Err if you put on a larger spur, then to maintain the same gearing (ie speed) you will need an even bigger pinion.

a 40t Pinion is already starting to get pretty big. Some cars start to get issues with physically fitting big pinions and spurs, but if you start getting spurs much larger you will have more trouble finding pinions bigger than 41 if i recall correctly.



The thing you need to remember is that because different cars have different amounts of teeth on belts and pulleys you often cannot look at the spur/pinion of another car and put the same spur/pinion in your car for the same speed.
This is why different cars have different internal ratios . Some cars even have options for different pulleys and belts which change the internal ratio for the car.

And just to make things even more confusing, the speed of your car is determined by the tyre size. Most on-road rubber tyres are the same diameter but if you are running foams the tyre size will shrink as the meet progresses.

People who talk in FDR (Final drive ratio) essentially do not take into account the tyre size. Rollout does take into account the tyre size.

So yeah a rollout calculator like www.gearchart.com is your friend.


Now ontop of this just to make things more complicated. Different motors and speedie combinations have different rollout preferences for optimal performance.
The best thing to do is find someone running the same motor and speedie as you and chat with them about A) what settings they are running on their speedie and copy them and B) then ask the rollout/FDR that they use.


When playing with gearing you should also run short tests for a couple of minutes to see how the motor is performing (heat wise), or you run the risk of blowing your motor if you take it straight out for a full 5 minute run during a race.


I hope that helps you, but i suspect you may need to read it all a few times.

Hang in there, once you get used to it, its not too bad....

Actually looking back there arent going to be many people runnning a GTB. For people in general to make a comment they could give general indications but would also need to know about the track. Which is also one of the reasons why dragonfire would have said to ask around the local track.

I dont know what things are like in QLD but where i race there is always someone willing to help out newbies. Unless people are rushing around trying to fix things i'd be surprised if there wasnt someone at your track who could help you. Just let race control know you are new to on-road when you register and ask if there might be anyone who could help you out with gearing. The guys in race control should know the people at the track pretty well.