Steel To Alloy Tyres

[omega]

6.5 is the width so a 6.5 is six and ahalf inch wide rim
the et is the offset on the rim
if you run the wrong offset the wheel will fit but you will have proplems with clearance on things like the brake calipers

[VND]

I have a Peugoet 406 1.9TD
I am lookig to add some alloys.

The ones I have seen are 6.5Jx15"ET18
Yet, when i check the service documentation it says that for this model it should be 6.0Jx15"ET20

will the 6.5J fit?
What exactly is the 6.5J measurement?
What is the ET18 or ET20 measurement that is referred to

Many Thanks

The "J " number refers to the width of the wheel across the Tyre mounting surface.
The ET (i.e. offset) number is refers top the amout that the wheel will stick in/or out from the hub. Dished wheels poke ot further etc.

Hope that helps.