Threaded to Threadless



P

Peter Howard

Guest
I've used Ebay finds to **** up an old MTB frame (Shogun Trailbreaker) from
the early 1990's because it fits me well, purports to be CrMo steel and is
of non-compact format without the characteristic willowy seatpost.

While renovating it I was intrigued to find that the steerer tube is
threaded 1 1/8" size which takes a 1" quill stem with wedge. I'm more used
to the skinny steerers and quills on elderly road bikes.

I wonder if it is possible to convert to a fork with threadless steerer tube
simply by fitting a threadless headset? The excellent Mr Sheldon Brown's
pages suggest that the frame cups for both threaded and threadless 1 1/8"
headsets are 34 mm od if I am reading him right.

I don't particularly want to take it apart again and bash out the frame cups
unless I'm sure so I'd like to hear from anyone who's done it.

Peter
Australia.
 
Peter Howard wrote:
>
> I wonder if it is possible to convert to a fork with threadless steerer tube
> simply by fitting a threadless headset?


For a 1-1/8" or 1-1/4" headset, yes. For a 1" headset, maybe. ISO
(30.2mm cups) and BMX (32.7mm cups) one inch headsets have threadless
versions. JIS (30.0mm), French, etc. are available only in nutted
versions.

> I don't particularly want to take it apart again and bash out the frame cups
> unless I'm sure so I'd like to hear from anyone who's done it.


Go ahead; there is only one set of diameter standards for 1.125"
headsets, and they are all compatible with the same head tubes.

Chalo
 
I wrote:
>
> JIS (30.0mm), French, etc. are available only in nutted
> versions.


I spoke too soon. Assuming that a normal ISO threadless fork is used,
French 1" frames can be converted to threadless, since they have the
same 30.2mm cup outside diameter as ISO. JIS frames would be
convertible to threadless if they were reamed to a 30.2mm bore size.

Chalo
 
On Dec 3, 3:08 am, Chalo <[email protected]> wrote:
> I wrote:
>
> > JIS (30.0mm), French, etc. are available only in nutted
> > versions.

>
> I spoke too soon. Assuming that a normal ISO threadless fork is used,
> French 1" frames can be converted to threadless, since they have the
> same 30.2mm cup outside diameter as ISO. JIS frames would be
> convertible to threadless if they were reamed to a 30.2mm bore size.
>
> Chalo


Nashbar carried a JIS threadless headset for a while, for an RST 1-
inch fork they had. It's long gone, but it did exist.
 
On Dec 3, 6:08 am, Chalo <[email protected]> wrote:
> I wrote:
>
> > JIS (30.0mm), French, etc. are available only in nutted
> > versions.

>
> I spoke too soon. Assuming that a normal ISO threadless fork is used,
> French 1" frames can be converted to threadless, since they have the
> same 30.2mm cup outside diameter as ISO. JIS frames would be
> convertible to threadless if they were reamed to a 30.2mm bore size.
>

Right. See: http://sheldonbrown.com/cribsheets/headsets for a table
with all of the relevant dimensions.

Sheldon "Numbers" Brown
+---------------------------------------------------------------------
+
| It is amazing how much "mature wisdom" resembles being too tired.
|
| --Robert A. Heinlein
|
+---------------------------------------------------------------------
+
Harris Cyclery, West Newton, Massachusetts
Phone 617-244-9772 FAX 617-244-1041
http://harriscyclery.com
Hard-to-find parts shipped Worldwide
http://captainbike.com
Useful articles about bicycles and cycling
http://sheldonbrown.com
 
"Chalo" <[email protected]> wrote in message
news:222508f7-9201-451b-94af-dbd2c483f3e2@n20g2000hsh.googlegroups.com...
> Peter Howard wrote:
>>
>> I wonder if it is possible to convert to a fork with threadless steerer
>> tube
>> simply by fitting a threadless headset?

>
> For a 1-1/8" or 1-1/4" headset, yes. For a 1" headset, maybe. ISO
> (30.2mm cups) and BMX (32.7mm cups) one inch headsets have threadless
> versions. JIS (30.0mm), French, etc. are available only in nutted
> versions.
>
>> I don't particularly want to take it apart again and bash out the frame
>> cups
>> unless I'm sure so I'd like to hear from anyone who's done it.

>
> Go ahead; there is only one set of diameter standards for 1.125"
> headsets, and they are all compatible with the same head tubes.
>
> Chalo
>


So it's do-able. Thanks! And thanks to all others who replied. Guess I can
start looking out for the right fork.

Peter
 
"Chalo" <[email protected]> wrote in message
news:222508f7-9201-451b-94af-dbd2c483f3e2@n20g2000hsh.googlegroups.com...
> Peter Howard wrote:
>>
>> I wonder if it is possible to convert to a fork with threadless steerer
>> tube
>> simply by fitting a threadless headset?

>
> For a 1-1/8" or 1-1/4" headset, yes. For a 1" headset, maybe. ISO
> (30.2mm cups) and BMX (32.7mm cups) one inch headsets have threadless
> versions. JIS (30.0mm), French, etc. are available only in nutted
> versions.
>
>> I don't particularly want to take it apart again and bash out the frame
>> cups
>> unless I'm sure so I'd like to hear from anyone who's done it.

>
> Go ahead; there is only one set of diameter standards for 1.125"
> headsets, and they are all compatible with the same head tubes.
>
> Chalo
>


So it's do-able. Thanks! And thanks to all others who replied. Guess I can
start looking out for the right fork.

Peter