Jaguar E-Type and XJ
Inboard Brake Upgrade
(Replacing Solid Rotors w/ Vented Rotors)
and install vented rotors that looks like this:
The rim of the original solid rotor is 1/2" thick. The rim
of the vented rotor is 3/4" thick, and the rotor assembly is
configured so that the entire 1/4" of additional thickness is
added to the outboard side of the original configuration.
The inboard friction surface remains in exactly the same location
as before. The OEM calipers are separated and reassembled
with 1/4" spacers between the halves to accommodate the thicker
rotors. Since the calipers are mounted by the inner half of
each caliper, they are thus positioned correctly for the thicker
rotor with no change in caliper mounting.
The example in the photo is a "two-piece rotor", consisting of a
custom hub and a generic disc bolted together. The outer
disc is a wear item but the inner hub will last the life of the
car. When buying replacement outer discs you can return to
the original supplier of the hardware for your upgrade, but you
don't have to; several places offer such discs. This is
discussed in greater detail on the two-piece
Note that the photos on this page are from Kirby Palm's own
upgrade, but the design has been revised in numerous minor ways in
the meantime. If you follow the plans on this web site to
the letter, your finished brakes won't look exactly like these,
but largely similar.
Upgrading the inboard rear brakes on a Jaguar E-type/XJ6/XJ12/XJ-S is a popular (and highly recommended!) modification, and three reasons are generally given for making the mod:
In general, there are two ways to upgrade your Jaguar inboard brakes to vented rotors: Buy a kit or fabricate the stuff you'll need yourself. Since this is a common upgrade and there are quite a few Jaguars out there that have the same basic rear brake arrangement, there are several outfits that offer such kits. Note: If you can't find it listed under XJ-S, try looking in a supplier's E-Type section; the rear brakes are the same, but some of these suppliers forget that owners of later models might also appreciate the upgrade.
XK's Unlimited offers a kit, catalog number 17-1214, that utilizes a two-piece rotor similar to the photos above.
Judging from the photograph in their online catalog, the kit offered by Terry's Jaguar Parts, code TJP190, uses one-piece rotors. This means that when the rotor is worn an entire new one must be purchased -- and such rotors are not likely to be easy to find elsewhere so you will probably need to go back to Terry's for replacements. Of course, you could opt for installing two-piece rotors then.
BG Developments in the UK reportedly offers a kit; their rotor is part number BGVD035-13.
Theoretically, you could actually get the parts necessary for this upgrade from Jaguar; the TWR XJ-S came off the showroom floor with two-piece vented rotors. Be forewarned, however, that TWR owners have some trouble getting parts to maintain their brakes from Jaguar, and sometimes opt for some of the ideas presented here for finding parts instead!The other way to upgrade your rear brakes is to fabricate the necessary hardware yourself, or have it fabricated locally. This has the potential of saving a bit of money compared to the kits, but will require some time and skill to assemble the various parts. If you happen to have the ability and equipment necessary for machining the hubs required, it could save you a lot of money; the actual dollar outlay will be comparable to a simple brake overhaul. At the other extreme, you could just hire a machine shop to make all the parts, but that might not save you any money over buying a kit! It is suggested that you read through the two pages linked below and decide for yourself if you're up to the work.
Kirby Palm did this upgrade by fabricating some of the hardware and having the rest made for him. Pictures and guidelines are presented here in two pages; one page describes the two-piece rotor itself, including the outer disc, the inner hub, and the bolts to hold it together. The other page describes the small parts needed for the job, most of which are involved in spacing the caliper wider.
Here's what Palm's brakes looked like when done:
The upgrade described herein reuses the original calipers. This works fine -- but most people don't even get involved in their rear brakes until there is a problem, and that problem as often as not is that the calipers need rebuilding or replacement. Hence, you might consider installing an all-new high-performance brake system such as those made by AP or Wilwood rather than simply upgrading the existing brakes to vented rotors. The cost of renovating the original calipers plus the parts needed to widen them would go a ways toward paying for a really nice set of aftermarket high-performance brakes.
One final comment: If you talk with Jaguar "experts", you may hear that installing two-piece vented inboard brake rotors is difficult and problematic. There's a good reason for those reports. An outfit called Gran Turismo Jaguar once offered a vented rotor kit that was horribly designed -- requiring grinding on the differential output shafts to install, believe it or not -- and shoddily machined, often resulting in runout problems. Unfortunately, this was probably the most popular kit of its time, since GT Jaguar was more adept at promotion than most such outfits.
Gran Turismo Jaguar is now history, which is just as well -- many of their other products were no better than their vented brake kit. But the stories about problems with brake upgrade kits remain as their legacy. Please don't take any heed; a properly-designed kit from one of the suppliers listed above or a set of parts fabricated according to the instructions provided will bolt right in and work splendidly. It's really an easy, no-hassle upgrade.
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