Loose quick release skewers can cause problems ranging from an annoying squeak to the wheel catastrophically coming out of the dropouts. Before you ride, check to make sure yours are tight.
Under-inflated tires can cause the tire to wear faster and increase your risk of getting a flat. Check on the side of the tire for the recommended PSI. For road riding, you should inflate it to within 30 PSI of the maximum recommend, depending on body weight (lighter riders should use lower pressures). For MTB 30-45 PSI is usually ideal, depending on trail conditions and body weight.
3. Stem Bolts
If your stem bolts aren’t tight, the next pot hole, tree root, or set of rail road tracks you hit could make your handlebars move out of position. To check, grab the brake hoods and try to push them downward. If they move, then reposition the bars and check that the 4 facebolt bolts are evenly tightened to spec.
Grab the front brake lever and try to rock your bike back and forth. If you can feel the fork steer (the part of the fork that extends up through the frame) moving or can hear a rattle, your headset is loose. To fix, loosen the two stem pinch bolts, tighten the top cap bolt (on the top of the steerer tube), and retighten the stem bolts. If the top cap is fully tightened but you still feel some play, you may need an additional spacer underneath the top cap.
Lift each wheel off the ground and spin it. If you hear the brakes rubbing at any point, move the caliper or open the brake arms using the adjustment lever until you don’t hear rubbing any more. With both wheels on the ground, grab the brake levers and try to roll the bike forward. If the wheels move, or the levers bottom out before the brakes are fully engaged, tighten the calipers using the barrel adjuster on each brake caliper.
If your seatpost isn’t fully tightened, you could find your saddle sliding down on you as you ride. Firmly grab the saddle, and try to push it down while twisting from side to side. If the saddle moves, reposition it and tighten the seatpost clamp to spec (be careful not to overtighten—especially with carbon frames and seatposts).
7. Crank Arms
Sometimes these can work themselves loose on newer bikes, and bikes with a lot of miles on them. Sometimes it can just cause some nagging knee pain, or the entire crankarm can fall off mid ride. To check, rotate the non-drive side crank arm so it’s inline with the downtube. Grab the crankarm and downtube and try to firmly squeeze them together. Look for movement near the BB cups. If you can see the crankarm moving or wiggling, you need to tighten your cranks.