Jess:


Sure, I am open to it. Drop an email to me, I would be happy to discuss this further.


On the ride height question: I have found the measurements that are published vary a bit by year and model, and the taking of the measurements on your car can be deceptively complicated. This is because you need to be sure several factors have been attended to:


1. Curb weight is at spec.
2. tire inflation to spec.
3. Ensure that the suspension is settled. By this I mean, don't drop the car off jack stands, and then take measurements. Drive the car, pull back to your garage and then take the measurements.


The ground clearance figures I have seen published for the XJS run 5.1-5.2", and the figure I have seen for the TWR XJR-S is 4.7". What I am interested in is the difference, really, to know, on a relative basis, how much I am looking for on a standard XJS.


Now, what is ground clearance, exactly, and where does one measure it? I think I found somewhere that it is the distance from the ground to the front jacking point supports. But if you are looking for TWR XJRS setup type numbers, you really need to focus on front height and rear height, individually, and let the 'ride height' come out in the wash.


For my purposes, I measure the front clearance from the ground to the bottom of the crossmember. The old OEM Jag ROM gives a value of 6" for this.


I measure the rear clearance from the ground to the tie plate flat face of the IRS (not the rim, which is rolled down, and gives a shorter measurement as a result). The old OEM jag ROM gives a value of 7.55" +/- 0.25" for this.


In the end, I think I ended up taking the measurement from the highest point of the fender well lip (more or less center of the wheel well) to the ground, or to the wheel center, either way. This tends to give something that can be understood in the context of the wheel and tire size. And, it is easy to make, even if a bit more variable (getting to the same point on the fender lip).


From what I have been able to determine from making measurements of these types along the way, I have lowered the front end by about .4 to .5", and have the rear close to the center of the range for the tie plate number (before putting in the spring spacers, the tie plate height was around 7.2-7.25, and after, it was more like 7.5).


So, from the ground clearance point of view, if you measure off the front jacking point, I am close to the XJRS spec, and this comes from a combination of removing the packing rings in the front spring towers, and from the use of 225/45-17 tires. At the rear, I am in spec (XJS), toward the center of the spec, probably. And I am running 245/50-17's back there.


The car looks reasonable visually, and things seem proportional (e.g., the somewhat smaller OD tire in front looks reasonable in the wheel well, in part because of the mild additional lowering I did) and the rear tires look reasonable in the rear wells- the fend lip keeping about 0.5-1" to tire top clearance here( don't recall, exactly, here, but it looks very normal- not high, not low). You may have seen the enormous cavernous rear wheel to fender gaps some have experienced on their cars after replacing the rear springs- like, 2 inches or more. I did not want that at all. At the same time, I did not want the lip of the fender at the tread line, either, so, I raised it up a bit.


Getting adjustment on the rear is tedious, but you can make the job of adjusting the rear much easier if you shell out the dollars for the GAZ shocks with the adjustable spring perches. This kills two birds: you have shocks with adjustable damping, AND, you have an easy means of dialing in rear ride height exactly to where you want it.


In the end, after looking at all the measurements I made and the published information I was able to locate for the OEM XJS across model years, and for the TWR XJRS, I ended up pretty close to this XJRS setup, in terms of tire OD F/R and ride height, F/R.


One other thing: the XJRS also has the big end radius arm bush rotated 90 degrees from stock, so that the holes in the bushing rubber are located side to side and not fore and aft as for the standard car. This provides a bit more stiffness in the rear suspension. I have used this same approach.


-M