tyre sizes

[Bazza]

if you had a 195/65/15 tyre

 

and you wanted to upsize to 17" tyres

 

what would be the correct size to maintain the original rolling radius

[Jap Devil]

Try this one Mr N:

 

Tyre size calculator

[Bazza]

Try this one Mr N:

 

Tyre size calculator

 

but you need to know the 17" tyre size to calculate it ??

[Jap Devil]

Try this one Mr N:

 

Tyre size calculator

 

but you need to know the 17" tyre size to calculate it ??

 

There is an option to input 2 sets of tyre data. It won't suggest a tyre size for you.

[Bazza]

Try this one Mr N:

 

Tyre size calculator

 

but you need to know the 17" tyre size to calculate it ??

 

There is an option to input 2 sets of tyre data. It won't suggest a tyre size for you.

 

but thats what i need !

 

through guesswork 220/45/17 come fairly close

[discount tyres dan]

you can work it out yourself,

 

first workout the heght of the rim without the tyre:

convert the 15" into mm [15x25 = 375]

 

then workout the height the tyre adds, the "65" part is the height of the sidewall as a percentage of the width, whitch in this case is 195mm:

65% 0f 195mm = 126.75mm

 

there are 2 sidewall heights to add so this number is added twice, the total is the overall height of the rim and tyre:

375mm + 126.75mm + 126.75mm = 628.5mm

 

so going by the above a 225/45x17 gives an overall height of 627.5mm and is therefore a close match

 

in my own case i have gone from a 205/60x15 (621mm) to a 225/40x18 (630mm)

[Mat]

205/50/17

 

it will make your speedo 0.2% faster

[discount tyres dan]

205/50x17 would be 630 mm, another close match, fitted to mondeos as standard, the higher profile will result in a ride that is less harsh than the 225/45x17 but will be less in contact with the road due to the narrower tread width, also it depends on weather you are fitting 7",7.5" or 8" rims.