Just so I don't ever have to ask again...

[Jack3559]

How can I tell what tyres I need for a set of wheels that come without tyres?

What do the numbers mean?

If I had a set of 17x7s and I wanted a little bit of stretch and a low profile... what tyres would I need?

[Wayne]

195/40/17 

[Jack3559]

195/40/17 

So... how did you work that out?

I'm guessing that 17 is the rim diameter in inches...

The 40 is the measurment from rim to tread in mm...

And the 195 is the width in mm?

[Wayne]

195/40/17 

So... how did you work that out?

I'm guessing that 17 is the rim diameter in inches...

The 40 is the measurment from rim to tread in mm...

And the 195 is the width in mm?

Yep spot on.

205/40/17 is the correct size but 195's will give you a little stretch