during the last couple of days, I did some research on XJ alignment specs (official Workshop manual, Haynes manuals on XJ6 and XJ12, this forum, etc.). The reason for me doing this is that I had my XJ12 (1983) aligned back in late autumn after doing some maintainance on the front suspension, and the garage managed to align the front suspension in a way that the steering wheel was completely out of center. So, I went to another shop the other day, and they were able to roughly center the steering wheel; but they claimed that front camber was way out of spec on the right side, and that they couldn’t fix it, as they were supposed to remove shims where there are none.
All that raised my suspicion, and I got even more suspicious, when I realised that where the shop mechanic wasn’t able to find any shims to remove, there were actually three of them, adding roughly 7.3mm at the upper wishbone! So, I had my next DIY project, wheter I liked it or not.
To cut the long story short: After some hours of fiddling around, I managed to set front toe to approx. 0mm. Front camber I set to -.3° on the left side, with -.5° on the right side, respectively.
But, what about the specs?
The official Workshop manual claims, with respect to the XJ12, for +.5° +/-.25° front camber and 0-1.6mm toe-out for the front wheels. However, for the XJ6, it states +.5° +/-.25° front camber as well, but 1.6-3.2mm toe-in (!). To make confusion perfect, Jaguar changed the XJ6 specs for front camber to -.5° (!) +/- .25°, and for front toe to 0-3.2mm (!) toe-in in late 1983 (from VN 360146 onwards)! (I skip the specs given by the alignment machines at the shops I visited – they add even more colour to the overall picture.)
I don’t think that all these variations make much of a difference. I decided to go for 0mm front toe, which I think I was able to set-up and which fits all the specs given; and I went for a small amount of neg. chamber, which might provide the car with a slightly better steering in turns. Good news is, the steering has improved significantly, compared to being completely out of any specs before (not to mention the uncentered steering wheel), so I think I will leave it now the way it is.
However, I am still puzzled by the variation of the official specs:
Why are there different numbers given for the XJ6 and the XJ12? Isn’t the front suspension/steering (more or less?) identical, regardless of the engine installed?
What made Jaguar change the XJ6 specs in 1983? If a take a look at the parts catalogues, there was no change whatsoever on the front suspension in 1983 – or do I miss something?
What’s the reason behind all this? I realise that there has been ample discussion on the topic in the forum, but I couldn’t find answers to these two questions. Are there any?