Learning about tyres

ok in as simple terms as i can the letter you see on your tyres n/s ect is your speed rating that the tyre is designed to be able to run at. n 140ks and s 180ks as for the tyre upgrade im not sure what the laws is where you are im in vic and the law here says no more than 15 mm increase in overall diameter of the tyre originally fitted or available as an option on your 4wd . i im pretty sure most gu came out with 265/7016 an an option of 265/75/16 easiest way is to look at your tyre placard fitted to your car usually in side the r/h/f door frame or glove box and find the biggest size tyre there then you can work out how much biger you can go.eg a 265/70/16 has an overall diameter of 772mm a 265/75/16 has an o/d of 800mm now a 285/75/16 has a o/d of 834mm so at least in vic theese tyres are considered illegal hope i didnt confuse you to much.

http://www.tyresave.co.uk/tyrspeed.html
or
http://www.4wdworld.com.au/tipstricks/tireterm_O4.htm

this diagram may help - on later model cars there is a 'sticker' which tells you what the speed rating is for that car.

Also, download the 'google' search engine - http://www.google.com.au/ - the 'answers' will usually resolve most questions - ie. I typed in "tyre ratings" for the webs above. Colin - Subaru Forester

Phil .. my understanding of tyres ( which is very limited ) is that the numbers etc on them equate to: eg.. P205/65R15
P.. Passenger vehicle
C or LT.. Commercial/ light truck
205.. Width of tyre in mm
65.. Sidewall height is 65% of section width
R.. radial
15 .. Wheel diameter in inches
speed ratings are.. s.. 180k, h.. 210k, v.. 240k, z.. over 240k

Hope this helps. All this still doesn't guantaree milage or handling