Hello Maurice.
Good questions, nicely presented.
Click this link for under and over inflation information.
http://www.google.co.uk/url?q=http://ww ... KoRGsoxfOA
In old money, let us convert Bar pressures to psi. We can all equate to it better.
The conversion factor is 1Bar=14.5psi
1.8=26.1psi
1.9=27.55psi
2.0=29.0psi
2.1=30.45psi
2.2=31.9psi
2.3=33.35
Good. Now we know what we are talking about!!
On the question of a 22% varience in running pressures, personnally I have never run to the extremes of either 26psi or 33psi.
I need not cover the wear patterns resulting from high or low pressures as the diagrams in the link cover that.
What I know from experience is that running at low pressures as shown above on both a V6 and V8 S-type make the car feel stogy, lifeless and liable to higher fuel consumption due to frictional tyre drag.
At the high end of the pressure scale, the car can become skitish on bumpy roads, suspension becomes very noisey and brutal, although fuel economy becomes as good as it will ever be.
I found 32psi rear and 30psi from to be my personal prefered pressures for all round general use on a set of 225/55/16 Pirrelli tyres.
Now with 245/35/19 rims and tyres fitted, I have reduced to 30psi rear and 28psi front which gives a similar level of comfort, handling and noise limitation.
At the end of the day, perameters are highly variable and so long as you work in those suggested limits, you will be within manufacturers suggested guidelines. Only you as owner can decide where you wish to operate within the suggested range of pressures.
My own opinion, a car like an S-type is not at its potential best at the upper or lower limits and I have found my optimum pressures by trial and error. As far as the two extremes of tyre wear are concerned, again I favour an even tyre wear pattern that favors even wear accros the tyre rather than wearing out either the centre or the outside sections before the remainer of the tyre is worn out. Economy of tyre wear kicks in here.
Hope this helps you Maurice. Nice to hear from you again.
Kind regards,
Mike Kennedy. JEC S-type Coordinator.
