Wednesday, June 1, 2011

handle bar stem attaches to the bicycle frame is loose?

Bicycles have two different styles of headsets. The headset is the set of components on a bicycle which provide a rotatable interface between the bicycle fork (to which the front wheel is mounted) and the bicycle frame itself. Depending on which style of headset you have, your handlebar will be adjusted in different ways. The two types of headsets are threaded headsets and threadless headsets.

Threaded headsets

For your purposes, the threaded headset steering systems will be comprised of three major interacting parts: the fork, a quill style handlebar stem, and the handlebar itself. The fork has two fork blades and a centered steering tube with threads (spiraled grooves) at the top of it. The steering tube of the fork is inserted into the frame of the bike and threaded into the headset. The handlebar stem, or the piece that connects the steering tube of the fork to the handlebars themselves, is a quill-style stem. It is a basic system. The stem is inserted into the steering tube of the fork, and there is an expansion bolt on top of it that is tightened. By tightening the expansion bolt, a wedge attached to the bottom of the handlebar stem is spread, fixing it in place in the steering tube of the fork.

What you need to know to adjust the handlebar stem on a threaded headset:

1) Turn the handlebar in the proper direction, making sure that your front wheel is facing completely straightforward as well.
2) If the handlebar stem is completely loose, tighten the expansion bolt on top just a little to hold the stem in place. This will make aligning the front wheel easier.
3) Align the handlebar to the front wheel, using the tire as a visual aid to properly center the wheel with the handlebar. Once aligned, completely tighten the expansion bolt. Do not feel the need to over-tighten it. 4) Perform a fail test. Standing in front of the bike, fix the front wheel between your feet and try to twist the handlebar. If the stem moves in the steering tube, it's too loose.

Threadless headsets

For your purposes, the threadless headset steering systems will be comprised of three major interacting parts: the fork, a threadless handlebar stem, and the handlebar itself. The fork has two fork blades and a centered steering tube. As opposed to the threaded system, this steering tube does not have any threads on it (hence the term 'threadless.') The steering tube of the fork is inserted into the frame of the bike. Steering tubes on threadless forks are longer than those on threaded forks, so the steering tube will extend beyond the top of the headset by several inches. The threadless handlebar stem is then clamped down on the steering tube itself. The threadless handlebar stem generally has three bolts on it. There is the top bolt (located on the top of the stem, sometimes under a plastic cap), which threads into a star nut inside of the steering tube, and two clamp bolts (located on the side of the stem) which further clamp the stem down onto the steering tube of the fork. Once all three are tightened, the handlebar stem will be firmly fixed to the steering tube.

What you need to know to adjust the handlebar stem on a threadless headset:

1) Turn the handlebar in the proper direction, making sure that your front wheel is facing completely straightforward as well.
2) If your bike has come to you fully assembled, the top bolt shouldn't be loose. If it is, tighten it until there is no longer any play in your headset.
3) Align the handlebar to the front wheel, using the tire as a visual aid to properly center the wheel with the handlebar. Once aligned, completely tighten the clamp bolts. Do not feel the need to over-tighten them.
4) Perform a fail test. Standing in front of the bike, fix the front wheel between your feet and try to twist the handlebar. If the stem moves on the steering tube, it's too loose.

Note: When making any adjustments on a threadless stem, don't loosen or tighten the top bolt unless the clamp bolts are loose. Tightening the top bolt while the clamp bolts are still tight won't do anything but pull the star nut in your steering tube out of place ,this can be done at local bike repair part store.

How to Fix a Loose Stem on a Bicycle Handlebar

A handlebar stem is crucial to the operation of a bicycle. The stem serves as bridge between the handlebar and the fork. When handlebars are turned in any direction, the stem ensures that the fork and wheel turn in perfect union. There are two common types of stems--threaded and threadless. Threaded stems are "threaded" into the bicycle frame head tube. Threadless stems slide over the fork tube. Fixing a loose stem ensures tighter and more accurate steering.

Threaded Stem Tightening

  • Use a 6mm hex wrench to loosen the bolt at the center of the stem. The bolt may already be loose, but loosening it further allows for adjustment of the stem prior to tightening.

  • Position the stem until it is aligned with the top of the front wheel.

  • Hold the wheel in place with both feet, and use the 6mm hex wrench to tighten the bolt at the center of the stem.

  • Move the handlebar back and forth to be sure the bolt is not too tight. If the bolt is too tight, the steering will bind when turned. Loosen the bolt slightly if this is the case, and check the adjustment once again.

Threadless Stem Tightening

  • Loosen the bolts at the side of the threadless handlebar stem with a 4mm hex wrench. Depending on the individual stem, there will be either one or two bolts. Loosening any bolts before tightening them allows for adjustment of the stem.

  • Loosen the bolt at the center of the stem with a 5mm hex wrench.

  • Turn the stem so that it and the top of the front wheel are aligned. Straddle the wheel to keep it from moving, and tighten the bolt at the center of the stem.

  • Tighten each bolt at the side of the stem.

  • Turn the handlebar back and forth to check the adjustment. If the steering binds when turned, loosen both side bolts and the center bolt one-quarter turn. Retighten the side bolts, and check the adjustment once again.


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    The stem (Figure 1) attaches the handlebar, the part you hold with your hands when riding a bicycle, to the fork. In addition, the stem works with the handlebar to define your position on the bike.

    This section explains how to inspect, adjust, and lubricate your stem.

    Adjustable angle quill-type stem


    An improperly adjusted or tightened stem can cause you to lose control and fall. Make sure the stem is positioned and tightened properly before riding the bike.


    Stems are attached to the bike in two ways:

    Direct connect type stem
    Figure 2- Direct-connect type stem



    � Quill stems have a tube, or quill (Figure 1), fastened inside the fork by an expanding wedge.

    � Direct-connect stems (Figure 2) clamp to the outside of the fork steerer.










    Some modern bikes have sealed, non-adjustable headset bearings. All others require checking the adjustment even if they are sealed.

    While the bike is on the floor, use two tests to check your headset adjustment. First, lift the front wheel off the ground by holding the top tube of the frame. If the headset is loose enough, the handlebar and front wheel will flop to one side or the other. Next, apply the front brake or hold the front wheel from turning, and push the bike back and forth an inch or two on the floor. A loose headset will click a little.

    A headset which is loose will wear out soon. One which is already worn out will be gravelly or self-centering like an old-fashioned bar stool. This will impede safe steering. A headset which is too tight will also make steering difficult.

    The bikes headset adjusts like most bike bearings. There is an adjustable cup or cone at the top, and a locknut above that. By screwing the adjustable cone or cup closer to the bearings, the adjustment gets tighter. On many headsets there is an interlocking mechanism that means you will have to loosen the locknut several turns. On some there are two locknuts that must be loosened before you can make the adjustment. One may be hidden under a reflector bracket, or brake cable holder.

    bicycle headset

    Two types of bicycle handlebar stems are in current use. The most modern type clamps around the top of the bikes fork and is tightened with one or two allen head bolts. If you ride in all types of weather, the bolts should be removed, greased, and retightened. With any steel bolts that thread into aluminum alloy, a thin coating of grease is helpful years down the line, when corrosion would otherwise lock them together.

    The older style is called a 'threaded stem,' and has an interesting design. In order to adjust the stem height, you must first loosen the top stem bolt two or three turns and then bang it down with a soft hammer. This releases an internal wedge. While the stem is loose, take it out and grease the shaft of the stem and the wedge threads. To reinstall, tighten the bolt once you are satisfied with the position. There must be at least 2-1/2 inches of handlebar stem inserted into the fork. Check to see that the stem is properly tight by trying to turn the handlebar while trapping the front wheel between your knees. Also check that the handlebar is secure in the stem.

    bicycle headset

    Older style, but still common 'threaded' stem.

    Long bolt at left goes through stem, pulls wedge tight against inside of steering tube (fork).

    If you feel that the bicycles handlebar is too low, and the stem cannot be raised enough, consider purchasing a taller handlebar.