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I have an Audi A4 with approximately 35k miles. My dealership has recommended that I replace both the brake pads and the rotors and helpfully forwarded a picture to me of the rotors indicating the rust around the edges. My understanding from doing a bit of research is that the rust itself is nothing to worry about and the surface area of the rotors do not appear bad at a glance... but I'm no expert. Thoughts?

Rim of rotor

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What year is your A4 ... reason I'm asking is, I was going to look up the price (average) for your Audi. In most cases, new rotors do not cost that much. The difference between new rotors and resurfacing is marginal. The test for replacement is the width of the rotor (surface to surface) after it is resurfaced. The dealership should be able to tell you why they recommend replacement. If they say it's due to width of rotor, ask them what the measured width is and what's Audi's minimum width. –  Paulster2 Jan 16 at 17:10
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Re-reading your comments about the rust ... in and of itself, rust on the outside edge means nothing. –  Paulster2 Jan 16 at 17:29

5 Answers 5

Rotor replacement is normally done when the rotor can no longer be resurfaced and still fall within the acceptable thickness range. The acceptable thickness range is based on stock brake pads though, so if you're using more aggressive aftermarket pads you may have to do replacement rotors sooner than is specified.

That rust on the edge doesn't concern me since my rotors look like that within weeks of installation on my cars. :-)

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In most modern cars, the rotors are so thin that they can't be resurfaced without making the rotor thickness fall below the minimum. My 2001 A4 usually needs new ones every other pad change (with factory pads). On my wife's Grand Caravan, the front rotors need to be changed every time you change the pads. They also tend to warp if you get them too hot, don't get me started on that! –  TMN Jan 17 at 19:52
    
On my MR2 and Eclipse, so far I've had to replace rotors each time I've changed brake pads. –  Brian Knoblauch Aug 14 at 14:11

That isn't mostly rust buildup. That is the edge of the rotor that your pads don't touch. If it feels raised then that just shows you how worn your rotor is.

You do not always need to replace rotors with pads, but it looks like you'll be replacing them next time at the latest.

I once had a rotor split while driving home from 6 hours away. When it cracked I was riving 60mph on a State Road, the crack seized the rotor when it caught on my pads. My rear tire locked instantaneously on a double lane, driving 60mph. Sliding through traffic isn't fun, and neither is changing rotors on the side of the road.

If you're concerned about money, call your dealer and tell them that you want them to use lifetime warranty parts. I they don't have any lifetime warranty rotors, tell them you will provide them with some. You can get them at any auto parts store and they don't cost much more. Autozone charges me $2 extra per lifetime warrantied part. Then when it naturally wears out, they'll replace it for free.

Worst case, changing rotors is literally one of the easiest tasks to do on a car, it's definitely one of the simplest. You can do it yourself if you want to save some money, but do it right after getting the pads or you'll sacrifice some of the pads life as well.

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Replacing rotors or drums every other time you replace the pads/shoes is crazy. For most daily drivers, that would be every year or every 2 years. Unless the vehicle is being used for something like a delivery service (IE, LOTS of miles with TONS and TONS of stops), there is no reason not to expect 50K-100K or even more from a pair of even stock or OEM-equivalent rotors/shoes. And the front brakes will always need more servicing than rear brakes, usually anywhere from 2 to 4 times the frequency. But the first rule is always to INSPECT the condition and service as appropriate, no matter what "rule of thumb" you're fond of.

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While you may think it's crazy to replace rotors every time you do a brake job, you are sadly mistaken. At the very least you need to have the surface of the rotor cut or you won't get proper bedding of your new pads (and further issues ensue). If you are going to get the surfaces cut, always look to see how much new ones cost, because realistically, they aren't much more. You cannot go wrong with new rotors. Also, it has been my experience, with rotors front/rear, the rears will wear out faster than the front, mainly due to the fact the rear brakes have less surface area than the front. –  Paulster2 Aug 14 at 12:41
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Not sure how most daily drivers would need brakes every 1-2 years. I autocrossed my daily driver for many years and still got 5 years out of my brakes. One would have to be driving like a maniac on public roads to burn out brakes in 1-2 years. –  Brian Knoblauch Aug 14 at 14:13
    
Obviously you don't have to commute in traffic. I have to haul my car down from 65-70 to 15-20 at least a couple dozen times on my way to or from work, every day. If your car's reasonably chunky (mine's a 2001 A4) it really doesn't take long to eat up a set of front pads. –  TMN Aug 15 at 13:22

If your rotors' wear surfaces are still smooth & flat & true, then keep the rotors and replace the pads alone. The dealer wants to replace the rotors because doing so eliminates one potential source of liability for them - the more they replace, the less their potential liability.

If the wear surfaces are NOT still good, then they should be measured to see whether it's practical to resurface them (provided that shop still owns a brake lathe - brake lathes are rapidly becoming extinct). If too thin, or if no brake lathe is available, replace the rotors.

But... that band of rust is NOTHING. It's not even enough to make changing the pads difficult. It's... a waste of metal in the first place.

35K seems awfully early to be replacing pads, though... do you rest your foot on the brake pedal a lot while you drive? Does your driving include a LOT of stop-and-go city traffic? My wife & I both drive '07 Toyotas, and both are still equipped with the original brakes.

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You've already got your answer, but I'll just add that as a rule of thumb, you should replace your rotors with every second pad replacement. Also, rotors can and should be skimmed when fitting a new set of pads. It restores a nice smooth surface. It's not a MUST, but it's a very good idea.

If you have drum brakes at the rear, it shouldn't ever be necessary to replace them. Unless it's a very high mileage car. Drums last extremely long and even the shoes tend to last more than 100k miles. This is just on tiny cars like the Ford Fiesta.

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This is blatantly untrue. Rotors will always need to be inspected. They could need replaced at any interval regardless of how long your pads last. Your drum brakes will need to be replaced at some point as well. Usually in my shop we replace the entire brake system on our cars (up to, and including the master cylinder) right around 160,000 miles, drums and shoes included, because these systems wear out, lines burst etc. . . and we are into preventative maintenance. Of course this is only on our own vehicles, not the public, as they don't feel the need to replace things until they're stranded. –  someDoge Jan 17 at 14:54
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You're the expert. I can only talk from experience. –  Juann Strauss Jan 17 at 15:07
    
Well I'm no expert. But I can tell you that drums/shoes do wear out and fail :P. Some people I know have driven on basically only front brakes for weeks without even knowing the rear had failed. They only found out when the rear cylinders were eventually over-expanded and the seals burst, causing failure of the entire braking system due to the air sucked back into the system. –  someDoge Jan 17 at 15:25
    
I'm not saying drums brakes don't fail. I'm saying they take very long. In the case of my two Opel Corsa's with 80 000 and 100 000 miles on the clock, I've never had a moments trouble with the drums and the shoes seem to still be 40%. But then, they only weigh about 900 kilograms, so you're never putting much strain on anything. –  Juann Strauss Jan 18 at 18:42
    
I don't know where you're from. But here in Indiana a huge amount of vehicles have over 150,000 miles on them. I'm talking about long term maintenance. My truck has 183,000, my families have roughly 80,000 - 180,000 - 210,000 - 240,000. These figures are realistic, if you pay attention to real concerns like changing drums. –  someDoge Jan 19 at 4:05

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