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slybunda

Odd brake disc wear

Question

so i was inspecting the brakes on the car and noticed that the front drivers side disc has a dodgey wear pattern to the inside of it. it looks like this:

 

dodgey.jpg.df301771c0407eceaaa6fd141a5ae682.jpg

 

the outside of the disc which is visible form just looking at the wheel looks perfectly clean like new. what would cause this type of wear to happen. looks like the pad is not touching the outer and inner part of the disc. and the rust is probably grinding up the pad.

 

the passenger side is a lot better but i could see that rust was starting to form on side of the disc that faces the hub.

the sliders are moving freely. its the avensis setup and discs and pads have done probably 10k miles, pads look like new with lots of meat on them.

if the sliders were a problem wouldnt the outside part of the disc be affected,the side facing the wheel? since that side grabs on using sliders?

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This sort of nonsense is very common on the inside of discs on all sorts of cars.

 

Did you fit all new discs and pads?

 

I'm not 100% on what causes it, ive seen it happen on cars with perfectly good sliders and calipers myself.  My own personal theory is that unlike the front face which is one continuous piece of metal to the hub part, the rear side is basically floating on the cooling fins.  Once rust starts naturally forming on those fins, it more easily "creeps" around to the friction side.  Once a big enough chunk of rust forms to "wear" a bit of that pad off, the pad no longer closely sweeps that part, allowing a little more rust to form, wearing the pad again, allowing more rust to form......

 

Another contributing factor, I think, is that there is a lot more potential angulation of pressure on the inside pad of floating calipers.  The outside pad really had no option other than being pressed totally flat against the disc and there is a lot more surface area of the caliper pressing against it, the inside however had a relatively small amount of surface area because only the piston is pushing - get a small chunk of crud on the back of the pad and the piston can potentially start going at effectively a bit of an angle

 

just a theory

Edited by G.Lewarne

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ahh cool, should i replace the discs and pads or can they continue to be used? they passed the MOT 3 weeks ago on the brake force meter.

last week i noticed this and bought new guides that go in the calipers that the pads slide on. old ones were bit rusty and had brake dust on them.

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personally, I would replace.  Ive never seen it happen when ive used pre-coated or painted myself discs (VHT paint)

 

Try some pagid discs from ECP they come pre coated and rust much much much less

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these were pagid discs and pads i got from eurocarparts. cost around 40 quid per disc.

if its gonna happen again then dunno if i should just get cheaper discs? i can get mintex or delphi discs for 50quid for the pair!!

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2 hours ago, slybunda said:

these were pagid discs and pads i got from eurocarparts. cost around 40 quid per disc.

if its gonna happen again then dunno if i should just get cheaper discs? i can get mintex or delphi discs for 50quid for the pair!!

 

Really? how old are they?  Ive used plenty of pagid coated discs over the years and never seen them go that crusty

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Hmm cant remember when the avensis setup was done. Im thinking 2 or 3 years ago. Car is not used much. One day a week usually or less.

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usually its sliders not moving freely or pads not moving freely in carrier that cause the inside to wear like that

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i had a feeling the pads not moving properly could be the cause. i replaced those metal things the pad slides on. hopefully it clears up the disc.

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some pads can come with too much paint on, making them tight in the carrier, EBC are bad for it

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Cool. Is it worth trying to use rust remover and wire brush? Or just go with new discs?

 

Does the rust affect brake force or balance?

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