fitting a 120 tyre on a rim made for a 110 tyre will make the tyre more curved.
this changes the characteristic of the tyre (which is 30% of the total suspension of the bike), sideward stability changes because the sides of the tyres are deformed.
and there is LESS grip because the tyre is more curved
which will have the following effects:
- the motorcycle will want to come upwards in turns
- the tyre will wear faster then normal
info available thanks to a tyre specialist, who is not me