Ok, i had some problems with this for awhile, so i figured maybe im not the only one , ok lets get to it
First of all, the format for ATV tire sizes was very new to me, example AT20x11-9, not very hard to understand i admit, but coming from race cars an tire sizing like 205/50R15, i just didnt understand it at the time :-[ so, just in case this is a normal thing.. ill try to explain it.
Size format AT##x##-##
First number represents Hight
Second number represents Section Width
Third number represents Rim Size
Example
AT20x11-9 signifies a tire that is 20 inches tall, 11 inches wide and is made for a 9 inch rim.
The first number in the tire size is also called, Overall Diameter, but it represents how tall the tire stands.
The Overall Diameter is often an approximate number, not the exact hight of the tire. Another thing that performance minded riders should understand is tire "roll out" that being the overall circumference of the tire, its called "roll out" due to the way circumference is determined, by sitting the tire upright, mounted on a rim an rolling the tire, the number of inches the tire travels before it makes one full revolution is the circumference.
I will give a short example of tire roll out or circumference, a tire with a 22 inch overall diameter and on a 9 inch rim should have a circumference of 72 inches, meaning to make oen full revolution the tire must roll 72 inches.
I measured my tires while on my quad to get the circumference, to find out the circumference of your own tires, take a piece of string, jack your quad up so the tires clear the ground, hold the string in the middle of the tire an roll it all the way around the center of the tire, then hold the ends of the string together and cut the string, then measure how long the piece of string is, that is your tires circumference.
Alot of things go into the formula for calculating tire circumference, rim size, rim width, sidewall hight and so on, so two different 22 inch tires on the same rim may have a different circumference. Understanding this is very important when fine tuning gearing for a quad
One last thing that i learned first hand building an setting up a circle track race car, that being tire camber and toe.
Its hard to explain toe-in and toe-out without pictures, so bare with me, think abotu the front tires of your quad, picture a line down the center of your tires pointing straight forward, if the lines down the center of your tires are pointing towards eachother in front and aawy from eachother in the back, that is toe-in, and the opposite is toe-out, that would be the lines pointing away from eachother in the front and so on, toe effects things such as tire wear and straight line stability, its best to have the tires set parallel for most common atv uses.
Tire camber determines the lean of the tire, positive and negative camber are important for handling in a turn, tires normally lean when cornering hard, camber is used to counteract the effects of tire lean. For example, on my race car, which is always turning to the left, therefore the right front tire leans outward at the top aqway from the car or its centerline, negative camber is used to fix this problem, the tire is leaned in at the top towards the car so when the car goes into a turn hard the tire, already leaning towards the car, will stand up straight in the turn and have maximum tread contact, while the left front tire which leans towards the car in a turn, is giving positive camber leaning the tire away from the car so in the turn the left front tire stands straight up getting maximum tread contact aswell.
Add anything you like if i missed something guys.
OK! thats all i can think of to say.. wow alot more than i thought it was going to be hope this helps.. someone.. maybe... i was just bored thats all :-[
-Hero
First of all, the format for ATV tire sizes was very new to me, example AT20x11-9, not very hard to understand i admit, but coming from race cars an tire sizing like 205/50R15, i just didnt understand it at the time :-[ so, just in case this is a normal thing.. ill try to explain it.
Size format AT##x##-##
First number represents Hight
Second number represents Section Width
Third number represents Rim Size
Example
AT20x11-9 signifies a tire that is 20 inches tall, 11 inches wide and is made for a 9 inch rim.
The first number in the tire size is also called, Overall Diameter, but it represents how tall the tire stands.
The Overall Diameter is often an approximate number, not the exact hight of the tire. Another thing that performance minded riders should understand is tire "roll out" that being the overall circumference of the tire, its called "roll out" due to the way circumference is determined, by sitting the tire upright, mounted on a rim an rolling the tire, the number of inches the tire travels before it makes one full revolution is the circumference.
I will give a short example of tire roll out or circumference, a tire with a 22 inch overall diameter and on a 9 inch rim should have a circumference of 72 inches, meaning to make oen full revolution the tire must roll 72 inches.
I measured my tires while on my quad to get the circumference, to find out the circumference of your own tires, take a piece of string, jack your quad up so the tires clear the ground, hold the string in the middle of the tire an roll it all the way around the center of the tire, then hold the ends of the string together and cut the string, then measure how long the piece of string is, that is your tires circumference.
Alot of things go into the formula for calculating tire circumference, rim size, rim width, sidewall hight and so on, so two different 22 inch tires on the same rim may have a different circumference. Understanding this is very important when fine tuning gearing for a quad
One last thing that i learned first hand building an setting up a circle track race car, that being tire camber and toe.
Its hard to explain toe-in and toe-out without pictures, so bare with me, think abotu the front tires of your quad, picture a line down the center of your tires pointing straight forward, if the lines down the center of your tires are pointing towards eachother in front and aawy from eachother in the back, that is toe-in, and the opposite is toe-out, that would be the lines pointing away from eachother in the front and so on, toe effects things such as tire wear and straight line stability, its best to have the tires set parallel for most common atv uses.
Tire camber determines the lean of the tire, positive and negative camber are important for handling in a turn, tires normally lean when cornering hard, camber is used to counteract the effects of tire lean. For example, on my race car, which is always turning to the left, therefore the right front tire leans outward at the top aqway from the car or its centerline, negative camber is used to fix this problem, the tire is leaned in at the top towards the car so when the car goes into a turn hard the tire, already leaning towards the car, will stand up straight in the turn and have maximum tread contact, while the left front tire which leans towards the car in a turn, is giving positive camber leaning the tire away from the car so in the turn the left front tire stands straight up getting maximum tread contact aswell.
Add anything you like if i missed something guys.
OK! thats all i can think of to say.. wow alot more than i thought it was going to be hope this helps.. someone.. maybe... i was just bored thats all :-[
-Hero