I have a Ford Fiesta zetec 2011 1.25 with standard 15” wheels, I am looking to change to 17” ST wheels with 4x108, will they fit my car with no problems?

17s usually come with a steering rack limiter from factory. 

Fitting these wheels will also alter the true speedo reading ?
Can't remember which way it goes but lets say you are doing 60mph but you are actually going faster, or if you are doing 60mph but you are actually going slower.

It'll look ridiculous unless you're going to lower it as well.  

Without the tyre sizes on both we can't determine rolling radius to decide whether the speedo will be affected much.

 

5 hours ago, TomsFocus said:

Without the tyre sizes on both we can't determine rolling radius to decide whether the speedo will be affected much.

On original wheels with brand new tyres fitted the speedo reading is accurate but tyres worn to minimum also effects the true speedo reading, I can remember this and the above as it was on the TV a while ago and it was about people modding their vehicle wheels & tyres, seeing who can go the fastest, yet not taking into account of gearbox ratios - big wheels - different sized tyres - new tyres - worn tyres, also in the same program was traffic cops who was using their speed camera gun to give the correct reading, was quite funny to watch where one guy who had actually made his car go slower when he thought it was faster...lol

Sorry I’ve made a mistake my car has 16” wheels with tyres 195/45R16 and the wheels I want to put on are 17” with tyres 205/40R17, are use able to tell me if they fit and will the speedo be affected?

And Will wheels nuts need changed or are they standard?

Input you info in to this. 
https://www.tyresizecalculator.com/tyre-wheel-calculators/tire-size-calculator-tire-dimensions