Why do my brakes make a noise?

[andyquantum]

I've checked the pins, copper greased the back of the pads, cleaned the discs basically done all the usual stuff

The pads and discs are fairly new, maybe 6 months/5000 miles. I bedded them in the same way I've always done and up until a couple fo weeks ago not had a problem.

After about 40 mins of driving, and up to motorway speeds I get a faint metallic catching noise that goes away when the brakes are applied, or lightly feathered

Warped disc? Something's got onto it and created a tiny burr? There's nothing noticable and to me they seem flat

Any input grateully received

[PhillipM]

Little bit of pad deposit on the discs perhaps, try cleaning them with some brake cleaner and stainless steel wool, then re-bed the pads in.

It could just be the composition of the pads and discs though.

Edited by PhillipM on Tuesday 16th September 21:22

[tegwin]

Sounds suspiciously like a warped disk....If you have one...run a dial test indicator against it to see how out of kilter it is!

[Davi]

going to sound daft, but check the backplate if you have one - I spent ages checking disks on an old car only to find that a bit of road debris had clobbered the backing plate. When it got hot it must have moved a bit and was just grazing the edge of the disk!

Failing that, yeah does sound a bit warpish.

Edited by Davi on Wednesday 17th September 14:10

[Huff]

It might not be the disc themselves, but some crud (or rust) on the mating face of the hub behind - which can have the same effect as a slight warp, becasue the disc won't sit square. Could be worth popping the discs off, wire brushing the mating faces and reassembling with the lightest trace of copper grease on the hub face to stop it recurring.

[andyquantum]

Cheers people. Its on the Mondeo but same principals for any of the cars really. Have no idea what discs were used, they're from the local tyre and brake place. Might be worth pulling them off again for inspection and getting them skimmed

Brakes are quite grabby if you know what I mean, which is fine for feel and it's strange I'm only getting this at speed. Cant replicate it at low speed or on the drive with the wheel off

[Holst]

Sticking caliper possibly.

I had a sticking rear caliper that had similar simptoms.

After a run down the motorway see if one wheel is warmer than the others.

Most likely is dirt somewhere as the other guys have mentioned, strip down and clean should sort that out.

[andyquantum]

It took a bit of investigating and swapping around pads and discs then taking on a high speed run but it was a warped disc in the end. Dont know how, they were bedded in as usual, possibly manufacturing fault but really couldnt say

Anyway, new discs/pads and all fixed

[ELAN+2]

sounds like mickey mouse cheapo part syndrome to me...any idea of the make/brand fitted?