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'99 M3 Brake Replacement

 
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lfein



Joined: 30 Oct 2000
Posts: 34
Location: Austin, TX, USA

PostPosted: Sat Aug 27, 2005 4:30 pm    Post subject: '99 M3 Brake Replacement Reply with quote

I replaced the pads, rotors, and sensors on my wife's 1997 328i (123K). After the first wheel, I got the hang of it and the other three were quite easy, except for a few very tight caliper bolts on the front wheels. I later discovered that they required a very high torqe setting upon installation. Of course I also bled the brakes.

Now I feel confident to do the same on my son's '99 M3 (60K). I noticed that the rotors are position dependent. This is no problem, but what else do I need to know. Wow, the range of rotors and pads is confusing. We are looking for value, since he does not race the car. Seems like OEM quality would be fine. What comes stock on this car? What do you have that is comparable? My son claims that he wants Brembo, but I really don't want to spend more than the car is worth ;-)
I've got plenty of help to manually bleed the brakes, but I read that this method may cause master cylinder problems. This did not seem to happen when I did the 328i. I really don't want to invest in a power bleeder if I don't have to.

Do I really need to replace the rotors? I have been told (by everyone that sells rotors) that because the rotors are "soft" that these should be changed along with the pads. What do you think.

Thanks,
Lenny in Austin, Texas
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jlevie



Joined: 01 Jan 2005
Posts: 553
Location: Huntsvile, AL

PostPosted: Tue Nov 15, 2005 7:01 pm    Post subject: Reply with quote

The wear limit should be stamped on the rim of the rotors. If worn to or below that thickness when replacing pads the rotors will need to also be replaced.

OEM rotors are always a safe bet. I'd say to stay away from cross-drilled rotors as the reduce the swept area and thus the braking force. Slotted rotors will provide more performance at the limit, but pad wear will be worse.

There are advantages to a pressure bleeder (about $60). It makes the job much easier and there's very little risk of running the brake fluid reservoir dry or in getting air into a caliper. If the reservoir ever runs dry on a BMW with ABS it will require a trip to a dealer or well equipped indie to fix. I don't bother with just bleeding brakes since I purchased a pressure bleeder. Now I do a full flush on every bleed because it only takes a few minutes longer.
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edjack



Joined: 04 Feb 2002
Posts: 3887
Location: San Jose, CA

PostPosted: Tue Nov 15, 2005 9:45 pm    Post subject: Reply with quote

jleive:

Do you put fresh fluid in the bleeder every time you use it, and discard whatever's left over?
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jlevie



Joined: 01 Jan 2005
Posts: 553
Location: Huntsvile, AL

PostPosted: Tue Nov 15, 2005 10:38 pm    Post subject: Reply with quote

Yes, I use fresh fluid (AP551) every time. The enemy of brake fluid is moisture, which it promptly starts to absorb when exposed to the atmosphere. Modern fluids aren't nearly as hrdoscopic as the stuff we used to have, but i'd rather not take a chance on fluid that's been sitting in a partially fillled container. Besides, AP 551 or ATE Type 200 is pretty cheap. I don't recommend using the ATE Blue as it will stain your brake reservoir.

I track my car, so it gets several fluid flushes each year. I start by sucking all of the fluid from the reservoir and replace it (to the very top) with fresh. The remainder of that liter of fluid goes in the pressure bleeder. Then I'll push 200ml thorugh each rear wheel and 150ml thorugh each front. At that point the pressure bleeder is almost empty, so there's not really much to discard.

AP551 is good for at least six months, or so my mechanic (a Grand Am racer) tells me. But it is cheap and if I'm going to bleed the brakes before a track session I figure I might as well do a flush.
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sailorbobk



Joined: 18 Sep 2007
Posts: 73

PostPosted: Sat Nov 29, 2008 9:34 pm    Post subject: Reply with quote

Gravity is the best pressure bleeder. Fill the reservoir, put a hose on the bleeder and the free end in an empty jar, loosen the bleeder then sit back and let the laws of physics do the work for you. If you're concerned about air bubbles sticking to the walls just tighten the bleeder a few times and pump the brakes to break them loose then open the system again. I'm not sure that is necessary, but can't hurt.

I recently used this system when I installed stainless braided brake lines. My brake pedal is rock solid.
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