Out of interest - what the largest diameter tyres one could fit to a standard height bus with stock steel wheels? Am thinking that might give me a longer top gear, maybe lower revs at 60mph.
I've seen the hollywood films mate I'm not daft - you have special bouncy Marmite tyres that squeal when you go round corners in your big "tractor engineering" 10L cars.
Bugcatcher has some huge tyres on his bus - although he had to do a fair bit of fettling to get them on. No idea what they are but they look great.
You could try contacting Southam Tyres as the UK importer of BF Goodrich and General Tires - General do the Grabber AT 2 in 27x8.5x14 (which would make the speedo read 5% slower than the factory-fit 185/80x14 tyres as that equates to roughly 215/75x14 - the BF Goodrich 195-75x14 tyres would read 0.5% too fast).
I have Goodyear Bigfoot AT's and Wranglers on my Westy. I presume they came fro the US but I think you can get them here... http://www.national.co.uk/tyres/brand/goodyear/wrangler-at---at-r/