Rust on rotors after non-use, mechanic said they need to be replaced

Question

I had my car brakes replaced about 2 years ago, since then I've driven about 4000 miles (I work downtown and tend to use public transit) after which I disconnected the battery and stopped using my car (for almost a year). Yesterday I took my car out and went to get an inspection sticker. The guy told me that I need new brakes/rotors and an oil change (despite the low mileage on my rotors).

The car is a 2004 A4 Audi, I went along with his suggestion but after realizing that he's changing the rotors too (which he didn't mention at first), I'm concerned that he may be doing unnecessary work. The final bill is coming out to be pretty expensive. He says that since the car has been unused for a while, this is expected although most online articles I'm reading are stating that fluid change is enough after car has been unused for several months to a couple years. Unfortunately I don't have a picture in front of me but the condition of my old brakes looks very similar to this: https://i.stack.imgur.com/BqPwz.jpg.

A few articles I found online state that rust on rotors is harmless: https://www.quora.com/What-are-some-ways-I-can-remove-rust-from-brake-rotors. What would you guys do in this situation? Is the mechanic correct?

Answer 1

I would get a second opinion. It's quite possible that your rotors have developed rust in that time. However, if they resemble the rotors in the picture that you provided then they should still be fine. That rust appears to be the same kind that develops inevitably over time with use.

There is a certain thickness that all rotors must be at in order to still be considered safe. Rust on rotors usually isn't a problem unless it is causing issues with your braking. Most times, a little rust on rotors will only wear brake pads a little differently.

You can actually have surface rust removed from rotors with a special grinding machine (called turning the rotors when I worked at a shop) at certain car repair shops (provided they still satisfy the thickness requirement).

Long story short, I wouldn't replace the rotors if they look like the ones in your picture. Get a second opinion from a different mechanic, have your current rotors turned if you wish, and continue on as you would normally from there. You should be fine.

Answer 2

The place where your rotors appear rusted is not an issue. Like @Moab mentioned, a few hard stops removes this, and you're good to go.

However, I'm not certain your mechanic suggested rotor replacement due to rust. I personally am far more concerned with the "undercut", or how thick the rusty bits on the outer edge are compared to the braking surface, which seems reasonably clean and missing much rust. But thinning!

Yes, there are some striations "grooving", and some severe pock marks as it gets close to the edge, but I would not panic just yet. If the pads aren't new, the pads have matching grooves, and the so-called "swept area" or area of contact isn't comprimised.

However, these rotors are shot. Like other experts have mentioned, the cost of "turning" such rotors is usually in excess of just replacing them, now that "Hecho in China" is a very common scenario. I use a brand [daily] called Centric, and they make (or at least sell) quality products despite the prejudice of origin. The only real case to "turn" rotors true is if you have some 50's classic (Buick with aluminum finned drums anyone?), or a large truck, wherein replacement rotors are exorbitantly expensive.

So, to summarize, if you brought this car to me, and you had decent pad thickness, I'm not in the business of ripping you off, so I would send you on your way. On the other hand, if you had low pedal and/or thin pads, I would insist on replacing rotors, regardless if you objected to the cost, because this is a proper job and those rotors are shot. I have a religion dead-set against the so-called "pad slap", because I firmly believe it does not do the customer justice. Missing rotor material means the pistons travel out beyond what they were designed to, which can damage seals, and even sieze/ruin a caliper.

I'm just summarizing what has already been said by some very erudite folks and throwing on my own never-humble spin.

Check your pad level, if it's good, drive on. But at no point should those rotors ever see new pads.

Answer 3

Unfortunately, if your rotors are anything like the ones in the picture, they are toast. They would either need to be replaced or resurfaced depending on the amount of meat which is left on the (thickness of the rotor). The reason I say they are toast is due to the scoring in the rotor itself. It isn't all about the rust, here. The rust may have exacerbated the situation, but the rotors themselves have some heavy scoring in them.

If the rotors aren't thick enough they'd need to be replaced. With the cost of rotors having come down in price mainly due to less expensive Chinese import products, I almost always suggest replacement over refurbishment. This, however, is strictly up to the owner who is paying the bills. A new set of rotors will usually cost only a few dollars more than getting them resurfaced, so it's a great trade off. If you were doing this at home, you have to weigh the amount of time it'd take you to get the rotors down to where the machining would occur, then wait for the job to get done or leave them there and come back for them. It becomes an issue of what is your time worth. Since you are having the shop do it, this tradeoff is much less prevalent.

Answer 4

It is very possible that the rotors are bad. I had this happen on a car that sat for a bit over a year, the problem was that the rust was not even like in the picture above. It had formed a much thicker layer under the pads, where they had presumably held in the moisture or condensation was more aggressive. Stepping in the breaks quickly removes the rust and after that the breaks would pulse, because every time the wheel turned back to that original point the rotor was thinner.

It is possible to use a lathe to true up a rotor and avoid replacing them, but new rotors being so cheep it often doesn't make financial sense.

That does not say for sure if you are being ripped off in this situation, but it is totally reasonable to expect to need to replace these parts if the car was sitting for a year. Particularly, if it was outside or in a damp climate.

Answer 5

I have had this problem repeatedly. Like you my car often sits unused for months (outside). Bare steel rusts under these conditions, especially if it was parked wet. The problem with rust on rotors is that the rust is more abrasive than the brake pads, so if there is too much rust, it doesn't get removed when you start using the vehicle again, but it cuts gouges into the brake pads so now they aren't flat and that's bad. Once you have such irregularity, it gets worse rather than better so it's important to avoid it, otherwise you'll need new pads and rotors.

You can deal with this by cleaning the rust off the rotors before significant usage. Whether you can easily clean them back to flat with steel wool or sandpaper, depends how bad the rusting is. The ones in your picture look good enough to me. Note that rotational flatness is very important in brake rotors so hand-sand evenly and not excessively if doing this. It's much better to use a lathe or some similar arrangement if you have one.

For bad rusting you need to get the rotors skimmed. For me this costs slightly more than just buying new ones, but I don't like to throw away really quite new rotors (I was getting new ones every year for a while) so I got them skimmed anyway. The bigger and fancier your rotors the more cost-effective this is.

If one side is rusting but not the other, then you probably have a sticking caliper, which needs either fettling or replacing.