find a new engine or part the old girl out. Good Lord willing, my car will be a one owner car all her life. That's how much I like the car!

WTF!? Half the E28s I know of have over 200K on them. Three of the five I've owned had 199K or more, including the one you see to your left, with ~240K. Of course, what could I expect from somebody who has a New Millennium car ...

Nice car!!

But like I said, the collectable BMWs are one thing; the E46 was a run of millions and they'll be around for quite a while. The idea of my car (and I keep it looking good) being worth anything over $5k-8k at 200k miles, with so many other E46's in the marketplace is absurd.

Now your car on the other hand is a collectable. Some e46's may make collectable but they'll be rare to boot: certain M3's and ZHPs (in concourse condition). The average car like my 330ci with sport and premium won't be quite so lucky.

A quick perusal of eBay confirms my suspicions...

personally i think one of the benefits to owning a BMW is that the car will tell you when you need to replace the pads as far as rotor replacement i would measure them using a micrometer and compare that number to the number stamped on the side of the rotor that is the factory minimum. If you are within two millimeters of that number i would suggest replacing the rotors because you will be below that number during the middle of the use of the new pads and you may than experience vibration caused by excessive heat as the worn down rotors can no longer properly cool down and get warped and also possibly glazing the new pads giving you a hard pedal. you should not need to bleed the brakes but i would suggest removing the cap of your brake reservoir as you push the piston back in to the caliper the fluid level will rise in the reservoir and may cause the excessive pressure and damage the reservoir. keep in mind you should flush your brake fluid every two years starting from the production date of the car regardless of how many miles you drive and this job does require bleeding of the brakes unless you use a pressure bleeder in which case i would follow the instructions on how to use the pressure bleeder.

I have never checked the rotor thickness..

When the pads are shot on my car the rotors get trashed along with the pads. It's the only way to do BMW brakes. But then again I don't track my car; that environment might waste a set of pads with the rotors still being serviceable and in that case just replacing the pads might be OK.

So far in the 120k miles my Bimmer has on it I replaced the front pads and rotors at 80k. The rears were gone at 120k and got the same stuff replaced. I checked the fronts while the car was on the lift and they are around half gone (40k since they were replaced). All my brake jobs include the caliper guide bolt kits as well. Brake flushes are done yearly.

That was an interesting observation about opening the bleed screw prior to pushing the caliper piston in - I had a friend that just pushed his pistons in forcing the brake fluid back up into the reservoir and he ruined an ABS system behind pushing some trash up into ABS system valves. This was on a Chevy truck and I made a mental note to never do that again. That was back when ABS was just becoming mainstream stuff.

As a side note, I have always used BMWs brake fluid; I don't know who makes it, but I have never been a fan of mixing brake fluids - mostly scared of what could happen if the two different brake fluids had a reaction inside my brake system. Have always been happy with the brakes on my 330ci; for street use they are very good. BMW has that part nailed, black dust on my wheels and all.

Cheers!