2wd 4pots do not fit behind the standard wheels.

They need 4mm machining off the mating face of the caliper and the hubs need drilling to 14mm (don't quote me on that)...

I did the 2wd caliper conversion on my s1... i found out that you have to bin the standard wheels the hard way

But... once on and working, boy do they stop IMO the most cost effective way of making a rst stop... if you don't mind loosing the standard wheels. Been in an rst with 4wd calipers and IMO theres no comparison