Fooked Brake Disc

[Dominic]

I have been getting a vibration that has been getting worse and worse for some time from my brakes. So, as I have Ali bells on the front of the car and not the rear, I hatched a plan. I have been offered another pair of ali bells from a pal [cough] Woody [cough], so thought I would put new rotars on the front, get the old ones skimmed and fit them to the rear, with the new ali bells.

So my shiney new disc rotars arrived, and I fitted them the other day. The front o/s disc looked fine from the outside, but when I removed it, this is what I found on the inside of the disc;



As you can see, the surface of the disc had broken up. Does anyone have any idea why this may have happened?

The pistons on the caliper are moving quite freely. Whenever I wash the car, I always take care not to soak/hose the discs - or at least not too much. Furthermore, I always take the car up and down my street after cleaning to clear the discs of water before it goes in the garage.

I assume that disc is beyond skimming?

TIA

Edit to add; the uneven wear on the disc is because I stuck some different pads in a few weeks ago to see if it helped the vibration - which unsurprisingly it didn't, so did not use it much since. It now has brand new pads to go with the new discs, and works perfectly.

[tut]

Beyond skimming? They would refuse that at the tip.

tut

[Dominic]

Beyond skimming? They would refuse that at the tip.

tut

Words from experience there tut? Hence the "free tyres and other spares" post?

[Claws]

Beyond skimming? They would refuse that at the tip.

tut

[robin]

What pads were you using? What did the inside pad look like?

[Dominic]

For years, carbon lorraines, rc5+, then last summer, I unknowingly put ebc yellow stuffs in. Done a few thousand miles on them. Recently (about 150 miles ago) put some old carbon lorraines back in. The vibration developed during the ebc usage. When I put the old CLs back in I was unaware of the condition of the inside of the disc, so did not pay any attention to the state of the pads. Will have a look and see if one is different from the others. None very warn.

[robin]

Those pictures show the radial slashes/grooves having been filled and then polished over for most of their length.

I wonder whether what we're looking at is the disk face or something deposited onto it?

If you get a wire brush and give the area around one of the grooves a going over and collect the material that comes off - see if it's attracted to a magnet and what it looks like.

I doubt the brake pad material of either EBC or CL5+ contains enough ferromagnetic material to be attracted to a magnet (ignoring the backplate, of course)! If you have some old pads you can prove that with a magnet.

Cheers,
Robin

[KennyT]

I fitted those discs new in June/July 2010 with a new set of CL5+ pads about the same time I put the braided hoses on, I'm a little surprised the discs are still in use with the type of use the car has had!

They were the Elise Parts own Ali belled discs so possibly not the best quality, does an AP rotor fit the EP bell?
In my experience with the 135 and my Exige I have tried Carbon Lorraine's pads, performance friction and now have Pagid RS42's and the Pagids are by far the best, I was never very happy with the brakes on the 135 hence why I made a few upgrades.

[mckeann]

I had one of the EP Ali bell rotors crack on me when I was racing. Unsurprisingly, this resulted in a locked rear wheel and a high speed off.

If your not sure about them, don't risk it. I was lucky it was at silverstone with tons of run off.

[Dominic]

Tested all old pads with a magnet: none are magnetic at all.

Deposits from disc groove are magnetic.

[Dominic]

I fitted those discs new in June/July 2010 with a new set of CL5+ pads about the same time I put the braided hoses on, I'm a little surprised the discs are still in use with the type of use the car has had!

They were the Elise Parts own Ali belled discs so possibly not the best quality, does an AP rotor fit the EP bell?
In my experience with the 135 and my Exige I have tried Carbon Lorraine's pads, performance friction and now have Pagid RS42's and the Pagids are by far the best, I was never very happy with the brakes on the 135 hence why I made a few upgrades.

Until recently the discs were lasting well. Stu had a look at them a few months ago, (through the wheels so would not see the damaged side), and thought they had plenty of life left in them.

[robin]

Tested all old pads with a magnet: none are magnetic at all.

Deposits from disc groove are magnetic.

OK that's conclusive then. The disks have turned to cheesium.

I don't know how disk surfaces are hardened, perhaps once you were through the outer layer you get to the softer inner? Anyway that disk is clearly destined for the tip.

[David]

Looks like corrosion to me. Light use, seized piston or caliper and/or poor quality disc.

[BigD]

Looks like corrosion to me. Light use, seized piston or caliper and/or poor quality disc.

I'd tend to agree with David although this may be worse due to reaching the softer metal as Robin has said. My 350Z front discs were like that, slightly worse, and it was due to it not doing many miles and just sitting. It was only the inside that was corroded too. Definitely scrap though.

4 years out of a set of discs with abrasive pads and track use is awesome though.

I'd be checking the calipers/pots to make sure they are working freely and have no corrosion at any points as this can make them sick at a certain point.

If you fancy a spanners and sponges day let me know as I need to look at my brakes too.

[woody]

Forgot about those bells, but they'll make a nice present for Anna!