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I just bought my used 2015 nissan altima 3 months ago with 33k miles. My lack of knowledge with cars may be catching up to me as I'm now realizing just exactly how rusted my rotors are, basically completely orange. All 4 look roughly the same. I drive it about 10 mins 4 to 5 times a week to and from the gym and then occasionally on the weekends. Are these as bad as I think? Do I need to get all 4 replaced? I feel like an idiot for not bringing this up to the dealer before I bought it. Any help would be greatly appreciated.

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    Welcome to Motor Vehicle Maintenance & Repair! – Pᴀᴜʟsᴛᴇʀ2 Jun 22 '18 at 10:54
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    That is normal rust for a non coated cast iron rotor, nothing to worry about. – Moab Jun 22 '18 at 13:05
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    Inconspicuously check out other cars at your gym parking lot for non-rusted rotors. – MonkeyZeus Jun 22 '18 at 13:42
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    If the rust bothers you for appearance reasons you can always buy stainless steel rotors, but they're more expensive and generally don't provide the same braking performance. – barbecue Jun 22 '18 at 17:20
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While I cannot see the back rotors very well, I can tell you without a doubt, the front rotors are brand new. You can still see the crosshatching on the surface which means it was prepped. It doesn't show any wear at all. The rear brakes (from what I can see) are in good condition as well, though appear to be a bit older and more used.

The misconception you have here is you are basing the wear of rotor on non-wear areas. There's almost always going to be rust in these areas, unless they are zinc coated or are made of carbon fiber. You should base the wear of the rotor on two things. First, the thickness of the rotor (between where the brake pads sit on them). There is a minimum thickness these need to be. This value is sometimes cast into the rotor, or you'd need to find it in a service manual. The second thing to look for is if there is a lot of gouging in the metal from the brake pads, which happens when the brake pad gets worn out.

Usually, you don't have to consider changing rotors until you need to change the brakes. Then, for the best results, you'll either need to machine the surface of the rotor or buy new ones. The idea is to have a completely fresh mating surface for the pads to ride upon, which will give you the best braking performance the rotors/pads can provide. Until then, don't worry about them.

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    It may vary based upon your location/ car/ mechanic etc. but any time I change my brakes I'm going to be putting on new rotors. Brand new rotors are comparable (or cheaper) in cost to the amount I've been charged to have the old ones resurfaced. – RIanGillis Jun 22 '18 at 20:35
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    @RIanGillis - That is my "opinion" as well. I wrote this generically without opinion. I understand where you're coming from and agree, though. – Pᴀᴜʟsᴛᴇʀ2 Jun 22 '18 at 20:40
  • Surely 70% of the time you just need new pads, use the existing rotors as is, no resurfacing, no machining needed. I've done it plenty and on track cars without issue. – RemarkLima Jun 24 '18 at 8:38
  • @RemarkLima - Just because you've done it and it works, does not mean it's the "proper" way to do it. As I stated in the answer, to get the best results with the best braking performance you need to either have new rotors or have them resurfaced. You could put two pieces of metal in for brake pads against a very rough surfaced rotor and the brakes will most likely stop the vehicle (for a time), but that doesn't mean it's the right way of doing it. Fresh pads with fresh rotor surfaces will always yield the best results. – Pᴀᴜʟsᴛᴇʀ2 Jun 24 '18 at 13:50
  • @Paulster2 I'd be curious to see the evidence on that. If there's no damage to the disc / rotor, and you're replacing pads before they've worn through you have a great mating surface for the new pads. If you go and machine off some surface, what would be the percentage improvement in life and performance? I've only ever seen people machine discs if they're warped, have some gnarly deposits or have a reason to machine them. So it's not common practise here in the UK, Just to complete the advise in your answer. – RemarkLima Jun 24 '18 at 21:39
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There's nothing wrong with your rotors as far as can be seen from your pictures, it's totally normal to have the edges rusty, it doesn't impair them. What's important is that the disk surfaces are in good condition, that is the part that's going to be in contact with the pad, and yours seems fine. There looks to be a good amount of metal left as well.

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Those rotors, from the images supplied, look in good condition. They do not need to be replaced, as you don't show the other sides then I cannot be certain.

However, the top image shows a rotor that has been cleaned and prepared so that one looks really good - I assume it is one of the front ones as it is thicker with the central cooling vents. The lower images look to be of the rear rotors and they seem ok as well.

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