Over the past year, I've been trying to educate myself on wheel fittments. But I sill don't know what the "J" or "JJ" size definitions mean. I think it has something to do with brake caliper clearence, But I'm not sure. My 15X7 SSR MKII's are a "J", whilst the Advan A3A 14X6's on the Roadster are "JJ"'s

Que es?

Hi Victor,

The J and JJ refer to the rim profile. If you cut the wheel horizontally through the centre you would see a profile of the section where the tyre bead sits on the rim. I think the JJ was an early safety rim designation, after the "J" style, and had a raised profile on the inside of the tyre bead to help hold it in place in the event of deflation. I can't find anything to confirm this yet but in the meantime here's a good site to browse

Jim.

J is Homers middle name.

J is Homers middle name.

Actually it's "Jay".