After talking to a few tyres techs I have some info......
Advice given to me is as follows. This is for fitting to 12" 1.85 rims.
Michelin pilot sport (powers arent made in 12") are the best option for racing as they are the softest compound tyre. Getting a 120 profile (tyre width) tyre is going to bulge on the rim and it actually distorts the tyre hence changing its properties which doesnt benefit in any way. Infact its bad.
Using a 110 however will be the perfect fit as it wont distort meaning the tyre will keep its shape improving overall performance.
The difference between a larger (120) tyre is that it will provide more grip while the smaller (110) tyre will provide better turn in. Seeing as these mini motards arent all that powerful the better option is to have better turn in rather than better grip.... having said the above.... you may not even have better grip with the 120 as it is distorted and changes the tyre properties.
In conclusion: 120 is cheaper, looks better and MAY provide better grip while the 110 stays its shape and turns in better.
I have ordered the 110/90x12 pilot sport
