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Check out the new pics at the beginning of my photobucket site..pic's 4 through 11..
!oZZ4QQcurrentZZhttp%3A%2F%2Fs28.photobucket.com%2Falbums%2Fc231%2FPaulGerdes%2F49%2520Ford%2520Coupe%2520Start%2520Mid%2520May%25202011%2F%3Faction%3Dview%26current%3DDSC01004.jpg
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Your unequal A-arm front suspension, at ride height, should look like one of these three types. This will give you a quick idea where to look for the roll center. I borrowed this image from a free download at Robert Q. Riley's website. 
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Paul,
Joe in the old forum did some mods to a stock cage. Can your new frame rails go a bit higher to allow the cage to go under?
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Hell, yeah..............
I'd rather use some sort of bushing/rubber/neoprene mount to the frame just to kill the high frequencies... but it surely seems reasonable to use it if possible. Did you see my latest posting on the other thread? (Jag Motion ratio's ) ?
Thanks again for your attention and help...
At least now I know how to post a picture... by the way, if one has pic's on photobucket, there is a box over to the right side of the screen with the links already "figured out" that you just click and paste where ever you want.. it works like a charm...
Paul
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Yup, I saw you over in the Motion Ratio thread and then I popped over here to see your drawing. The decision to use or not to use the original cage is a difficult one. On one hand it may save you some money and/or some fabrication time. On the other hand it can make changing the inboard brakes or doing other work a bit more painful. You pretty much have to make the cage assembly a removeable unit for maintenance. I remember reading that periodic upkeep of the stock cage mounts is important to maintain rear alignment and prevent excessive roll over steer. I borrowed a picture of a stock cage mount from this site. There are four of these 
Not that you have to do it this way, but this is just the way Jaguar did it. The next question is when you modify your lower control arms will you be able to relocate the top of the coil-overs in the stock cage without too much trouble? Also, when using the cage, control arms or radius rods are a must.
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Well, Stang... It would seem that the original control arms are good, they have good bushings, but I've not seen exactly how they mount on a Jag.. will peruse your link and perhaps they will have something........Hell, I DID see that the control arm bushings are something like 300 bucks somewhere a few weeks ago..
It appears that I "could" place some alternate hole locations by cutting out the upper shock mounts and weld in a multi-hole bracket. Just thought of something else...
I've seen/read about buying/adding/modifying the disks for vented disks, adding a spacer in the calipers, etc. and also saw a guy that makes an adapter somewhere.. I saved the link somewhere.. Am looking into "maybe" measuring out a Chevy front disk to machine it with adapter if necessary to use instead of the stock "scorcher" disks.. that should require making the cut on the axles shorter by the difference in the mounting thickness of the different disks... am I thinkin' right? Got the differential out of the cage last night.. pretty dang easy, actually... will be pulling the brakes off as soon as I get my registration numbers on the boat....ahahaha
I noticed a couple of things while pulling it apart... is there some info somewhere that defines the required shim thickness on the axle mounts? Not sure how they relate.. wouldn't seem that shims would be an issue/required there.. gotta do some more thinkin' I guess.. also, what the heck is the little "bushed" mounting bracket under the top and near the diff.? is it for a "service bracket" or something to drop the assembly out of the vehicle?
Thanks again for your attention..
Paul
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Yeah, I'm not a big believer in the stock control arms with their rubber bushings. I think radius rods are better and they are easy to make. I believe the stock Jag rear brakes are fine for normal street use. Vented discs are expensive. Daze has been searching for some low cost rotors. Last I heard he had not found anything. The shims you are talking about are for setting the camber. If one is rebuilding the IRS you have to put the shims back exactly where they were. Don't know what the bushed bracket is you are talking about. Could it be the e-brakes? Pictures?
There is a guy named John Carey that has a series of videos on rebuilding the Jag IRS. Here is a link to one of them: www.youtube.com/watch?v=W_ctphHIKbo
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I saw the John Carey (well, one of them where he was putting the brakes on) but the poor old guy hasn't got a CLUE how to make the vid so that it is really informative (camera 15 feet away, and goes for minutes at a time with nothing but his back and grumbling going on..hahah)
Will stick a pic of the bushed bracket thing in the next few days...
I finally figured out the camber angle this morning.... I have kept them on the center section with nuts .... I always put nuts/bolts back in holes when disassembly... a no-brainer...
Asside from the fact that the stock radius arms are BUTT UGLY, what is wrong with them ?
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On the stock Jags, the control arms go straight forward from the LCA. As the LCA moves up and down the dimension to the fixed point forward changes. Since the cage is mounted on rubber mounts the whole cage moves with suspension travel inducing toe steer. When you jump on the throttle all these compliant rubber parts allow the cage to move all over the place. Some Jag guys used to bolt the cage to the floor of the car and eliminate the control arms. This is not a good idea because you want the control arms to absorb braking and acceleration loads, not create a bind with suspension travel. I prefer to do something like this: 
Last edited by irstang (5/17/2012 7:04 pm)
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Thanks, Stang... I fully get the "centers of rotation" theory of the control arms.... but I got the thinkin'.......... was the original design in error? What were the engineers thinking when they chose the "straight ahead" swing arm design? Was the design a compromise in "where to bolt the static ends"? Were the engineers stupid? I have to think, given the fact that the entire system is rather incredible and cool, that they thought it through fairly well. After all, do Jag rear end components have a habit of failure in the control arms / needle bearings/pivot points? I can't say, because I don't have much/any experience on a day to day or even year to year basis. They chose needle bearings, I'm guessing for a very specific reason rather than bushings on the LCA's , and I'm just guessing they wanted ZERO lateral/radial movement of the LCA's and high strength at the same time. So they probably wanted no compromising of the "line of travel" of the LCA's. So, at least theoretically, the dang LCA's are GOING to stay in line with design line of travel, while the control arms are allowed to "give" a little back and forth, and in a twisting motion also.
Drag out your Trig tables, and follow me on this...
So here's what I'm thinkin'........Starting off with all links exactly level. Let's assume that the control arms are 20" long, and that you hit a bump that causes the wheel/tire assembly to bounce a TRUE 2" from the static condition. If you have a "true" 2" bounce, then given the dynamics of what the car does, the actual "bump" might be twice that amount, because the frame starts moving up immediately, absorbing the energy of the "bounce".
That means that with a 20" control arm, the tire end of the control arm will tend to want to move forward an amount equal to the difference between the Tangent and the Sine of about 5 degrees, or a maximum of 0.20 inches (roughly). That's theoretical if all parts are rigid. But studying the fixed end bushing of the control arm bushing, there are two holes in that big rubber bushing, giving an INTENTIONAL flex feature to allow the control arm to move relative to the frame, not only front to back, but in a twisting motion, too (big old donuts). So what happens is that big old bushing compresses toward the rear of the car by a theoretical 0.2".
Then ask this question: When a bump is encountered, is there any rearward component force to tend to push the wheel/tire toward the back of the car at the same time? Is it possible that those "not so stupid" engineers figured out that "bumps" compensate and impose a rearward force to the assembly, that may just keep everything correctly in line and compensate for the "goofy radius swing" of the control arms? hmmmm....
Do all those Jags ride pretty rough? Do they wear out rear tires in a goofy manner due to changes in tire alignment with the road? Do us hot-rodders have a habit of driving on shitty roads? HELL NO !...........ahahahaha
Just sayin'------ (for the benefit of thinkin')
Oh I was also wondering why those engineers chose to make the body mount a "reverse cradle" to hold it all together. Makes lots of sense, as the weight of the car tends to hold everything in place, while giving some vibration control back to the chassis.........ya think ? Did you ever notice the little tabs that are welded to the edges of the outside of the cage? Those dang stress cracks can be a "I used a word I shouldn't have", I bet...hahaha
Let's keep thinkin', y'all..........it's good for the synapses...
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If you choose to use the stock cage, far be it from me to not trust in the original design and transfer it intact to your application as a safe starting point. I got the impression you thought the control arms were ugly and new bushings were expensive and you were searching for an alternate path. Bear in mind, the rubber mounts way up at the top allow the whole cage to move. How much is described pretty well in this article:
I started my project differently than yours. The pile of XJ6 parts I purchased did not include a stock cage. Every application is different and in my opinion my Mustang unibody needed the extra strength of a cross member. One change always leads to another and once the differential is mounted solidly or with poly bushings and support rods, radius rods or Watts links become logical choices.
In answer to your other questions; Jaguars ride like a dream and the needle bearings are fine. I was advised by an experienced Jag guy to use them and keep them well greased. Error is a harsh word for the original design of the control arms. They were, however, eliminated in later Jags. And, yes, when all the rubber bushings and mounts get tired, goofy tire wear will result.
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Thanks guys.... and especially IRSTANG !..
Here is the latest. This is the "building the frame" sub-album of the Coupe Build.. the next sequence is "prepping for engine" sub-album you can check out the other sub-albums - the latest is the "prepping the body".
Prepping of Engine - best pics of finalized IRS installed
Prepping the body
And... Rebuilding the Jag rear end
But we surely can't ignore "building the engine"
Looks like rain for the next couple of days..
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Oh, sorry, guys.. I accidentally posted the last page on a couple of the links.. ya'll will figure that out though..haaaa
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I've been admiring your pictures. Where did you get the compressed shock length of 9-3/8"?
Last edited by irstang (5/09/2013 7:40 pm)
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It was in the specs paragraph on the Advance Auto parts website, where I bought them.. Guess I should have measured before putting the springs on...........hmmmm . do you think it should be something different???
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I was surprised by this number because I have been using Alden Eagle 654 data for my installation. They used to list their 654 coilover speific to Jaguar rear. The compressed length is 9.7 inches with a 3.7 inch stroke.
You are in good shape as long as the shock does not bottom, or the spring does not go solid, before firmly on the bump stop.
Monroe Part No. 39003 specifications:
Jaguar XJ6
Compressed Length: 9.375 in
Dust Shield Included: Yes
Extended Length: 13.25 in
Parts Pack(s): No
Travel Length: 3.875 in
Last edited by irstang (5/10/2013 1:13 am)
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I suppose I'll drop by the store and have them pull a shock and measure the dang thing. By the way,I had already "washered' the stop to the limit of the bump stop stud, but it would be easy to weld on an extension on the stud (being careful not to melt the rubber). Otherwise, if I ever hit a bump hard enough to bottom out, I surely would be angry with mysellf for not hitting the brakes first...hahaha
Also, I'm considering buying an Arnott compressor and piping it in to a pair of air shocks if I can find some with the correct travel/length with a manual switch to adjust the height/ride "on the run"...
By the way, if you look at this picture, you can see the spacers i already installed...Thanks again for your thoughts.
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Greg at Welsh measured some Boge early XKE shocks for me. They were 9.25" compressed and 13.0" extended. So it looks like I need to go back to the drawing board with the location of my bump stops. Sorry my error has caused you grief, as well.
This leads me to believe your Monroe spec is correct.
Last edited by irstang (5/10/2013 1:45 pm)
