Anyone run big rear tires on a kart

[ramairgtz]

Just wondering if anyone runs big tires on the rear of their kart and if you were able find the right sprocket combo to give it some punch off the line?

This kart I'm building is a carter trail runner with a gx390 and a comet 40 series set up. The kart has 16" tall tires on it now but I picked up some very nice 24-10.5x10 tires and rims. I wasn't sure if I ran a 10 or even 8 tooth sprocket off the jack shaft to the 60 on the axle if that be enough gear to make it move off the line and still run 25-30 on the top end. Any suggestions?

 

[sideways]

A 9:1 ratio will give you 29mph assuming the governor is still connected on your engine.

How many teeth are there on the sprocket on the torque converter?

Thanks

Hayden

 

[Doc Sprocket]

That's probably going to require some experimenting to get the ratio right. The Comet 40 is a big help, but since those tires are so huge...
Tough call. I have GX340, Comet 40, and 17.5" (measured) tires. I'm at 4.8:1 final, and could go deeper. Definately don't want to be any higher. I was at 4:1, and my top end was horrible. My kart's pretty heavy, though.

 

[ramairgtz]

I figured I would start with a 10 tooth on the jack shaft and 60 on the axle and go from there. If it's not enough to get it moving I could go with an 8 tooth either way the jack shaft sprockets are easier to change than the axle

 

[ramairgtz]

Or maybe I'll buy some 18x9.5-8 tires and play it safe. I only paid $20 for the 24" tires and wheels and I'll find a use for them somewhere. I bought some bolt on wheels hubs from BMI the rims on there now don't have lug nuts they just slide on the axle so changing tires will be easy if I wanted to try the big ones

 

[modelengineer]

I'm running car tyres (22" O/D IIRC) and my first gear has about an 8.8:1 ratio, going to a final ratio of around 3:1 in sixth.

It hauls ***, as the American's say.

 

[fowler]

got PACE as we would say

 

[pkgocart]

i have 19" tires a 12t clutch and a 54t sprocket but im in it for the speed

 

[huttronics0001]

my tires are 22" the biggest i've ever heard of on a kart, i had trouble getting torque but that was with a 4 to 1 ratio which is even pushing it with small tires, 8 to 1 would be pretty good but the fact that you have a jackshaft complicates things, what drives the jackshaft? a belt? what are the specifics of every gear and pulley you have, i'm working on a 3 speed jackshaft,
i'm no expert but i've learned a lot from my mistakes and am doing something which sounds very similar

 

[r97]

youl be more than fine herse the high end http://gokartguru.com/engineering_tool_kit.php, and heres your low end http://gokartguru.com/engineering_tool_kit.php

 

[fowler]

**** thats a complicated site

 

[r97]

which one the calculator? i like it cause its more precise and calculates your low end power

 

[fowler]

the whole thing
i guess if u wanted a perfect design then u would use this site

 

[r97]

i dont know about that, he made a good all around kart thatts really cheep but thats only if you happen to have tons of stuff, i sorta doubt a first time kart builder could build that for under 200, that kart would suck on the track or the trail but it is probably great on the drive way, one thing about that site is that he has alll this great info on center of gravity and stuff but his plans and stuff are wayyyyyyyyy ove priced its a ood site for alculators and liturature

 

[fowler]

i did screw around with the settings and i made a 18'000hp gokart that works in theory
EDIT
how does his centrifugal blower work

 

[r97]

no clue, but im shure it says some where, i think turbo charging a kart would be for fun cause its prob cheaper to get a bigger engine

 

[fowler]

its on the third page of the gallery it looks like he is relying on perpetual motion

oh yeah and the acctual topic id personally stick with the tyres u have unless there is somthing wrong with what u have now because its simpler cheaper and the bigger tyres are proberly only going to cause u more hasel than its worth

 

[r97]

bigger tires will look cool and raise your clearance, but also bog down your steering and make you more likely to flip.
p.s. fowler what time is it for you???

 

[ramairgtz]

I'm about to solve my problem I'm picking up another comet 40 series and putting a 11hp briggs on it. Still going to have a 10t on the jack shaft and a 60 ton the axle and if that doesn't work I can always go to an 8t on the jack shaft or buy smaller tires

 

[r97]

whats the advantage to that??? youl work great with gx390 40 sereis and 21" tires with 6 to 1 rateo