I replaced my rear rotors and pads with a set from R1 Concepts; the pads are semi-metallic and the rotors are slotted and drilled. Everything works well, but the grinding noise in the last few feet of the stop, or when reversing, is annoying. They have about 300 miles on them now. I’ve tried multiple hard stops to bed them in. Any hope of improvement with time? Anything else I might have done wrong to cause the noise? The front brakes are still ok but I am seriously considering changing out the rear pads, and buying new pads for the time when I have to do the fronts (I bought a four-wheel boxed set).

 

I had the same grinding noise on all three of my Jags (2010 XFS, 2010 XFR, 2014 F-Type) when I first got them, with stock rotors and pads. A loud annoying "graunch" just as the car comes to a stop, slightly better with warmed up brakes but still there.
On the XFS I had the rotors skimmed and fitted new stock pads (semi-metallic), made no difference.
I then fitted Power Stop Evolution Z16 ceramic pads, hey presto graunch completely gone and smooth quiet progressive braking all the time with the added bonus of almost zero brake dust unlike the incredibly dusty OEM pads (which are semi-metallic).
Power Stop don't make pads for the XFR so I tried Centric Posiquiet semi-metallic instead. Slightly better, a little less graunch but still some and about half the dust.
I then bought a full set of Hart brand slotted and drilled rotors with "ceramic" pads included as part of the kit, only to find that the pads were in fact the exact same Centric Posiquiet semi-metallic pads I already had on. Fitted them anyway with the new rotors, some slight improvement to the graunch and the dust but both still there.
On the F-Type I swapped over the Hart rotors from the XFR (exact same rotors front and rear) and fitted Porterfield R4-S "carbon kevlar" brake pads.
Very little dust but still some graunch with cold brakes but it disappears once the brakes warm up. I have put about 30,000 km on those pads and they have hardly worn at all and still perform the same as new.
Moral of the story - ditch the semi-metallic brake pads and fit ceramics.
I would recommend Porterfield R4-S but a quick search shows they don't make them for the XFR, instead my search comes up with EBC Red Stuff or EBC Yellow Stuff which are both ceramics.
My next recommendation was going to be EBC Red Stuffs anyway as they are well known for being quiet and low dust and they definitely make them for the XFR, while I have always struggled to find any other true ceramic pads for the XFR - lots are advertised as "ceramic" but most are not really.
Red Stuffs are for street use while Yellow Stuffs are more of a track pad - harder, noisier, dustier and slower to warm up than the Red Stuffs but perform better on the track.
Another one worth a try although I have not seen any feedback about them is Dynamic Friction 5000 Euro Ceramic, listed on the Rock Auto page, see here: https://www.rockauto.com/en/catalog/...brake+pad,1684
Rock Auto have a huge selection of brake pads for a 2011 XFR and in my experience they are almost always the cheapest price you will find.
Last but not least, are you sure the grinding/graunching is coming from the rear brakes and not the fronts, or the fronts as well? Coz on all three of my Jags with the stock brakes it was 95% from the fronts. For that reason and for braking balance if you decide to try some new ceramic pads I would get fronts as well as rears.

 

Thanks. The noise is definitely from the rear. I haven’t done anything to the fronts and had no noise at all before I did the rears. My concern was that I might have not torqued the rotor brackets sufficiently or overlooked another step, but I really do think the pads are the issue. The car only has 33,500 miles so I presume all the pads were original before I replaced the rears, but perhaps not.

 

Something else you can try - slather the backs of the pads and where they contact the brackets (ie the ends) with heaps of brake grease.
I tried that on my F-Type and it worked, but only for a short while, the graunch came back again straight after the first time I drove in heavy rain so somehow the rain washed the grease away. Also be sure to use hi-temp ceramic brake grease, I use Bendix.
Also lightly grease the caliper slide pins if you haven't already.
Just don't get any grease on the pad material or the rotors!

 

I haven’t used slotted rotors but I believe they are inherently noisier than non-slotted rotors.

I have R1 Concepts drilled rotors with their ceramic pads on front and rear and don’t have noise problems. Therefore, I think it may be your pads. Trying the ceramic pads is an inexpensive way to find out for sure. Also, ensure the caliper slide pins, the contact points between the pads and the carriers, and the backs of the pads where they contact the pistons are lightly treated with brake grease. Those surfaces need to be very clean before the application of any grease.

 

I did grease the pins but not the backs of the pads. I’d done front brakes on my XJR a few months earlier and have had no issues, but I did put grease on the backs of its pads. I’ll give it a try. Thanks.

 

As prolepsis says, not just the backs of the pads but the ends as well.
IMHO the ends, where the pads slot into the brackets, are even more important than the backs of the pads.

 

You can get Porterfield R4-S for the XFR. I have them on my 2010 XF V8 SC (same brakes). I had RedStuff before on the drilled slotted R1 Concepts rotors and I got uneven rotor wear and pulsating brakes after around 5000 miles - replaced the rotors and same issue again on the drilled / slotted. So I've gone back to traditional rotors with the Porterfield pad and so far no issues.

 

I’m going to try brake lube first, then will consider changing the pads.