Originally posted by Surge
I think the side pulley/belt changes the front overdrive. We run 2mm tires up front to compensate for the overdrive in the transmission with smaller tires. I don't think going with the bigger pulley/belt will do anything to top speed, but have the same diameter tire front/rear might give a slight bit more roll out equally a tad more top speed (assuming the 2mm smaller tire limits it) So try running bigger front tires and see if the topend changes. It'll probably only change steering and tire wear.
Changing the various tyre diameters between front & rear basically alters the % drive each end of the vehicle is receiving.
To get more top end speed out of tyres, you`ll have to go with the largest diameter tyre possible, preferably with a 2mm split between front and rear....according to the Kyosho table, a 64.5mm rear tyre diameter should give a roll-out of 40.51 using a 22t pinion and 55t spur gear, whereas a 60.5mm rear tyre will give a rollout of 37.99.......add a 23t pinion and you`ll add more top end again to this.
Keep in mind these gearings will have an adverse affect on acceleration in tighter parts of the track.