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I've taken my Ford Ranger to the garage for a health check test. The car has 2 years and 25k miles. Apparently there is corrosion on the inside part of the front discs. This affects the brake pads too. The thickness of the discs and pads is great, they say, but they recommend that the discs and pads be replaced.
...?
Brake pad profile shot:
Both that disc and pad look perfectly normal to me, although I can't see from the photo how much material is left on the pad - but with only 25k on the clock I would expect them to have plenty of life left.
You will always get light corrosion on the discs when the vehicle has been sitting for a while (as little as overnight if the weather is damp, a few days if it's dry). That is nothing to worry about and it will be worn off as soon as the vehicle is driven a few miles.
I'm going to disagree with my esteemed colleague about whether they need to be replaced. While there is no profile view to really tell the depth of what is left of the pad, it looks to me as though it's on its last legs. In the pad photo, if you look at the left side of the pad (by your fingers), it looks as though you can see metal wear, as though the pad's base metal has come in contact with the rotor. Also, on the right side of the pad (by the base of your thumb), I'm not seeing any relief, as in, there doesn't appear to much depth to the pad there. There is a dust relief slot cut into the pad, so there is some depth to it, no doubt, but I wonder just how much there really is.
Here's what you need to do ... measure the pads (yes, all of the pads) to see how much meat is left on them. Here is what I found for a reference:
Therefore, your brake pads need a minimum thickness of 6.4 millimeters or more. You may be able to get away with less thickness, but certainly nothing less than 3.2 millimeters. Between 3.2 and 6.4 millimeters is when you should replace your brake pads.
(Source: https://oards.com/minimum-and-recommended-brake-pad-thickness/)
If your pad is less than 6.4mm (about a 1/4"), you really need to see about changing them. You have to look at the thickness of all the pads on a given axle. If any one of them is below this thickness, do a brake job for that axle.
As Nick stated, though, corrosion of the rotor is not usually a big deal and will take care of itself with a little bit of driving (in most cases).
From your pictures I can see the outer ~10mm ring of rust on the brake rotor. A small ring of rust is normal, but if you look at the brake pad you can see the arc ~8mm from the outer edge of the pad. This arc is from the pad riding on that thick ring of rust on the rotor. The shop was right to suggest replacement. You also said corrosion on the inside of the rotors, but the picture is of the outside, so the inside is likely worse. This problem is often caused by rust between the caliper bracket and the pad hardware. The rust will pinch one edge of the pad restricting movement and cause tapered pad wear or a ring of rust on the inner or outer edge of the rotor's friction surface, so when you replace them you should make sure the pads slide smoothly in the caliper bracket.
The area of corrosion the shop needs to worry about is the area between brake pad backing plate and friction material. If corrosion gets between these safety-critical components, it can cause the friction material to delaminate. When this happens, the friction material could separate causing a reduction in braking surface. This will lead to longer than normal stops and brake failure. If you or the shop can slide a thin piece of metal between the backing plate and friction material, it is grounds to replace the brake pad set. Corrosion in this area is not a cosmetic problem, it is a safety problem.
Having lived for many years in the northern states that love to use so much salt that even the road furniture and bridges rot away at scary speeds, I've seen a lot of corrosion issues with brakes. Probably the worst place for corrosion is the pad backing material, which can tilt the pad relative to the piston, as can corrosion on the corresponding outer face of the piston, which starts once the (typically zinc) coating has abraded away). Corrosion on the pad side of the backing plate can creep under the material and eventually separate it. Fortunately that is not apparent on this pad. Sliding calipers can also suffer from corrosion that prevents their free movement and result in uneven force being applied to the pads such that one of the pair on each disc can wear much faster than the other. You need to look at ALL the pads to determine if the rates of wear are uneven. Usually it's the pad next to the piston that wears faster once the caliper starts sticking, but sometimes the other one wears faster if the caliper frame is holding it in contact. when the brakes are released.
The interface between the hub and the rotor is another area where corrosion can build up, and can push the disc out of true, usually resulting in a detectable judder on applying the brakes. If you're not doing tire rotations regularly, this can even put so much force on the studs that there'a risk of them breaking.
Onto the rotor itself - the vents between the discs that form the outer faces are spaces between a series of cast webs, and I've seen these corrode to the extent that the the rotor is close to the point of collapsing and the inner disc separating. The corrosion that builds up in this area is undisturbed by much that goes on around it, and can eat away at a lot of material unnoticed, though this usually take several years to get to a dangerous point.
And finally - the braking surfaces themselves. The bands at the inside and outside of the face can accumulate thick layers of rust. The inside of your looks to have a fair amount of rust, but that's because it isn't contacted by the pad, so nothing knocks it off. This isn't harmful. The outer edge also has a fair amount of corrosion, and this can go two ways - it can build up, and abrade away the pad material, as it's substantially rougher than the machined face that remains clean from pad contact (apart from the flash rust that will accumulate every time the vehicle stands, but is wiped of as soon as you use the brakes for the first time). Since the pad is riding over this surface, it can also keep knocking away that rust scale, and leave the disc surface lower than the active track of the pad over the face. Yours seems to have some of one or both of these effects, and there's a band around the outside of the pad that's distinctly different to the rest.
This is probably reducing the effective area of the pad. Will you notice any drop-off in braking performance? Probably not - pressure from the piston will be distributed over the remaining area and braking effort will not change noticeably. If it were my vehicle, I'd leave it for probably another year, there's enough meat left on the pad to not wear to a dangerous level in that time, but I'd be watching it. Eventually the pads and rotors will need replacing at the same time. I've given up on the idea of refinishing rotors with any corrosion issues, even when there's sufficient material left to allow them to be turned flat within the recommended minimum thickness. New ones are cheap enough to not make it worthwhile.
What I'd be looking for would be even wear across the pad... that is the same amount of pad material thickness on all sides and the face being flat and no chunks missing. Importantly the wear on the pad on one side should equal the wear on the pad from the other side. If the wear is uneven across a pad or different between the pads then you will need to have the caliper cleaned up so everything is moving freely and then put new pads in.
I would replace the discs if they're close to the manufacturers minimum thickness and/or if there's any surface damage or cracking. You can tell wear from the edge lip but really you should be measuring the thickness of the disc.
Brake parts generally aren't painted, and are left to rust. Painting them is hard because of the very high temperatures.
So you should expect rust on the calipers, non-working surfaces of rotors, and pads.
Generally rust does no harm, because the moving parts of the caliper - piston and floating slides to allow the brake to float - are behind rubber gaskets which are meant to keep moisture and rust out.
I have been known to sandblast rotors and pads, and hit them with high-temp brake paint, but you want to aim the sand stream away from the workong surfaces. Painting calipers must be done when they are freshly replaced; you can't sandblast them because any sand in the system will tear up your brake hydraulics.
Get the grinder out and grind down the ring edge and use them pads until they are practically gone.b wtf else are they gonna be used for? Unless you ate not stopping efficiently just change out the brackets get some copper lubricant and touch the proper points. Grind the ring away and bam. and check the rear end out too. Wait your at a shop... Yeah.. This should be.done your self. I never leave my brakes for another man to take care of...being able to stop can be life or death on the road.. I have to know its right.. Its like packing a parachute.. a parachute you use daily. It has to be right or dont uae it. The corrosion is normal and not an issue. They can come strait out the box orange and.be.fine..unless the pad its seperating from the backing or cracking its no issue.
