Tyre Pressures.

[johnny37]

Does a ZR tyre need a higher pressure than an R? If yes how much?

[bhg481]

Z is the speed rating, nothing to do with pressure. The car handbook should give the correct pressure for the tyre. There may even be a plate fitted to the car somewhere - inside the fuel cap, on the door pillars etc.

[johnny37]

Handbook says 30psi. When i checked them they were all at 36psi set by my Ford technician when serviced. I wondered whether whether this was because of the higher speed rating.

[johnny37]

I forgot to mention the wheels are non standard 18". Standard is 16" so the handbook may not be correct.

[bhg481]

Different size tyres may well have different pressures. The other thing to bear in mind is that tyre pressures are usually increased if the car is loaded. Also my Volvo has an "economy" setting - higher pressures reduce rolling resistance and so improve fuel consumption.
I think I'd give your Ford garage a ring and check their recommendations.

[stocksman]

I wouldn't bother asking the Ford garage, check with the tyre manufacturers, giving them the tyre details and car details, they will have a recommended pressure rather than a guess from a Ford garage. I'm not having a go at garages, but if it is a non-standard wheel/tyre then they may have taken an 'educated' guess, the tyre people should be able to advise on their own product more accurately.