Had a set on my fiesta turbo (should be same as the rs1800) Car was already lowered around 35mm maybe?

Used very narrow tyres 195/40/16 at the fronts and 195/45/16 at the rear. Wheels fitted straight on no need for coilovers/arch modding etc.... Ride was a bit harsh at types most likely due to the narrow tyres but i lived with it but then thats me so dont know.

Did have a set of cossy calipers and discs fitted at the front so dont know if that was an advantage or if it helped in anyway?

Tbh genrally had no problems with touching the shocks/arches or when turning etc so for me its was a great mod

Hope that helps

Reiss