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Rusty Brake Discs .... what's the criteria for an MOT pass or fail!

944psi

944psi

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[FONT=verdana,geneva"]Evening all,

Does anyone know what is the criteria is as to whether a brake disk is too rusty to pass an MOT?

The picture attached is of one of my rear discs. There is some surface rust on the face (and rear) of the disc that will be removed when (if) the car ever moves again. Are there any other areas of rust to be concerned with on brake discs?


TIA, Phil
[FONT=verdana,geneva"]
 
That doesn't look bad to me. Have you tried cleaning it up to get to that stage? If not then a wire brush in a power drill works wonders. I think I'm right in saying the MoT is only concerned with braking efficiency, so provided the brakes are able to provide sufficient braking force it doesn't matter how much rust there is on the disc. Of course deep pitting may be fail and I am no MoT tester so its effectively speculation.
 
I'm not aware of any specific rust criteria, other than rust on one face of the disc, or on 50% (say) of the "swept area" of the disc indicates uneven application of the braking force and therefore some sort of problem.

That image looks very much like "surface rust" as you state and would dissapear with a few braking applications.
 
[FONT=verdana,geneva"]I'll give it a go with my drill and a wire brush when it is time for the discs to go back on. I've also got a dremel type tool with some shaped grinding stones for the holes.

I'm hoping to make the dyno day on the 20th May so I'll have to start putting the bits back on soon!

Phil
[FONT=verdana,geneva"]
 
Don't waste time taking the wheels off and cleaning the disc. Take it for a run and apply the brakes a few times that should get rid of the surface rust. It is braking efficiency that is checked not overall condition (unless efficiency was down they may look for a reason. Your discs don't look bad at all.
Cheers,
 
Mine recently failed on one of the front disks - they are tested on braking efficiency as previously mentioned.
On the failure report i recieved apparently the poor one was only operating at 40% and on inspection when removed it was very scored .
I get visible surface rust on mine practically every time after they've been wet - soon dissappears after a run though.
 
I can't see that you have an issue. A few hard brakings should clean them up.
Even without that, there is a good chance you would be OK.

The drive to the MOT station is probably all you need.
 
Thanks for the replies. I'm still completing some work around my back end and will be glad to get it all back together. I took the discs off as I was swapping the calipers out and thought I'd check out the handbrake shoes. I've got some 'metal ready' from frost which I may use on the bells whilst brushing off any flaking rust around the edges. As you say it's the efficiency that counts. Fingers crossed!

On a related note - I have a choice of pads to put back in EBC Greens or Pagids? What's the difference?

Thanks,
Phil
 
I've not used EBC - i've got pagids in mine, they're ok but i find they make a hell of a lot of brake dust and i'm forever cleaning the wheels.When they need changing i'll try something else.
 
If the disks are corroded to such an extent there is any pitting on the disk then it will fail the MOT, but rust is OK as long as the efficiently is OK (oh and the ABS warning light isn't on but it doesn't matter if your ABS actually works or not, it's not even tested).
 
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