BMW Brakes - pads vs rotors and pads

brakes
bmw
325

#1

I have a 2003 BMW 325xi. Last time I had it to the dealer, they indicated that the pads had about 20% left on them, and that I should have them replaced before the brake light comes on to avoid having to also replace the rotors. I took it to an independent BMW shop last week, who said that at this point, I still have plenty of pads left, and that I don’t need any brake work at the moment. They also indicated that since the rotors on BMWs tend to be thin, they don’t recommend replacing the pads without replacing the rotors. They recommended that I drive it until the brake light comes on, and then bring it in to have both the pads and rotors done.

Can someone give me an opinion as to who is correct?



Thanks!


#2

It amazes me to hear myself say this, but if the car is stopping straight and true, the dealer is giving you good advice.


#3

Mountain maybe you messed this:

[i] I took it to an [b]  independent[/b]  BMW shop last week, who said that at this point, I still have plenty of pads left, and that I don't need any brake work at the moment.[/i]

 [i] Last time I had it to the  [b] dealer [/b], they indicated that the pads had about 20% left on them, and that I should have them replaced before the brake light comes on to avoid having to also replace the rotors.[/i] 

So I would guess it is a matter of who estimated the remaining wear and if they were right. My guess is the independent BMW shop.


#4

My impression was that the independent was telling him to wear the pads completely out and then change both pads and discs when the grinding started. My understanding was that the dealer was telling him that the pads were pretty worn but by changing them now, before they get metal-to-metal, he could continue with the same discs. It sounded to me like the dealer was giving him prudent advice.

But, I’ll agree that the answer is just based on an understanding of the post. A look-see at the pads might change my mind.


#5

No, you should never wait until a brake light comes on to inspect or replace the brakes. That’s horrible advice and a visual inspection is the only correct way to knowing.

How much pad is left could depend on how the brakes were inspected. Many people look through a wheel opening and make a decision based on how much of the outer pad lining remains.
Some (the proper way) remove the wheel before inspecting the brakes. This allows one to see the inner pad(s) which may be near gone while the outer(s) may still have some life left in them.

A proper brake job always involves replacing or resurfacing the brake rotors. At the dealer you were conversing with a service writer (and in some cases, a service manager) and very very few of these people have even a moderate amount of mechanical expertise.
Always take what they say with a grain or twelve of salt.


#6

20% left to what? Minimum permissible friction material thickness might be a good guess.

If your car stops smoothly with no brake pulsing felt with both hard and gentle braking then the rotors are good and would not be replaced if it was my car. Change the pads soon before the rotors become scored if your pads are riveted to the pad backing plates before the rivets score the rotors. If no rivets, I have had good success changing the pads when the wearing material thickness is the same as the steel backing. A little rotor scoring is not a problem as new pads will bed in to adjust to this. A little harmless rotor scoring can be a mechanic’s justification to push for new rotors.

You might want to help yourself by removing a wheel to look at the pads, both left and right on each front wheel every 5000 miles or so as the pads become closer to wearout.

One of our cars has well over 200,000 miles on the original rotors which have never been resurfaced. Changing rotors whether needed or not on every car is good insurance if you do this to earn your living as it reduces the chance of a comeback complaint. In addition, a mechanic can make a little more money selling and installing rotors which is not always necessary. Most customers don’t know much about brakes and take it on faith that the mechanic always knows what he is doing.


#7

I put a lot of miles and lot of parts on 3 Series BMWs. I currently own four of them. I do most of my own work, and certainly all my own brake work.

You have a lot of different advice here, and the only advice that was not correct was what you reported that the dealer told you.

  1. The rotors on a 2003 325 have almost no wear tolerance and if you are using BMW pads, which wear the rotors pretty aggressively, you should replace the rotors every time you replace the pads. You can get away with running two sets of pads on the same rotors but the rotors will have a severe wear pattern and will be well below minimum specification thickness by the time you get to the end of a second set of pads.

  2. The pad wear indicators fit in the edge of the metal backing of the brake pad. When they touch the ridge on the edge of the rotor (the very edge where the pad does not touch), it wears through the plastic on the indicator and the warning light illuminates. An illuminated light means the technician has to replace the sensor rather then re-using it. The sensor is cheap, but it is a little more work for the technician to put on a new one. It is easier to re-use the old one. This is where the dealer’s advice was wrong. The warning light will come on long before the brakes are metal-to-metal, so waiting for the light has NO relationship to whether you need to replace the rotors. Continuing to drive for several weeks or months after the warning light comes on, until the pads are metal-to-metal, would be dangerous and would damage the rotors, but you would not do that.

  3. If you are even a little handy, you can save a lot of money by buying name brand rotors and pads on the internet, downloading the instructions for replacing them, and spending a Saturday afternoon doing your own brakes. If you are tired of black wheels, you can buy a couple of brands of brake pads made in Australia that work well and are much cleaner than BMW pads. Always check the reviews and stick with well known name brands in brake parts. This is not a place to experiment.

  4. If you want to spend a lot of money on fancy brakes, slotted rotors are OK if you get good ones, but they will make a little bit of noise. Drilled rotors are not advisable on this car.


#8

Thank-you to everyone for your opinions and advice. The rear brakes have already had a pad replacement (same rotors), so it looks like I definitely need to get new rotors there. The front had new rotors, but quite a while ago, so I should probably do the front rotors as well.


#9

Manolite - What brand pad and rotors do you use. Also which is the one from Australia?

Thanks


#10

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