8 or 7 tooth driver

offtrail · Nov 17, 2008

I bought an old ultra wedge mod from a fellow snowster. It has a slp drop and roll running 9 tooth drivers with 3" pitch and a 153 attack twenty track in deep snow position. It seems that in that position it will clear the installed u cooler. It has rubbed a little but the clearance is low. Well I turned it around to hill climb position this weekend and it's definitely gonna rub. So my question is will I gain enough clearance with a 7 or 8 tooth driver. And does anybody have any Idea what gearing I would have to run to get back to a 19/39 equivelant?
Thanks

ultramike · Nov 17, 2008

Going to an 8 tooth 3" pitch driver will buy you 1/2" of tunnel clearance over the 9 tooth 3" pitch. To get back to the same final drive ratio, go with a 21 tooth top gear.

offtrail · Nov 17, 2008

Well a half inch will get me close. From your sig it looks like you're running close to my same sled. How did you get you're track to clear?

ultramike · Nov 17, 2008

I run 7 tooth sprockets, no rolled chained case, no u-cooler either. It is tight, but it just makes it.

offtrail · Nov 17, 2008

Well I just got done checking everything over. It already has 8 tooth 3" pitch drivers on it. It has the stock chain case with the slp drop and roll. Like I said before I didn't notice the problem until I turned the attack 20 around. Now when the paddle is fully extended not bent over it is hitting the ucooler and the jack shaft. I would say by an 1/8 inch. If I go to a 7 tooth will I gain a half inch or do I need to get an edge chain case?

xsummitx · Nov 17, 2008

offtrail said:
Well I just got done checking everything over. It already has 8 tooth 3" pitch drivers on it. It has the stock chain case with the slp drop and roll. Like I said before I didn't notice the problem until I turned the attack 20 around. Now when the paddle is fully extended not bent over it is hitting the ucooler and the jack shaft. I would say by an 1/8 inch. If I go to a 7 tooth will I gain a half inch or do I need to get an edge chain case?

I got a edge chain case in my wedge mod I am parting out..$115 shipped complete...it will give plenty of room

offtrail · Nov 21, 2008

Okay so I'm going with 7 tooth 3" pitch drivers. It should give me enough clearance. Otherwise it's new chaincase time. So Does anybody have a formula how to figure out gearing. Would like to get back to a 2.0 to 2.1 ratio. Thanks

offtrail · Nov 25, 2008

Anybody?

revpilot · Nov 25, 2008

offtrail said:
Okay so I'm going with 7 tooth 3" pitch drivers. It should give me enough clearance. Otherwise it's new chaincase time. So Does anybody have a formula how to figure out gearing. Would like to get back to a 2.0 to 2.5 ratio. Thanks

If you've dropped from 7.5" to 6.5" or 7.5/6.5 you've geared down 15% so you need to gear up 15% on the chain side to get back to where you were.39/19=2.05x.85=1.75 39/22=1.77-pretty close.

offtrail · Nov 26, 2008

Thanks so much revpilot! At least I can get it back to where it was. But does anybody have a way of telling exactly what my ratio is. If I have 7 tooth 3" pitch drivers with 22/39 gearing?

revpilot · Nov 26, 2008

Your looking at it. Your gear ratio is the # of teeth on one sprocket divided by the # of teeth on the other. 1.77/1 or the small sprocket turns 1.77 times every time the lower one (and your drivers) turn once. The ratio remains the same whether you run a 7,8 or 9 tooth just like changing tire sizes on a 4:11 rear end pickup. If you're trying to figure track speed, there's too many variables to get it exact but if your clutch was fully engaged @1:1 your engine would turn 1.77 times to turn your driver once. 3.1426(pie)x driver diameter gives you circumference. 3.1416x7.5"(8 tooth)driver=23.5" 8000rpmsx23.5" divided by 1.77 =106,215" per minute divided by 12=8,851 feet per minute x60 = 531,060 feet per hour divided by 5280(feet in a mile)=100 miles per hour. Take all that and subtract wind resistance, track slippage, clutching error ect. and you still don't really know exactly. BTW, your 7 tooth would be about 85mph. Plenty fast for a mountain sled. :face-icon-small-hap

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8 or 7 tooth driver

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