Threadless Headset Removal, Installation and Adjustment
Level of Difficulty: intermediate to advanced
This article will discuss removing the old headset, installing and adjusting
a new threadless headset.
For information on headset types and nomenclature see Headset
You can also go directly to adjustment.
Typical Tools and Supplies Needed
- Hex Wrenches, for stem removal
- Race Remover
- Headset Press
- Crown Race Installer
- Punch and hammer for fork race removal
- Measuring Caliper
Bearings on a bicycle allow the parts to rotate relative to one another.
The headset allows the fork to turn smoothly while riding. Bicycles, and
all two wheeled vehicles, make small self-corrections in steering while
travelling forward. If the headset is pitted or worn, these corrections
are not made smoothly and handling suffers. Very worn headsets tend to
"lock up" when the front wheel is pointing straight. Pick up the front
of the bike, and gently swing the handlebars back and forth from center.
Pitting in the cups will cause the headset to stick as it passes through
center position. A pitted headset should be replaced. New headsets are
pressed into the frame and fork.
All bearings on a bike have some friction as they rotate. This is normal
and does not affect the ride. Better quality bearing surfaces are ground
smoother and will have less friction and resistance to turning. Adjustable
type bearing systems use two opposing races which can be moved relative
to one another. If the adjustment is too tight there will be too much
pressure on the bearing surfaces and balls and the system will quickly
wear out. If the adjustment is too loose there will be movement or "play"
between the parts. This will cause a knocking in the bearing surfaces
and again they will wear out prematurely. Generally, the bearings should
be adjusted as loose as possible without play or knocking in the system.
The upper and lower bearing surfaces are connected by the steering column.
The two bearing surfaces need to be parallel in order for the bearing
to operate smoothly. If the upper and lower surfaces of the head tube
are not cut parallel, the bearings will tend to bind as the fork is rotated.
This can lead to premature bearing wear and a less than desired adjustment.
The head tube can become deformed by welding or simply less than adequate
manufacturing techniques. The base of the fork steering column should
also be cut square to the fork. If it is not properly machined, the fork
crown race will not sit square to the steering column and will add to
the binding effect. The head tube can be machined (faced) so the surfaces
are parallel by using the HTR-1 Head tube and Racing Tool. The fork can
be machined with the CRC-1 Crown Race Cutter. This process is best left
to professional mechanics.
1. If possible, disconnect the cables from the shift and brake
levers. Loosen the stem and remove the bars and stem from the steering
column. Note: If you are not removing the bars completely, use care not
to kink or damage the housing when hanging the bars on the bike.
2. Remove any washers/spacers from the steering column.
3. Pull the fork from the bike. It may be necessary to use a mallet
and tap the top of the steering column, driving the fork downward. Once
the fork is driven down as little as 25mm (one inch), lift the fork back
up and remove the center cone from the adjusting race. Remove the fork.
4. Note the orientation of the bearing retainer (if any).
5. Install a race removing tool (such as the Park Tool RT-1 Race
Tool) with the small side first upward through the bottom of the headset
cups. Squeeze the sides of the prongs and pull the tool fully into the
head tube. Do not push the bottom of the tool up by hand, as the prongs
will close and pinch your flesh. A clicking sound will be heard as the
tool engages the head tube cup.
6. Use a hammer on the end of the RT-1 and drive the cup from
the head tube. Use care as the cup approaches end of tube, as the tool
may pass right through the head tube and fall to the ground (or on your
foot!) on the last blow of the hammer.
7. Place the RT-1 with the small end first through remaining cup
8. Remove fork crown race from fork. Use the Park Tool CRP-1.
An alternative technique is to drive the race off using a punch and hammer.
In some cases this may scar the fork and crown race.
Installing Headset Bearing Races
Headset bearing races require a press fit. There must be an adequate
diameter difference between the two pressed surfaces. Typically, a 0.1mm
to 0.25mm difference is considered adequate for the head tube to cup difference.
When these cups are pressed, the head tube will flex and enlarge slightly
to allow the cups to press. This tension is what keeps the cups tight.
Use a caliper to measure the outside diameter of the cups. Next, measure
the inside diameter of the head tube in two places, each 90 degrees from
the other. It is common these numbers will differ, so simply take the
average. If the head tube is more than 0.3mm difference, it should be
reamed using the HTR-1 reaming and facing tool. If the difference is less
than 0.1mm, use a retaining compound such as Loctite® RC609.
Fork crown race difference to the fork crown should be 0.1mm to 0.15.
Much more difference than this may cause too much stress on the bearing
race. When the fork race is pressed, it the race that expands. Races made
of bearing steel are very hard and tend to be brittle. The same tolerances
in the head cup fit do not apply to the fork crown race fit. If the steering
column is too large for the fork crown race, it should be milled with
the CRC-1 Crown Race Cutter. If the difference is less than 0.1mm, use
a retaining compound such as Loctite® RC609.
Pressing Headtube Cups
This discussion will assume use of the Park Tool HHP-1 Headset Press
and the CRS-1 Crown Race Setter.
1. Determine the acceptability of the headset press fit as described
2. Adjust the threaded press plate of the HHP-1 until the top
is flush with the end of the hex shaft thread
3. Remove the sliding press plate and install the cups onto guides.
(Note: Use care not to pinch your hand between the lever stop pin and
press plate body.) Guides are used to maintain cup alignment while pressing.
Cup guides fit most 1in and 1-1/8in standard headset cups. Before using
the cup guide, insert guide into cup. If the guide appears to jam or is
a tight fit, do not use cup guides for that particular headset
cup. Do not use cup guides #530-2 if guides press on any pre-installed
cup-bearing unit (such as Chris King® headsets). For headsets not fitting
#530-2 cup guides, simply press using the threaded press plate and sliding
press plate. Pressure on the outer rim of aluminum head cups may visually
scar the cups.
4. Place the upper headset cup on top of the head tube. Hold one
cup guide onto the top threaded press plate and lower the assembly through
the top headset cup.
5. Install the second cup guide onto the sliding press plate,
and place the lower cup onto the guide.
6. Engage the sliding press plate onto the hex shaft, and push
the plate upward until the headset cup meets the head tube. Release the
lever. The sliding press plate lever must be engaged in one of seven hex
shaft notches. Pull downward on lower press plate to test engagement.
7. Turn the handle clockwise slowly and inspect the alignment
of the cups as cups enter head tube. Continue and press the cups fully
into head tube. If the threaded press plate has bottomed on the threads
of the hex shaft, turn the threaded press plate counter clockwise until
it is again flush with the top of the threads. Re-engage the sliding plate
to a higher notch, and continue to press cups. Note: Never use
a 'cheater bar' to extend the leverage of the handles. If the cups will
not press using the handles, other problems are present and should be
8. Inspect for full seating where the cups meet the frame. A gap
indicates incomplete pressing, as seen below.
9. Remove the HHP-1 from bike. Unthread the handle one turn, press
the lever of sliding press plate and remove the tool from the bike.
Pressing Fork Crown Race
The fork crown race must be pressed to the fork crown. Determine acceptability
of press fit as described above. Place the race on the fork crown and
select the most compatible CRS-1 insert. Place the tool and the insert
over the fork. Use a hammer and strike the top of the tool until the race
fully seats. The sound will change as it seats. Inspect the sides of the
race for seating.
The Star-fangled Nut
The threadless headset is adjusted by pressure from the top cap. The
adjusting bolt threads into the "star fangled nut". Installation of the
star-fangled nut will be addressed in a later article, as it is usually
not necessary to replace the star-fangled nut when replacing the headset.
If the headset is using bearing retainers, check the orientation of the
retainers before installing. Retainers have only one correct orientation.
The open side of the ball retainer should face the cone shaped race, not
the cup shaped race.
It is possible to replace retainer ball bearings with loose bearings.
Grease the cups to hold the bearings, and place balls into the cup shaped
races. Leave a wide gap the size of two ball bearings, do not attempt
to fully fill cup.
- 1. Grease the bearing retainers and bearing race cups. Note:
Do not grease steering column.
- 2. Install the bearing retainers into the cup shaped races.
- 3. Place the fork through the head tube.
- 4. Install the adjusting race and race centering cone onto the column.
Press the centering cone into the adjusting race to help hold the fork.
- 5. Install spacers and accessories as appropriate.
- 6. Install the stem and snug the stem bolts. Check for adequate clearance
from top of column to top of stem. Add spacer(s) under the stem if necessary.
Image left shows the steering column and stem. There is a gap between
the stem and the top of the steering column. This gap is necessary for
adjustment of the headset.
Threadless headsets work on the same principal as threaded headsets.
The bearing races need to press against the bearings. The bolt in the
top cap will put pressure on the stem, which presses on washers below
the stem, which press on the bearing races, which press against the bearings.
Note: The cap and bolt at the top of the stem do not secure the
stem onto the steering column. The bolt or bolts on the side of the stem
keep the stem from moving once the adjustment is made. The cap is used
for bearing adjustment only.
Begin by removing the adjusting bolt in the center of the steering column.
Next, remove the top cap. There may be a star-shaped nut or other fittings
inside the steering column. The bolt threads into this fitting and pulls
on the fork against the headset bearing surfaces, which acts to tighten
the adjustment. Note the height of the steering column relative to the
stem. It should be about 3mm (1/8in) below the level of the stem. The
stem needs to press down on the spacers in order to adjust the bearings.
If the steering column is level with the top of the stem, another spacer
is needed below the stem.
- 1. Remove the bolt and top cap to inspect the steering column.
Lubricate adjusting bolt and reinstall the cap and bolt by hand only.
Do not tighten.
- 2. Loosen the stem bolt(s) that secure the stem to the steering
column. Lubricate these bolts if they are dry. Note: Do not lubricate
inside stem or on steering column surface.
- 3. Wiggle the stem side to side to see that it is loose. If
the stem is jammed or rusted frozen to the steering column, no adjustment
can be made.
- 4. Align the stem straight to the wheel and gently secure the
top bolt. Stop when any resistance is felt.
- 5. Tighten the stem bolt(s).
- 6. Check for play by pulling back and forth on the fork. Turn
the handlebars in different directions while checking for play. There
may be play at this early setting. Use care when grabbing suspension
forks, because the legs may have play. Grab the upper portion of the
- 7. To adjust bearings, loosen the stem bolt(s).
- 8. Turn adjusting bolt in center cap only 1/8th turn clockwise.
- 9. Secure stem bolts, check for play again.
- 10. Repeat steps 7, 8 and 9 until play disappears. Remember
to loosen the stem bolts before turning adjusting bolt in cap.
- 11. Check alignment of stem and tighten stem binder bolts fully.
Note: Another test of play is to place the bike on the ground
and grab the front brake tightly. Press downward on the handlebars and
rock the bike forward and back. A knocking sensation may indicate a loose
headset. In effect this does the same thing as grabbing and pulling on
the fork. However, play in the brake caliper arms may also cause a knocking.
Front suspension forks may also have play in the legs, which can cause
If the adjustment seems very tight, there may be other problems in the
headset. Bearing surfaces may be worn out, or the ball bearing retainers
may be upside down, or a seal may be improperly aligned. If play always
seems present no matter the adjustment, the steering column may be too
long for the stem and top cap. Add spacers beneath stem in this case.
Bearing Adjustment and "Feel"
Bearing surfaces are made from hardened steel. The surfaces are cut typically
by grinding. Round ball bearings roll on the curved surface of the cup
and cone. Even the highest quality bearing surfaces will have slight grinding
marks. In the left image above is a high quality cone magnified two hundred
times. Notice the parallel marks from the grinding stone. Also note a
slight pit from wear. The right hand image is a bearing magnified the
same amount. It does show some surface marking, but is generally smoother
than the cone or cup. Bearing surface smoothness will vary between manufacturers
and between models. Some bearing system will simply "feel" smoother because
they are smoother. This is why it is difficult to adjust by using
a subjective feeling of smoothness. Generally, adjust bearings for the
loosest setting that has no knocking or play, regardless of this relative
Headset Sizing Standards
There are several standards for headsets found on bicycles. Headsets
are named by the diameter of the steering column, not by the press diameter
of the cups. For example, a "one-inch" headset is for bikes with one inch
diameter steering columns.
There are three different headset standards using one inch forks. Two
are common, the JIS and "Modern European" standard. The older BMX standard
is seen less and less. The JIS and "Modern European" standard differ only
in the diameter of the press fit. The two standards are NOT interchangeable,
even though both use 1" x 24 TPI threading. A bicycle that was machined
to the JIS standard may be reamed and cut to the "Modern European" standard.
The head tube would be reamed to 30.0mm ID and the fork crown seat cut
down to 26.5mm. A bicycle that was made in the "Modern European" standard
can not use a JIS headset.
Below is a list of headset standard sizing.
- One inch Japanese Industrial Standard (JIS)
- Common on many Asian manufactures bicycles, both road and MTB
- Fork column outside diameter: 25.4mm (1in)
- Head cup race OD: 30.0mm
- Acceptable head tube ID range: 29.75mm to 29.9mm
- Fork crown race ID: 27.0mm
- Fork crown seat OD acceptable range: 27.1mm to 27.2mm
- Threadless stem diameter: 25.4mm (1in)
- One inch "Modern European" Standard
- Many road bike and some mountain bikes
- Fork column outside diameter: 25.4mm (1in)
- Head cup race OD: 30.2mm
- Acceptable head tube ID range: 29.9mm to 30.1mm
- Fork crown race ID: 26.4mm
- Fork crown seat OD acceptable range: 26.5mm to 26.7mm
- Threadless stem diameter: 25.4mm (1in)
- 1 1/8 inch "Oversized"
- Many mountain bikes, tandems, some road bikes
- Fork column outside diameter: 1 1/8in (28.6mm)
- Head race cup OD: 34mm
- Acceptable head tube ID range: 33.75mm to 33.9mm
- Fork crown race ID: 30.0mm
- Fork crown seat OD acceptable range: 30.1mm to 30.2mm
- Threadless stem diameter: 28.6mm (1 1/8in)
- 1 1/4 inch "Oversized"
- Tandems, some mountain bikes
- Fork column outside diameter: 1 1/4in (31.8mm)
- Head cup race OD: 37mm
- Acceptable head tube ID range: 36.75mm to 36.9mm
- Fork race ID: 33mm
- Acceptable fork race seat OD: 33.1mm to 33.2mm
- Threadless stem diameter: 31.8mm (1 1/4in)
- Threadless BMX
- BMX threadless is same as 1 1/8in above
Content for this page courtesy Park Tool. For more on Park's range of
tools and workshop supplies, see: Park
Tool 's website
Suggested Park Tools
- AWS series hex wrenches
- RT-1 race remover
- HHP-1 headset press
- CRS-1 crown race installer
- CB-1, CB-5 degreaser
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