Automotive

Can rusty rotor pass safety test

  • Last Updated:
  • Aug 4th, 2021 2:57 am
[OP]
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Dec 27, 2007
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Can rusty rotor pass safety test

The car has been sitting in the garage since COVID stated, rarely drive it, now the rear rotors are rusty, After I went on highway for 50km, it’s better but not smooth and shinny as the front. Do you guys think that will pass the safety test?
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38 replies
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Jan 16, 2011
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Yes. The rear wheels are responsible for about 25% of your braking, the other 75% is the fronts. That's why the fronts got the rust off more so than the rear. Rusty rotors are not an issue for a safety. They will check the brake performance and the brake pads.
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Sep 4, 2006
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The brakes don't do any work on the highway ;-)

Go somewhere that you can get up to 60-80kph repeatedly, and brake hard to 5kph. Do this 5-10 times, and then drive home. Your brakes will look almost new.
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Jan 27, 2006
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jayoldschool wrote: The brakes don't do any work on the highway ;-)

Go somewhere that you can get up to 60-80kph repeatedly, and brake hard to 5kph. Do this 5-10 times, and then drive home. Your brakes will look almost new.
Or, someplace where you go down a long hill so that you can repeatedly apply the brakes will also have the desired 'cleaning' effect.
[OP]
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Dec 27, 2007
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jayoldschool wrote: The brakes don't do any work on the highway ;-)

Go somewhere that you can get up to 60-80kph repeatedly, and brake hard to 5kph. Do this 5-10 times, and then drive home. Your brakes will look almost new.
Yeah, I did that for about 20-30 km on the country road too, I also hit the break a lot when I drove on the highway (traffic was low). The rust didn’t seem to come off too much whereas the front brakes got supper hot after it. (the first picture is the after the ride).
I even used the sanding machine to sand the rust down before going for the ride, but didn’t help.
Btw, the break pads are good, still 80% left.
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jayoldschool wrote: The brakes don't do any work on the highway ;-)

Go somewhere that you can get up to 60-80kph repeatedly, and brake hard to 5kph. Do this 5-10 times, and then drive home. Your brakes will look almost new.
+1, you need to brake very hard, just before your tires lock up.
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[OP]
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craftsman wrote: Or, someplace where you go down a long hill so that you can repeatedly apply the brakes will also have the desired 'cleaning' effect.
Yep, thought about it but could not find a long downhill road like hwy90 in Penns:)
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hiker007 wrote: Yep, thought about it but could not find a long downhill road like hwy90 in Penns:)
What car is it? Are you braking hard enough to engage ABS?
If so, it could just be that your bags aren't aggressive enough. Also, for the rear rotors, if your car's parking brake actuates the rear pads, you can engage it will driving if nobody is around you.
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Oct 1, 2015
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Passing the safety is about minimum thickness. Why are you wasting time trying to make the rotors shinny again?
[OP]
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engineered wrote: What car is it? Are you braking hard enough to engage ABS?
If so, it could just be that your bags aren't aggressive enough. Also, for the rear rotors, if your car's parking brake actuates the rear pads, you can engage it will driving if nobody is around you.
Not sure the ABS kicked in or not, but I heard tire skid sound a few times :)
It has the electronic parking brake, so it won't move until you release it.
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Feb 6, 2011
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May or may not pass.

Dont know why some here say it's ok and to drive it.

Pictures only show the outside of the rotor. What's the inside look like? It could be rust grooved to below min thickness. No amount of driving is going to fix that.
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billford wrote: May or may not pass.

Dont know why some here say it's ok and to drive it.

Pictures only show the outside of the rotor. What's the inside look like? It could be rust grooved to below min thickness. No amount of driving is going to fix that.
Because the OP mentioned nothing that would lead anyone to think there are grooves in the rotor? If you have grooves then the pads are way past due and there would be noise coming from the rear brakes. OP mentioned nothing about any noise coming from the rears.
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kr0zet wrote: Because the OP mentioned nothing that would lead anyone to think there are grooves in the rotor? If you have grooves then the pads are way past due and there would be noise coming from the rear brakes. OP mentioned nothing about any noise coming from the rears.

At this point, nobody has seen the inner surface of the rotor. So nobody can say if they are good or bad.

I've seen people replace pads on undersized, grooved rotors many times.
It doesn't have to be noisy to be grooved.
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Mar 7, 2007
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It may fail because the thickness of the brake pad.

Or just because the greedy mechanic wants to charge you for new brakes. The usual story.
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jayoldschool wrote: The brakes don't do any work on the highway ;-)

Go somewhere that you can get up to 60-80kph repeatedly, and brake hard to 5kph. Do this 5-10 times, and then drive home. Your brakes will look almost new.
How's the wear on the tires?

Driving an EV, I try and brake hard after rainfall and car wash to remove moisture from the brakes. Otherwise the brakes never get engaged in normal driving and might rust/seize.

At the same time, I don't want to kill my tires. Would routinely hard braking once or twice a week kill my tires?
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Wire brush.
Maybe even some brake cleaner or CLR.
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mxthor3 wrote: Passing the safety is about minimum thickness. Why are you wasting time trying to make the rotors shinny again?
No, you also have to have a minimum of 75% pad contact with the rotor.
hiker007 wrote: Not sure the ABS kicked in or not, but I heard tire skid sound a few times :)
It has the electronic parking brake, so it won't move until you release it.
mxthor3 wrote: Passing the safety is about minimum thickness. Why are you wasting time trying to make the rotors shinny again?
hiker007 wrote:
Not sure the ABS kicked in or not, but I heard tire skid sound a few times :)
It has the electronic parking brake, so it won't move until you release it.
rugerty100 wrote: How's the wear on the tires?

Driving an EV, I try and brake hard after rainfall and car wash to remove moisture from the brakes. Otherwise the brakes never get engaged in normal driving and might rust/seize.

At the same time, I don't want to kill my tires. Would routinely hard braking once or twice a week kill my tires?
Braking hard is fine, just don't engage ABS. So like 90% full braking.
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engineered wrote: No, you also have to have a minimum of 75% pad contact with the rotor.
I think you meant to say 'as well as'.

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