Mountain bikes generally have a range of 1 to 3 chainrings on the front and up to 12 gears on the rear cassette. The number of gears can vary depending on the intended use of the bike and the personal preferences of the rider. A greater number of gears can provide more options for varying terrain, while fewer gears can make the bike lighter and simpler to maintain. Ultimately, the number of gears for a mountain bike is a balance between performance, weight, and ease of use.

To lighten a mountain bike, first identify the heaviest components such as the wheels, suspension, handlebars, and seat. Replace them with lighter ones made of materials like carbon fiber or titanium. Remove unnecessary accessories like mudguards or reflectors. Trim excess cables and wires. Use tubeless tires for less weight, and employ aluminum bolts instead of steel where practical. Finally, choose a smaller frame size as an oversized frame can weigh more.

Your mountain bike might be creaking due to various reasons, such as a loose chainring bolt, a worn-out bottom bracket, loose pedals, loose headset, worn-out bearings, or loose spokes. Creaking noise can also be caused by the saddle or seat post, seat clamp, and handlebars. You should thoroughly inspect the bike and find the source of the creaking to fix it as soon as possible, to have a smooth and safe ride.

Begin by removing the old fork by disconnecting the brake and shift cables and removing the stem and headset. Next, insert the new fork into the frame and secure it with the headset and stem. Connect your brake and shift cables to the new fork and adjust as needed. Finally, test the new fork for proper operation and make any necessary adjustments before hitting the trails.