gear ratio is gear ratio w/trans?

[swell searcher]

I understand the concept of changing spurs and pinion ratios to change torque and speed. If you have 2 different combinations of spur/pinion gears that gives similar ratios, is there an advantage over one or the other i.e. 87T spur/12T pinion (55.77:1) versus 93T spur/13T pinion (55.03:1). Maybe a cooler running motor with the larger pinion?

[Grizzly4x4]

More teeth on the pinion gear will give more tooth engagement for smoother running and more strength.

[bunyip]

I dont believe it matters
having said that From my racing days we always tried to go with the smaller / lighter combination, after all it is rotating mass.

there is also clearance issues especially with crawlers spur gears clearing output shafts etc

[hairba11]

Originally Posted by swell searcher

I understand the concept of changing spurs and pinion ratios to change torque and speed. If you have 2 different combinations of spur/pinion gears that gives similar ratios, is there an advantage over one or the other i.e. 87T spur/12T pinion (55.77:1) versus 93T spur/13T pinion (55.03:1). Maybe a cooler running motor with the larger pinion?

for one thing, 87/12 is 7.25:1 and 93/13 is 7.15:1
unless you are multiplying by your trans and diff and have your total reduction listed.

either way, the only major difference is spacing on the trans for the motor.

on a wheely king transmission, a 12/87 combo won't fit without clocking the motor plate.
a 93/13 combo might fit with mild shaving of the top of the case.
I was able to file the top on my WK trans and run a 13/96 setup, where most guys were running 15/96 because it was as tight as you could go without shaving the case.

other than spacing, it doesn't really matter with that many teeth.

theoretically speaking the minimum number of teeth you can have on a gear and still maintain full smooth engagement is 9

I know there are 6 tooth pinions out there for the clods, but if the options you have are a 6/36, or a 10/60, and you have the room, use the 10/60.

[swell searcher]

thanks guys. you basically answered my question and there is no really advantage. hb, those ratios where from the axial manual and i was just using them as references. i'm running 84t and 87t spurs on my axial rigs and vary the pinions until i found a good combo.