B44.2 final drive ratio help please

[richie.]

Hi guys I'm in the process of changing my gear over from a 44.1 to a .2, the question I have is what ratio to go with?

I currently run an 81 spur / 23 pinion that runs quite hot in our indoor slippy wooden gym floor. This ratio amounts to 8.80.

Should I be aiming for a better final drive ratio?

Also does it matter if the size of the spur is large or small as long as
the final drive figure is ball park to where you need it? The new car is fitted with a 73 spur so wondering if I can keep that and just change the pinion to match the final drive figure?

The hall we use is a typical sized school gymnasium, any advice would be great as I've never tinkered with this aspect of the car.

[cutting42]

The B44.1 and .2 have the same drive ratio of 2.5 so the gearing you choose will be the same. So as you probably know 81 divided by 23 times 2.5 equals 8.804, therefore to get the same final drive ratio:

8.804 divided by 2.5 = 3.5216; new spur of 73 divided by 3.5216 = 20.73 pinion.

This is exactly the same gearing however you may find that with such a small spur there is not enough adjustment in the motor mount to mesh correctly. The 71-73 spurs are designed for stock motors such as 17.5 which run a much larger pinion.

Gearing is normally set by the track needs and also based on the motor you are running. I run an 81/20 a ratio of 10.125 with a 6.5T motor on a medium track 28 sec lap on astro if that helps. I have no overheating issues.

[richie.]

Originally Posted by cutting42

The B44.1 and .2 have the same drive ratio of 2.5 so the gearing you choose will be the same. So as you probably know 81 divided by 23 times 2.5 equals 8.804, therefore to get the same final drive ratio:

8.804 divided by 2.5 = 3.5216; new spur of 73 divided by 3.5216 = 20.73 pinion.

This is exactly the same gearing however you may find that with such a small spur there is not enough adjustment in the motor mount to mesh correctly. The 71-73 spurs are designed for stock motors such as 17.5 which run a much larger pinion.

Gearing is normally set by the track needs and also based on the motor you are running. I run an 81/20 a ratio of 10.125 with a 6.5T motor on a medium track 28 sec lap on astro if that helps. I have no overheating issues.

Thanks for that, my motor is a 6.5 and our lap times can range from roughly 15 to 19ish seconds depending on layout. I'll order more Spurs and pinions on that advice. I've had no electrical issues as such but it's sticking hot to touch so any small reduction would be welcome