I was going through the McD’s drive-thru yesterday and noticed something rather odd, for the first time, on Harlem. It seems like I have to turn her steering wheel twice as far to turn her the same amount as it took with either Scrapper, my X-300, or with Superblue, my '94 XJS.
What is going on in that regard? I’m thinking maybe the XJ8s came out with finer teeth on the rack & pinion than on the other models, possibly, to make for smoother turning and/or with less effort on the steering wheel. 2x the # of teeth = twice as much turn on the wheel required. Is that possible?
I’ve always felt that Jaguar “softened” the X300 as compared to the XJ40 and then softened the X308 even more.
Always been a balance of Space, Grace and Pace but I thing tbe scale has been tipped over to Grace at the cost of Pace.
My own VDP wallowed far worse than the few inches of extra wheelbase could explain next to my '97 and tbe '97 never felt as “tight” as my much higher miles '91. Leaving the VDP wheels and tires alone but replacing the rest of the suspension with X300 XJR bits made a huge improvement.
So yes, i think the X308 has a slower ratio rack the X300.
The X308’s had a steering rack that took 2.7 turns lock to lock. It’s hard to imagine that the X300 steering rack was much more, if at all, quicker lock to lock. Also, the X308 rack came from the XK8, the sportiest of Jaguar’s line at the time.
With power steering, reducing the number turns lock to lock would be irrelevant in terms of comfort or ease of steering. With a more primitive power steering system, fewer turns could result in an overboosted, numb-feeling steering. Modern cars are usually around 2.2 turns lock to lock, possibly because better PS systems keep the steering feeling more natural.
But that also would imply that it’s not an issue of the steering being too twitchy for luxury car buyers, as everything from a Honda Civic to the current Jaguar XJR run 2.2 turns lock to lock.
Anyway, easy enough to determine, just turn the wheel all the way in one direction then count the turns going the other way until it stops!
My point was simply that tooth pitch (’“finer teeth” as it was stated) has nothing to do with turning circle distance or ratio. Turning circle has nothing to do with ratio or tooth pitch. Tooth pitch has to change equakly for rack and pinion or they wouldn’t mesh properly. It’s like you could have a 3:1 ratio using 30:10 or 27:9 or 15:5 - all the same effort (leaving aside power assistance design) all the same turning circle (if components sized for same linear movement or radial ‘sweep’, just smoother in the case of finer tooth count.
The thread actually states ‘steering wheel turn radius’ which has got nothing to do with any of these parameters except size of steering wheel and steering effort, which are of course identical in X300-308 and VDP/Lower trims of the same cars.
Which is not to say the suspension could not be/was not engineered to feel different from XJ40-X300 or with ‘Sport’ specs (green) dampers than touring’ (black) dampers and changes in wheel dimensions/aspect ratios etc. just that tooth pitch per se alters non of those features, whereas rack ratio, or travel, or pump/rack valving or steering wheel ratio ( had it changed) could.
So then why does it take so many more turns on the steering wheel on the X-308 than on my X-300 to turn the wheels the same amount? Does it have anything to do with my steering wheel being stripped out on the “in and out” adjustment feature?
Turning Radius has to do with WHEELBASE and turning angle of the vertical links. My wife’s 2001 SWB XJ8 has a smaller turn radius than my 1999 XJ8L.(not by much)
I remember my Dad’s Cadillac seemed to have a better turning radius than my 1966 E Type.
That E-Type was TERRIBLE in a parking lot. The Triumph Spitfire on the other hand could turn around in a narrow driveway.
Nothing to do with steering wheel adjustment. If there’s a difference it’s because of the rack & pinion ratio, like a diff.
If the steering wheels were different sizes the distance a point on the rim turned (but not the degrees) would be greater (and feel easier) for a larger wheel, but the turning circle would be the same unless there were mechanical steering gear changes as Bob said.
