Speedometer Calibration: Accurate & Reliable

Hello, I have a somewhat theoretical question to start with.
Despite having 6 gears, the Touran has relatively short gearing.
If I were to get a larger tire size with a greater circumference registered, it would only be possible with a speedometer recalibration.
"Would a tire size of 205/60 R16 make a noticeable difference? About a 9% difference?"
Would that be possible?
I wouldn't want to install a longer gearbox.

teileklaus wrote:

If I were to get a larger tire size with more circumference registered, it would only be with a speedometer correction.

... and only if it is absolutely certain that the tires will not rub anywhere in any conceivable steering and suspension position. Unfortunately, even with the standard tire sizes, there is not much room to spare on modern models.

Quote:

205/60 16 would already make a difference. ? 9% ?

Compared to which standard size?
In the download of the duct calculator software, there is a spreadsheet that calculates the circumference of the duct.

Normal 205/55R16.
3.24% change from 200 to 207 km/h is too little with +30 horsepower .

Here's the translation:

"To reiterate the question: would I need a different speedometer drive, or is it even possible to change this through software?"