If I put my leg on the side of the wheel and rotate my handlebars in the direction of my leg, the bars get out of sync with the front wheel as seen in the image below. This is a threadless headset. Do y'all have any ideas?
Tighten the pinch bolts, not the centre bolt.
I recommend putting a drop of oil on the pinch bolts thread or greasing them, as they are steel-in-aluminium, and prone to corrosion.
The two pinch bolts (on the back side of the stem) hold the stem on, and perform two separate effects
- They stop the handlebars rotating
- They lock the steering bearings.
The top bolt is for setting the pre-load of the steering bearings.
BUT once the pinch bolts are tightened, it does nothing, as the stem is now clamped in place. You cannot tighten the bearings UNTIL you loosen the pinch bolts. If you loosen the pinch bolts, then you should check that the bearings are still set right.
If you try to tighten the bearings by cranking down the centre bolt without loosening the pinch bolts, then you pull the star washer up or you can shear it, as it is only an M6.
Very likley you have to tighten the screw in the middle of the stem, aka the one in the middle of the cap that says "Giant". You don't want to tighten into too much however, because then steering will become very hard.
This video gives good explanations.
The procedure is both the same on roadbike and mountain bike.
If you feel unsure what to do, got to your LBS to repair this - if wheel/handlebar become desyncronized while riding the bike you'll face major injuries.