Urgent Help - Brake Discs

[angryfarang]

Guys,

I know this isn't motorbike related, but it is to do with brake discs. Can anyone look at this thread and help me?

http://www.thaivisa.com/forum/topic/640309-urgent-help-think-local-mitsu-dealer-is-trying-to-sell-me-old-discs/

Thanks.

[Spoonman]

They look new to me.

[angryfarang]

Where has the scoring come from? Surely the surfaces shouldn't have a mark on them?

[Spoonman]

Throw a set of verniers on them and measure the thickness.

[Gsxrnz]

They look new to me. New disks should not be "shiny" as they are machine scored to create friction against the pads. Look closely and if you see any non-uniform scratches (say from a stone/grit) formerly stuck in the old pad/disk, then they are old.

But to me they look like they're new and as you would expect them out of the box. Face it, if a disk was as shiny as polished steel or chrome, there is no way it is going to give any braking effect.

I wonder why you wanted new disks? Why not just get the old ones reconditioned - unless they're warped, a reconditioned disc is as good as a new one. All they do is machine/lathe them to an even surface and then score for improved friction.

EDIT: Are their any marks/imprints/rust on the mounting flange to suggest that a wheel/mag has been previously mounted on the disc? I can't tell from the pics, but that's another double check.

Edited May 18, 2013 by Gsxrnz

[angryfarang]

They look new to me. New disks should not be "shiny" as they are machine scored to create friction against the pads. Look closely and if you see any non-uniform scratches (say from a stone/grit) formerly stuck in the old pad/disk, then they are old.

But to me they look like they're new and as you would expect them out of the box. Face it, if a disk was as shiny as polished steel or chrome, there is no way it is going to give any braking effect.

I wonder why you wanted new disks? Why not just get the old ones reconditioned - unless they're warped, a reconditioned disc is as good as a new one. All they do is machine/lathe them to an even surface and then score for improved friction.

Hmm... the train track going around the disc in picture 2 of 4 I attached looks a bit suspect. Maybe I'm paranoid, I've never trusted garages back in the UK to do work properly, yet alone here...

[Gsxrnz]

They look new to me. New disks should not be "shiny" as they are machine scored to create friction against the pads. Look closely and if you see any non-uniform scratches (say from a stone/grit) formerly stuck in the old pad/disk, then they are old.

But to me they look like they're new and as you would expect them out of the box. Face it, if a disk was as shiny as polished steel or chrome, there is no way it is going to give any braking effect.

I wonder why you wanted new disks? Why not just get the old ones reconditioned - unless they're warped, a reconditioned disc is as good as a new one. All they do is machine/lathe them to an even surface and then score for improved friction.

Hmm... the train track going around the disc in picture 2 of 4 I attached looks a bit suspect. Maybe I'm paranoid, I've never trusted garages back in the UK to do work properly, yet alone here...

Ask to see the old discs, or the packets that the new discs came in, or another set of new discs from the store - do a comparison. Used discs will be smoother and shinier than a new disk due to the rough surface they create at manufacture, The surface on new discs should be a little coarse and have a satin/matt look to them.

Check for purple pad dust down the slots - that will be a dead giveaway. Yes I see the groove you mention, but can it be physically felt or is it just a quirk of the machining?

I used to take my bike discs off after every 2nd meeting and re-score them in both directions on a 45 degree angle from the outside edge to the centre. They always had a matt/grainy look compared to used discs.

[angryfarang]

Thanks for the replies guys.

I went back down and spoke to them very nicely, showing them a picture of a new disc.

They explained to me that they fitted the discs and pads new and went
for a test drive. They noticed an issue with the brake's, so removed
everything again to notice that the calliper piston seals were damaged.

This is how the explain the scoring on the discs. I asked them why
they didn't inspect the seals or notice this when they pushed the
pistons back to fit the new pads. I got a blank look.

Anyway, they showed me my old discs that they removed, they have
definitely recently been used (as there is no rust on the surfaces) and
also showed me the brand new box for the new discs with the Mitsubishi
part number.

I smiled and laughed and said no problem and will come and pick my
car up later... Maybe what they say is true, maybe they fitted
re-surfaced discs to my truck. Who knows. What I do know is that I
should have done the job myself and in the future I'll source parts
myself just to be sure.

[Gsxrnz]

Thanks for the replies guys.

I went back down and spoke to them very nicely, showing them a picture of a new disc.

They explained to me that they fitted the discs and pads new and went

for a test drive. They noticed an issue with the brake's, so removed

everything again to notice that the calliper piston seals were damaged.

This is how the explain the scoring on the discs. I asked them why

they didn't inspect the seals or notice this when they pushed the

pistons back to fit the new pads. I got a blank look.

Anyway, they showed me my old discs that they removed, they have

definitely recently been used (as there is no rust on the surfaces) and

also showed me the brand new box for the new discs with the Mitsubishi

part number.

I smiled and laughed and said no problem and will come and pick my

car up later... Maybe what they say is true, maybe they fitted

re-surfaced discs to my truck. Who knows. What I do know is that I

should have done the job myself and in the future I'll source parts

myself just to be sure.

OK, pleased it all turned out OK.

[yankee99]

Looking at the second pic that rotor is not right. New rotors should not have any grooves in them. Are all 4 the same? are they grooved on one side and not the other.

Assuming they were a return or something the question is what can you do about it in thailand? Why did you replace them in the first place?

[angryfarang]

Looking at the second pic that rotor is not right. New rotors should not have any grooves in them. Are all 4 the same? are they grooved on one side and not the other.

Assuming they were a return or something the question is what can you do about it in thailand? Why did you replace them in the first place?

The old disc's were warped, hence my wanting them changed.

As I said above, the garage told me they had already test driven the car before I had seen them, hence the scoring.

I'm not sure if I believe them, but will need to take their word for it.

This is a learning experience, in the future I will source my own parts and do my own jobs. I knew I should have changed them myself.

[yankee99]

Let me ask is that a groove that you can feel or is it just a surface thing? if on the surface then no worries if a groove that would be a different story.

[angryfarang]

Let me ask is that a groove that you can feel or is it just a surface thing? if on the surface then no worries if a groove that would be a different story.

The groove can't be felt, I ran my fingers over the disc. It's just on the surface.

[yankee99]

If it cant be felt i would take their word that its new.

[sotsira]

Another indicator that the discs are new is that the vent slots have no rust.

Any disc that has been used will show a brown discolouration inside the vents.

[angryfarang]

Thanks for pointing that out. Thanks for all the replies. Very helpful.