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11-20-2011, 02:05 PM | #1 |
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Why does BMW insist on changing pads AND rotors?
Ever since I had my NON-M E90, I came to realise that BMW never just let's you change the pads. They literally force you to do the whole set. I don't get why this is..
Can somebody please explain the life of pads in proportion to rotors and vice-versa. Also, how can you measure the life left in pads and rotors? Assuming it's in millimetres but have no idea how to do so. I'm also assuming when my car throws the light for a brake change I can just have StopTech Street Performance Pads installed, leave the rotors untouched and be on my way. Sorry if this sounds like a stupid question but I'd really like to understand this concept for future reference. |
11-20-2011, 03:40 PM | #2 |
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I bet this is only because you are paying for the service. Here in the US I've had the dealer change my pads only and tell me that my rotors were "fine," under the BMW provided 4 year maintenance plan.
If you can do it yourself, it's easy, or go find a good independent shop and you'll save yourself a sizable sum. Pads are by vision, just look at them and see how much you have if it's the same as the thickness of the backing pad you need new ones (your pad sensors will also go off). The rotors have their new specification stamped on the hub. You'll need a caliper to measure the rotor thickness and someone will need to tell us what's allowable. |
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11-20-2011, 03:43 PM | #3 | |
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11-20-2011, 04:57 PM | #4 | |
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I think you need to ask this question at the dealer and see what their reason is. Calgary winters are pretty harsh, and it could be that the sand wears the rotors fast enough that rotors won't last more than one pad set. Here in Vancouver, where our children don't grow up playing boats on liquid nitrogen puddles on the winter streets, you can pretty much count on two sets of pads per rotor change. Last edited by JAJ; 11-20-2011 at 05:01 PM.. Reason: Needed to be harsher about Calgary weather... |
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11-20-2011, 06:30 PM | #5 |
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Because they get paid about 4 times as much with the rotor replacement. The minimum thickness is etched in the rotor, so it's easy to determine whether or not they need replacing.
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11-22-2011, 10:12 AM | #6 |
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another explanation & some repeats
1) It maximizes rotor mass, which avoids problems w/overheating brakes and subsequent pad deposits and warping later on
2) It minimizes any return customers due to vibration in the pedal caused by mismatched pad compound to the rotor (even the factory pads/rotors). If there are bedded deposits by the previous pads, the new pads will not seat properly (at least not initially) causing pulsation in the pedal 3) If cost isnt' an object, it's the sensible way to go. It also keeps the parts dept in business Porsche takes the same path with regard to brakes. No pad slapping, only full brake replacement (rotors/pads). Also, they always recommend replacement of all hardware (clips, sensors, etc.). Again, more due to ensuring there are no issues afterward and no customer comebacks. Most BMW and Porsche buyers paid for an expensive car. Most are also probably okay w/an expensive repair/maintenance, as long as it is done right and perfect the first time (because they've paid for it). This is the likely BMW and Porsche philosophy with regard to repairs and maintenance. -Brian |
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11-22-2011, 10:56 AM | #7 |
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As long as the thickness on the rotors is still good, just upgrade the pads and go. If you can afford the new rotors as well, just do them.
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11-24-2011, 09:20 PM | #8 | |
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What really matters is the rotor thickness when you change your pads. If the rotor is not warped (most likely it probably isn't) then just change the pads. You will not feel vibrations. Just because you bought a car that is 70k you cannot be reasonably money conscious? I hear this over and over again and think this is one of the stupidest things I've heard.. Over and over again. Brakes are brakes on each and every car. While there will be applications of carbon ceramic or slotted or whatever, this doesn't change the practice of changing pads to rotors. Just because you bought a bmw doesn't mean you have to take magical care of brakes. Its just brake pads and steel. That's it.
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11-24-2011, 09:28 PM | #9 | |
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11-25-2011, 09:50 AM | #10 |
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Yes.. The pads and rotors on a Cayenne GTS last 40k..
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11-25-2011, 11:17 AM | #11 | |
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^ I'm assuming that's only the case if you buy the ceramic brake package at a cost of $8000+ |
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11-25-2011, 11:22 AM | #12 |
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When I was looking used Porsche the client advisor stated that their ceramic brake package CAN last up to 100k miles. It damn well better at the price of the consumables.
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11-25-2011, 11:25 AM | #13 |
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11-25-2011, 12:17 PM | #14 |
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atleast in the US and at the dealers I have used they change pads without rotors and change rotors every second time pads need changed. Free maintence window or not. You can ask them to measure your rotors at any time and they have to be within a set spec. If they are not then you can have them change them but they often will not do it automatically. I always get them to measure rotor thickiness when getting pads done.
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11-25-2011, 02:38 PM | #15 |
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hmmmm... i am currently at 50+K miles on my car and i have 70% - 60% front and rear not sure which one is bigger but im guessing im good till 100k miles.
all original
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11-25-2011, 04:41 PM | #16 |
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If the rotors are not warped and they are within spec you can just change the pads. New rotors and pads are always the best option however as a used rotor has lots of grooves that the pads must wear into before it makes full contact. This can result in spongyness in the pedal, brake squeal, uneven pad wear, etc.
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11-28-2011, 10:29 AM | #17 |
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Nope.. I am talking about the Stock, non upgraded brakes that come standard equipment with the car.
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11-28-2011, 06:18 PM | #18 |
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ditto, but I personally recommend changing both, it just makes me feel better/more confident and I don't put many miles on my cars, so the cost isn't a big factor.
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11-29-2011, 12:57 AM | #19 |
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11-29-2011, 08:55 AM | #20 |
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57k on the original brakes on my 335xi, 29k with about half the pad left on my M3. Stop using the brakes so much, they just slow you down.
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