Ad astra per aspera.
Tightening stem bolts and headset cap bolt
A few years ago I bought a new stem for my MTB. Thinking it would be a pretty straight forward process to make the switch, I went ahead and loosened the headest cap bolt and removed it. I then loosened the stem bolts and took off the old stem and replaced it. My problem is this - when I went to tighten it back up I had no issue. I put the headset cap back on and the bolt and tightened it back down. Here's where my problem began. For some reason I couldn't get the cap to tighten down and stay in place. So, is there a specific order or process to follow when re-tightening these? I'd like to flip the stem on my road bike this weekend but I don't want to end up in the LBS again asking for help.
Any advice you guys can give would be great.
The top cap and bolt are only used to preload the bearing system in the headset, and only works if the stem pinch bolts are loose. Once you tighten the stem pinch bolts, you can essentially remove the top cap and bolt and put them into your toolbox.
Originally Posted by roadnoob412
I'm not sure what you mean by "couldn't tighten down and stay in place". Assuming the pinch bolts are loose and you tried to tighten the top cap bolt, but nothing was happening, perhaps the star nut inside the steerer is slipping, or the bolt is not long enough to reach the star nut.
My guess is that the new stem clamp is not as long as the original and you would need a spacer to put under the stem to get the headset tightened. See Park Tool site for the detailed instructions.
Yeah, it's important that the top of the stem be about 1/8th inch above the steer tube.
The pinch bolts must be loose as you tighten the top cap bolt so that the stem can slide down the steer tube. Only don't compress the stack so much the the headset bearings are in a bind.
What the others have said is right on. Go to the parktool website and look for their section on threadless headsets. There's instructions on how to do that.