Threadless headset on (unthreaded bit of) threaded steerer?

Alan Braggins said:

If you had a 1" threaded fork which had too short a threaded bit for
your headset, could you fit a 1" threadless headset on it? Or is 1"
the outside diameter of the threads, leaving the unthreaded bit too
small? Or is it like tyres where one 20" is totally different from
another 20"?

It would be unlikely that the threads would stand proud of the diameter of
the tube - not practical to make stuff that way (not impossible, just a
pointless effort unless there's a specific engineering reason to do so), so
the outside diameter of the thread is very probably the same as that of the
tube itself.

--
Wally
www.wally.myby.co.uk
http://iott.melodolic.com

Alan Braggins said:

If you had a 1" threaded fork which had too short a threaded bit for your
headset, could you fit a 1" threadless headset on it? Or is 1" the outside
diameter of the threads, leaving the unthreaded bit too small? Or is it
like tyres where one 20" is totally different from another 20"?

No, this doesn't work. Shimano 105 headsets don't last very long, but
they have an unusually low stack height of 32mm and might solve your
problem. You could also buy a new carbon fork (£60-ish) or get a longer
steerer brazed into your existing one, if it's steel and has a cast fork
crown (similar price).

Alan Braggins said:

If you had a 1" threaded fork which had too short a threaded bit for
your headset, could you fit a 1" threadless headset on it? Or is 1"
the outside diameter of the threads, leaving the unthreaded bit too
small? Or is it like tyres where one 20" is totally different from
another 20"?

No, the diameters of the unthreaded bits are the same and you can do what
you're thinking of. Only potential dodginess is when any of the portion
of the tube that the stem clamps to is threaded, as the threads can act as
a stress riser, causing it to snap!

~PB

Pete Biggs said:

Only potential dodginess is when any of the portion
of the tube that the stem clamps to is threaded, as the threads can act as
a stress riser, causing it to snap!

Precisely. And this will be the case if it's already too short for a
threaded headset.

Wally said:

Alan Braggins said:

If you had a 1" threaded fork which had too short a threaded bit for
your headset, could you fit a 1" threadless headset on it? Or is 1"
the outside diameter of the threads, leaving the unthreaded bit too
small? Or is it like tyres where one 20" is totally different from
another 20"?

It would be unlikely that the threads would stand proud of the diameter of
the tube - not practical to make stuff that way (not impossible, just a
pointless effort unless there's a specific engineering reason to do so), so
the outside diameter of the thread is very probably the same as that of the
tube itself.

Almost any bolt will have rolled threads which have a greater diameter
than the base shank. Steerer tubes have cut threads, but that is a
historical necessity and pretty rare.

So the answer is correct, but no marks as the reasoning is totally off 😉

--
---
Marten Gerritsen

INFOapestaartjeM-GINEERINGpuntNL
www.m-gineering.nl

Zog The Undeniable said:

No, this doesn't work. Shimano 105 headsets don't last very long, but
they have an unusually low stack height of 32mm and might solve your
problem. You could also buy a new carbon fork (£60-ish) or get a longer
steerer brazed into your existing one, if it's steel and has a cast fork
crown (similar price).

I beg to differ. This depends largely upon the circumstances. Hooves 1
used a threadless headset on a threaded steerer (for engineering
reasons) and the only minor problem was getting the headset components
over the unthreaded portion of the steerer (Which was slightly greater
than 1" diameter!). If the stem is only clamping a over half or less
it's length then you are perhaps onto dodgy ground, but careful
selection of a stem can solve this.

Because of the threading, I would suggest buying a 1 1/8" stem and shim
(Often included for free) as this will put some extra material in over
the threading and perhaps prevent damage to the stem itself.

Zog is right in that it may well be easier to buy a new fork.

Jon

Zog The Undeniable said:

Pete Biggs said:

Only potential dodginess is when any of the portion
of the tube that the stem clamps to is threaded, as the threads can act as
a stress riser, causing it to snap!

Precisely. And this will be the case if it's already too short for a
threaded headset.

Not necessarily. If the threaded section is not long enough, but the
steerer is excessively long (e.g. cut and threaded for a long head
tube, and used on a short head tube) it is possible for the steerer to
be long enough to be used in a threadless setup. In this case it is
also possible to have your friendly frame builder cut the threads
further for you, although depending on the steerer in question that may
or may not be advisable.

Jon

M-gineering said:

Almost any bolt will have rolled threads which have a greater diameter
than the base shank.

The pile of M6 capscrews next to my little mill have threads that aren't
proud of the shanks.

Quoted message said:

Steerer tubes have cut threads, but that is a
historical necessity and pretty rare.

The question was *about* threaded steerer tubes and the diameters concerned.

Quoted message said:

So the answer is correct, but no marks as the reasoning is totally
off 😉

Your 'critique' is irrelevant - bolts with rolled threads was not under
discussion.

--
Wally
www.wally.myby.co.uk
http://iott.melodolic.com

In article said:

Alan Braggins said:

If you had a 1" threaded fork which had too short a threaded bit for
your headset, could you fit a 1" threadless headset on it? Or is 1"
the outside diameter of the threads, leaving the unthreaded bit too
small? Or is it like tyres where one 20" is totally different from
another 20"?

No, the diameters of the unthreaded bits are the same and you can do what
you're thinking of.

I'm an idiot. Somehow I completely forgot what a fork thread looks
like, and misinterpreted a photo as having a smooth top and threaded
lower part, which would need the thread larger than the upper part.
I'm not sure how I managed that, apart from concentrating more on the
tests I was running than the browsing and posting while waiting for them.

But it isn't, it's a cut thread in a fixed diameter tube, starting at
the top, and it will be long enough, I think.

So, the next question is, does anyone know of a 1" equivalent of
DAHONSTAJ118 on http://www.gaerlan.com/dahon/upgrade/stem.htm ?

Alan Braggins said:

If you had a 1" threaded fork which had too short a threaded bit for your
headset, could you fit a 1" threadless headset on it?

I've read all the replies to this thread, and it seems it might be possible,
but WHY? It's your forks. Not a minor part of the bike. Sell the threaded
fork (or give it to a good home) and just buy a new 1" threadless.

It won't be expensive and will do far more for your safety than those
helmet things 🙂

Arthur

--
Arthur Clune

Alan Braggins said:

In article said:

Alan Braggins said:

If you had a 1" threaded fork which had too short a threaded bit for
your headset, could you fit a 1" threadless headset on it? Or is 1"
the outside diameter of the threads, leaving the unthreaded bit too
small? Or is it like tyres where one 20" is totally different from
another 20"?

Quoted message said:

But it isn't, it's a cut thread in a fixed diameter tube, starting at
the top, and it will be long enough, I think.

I would be most surprised if you could fit a threadless stem and
headset onto a pair of forks that are too short for a threaded headset.
Most surprised indeed.

...d

David Martin said:

Alan Braggins said:

In article said:

Alan Braggins wrote:
> If you had a 1" threaded fork which had too short a threaded bit for
> your headset, could you fit a 1" threadless headset on it? Or is 1"
> the outside diameter of the threads, leaving the unthreaded bit too
> small? Or is it like tyres where one 20" is totally different from
> another 20"?

Quoted message said:

But it isn't, it's a cut thread in a fixed diameter tube, starting at
the top, and it will be long enough, I think.

I would be most surprised if you could fit a threadless stem and
headset onto a pair of forks that are too short for a threaded headset.

No - I thought the threaded bit was too short because I was an idiot.
I then thought the fork steerer would be long enough to be used as designed,
with a threaded headset. But, as it turns out, I was wrong about that as well.
Back to square one.

David Martin said:

I would be most surprised if you could fit a threadless stem and
headset onto a pair of forks that are too short for a threaded headset.
Most surprised indeed.

But as explained in Another Post(tm), you can have a pair of forks
where the steerer is long enough for a threadless headset but the
thread hasn't been cut far enough.

Jon

Jon is Away! said:

David Martin said:

I would be most surprised if you could fit a threadless stem and
headset onto a pair of forks that are too short for a threaded headset.
Most surprised indeed.

But as explained in Another Post(tm), you can have a pair of forks
where the steerer is long enough for a threadless headset but the
thread hasn't been cut far enough.

Ah! that explains it. The other posts just had me confused.

...d

In article said:

Alan Braggins said:

If you had a 1" threaded fork which had too short a threaded bit for your
headset, could you fit a 1" threadless headset on it?

I've read all the replies to this thread, and it seems it might be possible,
but WHY?

As mentioned in my earlier reply to someone else, because I'm an idiot
and had forgotten how threaded forks work, mostly. For the full answer
of why I was wanting to change the forks at all, read on.....

Quoted message said:

It's your forks. Not a minor part of the bike. Sell the threaded
fork (or give it to a good home) and just buy a new 1" threadless.

I haven't bought the threaded fork in question, I was looking at it
on eBay and wondering if it would suit the bike, which is a folder
with a longer than normal headtube. Its current fork doesn't have
cantilever studs, and I would quite like to fit V-brakes. I did try
an adaptor plate (http://pics.livejournal.com/armb/pic/00013bwb/g3),
but it flexed horribly. It works much better on the back
http://pics.livejournal.com/armb/pic/0001abd1/g3

http://www.sheldonbrown.com/raleigh-twenty.html has "modified Haro BMX
fork with an extended steerer", http://www.bikexprt.com/bicycle/mytwenty.htm
"I cut down a fork made for 27-inch wheels, and brazed in new dropouts"
(and earlier braked on studs). I could braze studs on my existing fork,
but I'm not sure I want to trust that.
Sheldon and John, apart from vastly more bicycle experience than me,
have the advantage of US spec Twenties being designed for 406 wheels,
UK ones are 451. Not that my Kingpin is a Twenty, but the headtube is
similar (part from the Twenty having a plastic bush rather than a
threaded top - but both Sheldon and John changed that, and if I had
a folding Twenty frame (more rigid hinge), I'd swap the headset over.
Unless I was getting a new one, which is where we came in.)

The current front brake (http://pics.livejournal.com/armb/pic/00018tt1/g3)
is a lot better than the original (and the original wouldn't reach the
406 rims (the originals were chrome 440 (500A - halfway between 20"
and the other 20"😉). It now has salmon KoolStop BMX pads too, which also
improve braking in the wet (alloy rims rather than chrome steel was the
really big improvement though).

http://www.gaerlan.com/bikeparts/frame/forks/fork.html has a possibly
suitable suspension fork, but with shipping it would cost about 20 times
what the bike originally cost me. If you know where I can get a cheap
1" 20" fork with studs and a steerer at least 220mm long, let me know.
(One browse later, http://tinyurl.com/aqsnw have longer steerers than
the ones I found before (http://tinyurl.com/bodof)

(That still leaves the problem of the existing stem being non-standard.
And yes I do realise the sensible boring thing to do would be give up and
just buy a decent new Dahon or Brompton.)

In article said:

(One browse later, http://tinyurl.com/aqsnw have longer steerers than
the ones I found before (http://tinyurl.com/bodof)

Or not. That's "2) 134mm" not "234mm".