Track Tac

Gearing change between grooved and slicks

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lewisracing00

New member
The local track is closed this weekend so I'm gonna head to another track. Some of the guys are running on grooved tires and gearing at 12-71 but I'm running slicks. What would a close gear for slicks be? The clutch driver is a 11t thats all i got to work with on that.
 
If prepped properly and your on the right tire your slicks are gonna hook up better, so in a perfect world if that 12-71 is there you would only need a 12-69 because you would generate more forward drive. So that would put your 11t at a 65,66 ish. If your way off on tires and not in the track your going to be way low on RPM's.

Good Luck !!
 
I would imagine your circumference on the slicks is 1.5-2" less than the treads so I think what you've got will certainly work. The 64 will be very close to the ratio with a 12/68.
 
Measure the circumference, if there is a difference, bigger tire will need more teeth., I can't tell you how much because we only run 1 type of tire.
 
My Excel spreadsheet has one page for comparing tires and gear ratios. You measure the circumference of the tire you have now, put in the gear ratio you have now, then put in the circumference of the tire you going to go to and adjust the gear ratio to match a ratio factor. If you know the circumference of the tire most people are using, it's easy to find a gear ratio to go with your tire and have the same factor. I also have a page for doing this with Jack shafts.
12/68=5.67 ratio w/34" tire = 6.0 factor
12/72=6.00 ratio w/37" tire = 6.0 factor
these are just for demonstration purposes, you can put in any gears or tire circumferences you want.

From the desk of Al Nunley
Comments compliments criticisms and questions always welcome.
If the data does not support the theory, get a new theory. (Al Nunley)
 
The grooved tires I have are 37-1/4" and the slicks are 34-1/4" I'm pretty sure their grooves are about the same. Its an outlaw class so I need to turn this engine up around 8200. The fellow that I talked to on the grooves is turning around 8000.
 
lewisracing00 said:
The grooved tires I have are 37-1/4" and the slicks are 34-1/4" I'm pretty sure their grooves are about the same. Its an outlaw class so I need to turn this engine up around 8200. The fellow that I talked to on the grooves is turning around 8000.
Click to expand...
my spreadsheet calculates that's about a 6 tooth difference.

From the desk of Al Nunley
Comments compliments criticisms and questions always welcome.
If the data does not support the theory, get a new theory. (Al Nunley)
 
Well ended up having to go with a 62. The track was horrible. When I got there it was about 6" deep in mud. They worked the track for a few hours but ended up like a motor cross track. I heard it was a little ruff last week but never expected it to be that bad off. I did end up 5th out of 11 karts so not to bad for the first night on that track. I think I could have done better if the track was right.
 
11/62 with 34.25 tires is pretty close, overall, to 12/71 with 37 1/4 inch tires. 11/60 would have been closer, in fact, almost exactly the same. I'm not saying the 62 was not the right gear, your assessment of the track conditions would determine that.

From the desk of Al Nunley
Comments compliments criticisms and questions always welcome.
If the data does not support the theory, get a new theory. (Al Nunley)
 
I think your right Al 60 would have worked better. I was turning the engine at 8380 but really like it to be around 8100 or 8200 at most seems like it falls off after 8200.
 
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