Typical Tools and Supplies Needed

• Hex or Allen Wrenches, for stem and top cap removal: Park AWS series.
• Race Remover, Park RT-1.
• Headset Press, Park HHP-2.
• Crown Race Installer, Park CRS-1.
• Degreaser, Citrus or Detergent based
• Crown Race Puller Park CRP-1. Other options are described below in procedures.
• Measuring Caliper
• Paper Towels

This article will discuss removing the old headset, installing and adjusting a new threadless headset. See also related articles:

• Visit our Headset 101 page 1 to read about Bicycle Headset Standards and Nomenclature.
• Visit our Headset 101 page 2 to read about Working with Traditional Threaded Headsets.
• Visit our Tool Use Tips page 1 to read about Reaming and Facing Tips.
• Visit our Tool Use Tips page 2 to read about Fork Crown Cutting Tips.
• Visit our Tool Use Tips page 3 to read about Fork Column Cutting Tips.
• Visit our Tool Use Tips page 4 to read about Fork Column Star Fangled Nut Tips.

To skip removal and installation, go to adjustment.

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 traveling 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 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 Park HTR-1 Head tube and Facing Tool. The fork can be machined with the Park CRC-1 Crown Race Cutter.

Threadless headset bearings are held secure by the stem. The upper adjustable bearing race will slide up and down on the steering column. The stem binder bolts hold the stem secure on the column, which keeps the race from moving. To adjust the race, the stem must first be loosened. There is a cap in the top of the stem that will apply pressure to the race when the stem is loose. A typical threadless headset on the bike, and the various parts are seen below.

1. If possible, disconnect cables shift and brake levers. Loosen stem and remove bars and stem from steering column.
2. Hold lower threaded race with spanner. Loosen and remove top locknut by turning counter-clockwise.
   
3. Remove front wheel if still in place.
4. Remove any washers/spacers from steering column.
5. Unthread and remove threaded race. Hold fork to prevent it falling to the ground. Note orientation of bearing retainer (if any).
6. Install Park Too RT-1 Race Tool with small side first upward through the bottom of the headset cups. Squeeze sides of prongs and pull tool fully into head tube. Do not press with hand on bottom of tool, as prongs will close and pinch flesh. A clicking sound will be heard as tool engages head tube cup.

   

7. Use a hammer at end of RT-1 and drive cup from head tube. Use care as cup approaches end of tube, as tool may fall to ground on last blow of the hammer.

   

8. Place RT-1 with small end first through remaining cup and remove.
9. Remove fork crown race from fork. Use the Park Tool CRP-1.

   

   
   
   
   
   An optional procedure to the above is to drive the race off using a punch and hammer. In some cases this may scar the fork and crown race.

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. Average the two reading. If the head tube more than 0.25mm smaller than the race, it may be reamed using the Park HTR-1 Head tube Reaming and Facing tool. If the race is between 0.01mm and 0.09mm, a different headset with a larger press race should be used. It is also possible to use a retaining compound such as Loctite® RC609. If the race is equal to or smaller than the head tube, a different race should be used. See discussion of press fit standards below.

The fork bearing race is pressed to the fork crown race seat. The fork race is smaller than the crown race seat. It is the race that expands as it is pressed. Races are commonly made of bearing steel, which tend to be very hard and brittle, and do not expand to the same tolerances as the head tube. The crown race seat should larger then the race by 0.1mm to 0.15. Much more difference may stress and crack the bearing race. When the crown race seat is too large for the fork crown race, it may be milled smaller with the Park CRC-1 Crown Race Cutter. If the crown race seat is only slightly larger than the race, 0.02 to 0.09mm, use a retaining compound such as Loctite® RC609. If the crown race seat is equal to or even smaller than the race, use a different race. See discussion of press fit standards below.

This discussion will assume use of the Park HHP-2 Headset Press and the Park CRS-1 Crown Race Setter.

1. Determine the acceptability of the headset press fit as described above.
2. Adjust threaded press plate of HHP-2 until top is flush with end of hex shaft thread
3. Remove sliding press plate and install cups onto guides. Guides are used to maintain cup alignment while pressing. Cup guides fit most 1-inch and 1-1/8-inch standard headset cups. Before using cup guide, insert guide into cup. If 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 (ex. Chris King® headsets). For headsets not fitting #530-2 cup guides, simply press using threaded press plate and sliding press plate. Pressure on the outer rim of aluminum head cups may visually scar the cups. If not using the guides, it can help to press one cup at at time.
4. Place upper headset cup on top of head tube. Hold one cup guide onto top threaded press plate and lower assembly through top headset cup.
5. Install second cup guide onto sliding press plate, and place lower cup onto guide.
6. Engage sliding press plate onto hex shaft, and push plate upward until headset cup meets head tube. Release lever. 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 handle clockwise slowly and inspect alignment of cups as cups enter head tube. Continue and press cups fully into head tube. If threaded press plate has bottomed on threads of hex shaft, turn threaded press plate counter clockwise until it is again flush with top of threads. Re-engage sliding plate to a higher notch, and continue to press cups. NOTE: Never use a "cheater bar" to extend leverage of handles. If cups will not press using handles, other problems are present and should be addressed.
8. Inspect for full seating where cups meet frame. A gap indicates incomplete pressing, as seen below.

   

9. Remove HHP-2 from bike. Unthread handle 1 turn, press lever of sliding press plate and remove tool from bike.

The fork crown race must be pressed to the fork crown. Determine acceptability of press fit as described above. Place race on fork crown and select most compatible CRS-1 insert. Place tool and insert over fork. Use hammer and strike top of tool until race fully seats. The sound will change as it seats. Inspect sides of race for seating.

Headset assembly

It is possible to replace retainer ball bearing with loose bearings. Grease cups to hold bearings, and place balls into cup shaped races. Leave a wide gap the size to two ball bearings, do not attempt to fully fill cup.

1. Grease bearing retainers and bearing race cups. NOTE: Do not grease steering column.
2. Install bearing retainers into cup shaped races.
3. Place fork through head tube.
4. Install adjusting race and race centering cone onto column. Press centering cone into adjusting race to help hold fork.
5. Install spacers and accessories as appropriate.
6. Install stem and snug stem bolts. Check for adequate clearance from top of column to top of stem. Add spacer under stem if necessary. Image below is view of steering column and stem. There is a gap between stem and top of column.

   

The threadless headset is adjusted by pressure from the top cap. The adjusting bolt threads into the "star fangled nut". For nut installation, see Star Fangled Nut Installation.

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.

1. Remove bolt and top cap to inspect steering column. Lubricate adjusting bolt and re-install cap and bolt by hand only. DO NOT TIGHTEN.
2. Loosen stem bolt(s) that secure 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 stem straight to wheel and gently secure the top bolt. Stop when any resistance is felt.
5. Tighten stem bolt(s).
6. Check for play by pulling back and forth on 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 upper portion of fork.
7. To adjust bearings, LOOSEN 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 adjustments as above until play disappears. Remember to loosen stem bolts before turning adjusting bolt in cap.
11. Check alignment of stem and tighten stem binder bolts fully.

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 ream 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 "conventional" headset standard sizing. There are now in use other standards and designs, see also Headset Standards and Nomenclature.

• One-inch Japanese Industrial Standard (JIS)
  • Common on many Asian manufactures bicycles, both road and MTB
  • Fork column outside diameter- 25.4mm (1")
  • 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
  • Stem diameter at quill- 22.2mm
• One-inch "Modern European" Standard
  • Many road bike and some MTB bikes
  • Fork column outside diameter- 25.4mm (1-inch)
  • 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
  • Stem diameter at quill- 22.2mm
• 1-1/8" Oversized
  • Many MTB bikes, tandems, some road bikes, BMX bikes
  • Fork column outside diameter- 1-1/8" (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
  • Stem diameter at quill-25.4mm (1 inch)
• 1-1/4 inch Oversized
  • Tandems, some MTB bikes
  • Fork column outside diameter- 1-1/4 inch (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
  • Stem size at quill- 1-1/8 inch (28.6mm)
• BMX (threaded, now older types)
  • Fork column OD- 25.4mm (1 inch)
  • Head cup OD- 32.7mm
  • Fork race ID- 26.4mm
  • Stem size at quill 21.15mm (0.866") (This allows use of thick steering column for strength)