Judder/notchy brake pedal. New pads

[Bowser]

I've changed plenty of brakes without issue, and generally meticulous about my work.
I've just fitted new discs and ferodo premier pads, and now bedding them in.
But now I'm braking a little harder I can feel a notchy abs type feedback through the pedal at the very end of the braking phases - so when almost stopped.
I can stab the brakes at 60mph and not feel anything untoward.
It's only as things slow right down I feel this through the pedal.
I'm going to check caliper bolts etc, but I know they're ok.
Any ideas?
The abs light is also on. .

 

[JB21]

Pedal fart...cracked ABS ring.

 

[Bowser]

Is this a thing? Bit strange as I didn't get it with the other discs.
Will check it out though.

 

[JB21]

The split ring slips on the driveshaft and at low speeds just before coming to a stop you get a judder like the abs kicking in. With the light on as well makes it even more likely as the abs sensor isn't reading the sine waves properly from the split/corroded abs ring.

 

[Bowser]

Sounds like that.
Easy enough to change?

 

[JB21]

The driveshaft needs to come out the hub to get the new ring on. Also if Cup pack suspension with 60mm spacing hubs you'll need the wider rings, think they're 16mm v 8mm for the 54mm hub spaced cars.

 

[Bowser]

Mare.
I only changed discs..
Thanks for your input

 

[Bowser]

Found the problem.
The new rear discs i fitted had the incorrect ABS ring. The notches were fractionally closer together than originals.