Hi All,
Tyres for cars, light vans and light trucks and the ilk use a standard coding of the ilk 145/80 X10 74N. 145 is tread width in mm, 80 is the tyre wall height as % tread width (and if it is omitted it is 80 or possibly 82). X=R means radial ply construction, X=B means bias belt construction - may be abbreviated to bias ply, X=D means diagonal ply (whatever that is!), and omitted X means cross-ply; bias belt is cross-ply with some additional reinforcing. 10 is the wheel rim diameter in inches, measured at the place where the tyre beads onto the rim. 74 is a load rating (74 means 375kg) and N is the speed rating (another look-up table shows this to be 87mph).
No way do you want to mix tyres of different construction types on the same axle (the law is there for absolutely right reasons), and I'd go so far as not mixing them at all on the same vehicle.
The problem for trailer and off-road tyres is that the manufacturers haven't agreed a similar progression from a number of earlier coding systems, so you often see 500X10 or 5.20-10 (and others!). Whenever I come across tyre ads with these kinds of codes I first groan, and then look for more info first from the website I am looking at but I'll often check with a website that I know carries such info - eg
http://www.allterraintyres.co.uk/index. ... =page&id=8. But they are mostly cross-ply..... And I'll ask around if I am still not sure - hence this Chat thread.
My current trailer tyres are 145 10 68M, so they are cross-ply, 315kg load limit, 81mph speed rating. I was concerned that the Autow 500X10 tyres were narrower, and I guessed someone (Steve Willis) would know better than me whether this was an issue.
I will be checking the tyre tread depths on my trailer in the next few days........ I'll ask Autow what the speed rating of their 500X10 4 ply tyre and wheel is.
I haven't sailed since Datchet. I hope to sail at QM this coming weekend. I hope to go to Grafham - I have fond memories of my last race at Grafham..... so it was really nice of Stuart to say he hoped to see me there!