Narrowing fork tube

Dimitris Stamatelos said:

I want to lower the bars as far as possible, but it seems that the
stem gets stuck after a point. I removed the fork (threaded 1"😉 and
it seems that the steerer tube get narrower after about 4" (10 cm)
from the top. Is this normal? Is there a tool that would restore the
inside diameter of the tube to what it is supposed to be (22.2 mm)
for the whole length of tube?

Any reasonable steertube has greater wall thickness at the high stress
junction with the fork crown. If this were not so, they would break
easily from the bending loads of road shock and braking. Your steer
tube is just fine, but I suspect you have a short one on a small
frame, so there isn't much depth for a stem.

How much are you missing in your adjustment? There were "drop stems"
(usually for track bicycles) whose reach angled down for such forks.

[email hidden]

Quoth Dimitris Stamatelos:

Quoted message said:

Quoted message said:

I want to lower the bars as far as possible, but it seems that the
stem gets stuck after a point. I removed the fork (threaded 1"😉 and
it seems that the steerer tube get narrower after about 4" (10 cm)
from the top. Is this normal? Is there a tool that would restore the
inside diameter of the tube to what it is supposed to be (22.2 mm)
for the whole length of tube?

Jobst Brandt noted:

Quoted message said:

Any reasonable steertube has greater wall thickness at the high stress
junction with the fork crown. If this were not so, they would break
easily from the bending loads of road shock and braking. Your steer
tube is just fine, but I suspect you have a short one on a small
frame, so there isn't much depth for a stem.

WARNING! This is a potentially DANGEROUS situation!

Most cyclists tend to want to get the bars as high up as they'll go, but
when you try to go low on a small frame there's a particularly nasty
failure mode to watch out for:

The hole in the steerer does, indeed get smaller near the bottom, as the
wall thickness increases. (The term for this in the biz is "butted."😉

When inserting the stem, if it bottoms out where the walls start to
taper in, you MUST raise it a bit (maybe 1/4" - 6 mm) so that the wedge
is engaging the cylindrical surface of the wide part of the steerer.

If you insert the stem so far that it is trying to clamp in the conical
region where the wall thickness is changing, it may work OK for weeks or
months, but it is at high risk for SUDDENLY and completely disconnecting
from the steerer! This is almost certain to cause a crash.

Tall folks like Jobst never have this problem.

Sheldon "Short People Beware!" Brown
+-----------------------------------------+
| Bicycling isn't supposed to hurt! See: |
| http://sheldonbrown.com/pain.html |
+-----------------------------------------+
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 http://sheldonbrown.com

Sheldon Brown said:

Quoth Dimitris Stamatelos:

Quoted message said:

Quoted message said:

I want to lower the bars as far as possible, but it seems that the
stem gets stuck after a point. I removed the fork (threaded 1"😉 and
it seems that the steerer tube get narrower after about 4" (10 cm)
from the top. Is this normal? Is there a tool that would restore the
inside diameter of the tube to what it is supposed to be (22.2 mm)
for the whole length of tube?

Jobst Brandt noted:

Quoted message said:

Any reasonable steertube has greater wall thickness at the high stress
junction with the fork crown. If this were not so, they would break
easily from the bending loads of road shock and braking. Your steer
tube is just fine, but I suspect you have a short one on a small
frame, so there isn't much depth for a stem.

Sheldon Brown increased the thread length like so:

Quoted message said:

WARNING! This is a potentially DANGEROUS situation!

Most cyclists tend to want to get the bars as high up as they'll go, but
when you try to go low on a small frame there's a particularly nasty
failure mode to watch out for:

The hole in the steerer does, indeed get smaller near the bottom, as the
wall thickness increases. (The term for this in the biz is "butted."😉

When inserting the stem, if it bottoms out where the walls start to
taper in, you MUST raise it a bit (maybe 1/4" - 6 mm) so that the wedge
is engaging the cylindrical surface of the wide part of the steerer.

If you insert the stem so far that it is trying to clamp in the conical
region where the wall thickness is changing, it may work OK for weeks or
months, but it is at high risk for SUDDENLY and completely disconnecting
from the steerer! This is almost certain to cause a crash.

Tall folks like Jobst never have this problem.

While I can't compare with the giants of wreck.bike.tech I'm not that
short at 182cm and I have run into this problem with my funny-ish bike.

It has a quill type stem and a short head tube.

My fix was to take the quill stem to the mitre saw and shorten it an
appropriate amount with an angle to match the original. In this
particular case the stem bolt had a sufficient length of thread and only
required a minor trim job.

If you decide it is too low and raise it back up.
WARNING! Dimitris WARNING!
The minimum insertion mark means nothing any more!
Make sure the expansion plug is below the threaded area.

As usual I am not responsible for those who are injured attempting or
after completing such a modification.
All I can say is it works for me so far....

Marcus Coles

Unfortunately, the builder didn't shorten the butted end of the steerer
before brazing the fork. For short steerers, this must be done (within
the specified limits). The proper repair is to ream the steerer, making
sure to leave a sufficient amount of butt so the steerer won't fail (as
Jobst indicated).

Quoted message said:

Unfortunately, the builder didn't shorten the butted end of the steerer
before brazing the fork. For short steerers, this must be done (within
the specified limits). The proper repair is to ream the steerer, making
sure to leave a sufficient amount of butt so the steerer won't fail (as
Jobst indicated).

reaming can be hazardous - leaves an internal circumferential stress
riser exactly at the point of maximum stress. very high propensity for
fatigue.

a competent builder uses an appropriately butted steerer tube. a
sensible modern rider takes this opportunity to upgrade to a threadless
steerer, preferably as part of acquiring a decent carbon fork.

Quoted message said:

Unfortunately, the builder didn't shorten the butted end of the steerer
before brazing the fork. For short steerers, this must be done (within
the specified limits). The proper repair is to ream the steerer, making
sure to leave a sufficient amount of butt so the steerer won't fail (as
Jobst indicated).

Why wouldn't the proper repair be to shorten the stem? It's easy enough
to do, as mentioned earlier on this thread.

--

David L. Johnson

__o | Become MicroSoft-free forever. Ask me how.
_`\(,_ |
(_)/ (_) |

The point of maximum stress is lower, just above the fork crown race.

Like Marcus Coles said, "WARNING! (If you shorten the stem,) The
minimum insertion mark means nothing any more!"

So, then what happens if and when the bike gets in the hands of an
unsuspecting rider who brings the stem up to the insertion line?

Dimitris said:

Hi everyone

I want to lower the bars as far as possible, but it seems that the
stem gets stuck after a point. I removed the fork (threaded 1"😉 and it
seems that the steerer tube get narrower after about 4" (10 cm) from
the top. Is this normal? Is there a tool that would restore the inside
diameter of the tube to what it is supposed to be (22.2 mm) for the
whole length of tube?

Quality bikes are built with butted steerers, 22.2mmID at
the top and 21mmID at the bottom. Even not-so-expensive
forks commonly have a brazed sleeve in the bottom 50~70mm of
steerer. (That can be annoying on a small bike if the
builder didn't proportionally trim the column)

There's no snappy solution other than a shorter quill or a
downward-sloping stem

--
Andrew Muzi
www.yellowjersey.org
Open every day since 1 April, 1971

Quoted message said:

Like Marcus Coles said, "WARNING! (If you shorten the stem,) The
minimum insertion mark means nothing any more!"

So, then what happens if and when the bike gets in the hands of an
unsuspecting rider who brings the stem up to the insertion line?

An ethical approach to that would be to replace the stem before selling
it. I think reaming out the steerer would be much more dangerous.

--

David L. Johnson

__o | "What am I on? I'm on my bike, six hours a day, busting my ass.
_`\(,_ | What are you on?" --Lance Armstrong
(_)/ (_) |

In article <[email hidden]>,

Quoted post said:

Like Marcus Coles said, "WARNING! (If you shorten the stem,) The
minimum insertion mark means nothing any more!"

So, then what happens if and when the bike gets in the hands of an
unsuspecting rider who brings the stem up to the insertion line?

Stem damage, fork steer tube ovalization, catastrophic failure as the
stem pops out of the steer tube, with a high likelihood of really
serious injury following immediately.

So, you know, you have to keep the stem for yourself, or put a new
insertion mark on the stem, or warn any other users.

--
Ryan Cousineau, [email hidden] http://www.wiredcola.com
Verus de parvis; verus de magnis.

Quoted message said:

Quoted message said:

Unfortunately, the builder didn't shorten the butted end of the steerer
before brazing the fork. For short steerers, this must be done (within
the specified limits). The proper repair is to ream the steerer, making
sure to leave a sufficient amount of butt so the steerer won't fail (as
Jobst indicated).

jim beam said:

reaming can be hazardous - leaves an internal circumferential stress
riser exactly at the point of maximum stress. very high propensity for
fatigue.

a competent builder uses an appropriately butted steerer tube. a
sensible modern rider takes this opportunity to upgrade to a threadless
steerer, preferably as part of acquiring a decent carbon fork.

Actually , one doesn't ream a column to build a small fork.
One trims the column from the bottom, so as to not leave a
ridge from reaming. Small forks still need tapered butted
columns - just not quite so long a section.

--
Andrew Muzi
www.yellowjersey.org
Open every day since 1 April, 1971

(Dimitris) said:

Hi everyone

Quoted message said:

I want to lower the bars as far as possible, but it seems that the
stem gets stuck after a point.

you need a track stem, maybe an older cinelli would work well (check
ebay to find one.) A good one will get your bars below the top
locknut of your fork. There is no need to try to manipulate your fork
steering tube.

- Don Gillies
San Diego, CA

jim beam said:

Quoted message said:

Unfortunately, the builder didn't shorten the butted end of the

steerer

Quoted message said:

Quoted message said:

before brazing the fork. For short steerers, this must be done

(within

Quoted message said:

Quoted message said:

the specified limits). The proper repair is to ream the steerer,

making

Quoted message said:

Quoted message said:

sure to leave a sufficient amount of butt so the steerer won't fail

(as

Quoted message said:

Quoted message said:

Jobst indicated).

reaming can be hazardous - leaves an internal circumferential stress
riser exactly at the point of maximum stress. very high propensity

for

Quoted message said:

fatigue.

a competent builder uses an appropriately butted steerer tube. a
sensible modern rider takes this opportunity to upgrade to a

threadless

Quoted message said:

steerer, preferably as part of acquiring a decent carbon fork.

Here's what America's premier framebuilder, Richard Sachs, had to say
about it on another list: "It is okay to ream or hone your fork a wee
bit in order to get the stem to fit in lower."

Most reamers have a bit of taper at the insertion end, anyway.

You'd probably have to do it yourself, though. I'm starting to realize
that not many bikeshops would touch it.

Dan Christopherson
Lopez Island WA