Brakes shudder

[Andyrs4]

Hi any one can tell me why my rs4 avant 2015 brakes shudder when I put my foot on the brake pedal at about 50,60 mph ? 

[Steve Q]

This could be caused by warped discs. 

[ninjag]

I had this issue with my previous car (common problem with Jaguar) and it would be at similar speeds and at its worst when lightly pressing the brakes. If I braked hard it wouldn't judder though.

I stripped the brakes down and found that the caliper slide pins were sticking from a combination of corrosion in the holes and also some swelling of the rubber slide pin boots, possibly from someone in the past using copper grease instead of something like Ceratec lube. I used my Dremel to clean up the corrosion in the holes (and also the rest of the brakes) and also some black gunk off the slide pins themselves. I also replaced the slide pin boots. This cured it for me but a year later the judder returned but only slightly.

Another possibility could be the mating face between the discs and hub not being 100% aligned. It could be worth inspecting for any debris, corrosion etc and if necessary cleaning it up.

You could also measure all around your brake discs to check for irregularities. I just bought one of those digital brake disc caliper gauges for less than a tenner. I'll link underneath to the Amazon listing if that's allowed? You might have to do the pound coin trick though if your discs have a lip.

 

Brake Disc Caliper Gauge Amazon link