Congratulations on your new brakes. Have you had a chance to function test them with traction fully off?

 

Once I figured out the blanking plugs in the calipers I had no problems bleeding the brakes. I haven't braked hard enough yet to invoke ABS though, fact is I can't remember ever invoking ABS on any car I have driven, and I've been driving for 45 years and around 1/2 million miles. Either I'm pretty good at COAST, or I'm just not trying hard enough!

 

Not yet.
When I bedded the new pads in (firstly the rear pads and then the next day the front pads) I hammered the brakes pretty hard and the car pulled up straight and true every time. Maybe later today or tomorrow I will try a test with DSC off.

 

One last update.
Over the first week or two after upgrading the rear brakes I noticed a gradual loss of brake fluid, just a little, but the level in the reservoir was dropping bit by bit.
I also noticed a build-up of wet and black muck on the inside edges of the rear wheels, especially the LHS.
Both of these things told me I had a slow leak where the brake lines attached to the calipers.
Made sense, as I had to add an extra 1 mm thick flat washer on each side before fluid stopped dripping. My theory was that reusing the original copper crush washers didn't create a perfect seal because one of them on each side (the inner one, nearest to the caliper) was now a little "crushed" on the inside edge (doh!), and this is why the Workshop Manual specifies ditching the original washers and replacing with new.
I went out and bought a pack of new crush washers, but of course they were completely the wrong shape and size.
So I rang the dealership and ordered a set of four OEM washers, $9 each, that's right each, total $36, when you can buy packs of 200 assorted sizes on Fleabay for $4! A day or so to come from the warehouse in Sydney, they would ring me when they came in.
As is par for the course for this dealership I never got that call.
So then I thought I would try something else. I removed the washers on the side with the worst leak (LHS), filed off the "ridge" on the inside edge of the inner crush washer, and filed the "spacer" washer I had added a bit flatter (it wasn't perfectly flat to start with, it was slightly domed on one side) then reassembled.
After about two weeks of testing no more build up of muck on the wheel on that side and no detectable drop in brake fluid reservoir level.
Just now I checked the wheel on the other side and it was showing a slight build up of muck on the inner edge. I whipped the wheel off and yes, there were signs of a slow leak from where the brake line bolts to the caliper. But I didn't pull it apart this time as I didn't have a helper to help me bleed the brake line of air, and it was obviously an extremely small and slow leak. Instead I grabbed my trusty big and boofy 1/2" socket wrench and 14 mm socket and lo and behold the brake line bolt did up another half a turn! Previously I had used only the piddly 3/8" wrench and trusted my son to do up the bolt "as hard as he could", and he's 6'3", young, strong and solidly built, so I had assumed (incorrectly in hindsight) it would be good and tight. It will take another week or two of monitoring and testing but I reckon I have now solved the leaks.
Moral of the story - you don't need new crush washers, instead file the old ones flat and reuse them, add 1 mm spacer washers, and do up those brake line bolts RFT!

 

MAYBE at some point the old ones were over torqued. When i changed form regular brakes to carbon ceramic calipers, i reused the old crush washers as they looked fine but glad you have had a successful conversion!

 

Another moral of the story: when it comes to tightening brake lines and torqueing lug nuts, do it yourself.

 

Yep.
Two days of monitoring and checking now and not the faintest hint of any brake fluid leak(s), problem solvered!

 

So what are your impressions regarding the improved performance? I'm considering upgrading all 4 brakes on my base and would like to know how much of an impact it would make.

The brakes feel considerably weaker in comparison to my Quattroporte GTS despite the weight advantage...

 

I haven't really hammered the brakes for any length of time so I can't say much about any improvement. I already had the 380 mm front brakes anyway so harder still to tell much difference. All I can say is they are very strong brakes. The main reason I went ahead with the upgrade was that I already had near new slotted and drilled rear 376 mm rotors to match the front rotors (both were after-market mods to my old XFR which I took off when I put the XFR on the market), and the existing OEM rear rotors weren't that far away from needing to be renewed (about 24k miles on them).
Other reasons included the fact that the stock 326 mm rear rotors and brakes look a bit puny and the 376 mm ones look a lot better, and I came across someone selling new 376 mm calipers with the integrated EPB motors for less than 1/3 of the normal asking price.
As detailed in this thread the rears are a relatively easy and cheapish upgrade but I don't know about upgrading the 355 mm fronts to 380 mm, it could be that besides rotors, calipers, pads, caliper brackets and splash shields you might need new hubs and/or new brake lines as well, which would make it a very expensive proposition.

 

A little update.
Zero problems with the new rear brakes since I fitted them.
I have now found the JLR part numbers for the 376 mm rear calipers - T2R7686 and T2R7690.
And good news for anyone who wants to upgrade their "base" front brakes (355 mm) to the 380 mm jobbies, someone on another forum with an XF with the 355 mm brakes has upgraded to the 380 mm brakes with zero problems, the new calipers bolt straight up. The only proviso of course is the stock 18" wheels on the base won't fit over the 380 mm calipers (but the 19" wheels will fit no worries).

 

So I'm sniffing around on eBay for the larger rear calipers... what visual giveaways can I look for to distinguish the 376 calipers from the 326 ones?
I'd imagine that some of the codes etched into the back would suffice?


Here's the one I'm looking at right now, for example:



I looked up the VIN; this one came from a 400 Sport, which I believe came standard with the larger brakes, HOWEVER, the seller's info mentions "12.80 inch rotors" (so, the smaller ones).

 

Nothing visual to tell the difference between the 376 mm and 325/326 mm rear calipers, they look identical and the size difference is miniscule with the 376 being maybe one or two mm wider than the 326.
But the part numbers imprinted on them are different, with the 326 RHS being 4345/A and LHS being 4344/A and the 376 RHS is 4317/A LHS 4316/A.
So the one in your pic is for the 376 mm brakes.