Hi, has anyone come across an issue with front brake discs either warping or wearing unevenly. I'm having to change my discs every 12 months/20,000 miles because my front near side disc is juddering. I'm on my 4th set!  and juddering  again. I was thinking caliper sticking but I can't see anything obviously wrong. Could it be ABS related?

Welcome David,

A couple or so questions:- 

Are you a ‘slow down in anticipation driver’, or have a tendency to be ‘last seconds on the brakes’? 
Are you renewing these discs yourself, or having them fitted for you? 
What brand/s have been fitted?

Have you read Steve Q’s excellent post about the mating surface of discs and hubs? 
Kind regards,

Gareth. 

Most of the miles are motorway. Very rarely brake hard! Thought it might have been an issue with getting the cheaper end disc so got Brembo for the last set, maybe lasted a little longer but the issues back. Changed the discs myself, as I have dozens of times on lots of cars for myself and friends. Always make sure the mating surfaces are perfectly clean and flat. Never had this issue before and it's always the same wheel. I'm at a loss!

I would suspect the caliper. 

Ok, in what way, sticking? Or is there another way they could contribute? It always looked to be OK but I'm going to take it off and strip it this time. I was interested to see if anyone else had come across the same issue.

Sticking. 

Make sure your brake carrier is clean as well so the pads are not tight and use some brake grease on the contact areas of the pads. Make sure the guide pins are clean and move freely. Use some red rubber grease on the guide pins. Easy to tell if you have a sticking caliper as the disc would most likely overheat. If the outside edge of the discs have an orange colour rather than a brown rusty colour, the disc has got too hot. 

Thanks, alway do all that. No discolouration on the disks. I've been putting my hand on both hubs after my journey home (40 miles) and neither are ever hot. Think I'll just change the caliper when I do the discs this time. At least it should rule it out!

Have you changed your brake fluid at all? When I change discs and/or pads, I always clamp the brake hose and open the bleed nipple when I push the pistons back in so I don't push dirty brake fluid back into the system. Are the pistons easy to push back in? Have you checked the pistons for corrosion?