I decided to dig a little deeper as to inflation on Superblue’s 15" Cooper Cobra GTs, in light of that possible “quandary”, VK.
Checking both Discount Tires’ and Tire Rack’s websites (NTB does not show max PSI settings for the tires sold on their website) as to the indicated size and type Coopers for Superblue (which are in fact the same ones on her), they both show the max. cold inflation pressure for same @ right at 44 psi (i.e. the same pressure rec as what Jag indicates for “other” brand tires). Same for two other listed “generic” brands of tires indicated for '94 XJS 4.0… I haven’t actually looked at what Superblue’s tires have stamped on them, but unless both websites are wrong on that max. pressure, it looks like 44 psi should work. Interestingly, Tire Rack’s website mentions something about 44 being the usual cold max. inflation pressure for 15" tires, but that this amount is not recommended as the usual pressure “unless indicated otherwise by owner’s manual or tire placard w. the particular make/model of car”. It then adds something about some car manufs. recommending that 44 lb. max. inflation pressure for their tires nevertheless due to unusual high performance handling, cornering or speed characteristics for their cars. Apparently Jag believes the 4.0 XJS fits into that category (?) So again, 44 lbs. seems to be the magic # for Superblue w. her Coopers.
Oddly enough, both Tire Rack and Discount Tire do state a max. cold inflation pressure of 36 PSI for B.F. Goodrich tires for the same size tire, not 44 PSI. Note that this is the same rec PSI for “normal” riding characteristics rec by Jaguar for the OEM Goodyear Eagle GT tires, at least in the rear. This makes me wonder if, had Jaguar made the tire call today, being that Eagle GTs are n/a now, whether it would consider the Goodriches to be an acceptable substitute for same. ?
I found it interesting too to discover that none of the 3 sources I mention recommend Pirelli for the 4.0 '94 XJS anymore, something which they all did, up until very recently. Is this b/c Pirellis are n/a anymore in that size, or is something else going on there?