rear diff/gearing question

[springer392]

sorry if this is a newb question, but im not getting past this. i dont know anything about these diffs and how they work but i'm trying to figure out my gearing so i can order sprockets and stuff.

anyways, my question. when i set my cart on the ground with 28" tires, one full rotation of the tires rotates the input shaft on the diff approx. 13 times. when i lift the tires off the ground, it only rotates the input shaft about 6-7 times.

because of the relationship of the 13 and 6-7, i'm guessing it has something to do with the two tires rotating when on the ground and only one while is it lifted up, but i still dont understand. do i need to gear it for the 13:1 ratio or the 6:1 ratio?

[planejob]

From my Jeep days:

Yes, the spider gears will allow additional differential between the input and the wheels if the wheels are not spun together.

Notice how when you jack up the rear end with both tires off the ground and spin one of them... the other will spin backwards and the input will remain (mostly) stationary. This is the spider gears working.

So place both wheels on the ground, the size of the wheel and tire is irrelevant as long as they are the same size, and count the input-side revolutions (as you have done.)

From your description it sounds like you have a rear-end that is geared 13:1. I don't know anything about ezgo rear-ends, but from a quick google it appears the stock ratio is 12.44:1... so that certainly jives.

6:1 gears are the highest gears I see offered by the aftermarket, and don't appear they were ever offered in a stock EZgo. 6:1 seems to me like they would burn up the belts, clutches, and lug the motor ... unless you have little bitty wheels.

Here's a great website, there are many like this, that will let you calculate how changing the differential gearing and tire size will impact your speed and rpm. Our clutches change things a little on the acceleration curve, but the final speed or rpm calculates out fine. And if you must get super high gears there are lots of snowmobile places that can tune your clutch to make it hit later and not lug your engine.

[springer392]

thanks for the help. i was leaning towards the 13:1 (apparently 12.44:1) ratio, but it just didn't seem right to me. all i saw online was the 6:1 and 8:1, so i just assumed i would have one of the two which is why i was confused.

as far as clutches go, i'm not using any. i'm using a gsxr 600 motor, so it will be sprocket to sprocket.

so, it appears that unless i changes the diff gears, my top speed will be around 56mph at 13000 rpm in 6th gear. crap. i couldn't care less about top speed, but i'm sure not gonna be cruising around at 13000 rpm all the time, so crap...

[planejob]

Holy hell, that would be awesome. Can you imagine how quickly you would need to click through the gears at full throttle!?!

Since you are using sprockets couldn't you just gear it with those? Like put a huge one on the motor and a little bitty one on the input of the diff?

Also, if you did put 6:1 gears in the rear your top speed would be 112! And it would still get there in a **** hurry!

Sent via carrier pigeon from an undisclosed unique geographical location.

[springer392]

I'm not really worried about to speed, but i just don't want to be at cruising speed with the motor screamin.

you are right about sprockets, but i can only go so big on the motor and smallest on the rear is 11.

[kingmods]

I have the same problem with a 125cc engine. I would be interested in what you end up running. Please post what sprockets you end up using.