Front rotors - which size 286mm or 305mm
 

IPD says this about my 2002 S60. "These models have two brake rotor diameter options: 286mm & 305mm"

Is there a way to know by looking which size is on my car?

20 mm is a bit less than an inch. (286/305)
Measure with a tape/ruler.
in inches from center of hub to edge of disk
times 2
Then times 2.54.
If you can see across the disk use a flexible tape measure

I'd call the dealer (Volvo parts) and give him the vin and he'll tell you.

That sounds easier than measuring. :cool:

Some won't tell you if you're not buying from them so you might have to call around.