I have been considering converting the solid rear rotors on my 1985 XJ6 to vented rotors for quite a while. The XJ6 is a heavy car, and although my V8 conversion took away somewhere around 150-200 lbs, I gained it all back by using a heavier transmission and a soon-to-be-installed roots supercharger. Combine tripling the horsepower, doubling the torque, and my area's fast stop-and-go traffic, it made sense to at least start by upgrading the rear rotors.

There are a few most things to do, like take care of the caliper crossover tubes, fit the parking brake, and other small details. I also bought a teflon+stainless steel brake hose and a set of EBC Redstuff brake pads that should make a difference in response and stopping power.

I included some pictures here, and there are more pics and info at my website here:
Dave's Jaguar XJ6 LS1 Swap

The custom brake rotors are Coleman brand from Hoerr Racing, and the hats were machined for me by a guy in Ohio. The hardware is all aircraft stuff from B&B Aircraft supplies. The only fitment problem I had was that the hubs had a radiused edge where inner diameter of the rotor tries to seat on the hub. The edge on the rotor was squared (not rounded) and would not fully seat, so I had to take that corner off with a carbide burr (not pictured here.)

I hope to install them onto my spare limited slip differential this week, and then put that whole assembly in the car next week.

Most of the ideas from this kit were borrowed from a page on the jag-lover.org website, which is cited on my webpage.

 

I have a similiar problem with my 406 SBC /700R4...it's all go and not enough whoa. I'm in the process of installing 12.15 wilwood aluminium hat rotors and calipers on the fronts. For the rear I decied against the inboard brake setup for a few reasons and I'm installing rear hubs from an Xj40 parts car which has outboard brakes.

1. Vented rotors give you more cooling not more stopping power. I need both.

2. Vented rotors on on XJ6/12 may cause interference with the exhaust pipe hitting the caliper if you have the stock exhaust routing like I do.

3. Inboard brakes get contaminated by diff oil or any other oil that blows back from the engine / trans. Not so much with out board brakes becasue they are sheilded by the wheels. .

4. Cant run bigger rotors or calipers with inboard. With outboard you are only limited by the wheel size.

5. Such a pain to bleed or switch pads with inboard setup.

I'm leaving the inboard disc for drive shaft spacing and e-brake but I'll be removing the very heavy calipers thus simplifiying my installation.

 

Ahh, interesting stuff - I never thought about the inboard brakes getting contaminated by blowby, etc. That could be a real issue for carb engines, or vehicles with older engines. I am pretty sure my newer engine captures every whiff of contaminant due to stringent EPA regulations - it's sealed up pretty tight. Though, if something failed I could totally see contamination happening.

I was thinking about going to the outboard brakes, but it seemed like a lot of work and I didn't like the calipers. They are the one-sided single piston sliding style. It seems like all of the performance applications are opposed piston like the SIII inboard calipers. I am pretty sure those outboard setups also use a solid rotor, which is what I was trying to get away from in the first place.

I was thinking about going to bigger calipers in the back - something like the SII 3-piston front caliper but I didn't want to upset the brake balance. (This setup is used on some Maserati vehicles w/Salisbury differential from the 80's.) Add more rear brake, and the rear brakes lock up prematurely and the back end comes around - never had this happen on a car but it's easy to do on a motorcycle, especially in the rain. Add more front brake, and the car will feel like it stops faster but actually takes longer to stop at the limit because the front brakes will lock up prematurely and the rear brakes (and tires) are relatively underutilized.

For more braking performance, increase both the front and rear brake effectiveness at the correct ratio - this includes the realm of brake pad selection, disc design, caliper design, etc. For more (harder) stopping performance at the limit, you need more traction, which usually equates to better tires and suspension tweaks.

This is one of my favorite sites for brake info. It's really, really, really good!
Technical White Papers

Also, if you can, think about taking those inboard discs out and having someone put them on a lathe and cut the friction surface off, leaving only the center hub section for spacing purposes. This will save you at least 5 lbs of rotating mass per wheel!

 

I'm looking at something similar as a way of gaining ABS. Did you use the XJ40 hubs and were there any problems?

I have a set of hubs and halfshafts from an XJ40, and I've been told it's a bolt on, I wanted to make sure that was the case.

 

It's sort of a bolt one. Depending on what diff you have, the output flanges may need a mod to provide clearance between them and the halfshaft flange so you can set the proper camber. The lower outer control arm to hub bolt is slightly smaller, (metric vs SAE) so you need to make spacers to take up the difference. I used short sections of steel tubing with the OD to match the control arm, and the ID to match the bolt. You'll need four spacers.
You'll also need to find a way to hook up the parking brakes, and different brake hoses and brackets to match.

Jon

 

I'm only going halfway, just a hub conversion and keeping the inboard brakes. I have the IRS from a Maserati Quatroporte and was going to use the vented disks from that. The Maserati has the parking brake already, it's the same calipers as the Jaguar with a spacer between the caliper halves to fit the thicker rotor.

 

I used late XJS stuff but I think your can use XJ40 items so long as you get the 1/2 shafts and spacers. You need the spacer in order to take up the spacer where the old rotor used to be. I'm doing a XJ6L at the moment...in progress but I'm using late XJS stuff again. Adding ABS is practical. You may want to see this link below. It covers the ABS. I used an ABS system from a early C4 corvette but I've also retrofitted a min 90's Teves system that has the integrated controller in the base of ABS pump. Good luck, it's worth the effort.

https://www.jaguarforums.com/forum/x...e-works-84536/

 

I saw that thread, and that was what gave me the idea of adding ABS. I'm doing the XJR engine transplant, so using the ABS from that is easier. I dismantled the entire XJR and kept all the wiring intact, so I can pick out the ABS wiring and use that.