Correct pressure when using non-OE tyres ??

[Moto]

I've put Yoko 195/65 R15 on the Vixen set at 20psi all round - just a finger in the air / gut feel approach and it does feel fine on the road.

But is there a more scientific way to calculate correct tyre pressures based on corner weight, contact area etc?

Moto

[P100]

H`mm 20 psi seems a bit low to me...

I run Uniroyals atm and have set the pressures to 26 f 28 r sems to handle ok and the tyres are not overheating

Roy