Headset Tech

This information is intended for the mechanic who already possesses a familiarity with headset installation technique and who is interested in both the finer points of proper headset setup and trouble shooting for best headset performance.

--------------------------------------------------------------------------------

PREPARATION:

Frame Preparation:

Head tube preparation is one of the most important and most often overlooked elements in headset setup and performance. Especially with high end frames, it is often assumed that if a frame is new or already has a headset installed that the frame must have been properly prepared at the factory. This is very often not the case. We recommend a careful inspection of the facing and reaming of the head tube before installation.

Ream and face the head tube as necessary to ensure that the head tube is faced square and bored to the proper dimensions (see chart below).

Using a small file or sand paper, carefully remove any sharp edges or burrs and slightly round the inside edges of the head tube at the top and bottom to prevent shearing any metal from the cups during installation.

Clean to remove any chips, shavings, and/or cutting oil.

The proper press fit should be with no more than .1mm (.004") of interference. See chart below for correct head tube bore size. Do not file or otherwise remove material from the cups to make them fit.

Facing Tolerance:
The recommended tolerances for parallelness of the end faces of the head tube is not to exceed .075mm (.003"). Because facing tolerance is actually more complicated than just having the faces parallel, there is really no accurate way for the average bike shop to measure it. We recommend inking the faces of the head tube with a marker and using the facing tool to see that it removes the ink evenly and completely all the way around. Be sure to use the center guide in the opposing bore to assure alignment. Cut metal as necessary until all of the ink is removed.

Bore Sizing:
Head Tube Bore Size
1" Standard 30.1mm
1" BMX 32.7mm
1-1/8" 33.9mm
1-1/4" 36.9mm

Most reamers are .2mm under the nominal cup size while we recommend that the head tube bore be cut to .1mm under. The use of these reamers will produce varying finished bore sizes depending on the properties of the material being cut, and how much reaming is performed. With many materials you may net the correct bore size, however, on materials such as titanium or hard aluminum, the reamer may cut a clean bore in its exact size or smaller. On the other hand, if you face a lot of material with the reamer in the bore, the reamed bore may become oversized. Because the equipment necessary to determine exact bore sizes is not commonly found in most bicycle shops, attentively pressing the cups is the most practical test. It shouldnít be necessary to ìreef" on the press. An exceedingly difficult cup press is an indication that the head tube bore is undersized. If the bore is still undersized after reaming, it may be necessary to use another method to achieve the proper size. One trick we have used is to first press cheap steel headset cups to smooth and stretch the bore slightly. Then, remove and press our cups.

**Note**
The SteelSet headset uses a 1" deep cup skirt that will require a deeper bore than a conventional frame will have. The depth of the bore must exceed the depth of the skirt by a minimum of .25" (~7mm) for a total depth of 1.25" (~32mm) in order to get a cup removal tool behind the cup skirt. Even then, the geometry of the inside of the head tube may make SteelSet removal impossible and some frames are simply not compatible with the SteelSet. Reaming your head tube bore deeper than its stock condition may void your frame warranty and could critically weaken your frame. Check with your frame manufacturer before installing a SteelSet in your bike or reaming your head tube bore any deeper than they did at the frame factory.

(back to top)

Additional Edge Preparation:
Another aspect of preparation that is often overlooked is the chamfer on the inside of the head tube bore (top and bottom) and the removal of any sharp edges or burrs. We recommend a chamfer width of .25mm (.010"). A clean chamfer allows the cup to be pressed without shaving metal and to sit flat against the tube face without cutting into the small radius in the corner of the cup skirt. A cut in this area of the cup may cause cracks to form over time.

--------------------------------------------------------------------------------

INSTALLATION:

Pressing Cups:
For proper installation of the cups, the press fit sizing and facing should be within our recommendations (See Frame Preparation, Facing Tolerance, and Bore Sizing above). After reaming and facing or verification of tolerances, test fit cups by attempting to insert them into frame by hand. This test will only indicate an oversize bore condition but is very important. The cup should only begin to fit into the bore less than a millimeter. If the cup can be inserted by hand more than 1/3 the total distance, the bore is too big for a proper fit. This loose fit may result in movement of the cup in the frame possibly causing creaking noises and stretching of the headtube. Oversize cups are available in incremented sized to establish proper fit into frame.

NOTE: We do not recommend using Loc-Tite and/or similar products to make up for a loose fit as the load forces tend to exceed their holding power causing them to disintegrate and allow movement. While they may seem to work at first, they will usually fail in less than a year. We recommend using our headset installation adapters on the headset press. These adapters help ensure that pressure is applied evenly across the top of the cup and not on the bearing and that the cups press straight into the frame without damage from the tool.

For proper alignment and fit, both cups must be inserted parallel and square to the head tube. Press in both bearing cups using a headset installation press fitted with our press tool adapters.

Note: We do not recommend for or against the application of grease, antisieze, or Loc Tite while pressing in cups with a proper fit – we leave this choise to the discretion of the mechanic installing the headset.

Once the cups are pressed in, they should be seated flatly against the head tube. If they do not sit flat, the chamfer on the head tube bore may be inadequate or the head tube bore may not be parallel to the head tube axis.

(back to top)

Fork Preparation:
Reaming and facing of the fork may be necessary, but is not critical unless it is grossly out of parallel or oversize. The crown race face and seat should be square and parallel to the steerer tube and its outer diameter should not exceed .1mm larger than the inner diameter of the base plate. Most available reamers/facers are adequate for these tolerances. Clean to remove any chips, shavings, and/or cutting oil. The proper press fit should be with no more than .1mm (.004") of interference. See chart below for correct crown race seat size.

Base Plate Seat O.D. 1" Standard 26.5mm
1" BMX 26.5mm
1-1/8" 30.1mm
1-1/4" 33.1mm

Note: Do not attempt to install a baseplate that does not press properly. Centerpunching, knurling, and/or the application of LocTite or similar products is not recommended as the load forces will exceed the holding power of any of these treatments and eventually allow the baseplate to move. This movement will seemingly create a loose headset effect. Baseplates with undersized bores are available in incremented sizes for proper fit.

(back to top)

Installation of Base Plate:
Slide the base plate, conical side up, onto the steerer tube. With the beveled side of the base plate installation adapter against the base plate, use a crown race setting tool to set the base plate. The base plate installation adapter helps to protect the conical bearing contact surface on the base plate from damage due to the crown race installation tool.

--------------------------------------------------------------------------------

Additional Installation Notes for Threadless Systems:

NOTHREADSET™
Cut Steerer tube and Install Star Nut:
Insert fork into frame.

Remove o-ring from bearing cap and slide bearing cap, then any spacers and the stem over steerer tube. Scribe a line flush with top of stem.

Remove stem and mark another line 3mm below the first. Cut on the lower line with a hacksaw. When sizing the steerer tube it is important to make sure it extends into the stem as far as possible without colliding with the stem cap. In fact the steerer tube may extend through the stem as long as adequate spacers are placed between the stem and stem cap. This method has been very popular and effective in BMX installations.

Remove all sharp edges from inside and outside of steerer tube. With sandpaper, round outside edge of tube to avoid shearing the o-ring upon installation.

Thread star nut onto installation tool. If installation tool is not available, thread bolt well into star nut and use it to drive the star nut 15mm below the top of the steerer.

With a soft hammer or mallet, drive star nut straight into steerer tube until tool contacts top of steerer.

Unscrew tool from star nut.

Use extreme caution when cutting and installing star nut to avoid injury.

Final Assembly and Adjustment:
Prior to installing the bearing cap on a threadless steerer tube, round off the top of the steerer tube to avoid sheering the o-ring on the inside of the bearing cap.

Re-install o-ring into bearing cap.

Insert fork into frame.

Taking care not to shear o-ring, slide bearing cap, any spacers, and then stem over steerer tube. Place stem cap on top of stem and insert screw through cap, threading into star nut. Tighten approx. 4-10 in.-lb. (Max. 15 in. lb.)

Adjust alignment of stem and secure according to stem manufacturers specifications.

Check headset for proper adjustment. When properly adjusted, the fork will rotate smoothly without play or restriction. Some settling may occur after 1st few rides; readjust if necessary. If necessary, adjust cap nut and stem bolts as above until proper adjustment is achieved. NOTE: New seals will produce some resistance in rotation for the first 50-100 hours of use. Avoid confusing this with rubbing or binding that may result from improper installation or stems that are not properly faced.

A Note on Threadless Stems:
We recommend using stems with a split clamp and either one or two bolts (preferably two).

It is important to check the bottom face of all threadless stems. Many are not square to the steerer tube and may cause headset parts to sit unevenly or rub on the cups.

(back to top)

--------------------------------------------------------------------------------

Additional Installation Notes for Threaded Systems:
GRIPNUT™

Size and cut steerer tube:
Insert fork into frame. Steerer tube should protrude 11-14mm above top of bearing cup. Cut steerer tube if needed.

Clean the steerer tube removing all metal chips, burrs and grease.

Assembly of GripNuts™:
Make sure the thread on the lock ring and the inside thread of the adjusting ring are lubricated thoroughly with anti-seize compound or heavy grease. Also apply grease to the tapered surfaces of the thread collet and lock ring.

Place the thread collet into the threaded hole of the adjusting ring, positioning the key on the collet in the corresponding slot.

Screw the lock ring into the adjusting ring/collet assembly until the collet has very little float inside the assembly.

Final Assembly and Adjustment:
Once the GripNut™ is securely on the steerer tube (about 4-5 turns and at least 1/8" prior to contacting the bearing), tighten the lock ring into the adjusting ring until it feels as though the GripNut™ is dragging as it turns on the threads.

Once you feel this drag, advance the entire GripNut™ as a unit down to touch the bearing (using headset wrenches on both the lock and adjusting ring if necessary).

Adjust the preload on the bearing and finish tightening the GripNut™ lock and adjusting rings together to 130-150 in/lb.

TEST: Using both wrenches, try to turn the GripNut™ as a unit in the loosening direction. It should be extremely difficult, if not impossible, to turn. If it turns easily, continue to turn the entire unit 1/4 turn in the loosening direction and re-torque.

(back to top)

2NUT™
Size and cut steerer tube:
Insert fork into frame.

Thread adjusting nut onto fork.

To size steerer tube length, make sure there are at least 5 full threads above the adjusting nut available for the lock nut.

Final Assembly and Adjustment:
Adjust our 2Nut™ headset as you would any traditional lock and adjusting nut headset.

(back to top)

--------------------------------------------------------------------------------

HEADSET SERVICE:
In general, headset service should be done at least every two years. In dry climates, service intervals may be longer. In wet climates, service may be necessary as often as every 6 months.

You may service your Chris King headset while in the frame using a light solvent based lubricant (e.g., Bullshot aerosol or WD-40,) to flush the bearings. If you have access to the correct tools for the proper removal and reinstallation of Chris King bearing cups, we have found it easier and more effective to remove the cups and use a solvent tank.

Remove snap ring and seal:
Take a pointed instrument, such as a penknife, insert it at the split in the snap ring, and lift the pointed end out. Once the pointed end is free, the remainder of the ring can be removed easily. Lift out the inner seal. At this point the bearing will be exposed.

Clean and re-grease the bearings and replace the seal and snap ring:
With a small brush (e.g., a tooth brush) clean the bearing while rinsing with solvent. If the bearing has been neglected and is frozen, let it soak for a few minutes. Then, rotate the inner race back and forth to work it free. Rinse in solvent and blow dry with an air hose to remove any excess solvent. Test the bearing for smoothness. If the bearing was frozen for too long it may have become damaged or may be too rough and need replacing. However, if the bearing has lost only some of its silky smoothness, it may not be evident at the handlebar once re-greased and reassembled. If bearing replacement is necessary return cup(s) to us to have a new bearing(s) installed.

Re-grease the bearings using Bullshot or any other waterproof grease. Carefully wipe off the inner seal and reinstall. Finally, insert the pointed end of the snap ring into the snap ring groove, working it around the bearing until the other end seats and a small gap is noticed. Inspect the rest of the parts for any wear. At this time, you are ready to reassemble the headset and adjust.

(back to top)

--------------------------------------------------------------------------------

HEADSET TROUBLE SHOOTING
Common questions and the likely solutions:

We are also available to answer your technical service questions during business hours Monday through Friday at 800.523.6008.

(back to top)

My headset always rattles and it won't tighten up when I attempt an adjustment.
The steerer tube may be too long and interfering with the stem cap (threadless) or lock nut (threaded). Solution: Cut the steerer tube or install spacer(s) so that there is the necessary clearance.

(back to top)

My headset won't adjust correctly. It's either too tight or too loose.
1. The bearings may be dirty or frozen. Solution: Service the bearings.
2. The frame and/or fork and/or stem may not be properly prepped. This can cause the top or bottom pieces to rub on the cups or the steerer tube to rub on the inside of the bottom cup. This is most commonly found on titanium and hard aluminum frames. Solution: Properly ream and face the frame and/or fork and/or stem and check for the proper head tube bore size.

(back to top)

My headset seems to be adjusted correctly, but it binds when the bars are turned.
1. The frame and/or fork may not be properly prepped. This can cause the top or bottom pieces to rub on the cups or the steerer tube to rub on the inside of the bottom cup. This is most commonly found on titanium and hard aluminum frames. Solution: Properly ream and face the frame and/or fork and check for the proper head tube bore size.
2. If it is a threadless system, the bottom face of the stem may not be perpendicular to the bore thus causing the bearing cap to cock and rub the cup. Solution: Face the bottom surface of stem square with steerer tube.
3. If it is a threaded system, the threads on the steerer tube may not be straight. Solution: Replace the steerer tube.
4. The bearings may be dirty. Solution: Service the bearings.

(back to top)

My headset won't stay tight--It just keeps coming loose.
A properly set up Chris King headset shouldn't need adjustment more than once or twice a year (depending on riding style). If your headset needs adjustment more often than once a month, check for the following:

Threadless models:
1. The pinch bolt on the stem may not be tight enough or the clamp method may be inadequate. We have found that stems with a split and one or two pinch bolts hold better with less chance of distorting the steerer tube than internal wedge designs. Solution: Tighten or replace the stem.
2. Steerer tube may not extend far enough into the stem. Solutions: 1) If spacers are being used to elevate the stem, remove as necessary to lower the stem to within 3mm of the top of the steerer tube; 2) Replace the steerer tube and be sure to cut steerer tube to extend to within 3mm of the top of the stem (steerer tube must not interfere with the stem cap).
3. Steerer tube may be pulling through the crown. This is more common with older suspension forks. Solution: Contact the fork manufacturer to determine the proper remedy for the steerer tube pulling through the crown. 4. Demanding applications (such as trials and BMX) can generate strong leverage on the handlebars and walk the stem up the steerer tube. Solution: In this case it is best to extend the steerer tube through and above the stem. Spacers may then be used on top of the stem to allow proper functioning of the stem cap. (We learned this trick from the boys at GT BMX racing.)

Threaded models:
(GripNut™)
1. GripNut™ may not be tight enough or may otherwise be improperly adjusted. If the lock ring was too loose as the GripNut™ was tightened to adjust the preload on the bearing, the collet will not clamp properly as the lock ring is tightened to hold the GripNut™ in place. Solution: Readjust GripNut™ according to the above instructions.
2. The adjusting ring may be rubbing on top cup due to misalignment of either the cup or the threads on the steerer tube. Solution: For misaligned cups, face and ream the frame; for misaligned threads, replace the steerer tube.
3. GripNut™ lock ring may be bottoming out on the top of the steerer tube. Solution: Re-cut the steerer tube so that there is a gap of approximately 1mm below the inner lip of the lock ring.

(2Nut™)
1. The lock and adjusting nuts may not be locked together tight enough. Solution: Tighten lock and adjusting nut together.
2. Adjusting nut may be rubbing on the top cup due to misalignment of either the cup or the threads on the steerer tube. Solution: For misaligned cups, face and ream the frame; for misaligned threads, replace the steerer tube.
3. The threads on the fork steerer tube may be undersized (in pitch diameter). If this is the case the adjusting nut will fit loosely on the threads. Solutions: 1) Switch to a GripNut™ top assembly--the GripNut™ will clamp onto undersize threads; 2) Replace steerer tube; 3) Regenerate the threads on the existing steerer tube after wishing metal back.
4. The lock nut may not be threaded far enough onto the steerer tube. It should thread on a minimum of four full turns to hold properly. Solutions: 1) Switch to a GripNut™--the GripNut™ offers a shorter stack height; 2) Replace steerer tube and cut long enough to allow adequate engagement on the lock nut.

(back to top)

My headset loosens over time.
Check all of the possible causes for "...loosens quickly,"as well as:
1. The head tube may be out of parallel. This can cause looseness due to premature wearing of the conical bearing contact surfaces. Solution: Properly ream and face the frame and/or fork. Check conical bearing contact surfaces for excessive wear and replace if necessary.
2. Cups may be loose in the head tube. This can happen if the head tube bore is oversize or if the material of the head tube is extremely soft and/or stretched out. Solutions: 1) If the head tube is oversize, we may be able to provide cups with oversize skirts; 2) If the head tube material is soft and/or stretched, contact the frame manufacturer for possible remedies.
3. The skirt of the headset cup or the head tube may be cracked. Solutions: 1) Contact us to replace a cracked cup. Then, check the head tube bore for proper size and ream if necessary. Additionally, the head tube bore chamfer may be inadequate or absent--cut or file according to above instructions; 2) Contact frame manufacturer regarding a cracked head tube.

(back to top)

My headset creaks and/or makes a ticking noise.
The following components are more often the cause of creaks and ticking noises than headsets:

Suspension fork:

Steerer tube and crown - both press fit and clamped
Stanchion tubes
Fork brace bolts

Bars, stem, cables
Cracked head tube

If these components are not the source of the noise, check the following:
1. Improper reaming and/or facing (e.g., cups not parallel) can cause abnormal wear on the conical bearing contact surfaces which can cause creaking and/or ticking noises. Solution: Check and properly ream and face head tube as necessary and check conical bearing contact surfaces for excessive wear and replace if necessary.
2. The conical bearing contact surfaces on the base plate may be completely dry. If the bike is ridden in extremely wet conditions, ridden or transported in the rain, or washed with high pressure spray, the lubrication on these surfaces may have been washed away. Solution: Lay a thin layer of antisieze on the conical contact surfaces.
3. The base plate may be loose on the crown race seat. This can result from a stretched base plate or an undersized crown race seat. Solutions: 1) Replace base plate; 2) Contact us for an undersized base plate.
4. The cup(s) may be loose in the frame. Solution: Contact us for possible oversized cups.
5. The head tube bore may be "bell mouthed". The cups then press fit only at the innermost ends. Solutions: Contact us with an accurate measurement of the head tube and the extent of the "bell" and we may be able to provide oversize cups that work in the head tube. If the degree of bell mouth is extremely pronounced, you may need to contact the frame manufacturer for possible remedies.
6. The bearings may be dirty or seized. Solution: Service the bearings.
7. On a NoThreadSet™, the bottom surface of the stem may be sliding on the bearing cap. This can happen if the o-ring is sheered in installation. Solution: Replace the O-ring and file the top of steerer tube to prevent sheering upon reinstallation of the bearing cap. Apply anti-sieze to the bottom of the stem where it contacts the bearing cap.
8. The steerer tube may be undersize. Steerer tubes should be ±.025mm (.001") of the nominal size. We often see steerer tubes as much as .25mm (.010") undersize. Solution: Replace the steerer tube.
9. Bottom surface of stem may not be flat. Solution: Face bottom of the stem.

(back to top)