brakes mystery

Wig

Replaced both discs and pads at the front, torqued properly.

Went for a spin and I get a banging on brake application on one wheel.
Removed disc, clean & refit, go for a spin - still banging.

So I swap the discs from left to right, now there is no banging. But the side where the dodgy disc went to now has what I assume to be ABS kicking in under heavy braking - the sort of braking you just don't normally do.

So I decided to check the run out of the discs. I got 2 thousands of an inch on the good disc and 5 - 6 thousandths on the dodgy disc. so it would seem the dodgy disc does have a slight run out problem. The safety label in the disc box says "Vehicle manufacturer maximum run out normally 0.1 mm - 0.15mm - if it is more than this then take it off and re-position in a different position", well you can't do that unless you don't fit the disc grub screw, so I didn't bother.
(0.1mm is 4 thousandths of an inch.) I forgot to check the book what the 2003 Corsa disc run out is, but my Carlton book says 0.1mm

One last time I decided, before taking the disc back for a refund..... was to swap them round again and see if it still bangs on the original side. I did this and could hear again the banging coming from the dodgy disc but this time it was much, much quieter it was now more of a "knocking".

My theory is that under all the heavy braking I have probably reduced the run out by a thousand of an inch or so and with prolonged driving the run out will go away completely.

I also cannot MOT now for 2 weeks as I have to go to France (in a different car). So I'm thinking if it fails the MOT on the dodgy disc (ABS or knocking depending on what side it's fitted to) I will just buy 2 more new discs, pass the MOT, refit the dodgy disc and let it wear down a bit and I'm certain when it has worn a bit it will become a good disc. I don't think it's worth making the retailer refund me for the disc as it will wear down and become good eventually.

What do you think? Has anyone ever had a new disc run out problem before? - it's the first time it's ever happened to me.

colino

I haven't came across this for a while, but there was a period when it seemed that every other box of discs was going back to the factor to get swapped due to crappy quality control at the factory.
If I was you I'd get them swapped as if its noticeable now, it is already causing you brake imbalance and its going to take a very long time for your pads to "machine" them true.
You've definitely ruled out hub, debris and wheel-bearing issues?

Wig

Not sure how to rule out hub, other than to measure run out with the discs on the opposite hubs to before.

There's no play in the hub and the bearings are good.

The discs are Juratek, not a name that inspires confidence, next time I'll go for QH no matter what the price is.

Looking at Juratek website they seem to be proud of their made in China factory pictures which you will see if you click on Quality Assurance and brake discs. :rotfl:

gilbert_and_sullivan

Wig, you did clean the hub face with scraper/wire wool/glass paper/wire brush as needed, seeing as the run out has seemingly decreased i wonder if a patch of rust on the hub face might be at play here.

Never had to return discs or other correctly supplied brake parts in over 40 years of working on cars, but i buy a name i know from trusted outlets,.

Wig

All sanded down and as clean as a whistle. Don't forget the problem only occurs on the wheel that has the dodgy disc, when the good disc is on either wheel that side has no problems.... return the dodgy disc to that side and you get the same problem.

mikey72

I'd get the disc swopped for a new one.
even if you're going away, I'd phone them, register the problem, and get it exchanged either now or later.

Strider590

I know from various owners websites that certain Vauxhalls seriously dislike non-oem pads..... they don't fit right and they rattle about. I see no responsibility reason why other cars wouldn't be just as picky.

Wig

Holy cow the corsa disc run out max is 0.03mm that's only 1 thousandth of an inch! no wonder its not happy...

Good grief. I will have to sort it out when I get back from France.