Predator 212 Gear Ratio

[akitchell]

My craigslist find came with a predator 212 with a 45t axle sprocket and 9t TC sprocket. I need to purchase a new TC, most of which come with a 10t sprocket. With 18.5" rear wheels, will a 4.5:1 gear ratio be ok? I can't imagine climbing massive hills but will have more fun bombing through the desert (which will inevitably have some hills), doing cookies etc.

What do you typically look for in a gear ratio and why? I'm new to this and am trying to learn as much as possible.

Is there a good website discussing gear ratios?

 

[ultralight01]

This is the website!
4.5:1 is a HORRIBLE gear ratio.
5:1 is good for racing karts with 11 tires.
if you have !!18.5 INCH TIRES!!, you need more like 7-8:1 or else you're gonna KILL that TC.
I suggest a 8 or 9:1 Ratio. Less speed but plenty of torque that won't waste hundreds in parts.

 

[Poboy kartman]

Yes...it's called DIY Gokarts.

 

[akitchell]

Does it make a difference what the axle vs TC tooth count is, or just the overall ratio? For example, if I were to go with a 9:1, I could use a 10t TC and 90t axle or a 9t TC and an 81 axle. Based on my very limited knowledge, the performance would be identical?

 

[ezcome-ezgo]

Yes, it's just math and physics and something or other.

 

[DeathMachine]

Black magic and wizards and unicorn farts.

 

[akitchell]

Black magic and wizards and unicorn farts.

Have you seen the squatty potty ad with the unicorn?

---------- Post added at 11:20 AM ---------- Previous post was at 11:18 AM ----------

If I purchased a series 40 TC, could that handle the lower ratio, say. 5:1 or a 6:1?

 

[DeathMachine]

It's as much keeping the engine in it's powerband as it is the strength of the clutch (or TC).

I'm not sure if a 40 comes in a 3/4" shaft either. Those are usually set up for 1" shaft.

 

[MrC.]

no, you need the gear ratio of 7- 9 to 1 if you want any type of hill and take off speed, those 18 inch tires are heavy and create a ton of load on the engine at take off.
get the largest drive or axle gear you think will fit 60 tooth or 72 tooth then put on the smallest TC gear you can find which will be an 8 tooth or 9 or 10 tooth that will get you in the 7 to 1 or 8 to 1 ratio, you may find you need even more gear. but start there you can always swap a gear if you ride on flat hard ground later.
MrC.

 

[Poboy kartman]

C'mon guys!!! WAKE UP!

To answer the QUESTION: No...it does not! Both of those would give you a 9:1 gear ratio, and it doesn't matter where the teeth are at all.

BTW: EZ answered correctly...just didn't make it completely clear.

 

[Joe-405]

I wasn't gonna say anything but a 9:1 is completely unnecessary. My dingo with those tires and a converter wasn't even close to that and it would yank the front tires upon takeoff. I bet the top speed is about 20-25 tops.

If it were me a 10 tooth front and about a 60 rear should be plenty.

 

[itsid]

well another major factor is weight..

you can run 4:1 on a dry clutch in a 11" race kart with only child on board (you shouldn't!! but it'd move well enough)

The thing is we deal with adults here, and most importantly..
some claim to use a kart, talk about karts and nothing but karts..
when in fact they mean heavy two seater mini buggies closer to 500lbs without any passenger whatsoever.

So yeah, gear ratio.. cool... wheels are important for sure..
most important: weight to wheel torque ratio;
if you're not at least par you'll be guaranteed to fail.

I know we're all lazy and we never know the weight of the karts or even ourself at times...
but I'm afraid weight is as important as the wheel diameter

'sid