Did a search - didn't find exactly what I was looking for.

My '09 XK has stock brake rotors - vented, of course, but solid, i.e. not drilled or slotted. With these cars, would there be any perceivable improvement to braking if I go to drilled, or slotted, or drilled and slotted rotors? Of course, new pads are required, and pads can make a difference on their own. But higher performance pads always have a trade-off, usually needing some heat to work really well. So, the potential objective here is to get a little better performance via a rotor "upgrade" so I can stay with a street pad.
As you guys know, the stock brakes are quite good, but as a racer I'm always looking for some modest performance improvement in a daily driver/street car.
Opinions and recommendations welcomed.
Cheers.

 

Why not get the OEM 380mm front rotors? I don't know what all would be required to install though, maybe just swap the caliper bracket also. Worst case, change the entire hub. The 400mm Alcons are even better, but way more expensive.

 

Are those drilled or slotted? (are mine not 380mm fronts?) Forgive my newbee-ness. I was thinking I would do all four corners, not just fronts. But that's why I'm turning to the experts.

 

You 'probably' have the 355mm fronts and whatever the corresponding rears are since 4.2 N/A.
Of course you'd do all four, but I don't recollect what the rear sizes are for both.
Not drilled, not slotted.

 

Don't be fooled by inexpensive drilled and slotted brake rotors that are made in China. Brake shops are a graveyard for those rotors that looked nice during their short lifetime. Buyer Beware of the hype, and get real user reviews before buying.

If drilled and slotted brake rotors actually provided improved performance with longevity, Jaguar would have offered them as standard or optional original equipment on the X150.

My 2009 XKR Portfolio has the Alcon Performance Brake Package, a $5,000 option with 6-piston front calipers and 400mm rotors that have crescent-shaped grooves, not holes and slots.

 

^^ Thanks Stuart. Yes, I want to avoid any cheap Chinese-made rotors like so many seen online for cheap. I'm not going to spend the money to upgrade to Alcons although that would clearly be the preferred upgrade. Is there a good recommendation for drilled and/or slotted quality rotors. StopTech rotors have always been quality rotors, and I use Stopech components on the 996 race car - a very strong product for the race track. They have some options for an X150 XK.

Other suggestions?

 

For privat people on public roads, there are no reason for racing-sport-brakes.
Drilled or slotted brake discs do lower fading and helps reducing heat, but when does a human need it on public roads.

In Germany, it´s different, we can drive as fast our cars go, on the "Autobahn", but on all other places on earth, you won´t need that kind of super-brakes.

But ... we are always upgrading our brakes on our cars either with Tarox brakes and factory size or upgrade to the next higher brake-version. In your case it would be Alcon / R-Performance. But, do we need that really? Some made awesome experiences with EBC stuff

 

Yeah, but the Autobahn sure isn't what it used to be. WAY too much traffic nowadays.

 

@David993S Having oodles of experience here, drilled rotors will do nothing for you, even pro race cars don't use them, too much risk in cracking. Slotted rotors however will improve stopping distance but will also wear brake pads faster. There's many quality aftermarket suppliers (centric, zimmerman, brembo, etc).

 

Thanks for the additional aftermarket suppliers. I had forgotten about a couple of them (such as zim or centric). I do like the suggestion of slotted rotors, and will search for those.
Regarding drilled vs. slotted - many high-end performance cars come with drilled rotors as standard. For example: my Ferrari, SL550 and both Porsches came with drilled from the factory. Some pure race cars do have drilled - my Reynard Formula Continental and my Reynard Formula Atlantic both had drilled rotors. My Swift Formula Ford did not have them. My 996 race car (when it was still stock and before being converted to a race car) came with drilled rotors. I currently use Stoptech drilled rotors on the 996 with many racing miles on the rotors. As you know. racing puts extreme conditions on all parts. I have not experienced any cracking on the drilled rotors. Not saying they can't or won't develop cracks (eventually they will), but I've found even in racing conditions the drilled rotors hold up fine. Drilled rotors in a street application would be unlikely to develop cracking. That's why I was thinking drilled or slotted would be a modest upgrade on the XK, even for the street.
Thanks again for the input.
Cheers.

 

@David993S not to belabour this, but I was referring to pro sanctioned race cars (IMSA, Indycar, SRO, and more) which do NOT use drilled steel rotors for safety reasons, though some use slotted. You can check the rules books to confirm this. Porsche, Mercedes and some other sports street cars use drilled rotors for appearance as options or so called "upgrades". Every factory OEM drilled rotors I've seen have had cracks of some sort which only get worse, requiring more frequent and expensive disc replacements. Pic is from a Porsche.

 

They can all crack under the right circumstances.

 

Surely, the choice of disc type depends on how you drive. Flat discs provide the greatest actual swept area so will provide the most friction. Drills and slots help cooling so will work longer better as heat in the discs/pads rises as long as the pads themselves are still maintaining friction at those higher temperatures. Drilled discs are noisier and corrode more readily outwards from the holes. As usual, a balancing act of characteristics to consider.

Also, all modern braking systems can trigger the ABS when working well, so the limiting factor is the choice of tyres. Better tyres, better absolute braking performance.

Higher quality components do provide some other benefits. Jaguar used high-carbon discs, which dispate heat better than plain cast iron. They selected very good pads, especially at the front and most aftermarket equivalents don't appear to reach the friction levels of the original Jurid-sourced front pads. High friction pads work with less pressure so feel more responsive and provide a wider range of modulation. Downgrading the stock setup is easy!

Old discs that have had hundreds of corrode/clean/corrode cycles exhibit lower friction from embeded rust inclusions that then lead to cementite formation. A simple disc change will almost always improve braking performance.

The XK 4.2, IIRC, has the 326 mm brakes??? For my style of driving, fast but where I don't usually over heat brakes, good initial bite and reassuring feel is more important than race-style heat disipation. If I was sticking with stock disc size, I would go with good plain discs (ventilated dics disipate heat quite well anyway) and the best road pads I can find (DOT edge code GG grade). This is what I did with my S-Type which also has unfasionably small discs for the size of car and it feels noticably better with good pads. When I fist got my XKR (380 mm/376 mm discs), the front pads were a bit low so I replaced them with what I thought was a good branded road pad - TRW. I noticed immediately that braking was worse, especially needing more pressure and was less smooth. At the next TÜV test, they measured 260Nm. Before the next test, I put new stock pads (Jurid 310 GG) back in and the braking was just right again and measured 330 Nm. Quite a difference. Those Jurid pads Jaguar often use were definitely chosen for performance but some say they are dusty.

If you are a more "aggressive" style of driver than me, you might want to compromise on the braking area for slightly better cooling.

There a a good article here: https://www.roadandtrack.com/car-cul...lotted-rotors/

However, I expect you actually know all of this. It is more down to the comprimise you wish to make.

 

As CeeJay suggests above, as yours is an xk, the "upgrade" could be moving to the xkr brakes. Though as jahummer points out, there are a few good brands out there.

If you're feeling that the brakes are inadequate, overhaul the callipers (a proper calliper service) change the rotors and the pads. Usually, many are surprised.
Or, if its looks you are going for, have at it and be prepared for high maintenance pretty, but reduced performance.

 

355 rotors (single piston floating caliper )
380 rotors (twin piston floating caliper )

Anything calipers from xk5.0 /xkr/xkrs / f type / xf 5.0 / xfr / xfrs/ xj.5.0 / xjr / xjrs will all bolt straight up
​​​​​​
The alcon calipers from the 4.2 are the largest rotors and carry 6 piston in each caliper however it's virtually impossible to find the brackets in order to bolt them up to the hub

 

Only the front Alcon calipers have 6-pistons. The rear calipers have 4-pistons.

 

I thought it was quite clear I was referring to the front calipers however to be more precise
alcons 400 6 piston front / 350mm 4 piston rear

Xkrs/xjrs/xfrs / f type rear 376mm single piston floating

In terms of OP looking to upgrade the 355mm / 380mm front rotor / caliper are readily avail and it's a straight forward bolt up ...alcons will be extremely challenging due to locating the brackets in order to complete this conversion.

 

How I read the original post, David doesn't want to do major surgery and is just looking for pad/disc options???

I tried drilled discs on the S-Type and EBC Redstuff pads. Neither were good. The Zimmermann drilled discs were noisy and showed no extra performance and corroded badly in our climate (Germany), both on the S-Type and the FIAT Coupe. The Redstuff were only adequate when warm but poor cold, however, they were a bit cleaner with grey dust.

As I said before, the S-Type went back to normal components but good ones and is better than factory as the spec is better than factory. The FIAT currently has a set of ATE Power Disc groved discs and they seem to be an OK compromise, but probably because the disc quality is better.

I would clean up the calipers to make sure they move freely, get high-carbon disc like the original ATE ones and the grippiest road pads out there - the Jaguar Jurid 310, which are hard to find, or something eqivalent (maybe look at Delphi https://www.ebay.com/itm/295324913061 and https://www.ebay.com/itm/302260098289).

 

^^Exactly, and thanks. You are correct in that I am not looking for "major surgery", rather just a rotor upgrade. Based on a few of the responses that were more on point, it seems as if an upgrade with a quality drilled or slotted rotor would only provide a minimal increase in stopping performance. In a DE car or race car, every little degree of improvement is desirable, but a waste of money on a car that is used for daily driving/weekend trips. Sounds like the juice is not worth the squeeze, and I'm not wanting to do it just for a visual change. I will probably just stay with the current stock rotors as the braking performance is more than adequate for street driving.

Thanks to all for the input.
Cheers.