Grooves on Slotted rotors are being grinded away

[lab4games]

Hi guys, 

 

I have been using slotted front rotors on my 2016 Octavia. Using original brake pads. Pads are 50% used. For the last 3 months I have been hearing some  screeching sound when braking. Finally I saw the grooves on the rotors disappearing.

 

Is it normal for slotted rotors to become smooth as part of its wear and tear?

 

Would there be other components that I should check for this case?

[OldAndyMac]

I would say its a quality issue, the grooves are not uniformly deep so they are wearing at different rates.

[Ootohere]

The lowest point is not being worn away, it is the braking surface that is getting thinner.  Same as if they were on a lathe and being skimmed.

Pads wearing, discs wearing.  They are consumables. 

[varooom]

That second image looks odd, half the disc is smooth now and other half with groove's.  Warped disc?

 

Anyhow, looks like needing replacement soon enough, perhaps once pads are fully worn.

 

Not a mechanic, just pointing out as I see it from my POV.

[Ootohere]

They were more Stylee than actual performance discs anyway.

 

Not really cooling the discs just a reduced braking surface.  But good to see they have done the job and are not a corroded mess that OEM ones can be. 

[Gaz]

58 minutes ago, varooom said:

That second image looks odd, half the disc is smooth now and other half with groove's.  Warped disc?

 

Think that's what Andy was getting at; the depth of the grooves not being uniform around the disc, so the shallower ones have already worn away.  Warping could also account for it, but I reckon that'd be horrendous to drive.

 

Gaz

[varooom]

7 minutes ago, Gaz said:

 

Think that's what Andy was getting at; the depth of the grooves not being uniform around the disc, so the shallower ones have already worn away.  Warping could also account for it, but I reckon that'd be horrendous to drive.

 

Gaz

Yup the car would be vibrating hard looking at that single disc if it is warped.

 

Hopefully they get replacement soon.

 

EDIT: Can also see that it could be just a manufacturing fault too, with the grooves not being cut to same depth on one disc

Edited 21 September, 2022 by varooom

[Ootohere]

A picture of them when new and how the slots were machined would be marvellous.  Were the grooves of even depths the full length of them or deeper at one end?

Saying who these discs are maybe by or sold by would be super-duper.

 

How long and how many miles /km has been done using them would be interesting.  IMO.

 

http://briskoda.net/forums/topic/455363-aftermarket-brake-pads-or-brake-set

 

 

 

 

 

 

Edited 21 September, 2022 by roottoot

[J.R.]

13 hours ago, OldAndyMac said:

I would say its a quality issue, the grooves are not uniformly deep so they are wearing at different rates.

 

Unlikely to have been manufactured like that and if they were it would have been immediately apparent visually as the groove width would be reduced.

 

The second picture could fit that description if the disc was not located correctly at 90° to the cutter axis but if you look that too is showing more wear at the centre of the pad area like the other disc.

 

Putting a straight edge across the pad swept area will show the uneven wear which would be exactly the same on an ungrooved (they are not slotted) disc.

 

It's a 3rd world problem of the same ilk as red painted brake calipers  looking dirty.

Edited 21 September, 2022 by J.R.

[Gaz]

22 minutes ago, J.R. said:

...but if you look that too is showing more wear at the centre of the pad area like the other disc.

 

Aye.  In the second photo there appears to be a good wear lip on the outer edge of the disc at 6:30-ish, with the groove making it all the way to disc edge.  But two grooves around (counter clockwise) at about 4:00 the groove's not even making it to the edge of the disc.  In both photo's there's a noticeable wear line about 2/3 of the way in to the area of the wear face, and it looks like there's a wear lip on the innermost edge.  Perhaps just well worn discs, as George alluded to.

 

Gaz

[KenONeill]

Alternatively, inconsistent mu across the brake pads that the worn disc surfaces press on.

[cheezemonkhai]

16 hours ago, lab4games said:

Hi guys, 

 

I have been using slotted front rotors on my 2016 Octavia. Using original brake pads. Pads are 50% used. For the last 3 months I have been hearing some  screeching sound when braking. Finally I saw the grooves on the rotors disappearing.

 

Is it normal for slotted rotors to become smooth as part of its wear and tear?

 

Would there be other components that I should check for this case?

 

 

 

It's a friction brake. The friction lining (Brake Pad) rubs against the brake disc to create friction to slow the car down.

They wear, that's the point of the disc, albeit slowly.

 

You can't put too big or deep a groove in it or you harm the performance of the disc and if you drill the disc it can crack around these.

Most people I knew who had proper fast track cars (not off road going through dirty standing water) used solid discs as the extra mass gave better cooling.

 

There's a whole series of possible factors from:

• Discs are worn out
• Pads are not applying pressure evenly (that would really only go for the wear ring you see about 1" out from the centre)
• Discs are not on the hub quite straight (fraction of a mm, meaning a tiny tiny bit more wear on one side of the disk than the other
• They were not milled consistently (I'd assume a machine did them, so it would be unlikely but you know what they say about assumptions)
• The material the original disc is made from.
• Many more

Where did you buy them from? Not an e-bay special I hope?

What is the wear pattern like on the inside of the disc (Is that face slotted too - it should be and if so is it worn in the same or mirror image)

How many miles have you done on them and of what sort of driving.

 

It's normal for slots/groves to wear as the disc wears, but how much depends on the brand.

I know some makes had a certain bit wear flat at minimum thickness, so you could easily tell when it was new disc time. Perhaps it's that?

 

I personally wouldn't bother and would put bog standard discs of a decent brand/quality on them (OEM Equivalent brembo for example)

 

Regardless of what we all say, I would be getting the brakes checked by a qualified person if you are not 100% certain what you're doing as they are the one thing not to take any chances on.

Edited 21 September, 2022 by cheezemonkhai

[J.R.]

Good point about the wear marker amongst all the other good observations.

[lab4games]

appreciate all the inputs. here's a photo of the slotted rotors when all the grooves were intact. i recall there were from ATE.

 

I did a 288mm to 312mm rotors upgrade by changing to this rotors and by changing the clippers carrier brackets. 

the current pads have done 15000 miles. 

 

the rotors had done about 70000 miles.

 

car drives well, brakes well with no vibration like those of a wrapped disc. 

 

so i suppose i could just use it and change to new discs and pads together at the end?

[KenONeill]

24 minutes ago, lab4games said:

the current pads have done 15000 miles. 

 

the rotors had done about 70000 miles.

Well, there you go then; the discs are just plain worn out, particularly given that grooved discs are normally made by cutting grooves into cast iron, and then case-hardening them.

[OldAndyMac]

70,000 miles! as Ken states above, they are just worn out.  Still a little strange that they have not wore evenly though.

[StevesTruck]

Looks like there's a bit of a lip on the edge of the disc as well which would explain the screech. I've found that grooved discs do wear fast. 

Edited 27 September, 2022 by StevesTruck

[Ootohere]

70,000 miles is not fast wear for what are maybe supposed to be sporty discs for sporty drivers who use brakes to go faster unlike others who hardly touch their brakes and discs are just a rusty mess.   If the last a nice long time maybe not much braking gets done and pads get changed at the rate of 3 sets for 1 set discs. 

[J.R.]

On 23/09/2022 at 04:39, KenONeill said:

grooved discs are normally made by cutting grooves into cast iron, and then case-hardening them.

Cast Iron cannot be case hardened, it already has an excess of free graphite.

Edited 27 September, 2022 by J.R.