Threading a threadless steerer

[Sscarich]

I have a brand new Marzocchi fork, with a untheaded steerer that was cut too
short, by about 2". I am considering the options to make it work on my
mountain bike. I could put on a riser, but that would look kind of cheesy.
One bike shop said they would cut threads into the cro-mo steerer, install an
NOS XT 1 1/8" HS and a quill stem, that I happen to have. I talked to another
shop, just to check the concept, and they said they would not do it, that they
do not cut new threads into an ahead steerer. I seem to recall that there is a
slight difference in diameter between threaded steerers and unthreaded. Is
that true, or does anyone have an opinion about this project?

Thanks,

Steve Scarich

 

[Sscarich]

Thanks for the advice..I knew there was a potential problem. I wanted to
replace the steerer, but was told that you have to send the fork to Marzocchi,
where they remove the old steerer by freezing it. The cost would be close to
$100.

Steve

 

[Sven Longren]

DON'T DO IT!!! Threadless steer tubes are much thinner wall than their
threaded counterparts and by adding threads, you almost insure a
catastrophic failure. . .

Bite the bullet and buy a new steer / crown or a new fork.





"Sscarich" <[email protected]> wrote in message
news:[email protected]...
> I have a brand new Marzocchi fork, with a untheaded steerer that was cut
too
> short, by about 2". I am considering the options to make it work on my
> mountain bike. I could put on a riser, but that would look kind of
cheesy.
> One bike shop said they would cut threads into the cro-mo steerer, install
an
> NOS XT 1 1/8" HS and a quill stem, that I happen to have. I talked to
another
> shop, just to check the concept, and they said they would not do it, that
they
> do not cut new threads into an ahead steerer. I seem to recall that there
is a
> slight difference in diameter between threaded steerers and unthreaded.
Is
> that true, or does anyone have an opinion about this project?
>
> Thanks,
>
> Steve Scarich

 

[Mike Jacoubowsky]

> Thanks for the advice..I knew there was a potential problem. I wanted to
> replace the steerer, but was told that you have to send the fork to
> Marzocchi,
> where they remove the old steerer by freezing it. The cost would be close
> to
> $100.

If it's a decent fork, that $100 doesn't sound like such a bad deal. Kudos
for Marocchi for even offering that as a reasonably-priced option; I don't
think that's the case with most others these days.

--Mike-- Chain Reaction Bicycles
www.ChainReactionBicycles.com

 

[James Thomson]

"Sven Longren" <[email protected]> wrote:

> DON'T DO IT!!! Threadless steer tubes are much thinner wall than
> their threaded counterparts and by adding threads, you almost
> insure a catastrophic failure. . .

That's not generally true. Steel steerer tubes often have a common wall
thickness (1/16"), whether threaded or threadless. Aluminium steerers can
be thicker-walled. In any case, if Steve's threadless steerer isn't of the
same dimensions as a threaded one, he won't be able to use a quill stem
with it - so tube wall presents no problem. If the quill fits, he's good to
go.

As to the question of cutting threads, I'm told that steerer threads should
be lathe-cut, and only extended using a die. If the shop that offers to do
the work seems competent, I would let them try. At worst, you can cut
another inch off the steerer and sell the fork (or crown/steerer) to
someone with an even smaller frame.

> Bite the bullet and buy a new steer / crown or a new fork.

Crown/steerer assemblies often come up on eBay. It's a fair bet that the
right model will come along sooner or later.

James Thomson

 

[Sscarich]

The steerer ID is correct for my quill stem. I stuck it in, and it tighened
nicely. Speaking of catastrophic failure; if the threads were a little too
deep, wouldn't I get signs like loosening HS well before a failure? The
threading wouldn't seem to affect the interface between the quill and the
steerer, where one might anticipate a catastrophic failure.

Steve

 

[A Muzi]

Sscarich wrote:
> I have a brand new Marzocchi fork, with a untheaded steerer that was cut too
> short, by about 2". I am considering the options to make it work on my
> mountain bike. I could put on a riser, but that would look kind of cheesy.
> One bike shop said they would cut threads into the cro-mo steerer, install an
> NOS XT 1 1/8" HS and a quill stem, that I happen to have. I talked to another
> shop, just to check the concept, and they said they would not do it, that they
> do not cut new threads into an ahead steerer. I seem to recall that there is a
> slight difference in diameter between threaded steerers and unthreaded. Is
> that true, or does anyone have an opinion about this project?

Don't do that.
The 1-1/8 thread standard is 26tpi which means the thread
height is even less than the 1" x24. Odds of getting a good
clean thread are very small as the columns tend to be
undersized.

To cut a fork, drop the column into the frame before you
install the headset. Measure the column sticking out the
end of the frame and mark it with a file. Remove fork and cut.

Or lay the old fork on the new one and Mark with a file.

Bicycle mechanics are notoriously bad at arithmetic on
paper. They'll more often than not subtract the head tube
length fron the column length with a 1cm error. Or add the
head tube length to the stack height with a 1cm error. If
they used inches we'd have one inch errors so I guess it
could be worse.

As the owner of many short forks I have heard, "Gee, sorry
boss" enough to insist on no paper efforts. Direct measure!
--
Andrew Muzi
www.yellowjersey.org
Open every day since 1 April, 1971

 

[Werehatrack]

On 12 Dec 2004 22:56:42 GMT, [email protected] (Sscarich) wrote:

>I have a brand new Marzocchi fork, with a untheaded steerer that was cut too
>short, by about 2". I am considering the options to make it work on my
>mountain bike. I could put on a riser, but that would look kind of cheesy.
>One bike shop said they would cut threads into the cro-mo steerer, install an
>NOS XT 1 1/8" HS and a quill stem, that I happen to have. I talked to another
>shop, just to check the concept, and they said they would not do it, that they
>do not cut new threads into an ahead steerer. I seem to recall that there is a
>slight difference in diameter between threaded steerers and unthreaded. Is
>that true, or does anyone have an opinion about this project?

I've never tried it with a Marzocchi, but I have had two other forks
whose tubes measured at the correct ID and OD for threading, and they
both were successfully cut for threaded headsets. In both instances,
they were going on bikes which had very long head tubes which made it
difficult to locate an economically priced fork to fit. So far, all
of the (admittedly inexpensive to midline) steel steerer tubes I've
checked had the same diameters (inside and outside) as their
same-nominal-dimension threaded counterparts. As long as that's the
case, I see no reason why they should not be possible to thread...but
I will warn that in my experience, most bike shops do not have the
tools to do the job, and many will deny that it is safe, advisable, or
even possible to do it. Fortunately, the guys at one of the local
hydraulic cylinder repair shops had no trouble cutting them on their
lathe.
--
Typoes are a feature, not a bug.
Some gardening required to reply via email.
Words processed in a facility that contains nuts.

 

[Weisse Luft]

Dies for steerer tubes are for cleanup or extending. Cutting new requires a lathe because you need to index the threads off the crown race. If you don't, bearing life could be hurt if threads are not square.

 

[Ronald]

> I have a brand new Marzocchi fork, with a untheaded steerer that was
cut too
> short, by about 2". I am considering the options to make it work on
my
> mountain bike.

You could try one of these:
http://www.bbbparts.com/products/bike_parts/headparts/bhp20.htm


"Sscarich" <[email protected]> wrote in message
news:[email protected]...
> I have a brand new Marzocchi fork, with a untheaded steerer that was
cut too
> short, by about 2". I am considering the options to make it work on
my
> mountain bike. I could put on a riser, but that would look kind of
cheesy.
> One bike shop said they would cut threads into the cro-mo steerer,
install an
> NOS XT 1 1/8" HS and a quill stem, that I happen to have. I talked
to another
> shop, just to check the concept, and they said they would not do it,
that they
> do not cut new threads into an ahead steerer. I seem to recall that
there is a
> slight difference in diameter between threaded steerers and
unthreaded. Is
> that true, or does anyone have an opinion about this project?
>
> Thanks,
>
> Steve Scarich

 

[Werehatrack]

On Mon, 13 Dec 2004 17:16:16 +1100, Weisse Luft
<[email protected]> wrote:

>
>Dies for steerer tubes are for cleanup or extending. Cutting new
>requires a lathe because you need to index the threads off the crown
>race. If you don't, bearing life could be hurt if threads are not
>square.

A good die and stock could make good, square threads. Unfortunately,
this is not a very useful observation inasmuch as most of the die
stocks available are not good enough, and most of the dies supplied
fall even farther short of the mark than the stocks.

That said, I reground the leading edges of the teeth of a Hozan die a
while back and had good results using it to extend the threads of a
steerer that was merely common steel; I doubt that its teeth would
have survived a full revolution against 4130, though.
--
Typoes are a feature, not a bug.
Some gardening required to reply via email.
Words processed in a facility that contains nuts.

 

[John Thompson]

On 2004-12-13, Weisse Luft <[email protected]> wrote:

> Dies for steerer tubes are for cleanup or extending. Cutting new
> requires a lathe because you need to index the threads off the crown
> race. If you don't, bearing life could be hurt if threads are not
> square.

But the threads only hold the upper cup, which has to align with the
top race on the frame, not the crown race. And the cups on most decent
headsets (with the exception of the old Stronglight Competition's V-shaped
races and some roller bearing headsets) have eliptically ground races to
accommodate some misalignment without binding. Besides, a good piloted
stock and die can index off the steer tube itself, yes?

--

-John ([email protected])

 

[Werehatrack]

On Tue, 14 Dec 2004 15:49:18 -0600, John Thompson
<[email protected]> wrote:

>...Besides, a good piloted
>stock and die can index off the steer tube itself, yes?

Therein lies the rub. A lot of die stocks do not properly center and
square the die in the recess of the stock, whether they have a good
pilot collar or not...and a lot of dies will **** slightly as the
first few teeth grab on the beginning of the cut, producing a
non-square thread. (Having cut quite a lot of threads in things like
custom motorcycle axle shafts over the years, I can attest to the
hazards of assuming that a good die and stock will make a square cut.)
On the other hand, as you point out, a slight misalignment may not
produce a problem in a lot of instances; this would be dependent upon
many factors, not the least of which is the actual amount and type of
riding that the bike gets. For a recreational mostly-street
weekender, a little off-square's probably not going to make any
difference. For a bike messenger's long-term curbjumper, I'd want it
dead on. And "how much can it be off without causing a problem" is a
question that I'd be really leery of trying to answer. If at all
possible, just get it done dead square by whatever method is
available...and then there's unlikely to be a problem.
--
Typoes are a feature, not a bug.
Some gardening required to reply via email.
Words processed in a facility that contains nuts.