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Corroding Brakes

I live in NY and recently bought a 2006 Subaru Legacy wagon in PA. When I bought it, there was some slight surface rust on the rear brake rotors - just the section between the ‘disc’ and the wheel. After driving in this winter, on our salt covered roads, I am seeing surface corrosion on the ‘disc’ section as well, and even some on the calipers. I understand that salt will do this, having lived here all my life, but why is it happening so quickly, and why do I not see this on other Legacy’s that I have looked at? What can I do to prevent it? As the wheels are 5 star alloys, you can see much of the brakes, and it loooks unsightly (plus it obviously does not bode well for brake performance down the road). Also, I have read numerous opinions online about car washes (at home, touchless, automatic with cloth/brushes, and wand). Aside from doing it myself (which is touch as I live in an urban area), what is the safest way to wash it and not harm the finish?

I don’t know what you mean by “just the section between the ‘disc’ and the wheel”. If you are speaking of the area that you can see behind those 5 star alloys, it is normal for that area to appear rusty. I suspect that you are seeing more of your brake rotors than you are used to seeing due to the wide spoke spacing of those wheels. Even a slight rain without the salt can rust it. It MAY cause your brakes to be a bit grabby, but will wear off with the first brake application.

Salt And The Resulting Rust Screws Up Brakes (And The Rest Of The Car)!

Driving through slushy salted snow and then parking your car for several days is probably the worst thing to do to brakes, beyond just wearing them out.

I too am having trouble understanding what you are seeing. Each of your brake rotors should have a shiny metal “band” going around the rotor where the brake pad contacts it. You will get some surface rust on the shiny band in a very short time of parking the car (not using brakes) in foul winter weather, especially. After a drive, the surface rust should be cleaned right off by the brake pads when you make stops. Should the rust not be disappearing from a particular rotor, it is possible that the caliper has stopped “floating” or sliding as it is designed to do. Salt and rust do this, too. Cute, eh? When this happens, only the inboard pad that you don’t see will be shining the rotor on the “inside”. This will cause poor braking and quicker wear of the inboard pad.

That is good that you are monitoring the brakes. Should you spot a rotor that is not shining up the entire “band”, have a mechanic remove that wheel and inspect for a caliper that is corroded to it’s slides and not floating.

I dislike the use of salt on roads immensely. They tax me so that they can buy tons of salt and dump it all over where I live, even though there is virtually no traffic and when and where it’s not needed. They sometimes make the roads slipperier. Then my cars rust-out. This is kind of a sore spot with me.

I suspect you are worrying too much. All brakes develop some rust even if there is no salt. Look at the right side, then the same spot on the left do both the front and back. It should be about the same, if not have the brakes inspected by a trusted local mechanic.

Likewise on the car wash. Unless you are going to detail the car and polish and shine very often, it really does not make much difference which system you use. The all have their advantages and disadvantages. Touchless may be a little safer for the finish, but it does not clean as well. If you want a great look, DIY or find an detailer. They will cost you, but they will do a great job.


Joseph, we get ticked when people neglect their cars or don’t take an interest in their maintenance. Mr. or Ms. Jaroo was asking for a better understanding. Since on this particular car, it is easy to get a walk-around glimpse of the outboard side of the rotors, why not make it part of a fluid check / visual inspection routine? It won’t tell the whole brake story, but it can’t hurt.

I did not suspect the owner was worrying too much, only wanting a better understanding. Jaroo’s rotors may not be shining up compared to other Subarus, because the car is not driven enough to have the brake caliper / pads keep the rotors clean, or there is a problem with one or more brakes.

I’m not worrying too much when I inspect and maintain my car. An ounce of prevention can be worth a pound of cure.

Is it really worth using chemical warfare to burn the snow and ice off every inch of every road and in doing so, dissolving $20,000 - $40,000 vehicles, turning them into worthless rust-buckets? It must be, because that’s what we do…

An aluminum wheel bolted to a cast iron brake…Spray it with salt water…FFFFfffiiizzzZZZzzzz… Galvanic action!

Thanks for the replies. I am not too worried about performance, and have noticed that applying the brakes does seem to wipe off the surface rust. I guess I am more worried about the appearance of the section between the ‘disc’ surface and the wheel that does not get touched by the pads. Not a big deal, just looks bad. I am not used to seeing so much of the area, as I previously had a Tacoma, and the wheels covered much more of the brakes.

Thanks again.

Caddyman, No, It really Isn’t Worth It. It’s Idiotic!

Where I live, the County actually makes the roads much more dangerous by salting the roads at times when temperatures dictate that it should not be done. The State put out a table of temperature ranges and appropriate applications of salt. Much of the time, salt should not be used. Our County does not use the information. Instead, they tax the crap out of everybody, buy salt with it, and dissolve everybody’s cars while often times making the roads more dangerous. They’re from the Government and they’re here to help. This is kind of a touchy subject with me. I live in a very rural area. Town is a 40 mile round trip. There is no traffic. That makes it even more stupid. The plows operate from 7:00 a.m. to 3:30 p.m. Monday through Friday. The weather is on a slightly different schedule. Most storms hit while no plowing is available. I figure that if we drive on unplowed, unsalted roads most of the time, why bother wasting my tax money ?

Here’s some quotes from the State:
" Driving on road surfaces that have been salted can be more dangerous, at times, than driving on roads that have been plowed, but not salted. This is because of the action of salt, which lowers the freezing point of water, takes longer to work, and refreezes at a much faster rate when temperatures are below 20 degrees."

“In addition, when wind speeds exceed 15 to 25 mph, the snow that would normally blow across a dry road will adhere to the wet pavement, also speeding the dilution of the salt and creating a packed-ice type condition with traffic driving over it.”

Translation: Tax you up the ying-yang. Screw up the roads. Trash out your car.

It may be my response sounded a little different than I intended. I agree that maintenance, including inspection are important on any car. I would suggest that the OP not worry about those items he listed, but not worrying does not mean not checking them or performing all the recommended maintenance.

If someone sees a light rusting of a rotor, and worries about it, then I would say they are worrying too much. That worry could be due to lack of personal knowledge about cars. Nothing wrong about that, but don’t worry about a small amount of rust on a rotor.