tyres

[rocket]

I have 185/60x13 tyres on at mo,iv found some new ones which are same size according to the writing on the tyres,however when stood next to the tyres i have on they look larger in diameter.Obviously this may change when fitted to wheel.But,if when i come to fit this is so i dont believe il have room under arches for them.Anyone know if i would then simply replace with a size down? would that be 175/60 or maybe 185/50? Any thoughts?

[Galwaylotus]

With radial tyres, the diameter shouldn't change too much mounted or not. The tyre manufacturer should give the installed diameter so you can compare. In terms of upsizing/downsizing, the aspect ratio ("60" in your example is multiplied by the section width (185) and converted to inches (divide by 25.4). Add twice the resultant height to the rim diameter to get the overall diameter (approximate). Rule of thumb: for every increase of 10 mm section width, the aspect ratio should be reduced by 5 to get a similar rolling diameter, e.g. 155/80 R13 should be similar to 165/75 R13 or 175/70 R13. See: http://www.carbibles.com/tyre_bible.html for more tyre information.

[rocket]

Thanks for that..i had them fitted this morning and there fine,was just me worrying about nothing..