i have a fiesta with 16 inch wheels and on concrete rds the joints in the rd make it a bit uncomfy and noisy, i was wondering if i changed to 17 inch it would make it ba better and quieter ride if somebody has any experience on this subject id be glad to have your imput.

17" will make it ride worse - you will feel even small bumps, as you need to reduce the sidewall height of the tyre to keep the overall diameter the same. If you want more comfort get some nice 15" wheels and some high quality comfort orientated tyres. You will sacrifice some high speed cornering ability but it will ride nicely. I changed from 15" to 17" on a honda civic and the difference in ride quality is dramatic. I think the fiesta S has sports oriented springs / suspension, so the ride was mean't to be a bit sporty. Also check your tyre pressures are not too high.

Your going the wrong way 15" with same O/D tyres as the 16" might help.

First step is just change the tires - OEM tires are rarely good performers in any regard. A high quality tire with the correct pressures could very well make a night and day difference to both comfort and noise.

As pointed out by Culicine, going to a larger rim/lower profile is more likely to worsen the situation, than improve it (unless top-shelf tires are fitted).