I don't have warped rotors but something odd is going on.

[M1911]

I was wrenching with a buddy last week. Doing spark plugs and a few suspension things on his car.

Funny thing as he's a recent transplant from the snow belt. Common strategy was to slather anti-sieze on everything that had threads. My experience and research tells me it's to be used much more pointedly. Not taking a side, but I can certainly understand why for a vehicle used in corrosive vs arid environments.

I typically change over the wheels on my vehicle and my wife's car Spring and Fall -- snow tires go on in the Fall, come off in the Spring. I've done this on a 2002 Mercedes C240, 2003 4Runner, and 2010 Mercedes C300. If you don't put anti-seize on the hubs, the aluminum wheels stick to the hub. They can stick to the hub with enough force that I can't physically pull off the wheel. The only way for me to get the wheel off is to take a sledge hammer, slowly swing it horizontally under the vehicle so that the sledge hits the tire gently (not the wheel). That pops the wheel off the hub.

Once the wheel is off the hub, you will see white corrosion from the aluminum wheel stuck to the hub. It comes off with a stiff wire brush.

I put a thin coat of anti-seize on the hub (not the lugs) to prevent this. It doesn't take much and clearly you don't want grease flung out onto your brake rotors.

If you don't use anti-seize on your hubs and you get a flat, chances are you won't be able to get your wheel off your hub (unless you carry a very big hammer around with you).

Up here in the snow belt, you can assume that most every bolt under your vehicle will be rusted and stuck.

 

[JeffH]

The rotors are typically ductile iron or grey iron. To me it looks like the material is not fully homogenized (not exactly the same all over with regard to alloying elements). In other words the area of a different color may have just a bit more or a bit less of Carbon or Graphite, etc. This can occur in castings and the difference can be very subtle. The heat of braking has etched the material which brings out this subtle difference in the elements. At least that what it looks like to me.

 

[RTaylor]

Mine look the same. Original pads and rotors at 66k.

 

[bloc]

Mine look the same. Original pads and rotors at 66k.

Have your rotors ever been turned?

 

[RTaylor]

Have your rotors ever been turned?

No

 

[bloc]

Got the rotors and TRD pads installed. The back face of both front rotors had very slight marks like the outside, but nowhere near as bad. I filed the lip off one and they measured about 29mm. The new OEM parts were 32.

Also the OEM pads on the pass side looked odd.. the outside edges looked like I’d expect a pad to, but the inside/middle of each block had a much softer and more loose surface. I scrubbed it with a wire brush and some material came off the loose spots.
Driver side

Pass side. The light spots are not odd reflections.. it is the same thing as the outside.

Good pads from drivers side

Pass side pad before scrubbing

After scrubbing. The darker areas were very very slightly concave due to the removal of loose material.

I’m thinking I got the pads too hot at some point.. and the rotors having 10% of their thickness removed either from wear or being machined doesn’t help.

Thanks for your opinions.. now waiting on TRD pads for the rear then I’ll go bed them in and start worrying about brake dust.. hah

 

[BW200]

It would be interesting to know if the dealer installed Toyota rotors or aftermarket rotors, on the second set.

I agree with @JeffH, that this just looks like variation in the casting that has been exposed through the polishing of the material. I've seen it before on other vehicles. It's probably not a major problem to be concerned about, but it would be an interesting comparison of quality control if these are aftermarket rotors. Some of the more expensive post-processed rotors that are held at a high temperature after casting, and the cryo-treated ones probably wouldn't show this variation, at least not as much.

And, if I read the maintenance specs right, 29mm is the discard measurement anyhow, so they were ready to be replaced. The minimum should be stamped somewhere on the rotor.

 

[TeCKis300]

The loose material is definitely a sign that they've been overheated. Exceeding its operating temperature such that the pad material starts breaking down.

Those irregular patterns on the rotor are now looking to me like localized overheat spots. I'm use to the whole rotor turning colors after a track day, rather than just spots.

New rotors will make a huge difference in moderating peak rotor temps so good choice on that. TRD pads should help too as their composition should be capable of higher temps. Might as well flush the brake fluid while your at it if it hasn't been serviced.

Was there a particular drive that your remember that you were hard of the brakes? Usually an extended downhill leg, with lots of gear in vehicle? May have been awhile ago.

 

[bloc]

It would be interesting to know if the dealer installed Toyota rotors or aftermarket rotors, on the second set.

I agree with @JeffH, that this just looks like variation in the casting that has been exposed through the polishing of the material. I've seen it before on other vehicles. It's probably not a major problem to be concerned about, but it would be an interesting comparison of quality control if these are aftermarket rotors. Some of the more expensive post-processed rotors that are held at a high temperature after casting, and the cryo-treated ones probably wouldn't show this variation, at least not as much.

And, if I read the maintenance specs right, 29mm is the discard measurement anyhow, so they were ready to be replaced. The minimum should be stamped somewhere on the rotor.

I forgot to check closely but I do think they were OEM toyota rotors. There was enough rust that some of the casting numbers weren't visible without some scrubbing work, but the vanes and machining seemed exactly like the new OEM parts.

If it is metal that isn't homologous it'd surprise me from an OEM toyota rotor.

The loose material is definitely a sign that they've been overheated. Exceeding its operating temperature such that the pad material starts breaking down.

Those irregular patterns on the rotor are now looking to me like localized overheat spots. I'm use to the whole rotor turning colors after a track day, rather than just spots.

New rotors will make a huge difference in moderating peak rotor temps so good choice on that. TRD pads should help too as their composition should be capable of higher temps. Might as well flush the brake fluid while your at it if it hasn't been serviced.

Was there a particular drive that your remember that you were hard of the brakes? Usually an extended downhill leg, with lots of gear in vehicle? May have been awhile ago.

I don't remember any drives like that. Have been driving to the mountains for 30 years and learned about engine braking early on.. while I do drive the truck pretty hard I also try to take care of it in terms of not ragging on it. as mentioned with never stopping with foot on brake, etc.

The fluid (even the stuff in the calipers) appears brand new and tests at <1-2% moisture per my cheap amazon tester so it's staying in for now.