Yes you are correct. And to remove it, take ratchet, and put the square part inside the plug. It fits. If you need to use a short extension, go for it. I think it takes a 1/2" ratchet.
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Ditto Kirbert. I had same situation with hand brake caliper pin not lined up when installed.Found it when I dropped the cage to do output seals. Would really suck if cage is in car.
the cattywompuss thing happened to me , when car was delivered to shop on a ROLLBACK truck, in the seat let go of foot brake ,rolling to fast backward, pulled the E brake and the whole rotten mounted cage just pulled loose and twisted sideways, "cattywompuss,"locked the wheels and stopped moving, Royal PITA to get in garage!
all and all , like the inboard brakes , at shows etc, i say what do you think of my rear brakes?
they freak and say it dont have any rear brakes, OH yah look way inside!
ron
Did my handbrake calipers twice with the cage in the car, PITA but doable.
Yeah…but the inboard brakes come with a natural advantage over the conventional solution at the time…which was outboard brakes…and that is reduced unsprung weight…which WILL improve the dynamic response of the rear suspension…and MUST have been considered worth the effort by the XJS designers…
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There’s another thing, too. With regular outboard brakes, applying the brakes exerts a considerable torsional load on the suspension; the caliper is trying to twist the hub carrier around the axle. With inboard brakes, this torsional load is eliminated entirely, replaced by a torsional load on the axle itself – which is already designed to handle torsional loads.
This may not be significant, especially in an IRS as robust as the Jaguar. But besides the stresses involved, it could also result in issues in braking performance as the twisting of the suspension causes a “judder” when braking. Of course, the axle could do the same thing with inboard brakes if there is any axle windup. All of these are factors the designer must consider, though.
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Yes…good point…
And also the Alfasud front brakes of a similar period. But strangely not by any other significant auto engineer that I can think of since then. If it was any real performance benefit then surely the likes of Porsche, Ferrari, Lamborghini, Aston Martin etc would all be doing it.
One reason Jaguar went for inboard brakes is that it was what all the cool kids were doing in the 50’s. Same reason these subframes end up in hot rods today. Same reason Jaguar went tor a V12 instead of V8… product differentiation! I’m sure engineering was somewhere on the list too but most of all, you gotta admit, inboard brakes are still kinda cool.
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…NOT when ya gotta work on them… like the front brakes of an Audi 100 LS. Or on a P6 Rover’s rears.
As for the effect of unsprung weight, in a street car?
Inconsequential. It’s just “cool.”
There was a Formula Ford, in the early 80s, that went to great lengths to make the front brakes inboard: Cool, but the designer, David Bruns (who later designed the revolutionary and highly successful Swift DB1 FF) came to realize it wasn’t worth the overall weight increase.
Cool, except when those Jag inboard brakes need cooling…
I remember seeing many 70s custom cars in the UK, jacked up rear end with the classic Jag IRS, cage removed, chrome plated UJs spinning out in the open. Luverly. But it still would have looked much the same with outboard brakes.
As a product differentiator, inboard discs and V12 engines are good bragging rights down the pub for the first new owner. But once those repair bills start coming in, still a differentiator, but not in a good way 
I think inboard brakes are a good idea. Jaguar just screwed up the implementation, making them a PITA to get to and work on. I understand somebody, perhaps Aston Martin, uses the exact same brakes except the calipers are rotated around to the back side of the diff, so there’s plenty of room to get at them. And some of the saloons have access panels under the back seat.
And, of course, any inboard brakes should have been fitted with a deflector to keep oil from leaky diff seals from getting on the rotors. That’s just common sense.
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Either way has its drawbacks.
However every rose has its thorn big hair band of the 80’s Poison. Don’t judge me…
A lift is real handy for this. A floor jack aka trolley jack or transmission jack works too. Get the car up at least 26 inches off the ground. You’ll need the wiggle room. A friend always helps. well mine don’t…
blocks of wood None of my floor jacks raise more than 20 inches.
Cage Out
The drawback is you’ve gotta get it out and then back in.
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corrosion and time. The radius arms will put up a fight. Hopefully there isn’t any corrosion on or around the seating cup. If the cup comes off with the radius arm, then it’s okay to throw a temper tantrum.
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Some forethought (aka game plan) is required to minimize the amount of time on your back, swearing, and reduce the amount of knuckle bleeding.
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take a look how the exhaust is attached. If some argon sniffing, welding torch wielding muffler guy decided to weld the bendy bits (exhaust pipes threaded through the cage) to the pipes on either side of the cage, it will be something to contend with when putting it back in.
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while the cage is out you’ll probably want to replace all of the rubber its too. including the radius arm bushings. check out my channel Youtube Jag Mods. I’m doing an IRS rebuild.
btw I opted for out of the car.
Cage still installed.
The only way feasible is to be able to drop the fulcrum so their perpendicular to the car aka pointing down. This is where a 2 post lift really comes into its own. if you can get the car up in the air enough to drop the fulcrums down 90 degrees, and are a 5.5 foot 90 pound contortionist, or you know a contortionist, then sitting under the car won’t be a problem. Me, I’m not and I don’t like spending too much time on my back… Well at least under a car.
I like the check box! did you drop in HTML code to do that? message me how, please.
Mark
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Early P6 Rovii used the same mechanism as the Jag, but the calipers are in the FRONT, and not terribly accessible: the following Dunlop self-adjusting calipers (the WEIRDEST design you’ve ever seen) are on top, making them difficult to work on.
Being a DiDion rear, at least there is no IRS cage in the way, and the calipers have better cooling than the Jag.DKW Juniors, had inboard front drums.
I’m not a fan of inboard brakes…except on Formula car rears!
Citroen DS of 1955 on, had huge inboard front brakes.Powered by high pressure hydraulics, best brakes ever.
Well… they were darn good, but not “the best ever,” unless we constrain the term, “ever”.
John, been using bronze bushes in fulcrums for 50 years. A totally incorrect use of high speed bearing in an oscillating part, resulting in “brineling” of bearing sleeve.
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Some good points posted here on inboard breaking system. I remove the back seats and had two holes drilled 6 inch s round as inspection hatches making easy to work on the brake system . I fabricated it’s so that the pieces taken out can go back in , its a bit of work to start much easier for future maintenance. When I work on breaks next I ll take some pics and post it on here
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doing a the rear inboard brakes on a XJ is layers of an onion. as you strip the IRS down you’ll realize how much “should be done” while the IRS is apart. mainly the output shaft seals and bearings. you’ve got a really big heat source the brakes within inches to a rubber seal and bearings that is supporting and driving the wheels out the sides of the car.
The video that covers the pacer and how to measure it isn’t done yet, but will be very shortly. I do have the raw footage If you want to look at it.
Shameless plug check out Jag Mods I’m covering the whole IRS rebuild and tear down; and in some cases rebuild again. I’m not perfect. I’m learning too.
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Same for me. What I thought would be a straight swap of my diff into the donor cage turned into a full rebuild. Saves doing it all again in the future I kept telling myself. Only thing I had to revisit was rerouting the brake lines I had fabricated.
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