Bad factory rotor casting?

[sequoiasoon]

Not the best pics but this is my left rear rotor on my Sequoia. I noticed first when I changed rear pads (about 10k) because it was a dark line. As I went to put snows on I looked closer and it is actually little pock marks kinda like rust holes. That area I think is harder because it is higher than the rest of the rotor and my pad is concave in the middle as t has formed to it. The old pad was the same way but it was cold and dark when I changed last time so couldn't really "get into it". My right rear has some small marks just like it but only a couple randomly spaced. It still smooth and quiet but it's the first time I've seen something like this. Next pad change I might just get the SP slotted rotors for the rear and replace them.

[MEvang]

This is not a bad casting, it is rust. This is very common to rear disc brakes and sometimes happened to front rotors. This is also very common to areas that see a lot of bad weather, road salts and snow. (Like here in Ohio)
Not much you can do to prevent this. If you see a rust area starting you could have the rotor resurfaced before it get this bad. Right now you can only replace the rotors and pads.
Slotted rotors won't help. The slots will clean the pads but do nothing for rotor rust. Some after-market rotor may be less porous then the factory parts but could also be more noisy and prone to squeal.
Mike

[sequoiasoon]

Originally Posted by MEvang

This is not a bad casting, it is rust. This is very common to rear disc brakes and sometimes happened to front rotors. This is also very common to areas that see a lot of bad weather, road salts and snow. (Like here in Ohio)
Not much you can do to prevent this. If you see a rust area starting you could have the rotor resurfaced before it get this bad. Right now you can only replace the rotors and pads.
Slotted rotors won't help. The slots will clean the pads but do nothing for rotor rust. Some after-market rotor may be less porous then the factory parts but could also be more noisy and prone to squeal.
Mike

I've had rust on rotors and on the untouched parts but this is just a complete line dead center of the face where the pads touch, the rest is fine. I know the slots don't help rust but they did improve performance on the fronts and on my Corolla. If I have to buy rotors I'll get them instead of the factory.

[MEvang]

It very strange how this can build up. I've read at lest one article about it but they never went into how it forms. Usually it does work its way in from the sides some times covering most of the rotor, but I have seen it start in the middle just like yours or start in several rings around the rotor.
This is very unsafe as rust is not a good surface to stop on. Rust is very poor at transferring heat and this alone makes the brake ineffective and lead to more rust. It can also cause the pad material to break away from the pad backing. If you have never had this happen it can be a scary thing or could cause and accident as the pedal can temporarily go away.
Which ever rotors you uses get it fixed ASAP.
Good luck
Mike