JIS Compatible 1" threadless steerer Judy TT
- Thread starter andrew143
- Start date
From this is sounds like you can't
"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)
o Common on many Asian manufactures bicycles, both road and MTB
o Fork column outside diameter- 25.4mm (1")
o Head cup race OD- 30.0mm
o Acceptable head tube ID range- 29.75mm to 29.9mm
o Fork crown race ID- 27.0mm
o Fork crown seat OD acceptable range- 27.1mm to 27.2mm
o Threadless stem diameter- 25.4mm (1-inch)
* One-inch "Modern European" Standard
o Many road bike and some MTB bikes
o Fork column outside diameter- 25.4mm (1-inch)
o Head cup race OD-30.2mm
o Acceptable head tube ID range- 29.9mm to 30.1mm
o Fork crown race ID- 26.4mm
o Fork crown seat OD acceptable range- 26.5mm to 26.7mm
o Threadless stem diameter- 25.4mm (1-inch)"
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