OK took my 12 teg Focus zetec s down to West Wales over the last few days ,the car ran fine but on some road surfaces the road noise was horrendous,  couldn't talk without shouting  and forget  the radio ?  Now wondering wether to go onto 17 in , my question to anyone using this size on their car, do they run any quieter with the smaller  wheel ? Or am I fighting a losing battle? Surely all Focuss can't be this bad?,  love the car hate the noise 

I doubt you'd see much difference tbh. My Fiesta is on 17" with 205/45 tyres and is pretty much as you report - radio/conversation are impossible on some roads. I've had 3 previous cars with similar wheel/tyre specs and they were the same.

My theory is it's the road surface nowadays - so many round my area are now "surfaced dressed" with chippings thrown on top of a bit of wet tar rather than being properly resurfaced. When you do come across a length of properly tarmacced road the silence is amazing!

OK but my concern is that we also run a Peugot partner and the noise difference  is amazing, never seem to have an issue with noise on any type of  road surface  , cannot figure out whst is going on, now you  say there  is no real difference  on 17s,  then I am  more confused 

42 minutes ago, robdalej said:

we also run a Peugot partner and the noise difference  is amazing,

Don't know the wheel/tyre spec on the Partner, but I'm guessing the tyres will be a lot higher profile than 40 or 45. It's the combination of low profile tyres and crappy road surfaces that causes the problem imo. 

A few years back I had a Mk 2 Focus with standard suspension on 16" wheels and correspondingly higher profile tyres which had a much quieter ride. My Mrs has a SEAT Mii with 175/65x14 tyres and it's a lot quieter on all types of road surface.