Fabia II 3 1.9 TDI tyre size questions and gearing.

Hi I just picked up a 4 year old 17000 miles fabia 3.

The front 2 tyres have been changed, but the rear 2 are the originals the car was born with....thus 4 years old and getting a bit perished IMO. The 2 newer front 2 are some really rubbish chinese makes.

The tyres are 205 45 16's.

I was wondering whether replacing them with 205 50 16's as having 50's would improve the tyre noise ride etc etc. and I,m not bothered about having the slim tyre look.

This would increase the circumference  by 3.38 % and speedo by the same factor.

It would also increase the gearing and drop the rpm a little.

Has anyone done this before? and what problems if any it caused?