Hi folks,

I need an opinion on the following:

Last week I had my vehicle inspection, which is the only time I take my car to the local Volvo dealer.
The car did not pass the inspection because they found that my rear rotors are defacing not allowing full contact with the brake pads.

I bought two new rotors and installed them today.

Below you see the 'defacing' genuine Volvo rotors:

https://postimg.cc/ZvcBDNgK

https://postimg.cc/K3XwskTV

Do they look defacing to you?
Maybe I have a different interpretation of 'defacing', which is why I am asking.

Thank you!
Alex

A couple of likely explanations:

1. The ridge that has developed at outside of rotor contact surface prevents full contact of new brake pads.

2. Also, the thickness of the worn rotor surface is below minimum safety spec measurement.

The dealer should be able to provide additional details.

Alex, I don't normally post in the AWD forum, but your rotor pics caught my attention. I'm not sure what you mean by defacing, but the condition looks a lot like ones I've recently had. I'm really curious, which brands of pads and rotors are these and roughly how many years and miles on them? When you installed the rear pads, did you "bed" them in or just start driving like many people do? Do the brakes "chudder" and get worse when hot?

Depending on the mileage, what I'm seeing here for wear is mild scuffing/scoring of the faces, so no big deal there. What I'm really noticing is the outlines of the edges of the pads. That's typically from the pad binder material melting and not depositing evenly around the rotor, such as parking/stopping with really hot brakes after a good highway drive and letting them cool. I've had a recent bad case of pad material buildup with Bosch Quietcast pads on fairly new Bosch Quietcast front rotors in one of my two 940s. The built up ridge of pad material allows a bit of rust pitting to show the outline of the pad. I even dial mic'd my rotors all the way around to prove it was pad material and not wear.

Two things you can try, and you may well not have success and decide to replace the rotors and as well the pads:

o Try re-bedding the pads doing a number of high speed stops to get the pads good and hot. Unfortunately, bedding rear brakes often takes a lot more effort than the fronts as the fronts do most of the braking. I tried this with mine and found that they did improve a bit, but that it didn't last long and the brake chudder problem started to return.

o Sand the surface first to try remove the pad material ridges then re-bed the pads. I used a metal flap disc and was very careful to work the high spots more than the low spots using a dial mic. Better would have been to have the rotors turned in a lathe, but that's generally not worth the cost, reduces the remaining life of the rotor and can actually make things worse if not done carefully. This re-surfacing did last longer, but the problems still eventually came back.

I eventually said screw-it and put in new rotors and pads. All has been fine since then. I'm no longer a fan of Bosch Quietcast brakes as I figure they've made too many compromises in materials for the sake of being able to advertise quieter braking, leastwise for the kind of driving I do.
--
Dave -still with 940's, prev 740/240/140/120 You'd think I'd have learned by now

Hi,

Maybe you should look into this web sight of shop that shows some bad rotors.
The site has a few other helpful maintenance tips as it an independent repair garage that gets repeat customers for giving explanations.

https://www.ferrelsgarage.com/the-garage-blog/common-brake-problem-in-winter

Heed to what he says about the pads and the calipers pockets causing the problem in the first place.

He doesn’t go into depth about brake pad cross contamination’s getting into the rotors pores.


Whenever replacing pads I always scuff the rotor, using brake cleaner. I use brake cleaner twice! Before and after a scuff. Turning only if necessary
Used rotors and pads can be used if treated the same way as long as they are flat and even.
All pads and rotors are bigger coming out of their molds and receive final machining with inspections as batches in stages. It’s mass production with many techniques to match.


Each brake pad manufacturer can have their own recipe for friction materials.
For a pun … the materials get rubbed the wrong way 😊

There is no standard specification out there other than say SAE. A “DOT’s” requirement could be less on pads than that of brake fluids. There is a limited number of manufacturers of brake fluids.

I haven’t seen pads with specific certifications other than their own bragging of advertisings.
Similar to the snake oil.
Different grades of performance or levels of expense varies the materials and of course the mind games played within a consumers own wallet folds.
I try for the middle of the road on products, as the law of averages works MORE BLINDLY. IMHO.

The best thing to do is keeping the calipers serviced in climates that promote corrosion or are running in environments not conclusively allowed not to be harmful to either components.
Example… You shouldn’t go racing on a dirt track made or built inside a cement or rock quarry. 🤭
I don’t think I could stand to own a vehicle that lives in a salt belt area myself.

The rear brakes do work less than the front brakes and consequently run colder. Moisture in brake fluid migrates to there due to its natural composition too.

Since most of the stopping work is done up in the front of car, the rears get ignored rather easily.
It's probably a pet peeve with area mechanics, having to idle themselves with doing vehicle inspections. Ho-hum attitude plus it’s a set fee that might affect their credentials and that keeps them away from doing larger $ jobs.
You can’t blame them there!
They like whole axle pricing so you doing it yourself stops that opportunity too.
Inspection got started for a reason and mostly it’s about public safety with some sliver lining in the fringes.
The inspection doesn’t make a boat payment but it keeps the lights on and the rent paid.

With you get the whole story or information about brakes, or anything else of desire, can always be a good move!

The patrons of the BRICKBOARD have appreciated getting and giving so it feels good that we are still a bunch of needed fixers no matter our age differences or individual mannerisms.
The web site above appeared the same to me.

Phil