changing rotors / discs
 

In the USA you call them rotors - in the UK we call then discs

I took a look at my front discs this weekend. I removed the wheel and turned the disc by hand. I could clearly see that the disc was warped by about 0.25mm.

question - would this small amount of warp cause judder whilst breaking?

question - do I need any special tools to remove and replace the discs? is it a simple job to do?

Simple job, no special tools really.

Disks don't really warp, it is the material wear and pad deposits that make it seem like they are warped.

Yes, at speed, heated rotors, the vibrating can be felt. I would check the thrust arm bushings first though.

Those are the ones that are on the arms which go to the front of the car. Those can cause similar symptoms.

I agree with Slick. Also try to re-bed them first. That's the easiest solution. It worked for me.
There is a procedure on the net on how to do it.

Something like that:
Stock Brake System Bed-in

To remove the Disk just take the whell off. use the 7 or 8mm hex key annd remove the caliper, then undo the 6mm i think set screw on the rotore and try to tap it off with a soft hammer if you wanna reuse them. Or wack it hard with a normal hammer.

Pro tip: leave a lugnit in so the rotor doesnt fly out

.25mm is a lot of warpage for a brake rotor, I think the maximum allowed specification is .1mm
So, yes that would cause shaking when you brake, but also check the thrust arm bushings.

Judder on my X5 was so bad I did a complete front end rebuild. Bedded the brakes twice(different compound pads). Changed the front discs and pads, twice. Balanced then changed the tires, all four. Did an alignment until I was at my wits end.

Not until I changed out the rear discs did the judder go away. One was as warped as the OPs.

Got my thrust arms changed, and the shudder at speed and braking went away. Of course I went ahead and changed a tie rod end, and added new tires. But the bushings were so bad on the thrust arms, that to me was clearly the main cause.

I have checked my bushes and they are perished. I am going to change the tension arms and bushes along with new discs and pads. Hope this cures the judder under breaking.

Yup, nice and easy fix. Very, very common.

Worn thrust arms are notorious for creating judder upon breaking when all else in the system is relatively good, and often makes one think they have warped rotors. This is true going back to my e24 M6 and e34 M5.