Welcome to our Tech Talk page!!! We will be adding technical information as it comes in or I find the energy to discover it on the www. If anyone has any technical information/tips on issues as simple as installing grips or as hard as fixing chain alignment issues, please send it to me at brad@younggunsbmx.com and I will make sure it gets on the site.
Gearing Information
Gear Ratio
Gear ratio, in bmx terms, speaks of the relationship between the front sprocket and rear cog as they are connected to the chain. It is measured by dividing the front sprocket by the rear cog.
Example= 44 front tooth divided by 16 rear tooth (44/16)= 2.75 gear ratio
Gear Inches
Gear inches is simply the distance traveled by the tires upon one complete rotation of the crank arms.
It is measured by multiplying the gear ratio by the diameter of the inflated tire.
Example=2.75 gear ratio multiplied by 20 inch inflated tires (2.75x20)=55 gear inches
Circumference
The distance around the outside of the tire. Must be measured with the tires inflated.
Diameter
The distance from one side of the wheel to the other crossing through the middle of the tire.
It is figured by dividing the circumference of the tire by pi (3.141)
Example= a tire with a circumference of 62.82 divided by pi (62.82/3.141)=20 tire diameter
Figuring Gear Inches
DIAMETER x GEAR RATIO
Figuring Gear Ratio
FRONT SPROCKET / REAR COG
Figuring Diameter
CIRCUMFERENCE / PI (3.141)
Click here if your too lazy to run your own numbers and you want to use a chart.
Gain Ratio
Gain ratio takes into account the crank arm length on a given bike and its effect on the gearing. While gear ratio and inches does not change no matter the crank arm length, it does change the "gearing" or the effort used to turn the gear. Sheldon Brown covers this quite well on his site and therefore I will allow him to share his info with you by clicking here. Otherwise, I recommend experimenting with gears and crank arm combinations yourself to find the optimum gear/crank combo for your rider. Don't be afraid to experiment. What works for some doesn't always work for the whole.
Gear ratio, in bmx terms, speaks of the relationship between the front sprocket and rear cog as they are connected to the chain. It is measured by dividing the front sprocket by the rear cog.
Example= 44 front tooth divided by 16 rear tooth (44/16)= 2.75 gear ratio
Gear Inches
Gear inches is simply the distance traveled by the tires upon one complete rotation of the crank arms.
It is measured by multiplying the gear ratio by the diameter of the inflated tire.
Example=2.75 gear ratio multiplied by 20 inch inflated tires (2.75x20)=55 gear inches
Circumference
The distance around the outside of the tire. Must be measured with the tires inflated.
Diameter
The distance from one side of the wheel to the other crossing through the middle of the tire.
It is figured by dividing the circumference of the tire by pi (3.141)
Example= a tire with a circumference of 62.82 divided by pi (62.82/3.141)=20 tire diameter
Figuring Gear Inches
DIAMETER x GEAR RATIO
Figuring Gear Ratio
FRONT SPROCKET / REAR COG
Figuring Diameter
CIRCUMFERENCE / PI (3.141)
Click here if your too lazy to run your own numbers and you want to use a chart.
Gain Ratio
Gain ratio takes into account the crank arm length on a given bike and its effect on the gearing. While gear ratio and inches does not change no matter the crank arm length, it does change the "gearing" or the effort used to turn the gear. Sheldon Brown covers this quite well on his site and therefore I will allow him to share his info with you by clicking here. Otherwise, I recommend experimenting with gears and crank arm combinations yourself to find the optimum gear/crank combo for your rider. Don't be afraid to experiment. What works for some doesn't always work for the whole.