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What is the purpose of the top cap and screw on the top of the headset? How does it work in relation with the stem/ fork or whatever it attaches to? I am kinda new to bike maintenence and need some advice. I recently put on a new Azonic Aggro stem and had to take the cap off and now it is loose and needs to be tightened. How do I install it and how does it work/ what does it do?

Thanks, Shredder111:cool:

 

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well when you tighten the screw into the starnut, the top cap pulls the stem down and everything tightens up causing the heaset cone to set. without a topcap it would be really hard to get a headset adjusted just right, almost impossible, because you need that cone to set or your headset will be loose. untighten the sten bolts that clamp the stem to the steertube then tighten the headsetbolt as much as you can before you feel any drag when you turn the bars. then line up your bars and tighten the stem bolts.
 

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Make sure your strear tube is a mm or 2 shorter than the top of your head set or put a small spacer on top if you don't feel like cutting your tube. That small gap is nessary for the top cap to pull up and tighten the rest of the set up.
 

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basics

tightens down headset.....you crank on that to get it all together then back off to make it spin freely....then tighten everything else down
 

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yeah what xsl_will said. if you dont know, you should bring it to your lbs for them to explain... its a little hard to type out without having the parts in your hands. basicall though, take off that cap, the stem and if you have one loosen your top crown. put you top crown on loosly and then the stem, just slide it on, dont tighten anything yet. if the steerer tube is at least 2 or 3mm below the top of the stem your in good shape. now thread in the cap and tighten it down till you feel resistance when turning the wheel. you should have to turn the actual wheel not the bars because they should be loose. now back it off till it feels smooth. tighten the crown first then your stem. now, if you turn the bars all the way in one direction and let go with the front end off the ground, the wheel should go almost if not all the way back to center. if is doesnt its too tight. loosen the stem then crown and back the cap off a little more.

oh and if you see that the steerer tube is poking out of the top of the stem and you dont have that 2 to 3mm. you need a spacer. i would put it under the stem. on the other end of the spectrum, if the steerer tube if more than about a quarter inch below the top of your stem your in trouble. you either need to take out any spacers you might be using, go to your lbs to try to find a longer bolt for that cap or get a stem with a shorter tube.

hope that helps
 

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Here's how to adjust a headset:

-Loosen your stem bolts
-Loosen the bolt on top of your headset until there's a fair bit of play
-Tap the front tire inwards so you hear the rattle of the play, and tighten the bolt on top until you just hear the play go away
-Tighten your stem
-Repeat as neccesary
 

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First off, let the bike shop install it. The old hammer and 2x4 thing doesn't fly as you can crack your head tube. Also you might not have it in straight which will screw up the headtube by ovalizing it...

To answer your ?.

You need a star nut inside your steerer tube of your fork. The bolt that sticks through the top cap goes into the star nut (Let the shop install it if it's not already installed). Tighten the bolt and it'll tighten the headset, spacers and stem together. Leave a couple mm's between the top of the stem and the top cap. Hold the front brakes and move the bike back and forth. Tighten the top bolt until you get rid of all the play. Don't overtighten it! If you overtighten it, it will be "twitchy". Tighten the bolts on the side of the stem to secure everything in place. If you tightened the top bolt and there's still play in it, you need to add a spacer or cut the steerer tube some. Fahn
 
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