Brake Disc Ridges

Horizon81

Just wondered if minor ridges on brake discs were normal? I had new front discs and pads fitted a couple of months ago and the outer faces are as smooth as glass, but on one of them, the inner face has a couple of ridges/high points on it - I'm not talking about a lip at the edge - these are minor ridges around the middle(ish) of the disc surface.

I've had scored discs in the past where there was a pit/rust, but this is a high point/ridge - what causes it?

I regularly brake hard to clear surface rust.

Wig

seen it before many times, can only assume it's normal.

Possibly there is an area of hardness on the disc, as it's harder it causes greater pad wear, as the pad is less thick now in this area it causes a ring on the disc.

gilbert_and_sullivan

When you brake hard do you come to a stop, that can leave an imprint of the pad indeed some of the pad, best to not actually come to a full stop if you're glaze busting, but use them heavily then continue for a bit wihtout braking to allow the whole disc to cool uniformly.

Horizon81

Wig wrote: »

seen it before many times, can only assume it's normal.

Possibly there is an area of hardness on the disc, as it's harder it causes greater pad wear, as the pad is less thick now in this area it causes a ring on the disc.

By that token I suppose it could either be an area of hardness on the disc or an area of softness on the pad??

boogiemaster

Its normal all of my cars have had the same ridges its called bedding in the brakes

Its when the disks are warped then you need to worry because when you break you get a shudder in your stearing wheel.

Biketrials08

Would be useful if people got hold of a brake pad and had a look at it, you would see that the material is not homogenious. So therefore there are harder areas which create these score lines, it's normal stop worrying. Car garages love to rip people off by making out this is a problem that needs rectifying.

Wig

Horizon81 wrote: »

By that token I suppose it could either be an area of hardness on the disc or an area of softness on the pad??

I ruled that scenario out in my thought process.

If there is a hard point on the disc it will wear away the pad in a ring, that ring will be replicated on the disc around the whole disc (in a ring) even though the hard point would only be at a single point on that ring.

If it was a soft point on the pad, it would not create a ring, because the rest of the pad surface would compensate , i.e. you wouldn't get a ring shaped area of softer material on the pad..... would you.

So that's why I ruled put soft pad....

Mind you I'm only guessing here.

skiddlydiddly

Maybe a little stone got flicked up onto the pad, made a little groove on it so until the rest of the pad is worn to the same level it will leave a raised area on the disc.

cyclonebri1

It'll even up in time.

The problem youve had in the past will be down to others usage not your own, ie, if the car is left outside or in a damp garage for long periods corrosion will set in. If used every day this isn't a problem.
Most damage occurs at change of ownership, when the car my spend weeks sat on a garage lot without moving.

When a certain level of corrosion is reached this becomes more abrasive than the pads so is not removed. Corrosion carrys on below the surface and eventually the polished rust becomes the braking surface of the disc:eek: When that starts to brake up you really would notice;)

I'm pretty certain my old Vectra was run every day of it's life untill at 8 years old the original front discs had to be changed as they were worn out, perfectly smooth but toooo thin, it was still on it's original pads at 80k.