Over the seven years I've owned my 35i I've had steering judder under a braking a few times.
Not long after buying my 35i I fitted Pagid discs all round with Red Stuff ceramic pads.
First time it happened I had the discs skimmed whilst on the car to eliminate run out. This cured it for a few thousand miles only for it to return, so I fitted new discs, Brembos this time & the juddering was cured for 18,000 miles.
When it returned it turned out to be the right hand side (drivers side for those of us that drive on the correct side of the road) lower control arm, it was only diagnosed by an experienced tech with the car on a shaker ramp. I replaced both lower control arms and the juddering was again cured..for 8 months or so until it returned a couple of months ago.
I have now replaced both front discs with Ate discs & have swapped out the Red Stuff pads to none ceramic Brembo pads. The shuddering had now gone & the brakes feel much smoother & work better at low speeds although they are not as good when braking hard from high speed & they give off more brake dust.
When I took of the old discs they were quite badly scored with & I could feel & see circular ridges especially on the inner face of the discs.
Each time I've changed the discs I've cleaned the hub & all the other parts & carefully reassembled and I've fitted new slider pins.
Hopefully this time the brake judder won't return as I suspect that the ceramic pads may have been the cause of my problem....time will tell.
I've attached a link to the brake reskimming machine used on my 35i for those of you that may be interested
https://www.google.com/url?sa=t&sour...k5sQUUArd_2mmi