gearing

Just wondering of what size spur gear to get and what size pinion and is it best to use the z-drive because i can not find a 48dp spur gear that fits on the z drive

use the Dave spur gears he makes 48dp

Its only the mardave gears that will fit onto the 'Z' drives.
have a look at Tic racing or mardaves online shop.

Ive got a gtb2 esc and decided to get a Team Powers Plutonium 13.5 motor Ime a bit lost on gearing.
Just need to know what is good gearing to start with if i get a z-drive.
What number of teeth for the spur and also for the pinion.

Z-Drives are good, far better IMHO than the plastic spurs. Just remember to file 3 small flat areas on your axel for the grub screws to seat themselves in, otherwise they will dent the axel and make it very hard to get the bearings off. Most people I run with use either a 70 or 73 tooth spur gear but this will depend on the size of track you run on.

As for gearing, I am assuming you are running brushless? If so, what motor and speedo are you using and what sort of sized track are you running on?

For brushless motors (and to a lesser extent, brushed motors too) simple spur gear and pinion gear choice is not enough - our tires wear down and we must take their diameter into account to get our gearing accurate. In fact, most people who race any type of foam wheeled class calculate their gearing by working out their "milimetre per rev". In otherwords, how far their car travels for one complete revolution of their motor.

The maths...

mm/rev = (3.142 x Tire Diameter x Pinion) / Spur

Or, if you know the mm/rev you want and need to find out what pinion to use:-

Pinion = (mm/rev x Spur) / (Tire diameter x 3.142)

So, if you have a tire diameter of 50mm and are using a 24t pinion and 73t spur you will have a gearing of 51.6mm/rev.

Or, if you have the same tires and a 70t spur and want to run at 56mm/rev you will need a 25t pinion.

If you don't want to crunch the maths each time then there is an iPhone App called "Gear It" that does all the hard work for you. Android have something similar but I can't remember its name.

When I run my HPI Flux on my local tracks (12x20m) I usually run at around 54mm/rev. On bigger tracks, such as Leominster (16 x 35m?) I ran 58-60mm/rev. On the other hand, the guys who were running the Team Powers motors got their gearing much higher, up to 68mm/rev at Leominster!

One tip I heard a while back was to run your new motor on zero timing to begin with and adjust your gearing so that your car hits top speed about 2/3 of the way down the straight. Once you get that, increase the timing on the motor until you come off at the end of the race at around 60'C. I have tried this method and it works, to an extent. I can get a good gearing but my motors never have much timing adjustment available - even if I crank them round to the max my motor only comes off at 50'C max. If I upped my gearing all I got was a hotter motor and slower car out of the corners, and therefore slower laps.

Good luck,

J