Building single track mountain bike trails involves the following steps: 1) Obtain necessary permissions or permits from the landowner or local government. 2) Plan the trail layout and consider factors such as terrain, elevation, corners, and obstacles. 3) Clear the trail path using hand tools or heavy machinery, being careful to minimize environmental impact. 4) Build features such as berms, jumps, and rollers to make the trail more exciting for riders. 5) Add signs and markers to ensure the trail is easy to follow and safe for riders. 6) Regularly maintain the trail to ensure safety and sustainability.

Sag is the amount of suspension travel that is used up when a rider is on their bike. To set sag on a mountain bike, the rider should first set the recommended air pressure for their weight and bike model. Then, they should sit on the bike in a normal riding position and bounce up and down. The suspension should compress a few centimeters, and the rider should then dismount and measure the amount of compression. The ideal amount of sag is typically around 25-30% of the total travel, and can be adjusted by adding or removing air pressure from the suspension.

To fix a bent mountain bike rim, you should start by loosening the spokes on the side opposite the bend. Then, use a spoke wrench to turn the spokes on the side of the bend in the opposite direction of the bend until the rim is straightened. Finally, tighten all the spokes evenly, and true the wheel by making small adjustments until the rim is centered between the hub and brake pads.

To adjust the rear gears on a mountain bike, start by shifting into the smallest chainring and the largest cog. Then, loosen the cable tension until the chain jumps to the next cog without making any noise. Finally, fine-tune the shifting by using the barrel adjuster to eliminate any rubbing or chain skipping. Test the gears by shifting through all the gears to make sure they shift smoothly and quietly.

The lightest full suspension mountain bike refers to a mountain bike that has both front and rear suspension and is designed to be lightweight. The weight of the bike can vary depending on the materials used in its construction, such as carbon fiber, aluminum, or titanium. Generally, the lightest full suspension mountain bikes weigh around 20-25 pounds and are designed for high-performance riding on rough terrain. These bikes are popular among serious mountain bikers who want a bike that is both nimble and fast on the trails.