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Hi all. Just found your forum, looks like a good place. I've developed a bolt-in IRS conversion for the MGB based on the early Jag XJS assembly shown here about 3/4 down the page:
,274,page=8
I'd post a photo but I haven't figured out how to do that here yet.
I've installed this assembly in two cars so far, and plan to develop a Mark-II version of it, hopefully beginning sometime this summer, for which I plan to make fabricated aluminum LCA's and tubular half shafts, also possibly of aluminum. The new LCA design will incorporate the forward brace into one piece. If you study it you will see that this design stabilizes the differential while eliminating the diagonal braces to the body. So far, in parking lot testing of the 455 Buick powered MG-Roadmaster project car, a '69 MGB-GT, the rear suspension seems quite stable and controllable, with about 8" of suspension travel and no indication of bad behavior.
That doesn't mean I consider myself an expert on the Jag IRS by any means as there is much about it I simply do not know. As such I would hope to benefit from those of you more knowledgeable than myself, and perhaps I can contribute from time to time.
Regards,
JB
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Welcome to the forum!!!!!!! I like the pix of your assembly
Are you worried about twisting forces on the wish bones by only running one shock per side?? not being critical, just seen this debated a lot on various forums and wanted to get your take. over all it looks like a quality assembly. One again welcome to the forum!!!
BTW If you are looking for directions to posting pix check out this thread
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Can't really see it being a problem. Admittedly there will be a bit of torsional loading on the inner pivot bearings but it will be way lower than the loading imposed by acceleration forces multiplied through the offset of the upright above the LCA. I've run the calculations on those forces and they amount to thousands of pounds, where the coil-over loading will be well under a thousand in the worst case. The bearings are built for it, might as well use them. I don't even think it will significantly impact wear, and the only reason I think it is an issue at all is because Jag built them with dual units in the first place.
Anyway, thanks for the kind comments, I think you have a decent site here and some good knowledgeable experienced people.
JB
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Jim Blackwood wrote:
Can't really see it being a problem. Admittedly there will be a bit of torsional loading on the inner pivot bearings but it will be way lower than the loading imposed by acceleration forces multiplied through the offset of the upright above the LCA. The bearings are built for it, might as well use them. I don't even think it will significantly impact wear, and the only reason I think it is an issue at all is because Jag built them with dual units in the first place.
JB
I once asked on a Jaguar forum what they thought of running just one shock. At the time I was thinking of running some QA1s and didn't want to fork out any extra $400 for a second set. you would have thought I was asking them to trade in their Jaguars for a bicycle. I think had I asked in person rather than over the internet they would have broken out the tar and feathers 
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Jim,
May I ask why you chose to mount the shock/spring in front and not the rear?
Ralphy
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I think it was just a packaging issue. There may be enough room to put them in the rear. But in either case they are hidden by the bodywork. In the MGB the gas tank takes up a lot of space so that probably had a lot to do with it, but I have one of the cars up on the lift so it would be easy enough to look.
JB
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Jim, the reason I ask is that I have seen both. Street rodders seem to use the rear mount and racers the front. I have never heard it explained.
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Well the rear mount would be the most visible of course. Other than that I don't think there is any real reason other than space.
JB
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Just finished reading the whole thread over on british V8, what a build! great work
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Here's the other car:
,166,page=63
This one uses the same IRS but is a group project we set up as a non-profit. It has a 455 Buick engine and just got back from paint. We're prepping it for the annual meet and for wiring this weekend.
JB
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