9 Tooth driver vs. 12 tooth driver for short track?

Straightaways about 120 feet long & hair pin corners. Which do you prefer for box stock Predator with 10.8 lb valve springs, header, aftermarket air filter & re-jetted. Tire sizes range 38-41 inches. Thanks
 

alvin l nunley

Premium User
Straightaways about 120 feet long & hair pin corners. Which do you prefer for box stock Predator with 10.8 lb valve springs, header, aftermarket air filter & re-jetted. Tire sizes range 38-41 inches. Thanks

Straightaways about 120 feet long & hair pin corners. Which do you prefer for box stock Predator with 10.8 lb valve springs, header, aftermarket air filter & re-jetted. Tire sizes range 38-41 inches. Thanks
9/54 = 6.0
10/60 = 6.0
11/66 = 6.0
12/72= 6.0
What ratio do you plan on running? What RRPM? Is the 41"tire on the RR?What's the largest rear sprocket you can run?
 

alvin l nunley

Premium User
I left the 9 tooth off, I think that's too small, but I like the idea of the 10, or 11. Something to try, what could hurt?If you add a tooth to the axle, and don't lose more than 80 RPM, you'll be going faster down the straight. It may hurt you coming out of the corner, testiing will tell! And
 

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flattop1

Dawg 89
I think I'll order a 10 tooth and try it. Lol, Thanks Alvin.
What chain ? You do realize that on #35 chain a ten tooth is either out board with an extension or has no bushing or bearing .
 

flattop1

Dawg 89
41 " tire , 10 tooth driver , maybe #40 chain .
mini cup , wing sprint , off road , lawn mower or turf tires . No telling .
A three inch circumference change alone would require a gear change .
 

GClary

Member
Must be on treads if it's 38/41 . I would do as Racing Promoter said , 12 driver and target rear gear to get 4900 or so . I might even try an 11 driver and target the 4900 rpm's
 
I always choose the biggest tooth driver possible as it is the best mechanical advantage and lowest friction.
Lots of big money races are being won with smaller gears and drivers.
GKK winner of $10,000 was on a 14, where use to be 17. Lots of the other big AJC races are being won on the smaller also.
 

alvin l nunley

Premium User
box stock looses power @4600 . 4900 is too far out of range
"Losing power 4600 RPM and." But that doesn't mean there's not enough horsepower above 4600 RPM to keep accelerating. The acceleration rate may be a little slower, depending on the horsepower, but it can keep accelerating after peak HP, just at a slower rate.

For instance, a KT100 reaches peak HP at about 11,400 RPM, but they can't easily turn 15,000 and be accelerating all the way.
 

"J'-remy

Member
Lots of big money races are being won with smaller gears and drivers.
GKK winner of $10,000 was on a 14, where use to be 17. Lots of the other big AJC races are being won on the smaller also.
doesn't matter who won on what the bigger the front driver the better the mechanical advantage plus lower friction. if you are looking for every possible advantage go with a bigger front driver you can't argue physics.
 

alvin l nunley

Premium User
doesn't matter who won on what the bigger the front driver the better the mechanical advantage plus lower friction. if you are looking for every possible advantage go with a bigger front driver you can't argue physics.
Actually, if the gear ratio is the same, there is no mechanical advantage whether you have a 10 tooth or 15 tooth on the engine. 10/40, and 15/60 are both 4.0 – 1 ratio. Where's the mechanical advantage?

Wikipedia has a good explanation of what the term "mechanical advantage" means.

Now the argument has been made that bigger drivers and sprockets are better (sometimes), but that argument has been going on for years with no settlement insight. lolIn
 
doesn't matter who won on what the bigger the front driver the better the mechanical advantage plus lower friction. if you are looking for every possible advantage go with a bigger front driver you can't argue physics.
Not sure about the lower friction. Im not a science type of guy, but i do know the more something ( here is size between the 2 gear sets ) is rubbing creates more friction than something thats smaller. Maybe it isnt the case here, but i also know for a fact here that with the smaller gear set the axle spins freer than with a larger gear set, creating less friction maybe.
 
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