Brake Judder, Help I am stumped

[craig2003]

Hey folks, thought I would put this out to the masses for advice.
There is a judder coming from the front mainly under braking from 70 -40.
The car has just had the wheels refurbished and balanced with the newish tyres refitted. Also had the Hunter laser alignment done, a set of KW coilovers, all the bushes in and around that area were fine.
The discs are new but I used the existing DS2500 pads which were around 10% worn. Bedded in as usual, the wobble stops if you really stand on the brakes, car is a B7 RS4 with the 8 pot calipers, could one of the pistons be sticking? Maybe I should be getting the wheels rebalanced too?

[Hoonmeister]

Good science says look at what has changed.
My money on powdercoat on centre bore or rear wheel face.
Wheels off sandpaper out.

[slipstream 1985]

Could a counter weight have come off?

[jagracer]

Change the pads

[craig2003]

Good shout, will get it looking shiny and then a rebalanced, failing that I shall have to go for the pad change

[jagracer]

You could try giving the pads a face off on some coarse emery paper on a flat surface. I've never had much luck with DS25/3000 pads, they always seemed to glaze (which also transfers to the discs) as soon as I looked at the brake pedal plus they aren't really a road pad.

[craig2003]

Yeah I gave them a good sanding before I put them on and plenty grease on the backs, they were almost new, I should have just changed the discs at the time really

[DCL]

Sounds like the disc may have a little bit of run-out. It is worth sorting before it leads to permanent damage to the discs. I would remove the disc and check they're perfectly clean where they sit on the hub - dress with a fine file if there is any bruising, or marks that stop them matting perfectly square. The same applies to the wheels as said above.

[Angelus]

DCL said:

Sounds like the disc may have a little bit of run-out. It is worth sorting before it leads to permanent damage to the discs. I would remove the disc and check they're perfectly clean where they sit on the hub - dress with a fine file if there is any bruising, or marks that stop them matting perfectly square. The same applies to the wheels as said above.

This ^^^ Check there isn't a little bit grit between the hub and the disc. Sorry it means stripping everything back down, but I'd double check this before going half way, re-building then having to strip completely again.