Hello m8,

Yes they will fit. Mondeo Si 16" five spokes come in two different offsets (marked ET on the inner spokes of the wheels) which are ET35 and ET40 and they also come in two different width flavours too which are 6.5j and 7j wide. The ET40's are more commonly found than the ET35 ones but the ET35's are a more appropriate offset which is a bit of a pain in the RS !!! If you do get a set of ET40's then depending on suspension set up they can sit to close to the stuts on the front but you can use 5mm spacers on the hub to get the desired effect with no problem and they don't cost too much. Tyre choice is also a factor to consider and most people put 195/45/16's on with no probs. I'm just about to put some 16" Mondeo five spokes on my Fiesta RS1800 and these are ET40 wheels so i'll be using the 5mm spacer but i've opted to go for 195/40/16 tyres which are a bit more expensive but reduce any potential clearnace problems and also to decrease the rolling radius. My RS1800 currently has 7x16" alloys with 215/40/16 tyres and they clear without rubbing except on very full lock so even with that combination it clears. You should be fine m8 !!!

Cheers

James