Bike 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. Bike bars out of sync This is a threadless headset. Stem Do y'all have any ideas?

  • In your last photo - it looks like you're missing a pinch bolt completely. One's not enough, and runs risk of you overtightening it. Get another bolt from a bike shop. --- scratch that I see its coming in from the far side.
    – Criggie
    May 29 '18 at 1:10
  • @Criggie: The top pinch bolt is visible on the first picture. But what worries me is the fact that the end is not visible in the threads. On all the bikes I have of the type the bolts sit deeper.
    – Carel
    May 29 '18 at 8:11
  • Yes they do look oddly shallow. A rule of thumb is 7 threads gives full strength. That is 7mm of thread for M6 bolts
    – Henry Crun
    May 29 '18 at 11:49
  • @Henry Crun: IMHO they have been replaced by shorter ones which might be an explanation for the slipping stem (?)
    – Carel
    May 29 '18 at 20:55

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.

  • Good answer addressing some incorrect information in other answers. May 28 '18 at 22:39

Tightening the two bolts on the back side of the stem should prevent it from turning freely. Make sure you align the stem and front wheel before tightening.

The bolt on the top is for adjusting the headset. If the headset does not have problems, you should not need to adjust that bolt.


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.

  • I forgot to say that this happens even though I have tightened my stem bolt to the max, without a torque wrench.
    – ayxzer
    May 28 '18 at 19:56
  • 2
    The centre bolt is used to adjust the bearing preload when the pinch bolts are loose , it does not clamp the stem.
    – Henry Crun
    May 28 '18 at 22:38
  • 2
    Sorry, this answer has incorrect information. The bolt in the steerer cap does not tighten the stem, it is for preloading the headset bearings. The two bolts in the back of the stem are for tightening the stem to the steerer tube. Follow the The GCN video and you'll be OK. May 28 '18 at 22:38

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