Zinc coating on discs

Site Subscriber Joined: 29 Jan 2005 Posts: 1108

Y'know the zinc coating they put on a lot of disc brakes these days to prevent corrosion (like in the pic of mine below), well I assume this is to prevent corrosion whilst they're stuck on the shelf in the shop, and not actually while they're on the car? Cuz as soon as I put 'em on the car and used 'em a bit, that goldy looking coating has now gone and they look 'normal' & silver, like the surface of a cd y'know.

Well anyway, is this coating meant to be cleaned off before you put the discs on the car & use 'em? I had no sort of instructions telling me to remove the coating before I used 'em, and I dunno how I would remove it if I had to.......but I'm sure I read somewhere on the net that this coating has to be cleaned off before you use the discs? Did I make that up?

So anyway, I only found that out after I'd fitted my discs (this was a while ago now), so I fitted 'em to the car with the coating still on. Put new pads on aswell. The only reason I'm asking about this is that my brakes aren't as good now as I thought they would be, and I'm wondering has this zinc coating now shitted up my pads and reduced my braking performance? Do you reckon if I get new pads now & use 'em with the still-fairly-new discs that no longer have that coating on, they'd be much better?

Or.........as usual.........am I talkin complete bull shite?! Laughing

FCS Event Manager Joined: 04 Jan 2005 Posts: 3680

new discs always come with sort of coating on them to prevent corrosion whilst in storage so yes u always need to clean them before you fit them.
when you put them on the car did the discs feel slimey or slippery at all?

it is possible you have contaminated your pads if you did not clean off the coating so a pad change would need to be done.

Forum Moderator Joined: 02 Mar 2004 Posts: 19978

its a fine oil film, if thats gone and the gold zinc coatingsgone then its not an issue.

Why did you expect the brakes to be better?

Site Subscriber Joined: 29 Jan 2005 Posts: 1108

Chris H wrote:

Why did you expect the brakes to be better?

Well......um......I am not as much of a Renault expert as you Chris, but I think most people would expect new discs & pads to function better than old knackered ones? In much the same way I expect new tyres to be better than old tyres. If that is wrong then........well I give up

And you say if the coating has now gone then it's no longer an issue? Well the issue is possibly that it's now on my brake pads & making them shite. But that's a silly question to ask on here, you lot obviously won't be able to tell that. I'll just have to try new pads & see if they improve.

I just wanted to know about that coating that's all, and Neo has confirmed what I thought. I should've cleaned it off. Doh! Rolling Eyes

Forum Moderator Joined: 02 Mar 2004 Posts: 19978

I just wondered if you thought the pads/discs were the fault or maybe a hydraulic issue.

How bad are they?

Grooved discs wear pads and any contaminants from them pretty quick btw.

Site Subscriber Joined: 29 Jan 2005 Posts: 1108

Oh well if they get rid of contaminants then that probably isn't my problem then. I spoze it could be so many things. I have only changed my front discs & pads, haven't done the back yet so I spoze it could be them? They seem to be in quite rubbish condition, like the disc isn't even flat if you rub ur finger from the inside of the disc to the outside edge if that makes sense? Kinda dips in just by the edge. The brakes on my mates FTO were shit and he found out his rear ones weren't working at all and that was why. So maybe it is something to do with my rears. It got through it's MOT fine tho, and I thought brakes not working properly would've been picked up!

Could be hydraulics, I don't really know enough about it like. Pedal feels good & firm. It's just as if the pads are made of something that isn't really designed to grip the disc lol. Pedal feel is good tho, just doesn't stop anywhere near as well as I would expect. Confused

Level 10 User Joined: 05 Mar 2005 Posts: 570

They picked up my brakes on the MOT, cost a fortune Sad

Forum Moderator Joined: 02 Mar 2004 Posts: 19978

rear brakes only need to work at 25% efficiency, rear handbrake has to onyl operate at 7% but be balanced.

I knwo what you mean, they get thinner at the edge for some reason.

Site Subscriber Joined: 29 Jan 2005 Posts: 1108

Well I think I will just get rear discs & pads because they look like they could do with a change anyway, and then if the brakes are still shite then I'll start worrying about it.