I will be drag racing my quad in Sept . and was wondering which size tire would be the best fror a 300ft drag race in the dirt . Its 300ex with a stock 350x atc motor and 350x swingarm and rear shock . I am running a 12 /36 sprocket combo that equals 3.00 .Thats with 20" tall tires . A stock 350x runs 13/40 sprockets and 22" tall tires= 3.08 . I plan on changing my rear sprocket to a 37 tooth and still run the 12 tooth in the front that would get it back to a 3.08 . I know the taller tires will make it faster but will I notice it in 300ft ? I had a 350x atc back in the mid 90's and it had the stock 13/40 gearing and the 22' tall tires and it outran a lot of bikes , but I'm not sure how far we were racing . We would just run across a big field . Will the .08 in my gearing be noticeable ? I can launch it pretty good now in 2nd gear . Last time I raced I was in 6th gear at the end of the 300ft race and it seemed to be topped out . Thaks for any input

 

I found this on 3 wheeler .org


Stock gearing on 350x is 13-40. Ratio of counter sprocket (13) to rear sprocket (40) is 3.0769 to 1. Takes counter sprocket 3.0769 revs to turn axle 1 rev. Stock tires are 22" with circumference of 69.115" (Honda has 68.3" in their manual.) Tires vary in circum. from brands and wear. I used "pie" to understand ratios. Divide circumference (69.115) by ratio (3.0769) = 22.4625 (inches of tire travel per one counter sprocket revolution.
20" tires would have 62.8318 circumference. Divide ratio and you have 20.42 inches of travel.
14-40 gearing with 20" tires would be 2.8571 to 1, 21.99" tire distance.
14-39 gearing would be 2.7857 to 1, 22.55" tire distance (closest to stock)
13-36 gearing is close also. If you can get a 36 tooth?


After doing the math with my 12 /36 gearing I came up with a final drive of 20.943 so I think I am going to get the 22" tall tires and move up to a 37 tooth rear sprocket .