If I change the rear wheels on my LT250r from 20 inch to 18 inch tires do
I need to change the rear sprocket? If you have to change the
rear sprocket how do you calculate the increase or decrease?

thanks

 

You don't have to change the rear sprocket. You're quad qill be lower geared with the smaller tires. If you don't like the gearing after you change the tires just go with a 2 tooth smaller rear sprocket and you should be right around where you were with the 20inch tires.

 

You mean tires, not wheels, the wheels go in the tires.
Anyways, smaller tires means less speed more acceleration. Smaller rear sprocket means more top end less acceleration.

 

he should go up one tooth on the front sprocket to compensate plus its cheaper than a rear.