See the "how to" in the link of my signature. Read carefully, if needed two or three times.
To find the right motor specific angle: Set all speed limits to 100, set Gear Ratio to 100. This makes sure, that no speedlimit cuts the power at high rpms.
Than change the motor specific angle in steps of 5 in both directions starting from zero (0, 5, 10 .... 255, 250, 245) until 20 and 235.
Look at the current draw with wheel in the air at full throttle. The setting with the lowest current is the best. If you found the optimum, you can finetune with steps of 1.
The gear ratio has no effect on the commutation, it only defines the threshold where the motor cuts the power due to the speedlimit. So just check the speed where the motor cuts the power with a normal speedometer, when you set the speedlimits to e.g.25 kmph. Then adjust the gear ration and the wheel circumference.