Headset wear indicating head tube needs facing?

[TomYoung]

Hi all:

I'm taking apart a 1985 Trek I recently purchased and I'm wondering if
the uneven wear pattern I'm seeing on the headset fixed races is
telling me the ends of the head tube aren't parallel.

The crown race and the two fixed head tube races are all showing
"normal" wear in an arc about 270 degrees or so around the
circumference, oriented toward the front of the bike, with no or
virtually no wear in the remaining 90 degrees or so at the rear of the
races.

Even though this is an old bike I'm guessing it saw very, very limited
riding miles, so maybe what I'm seeing is an artifact of that?

On the other hand, this wear pattern suggests to me that a cross
section of the head tube in the plane of the bike is in the shape of
an isosceles trapezoid, with the long side of the trapezoid oriented
toward the front of the bike.

Thoughts?

TIA.

Tom Young

 

[A Muzi]

TomYoung wrote:
> I'm taking apart a 1985 Trek I recently purchased and I'm wondering if
> the uneven wear pattern I'm seeing on the headset fixed races is
> telling me the ends of the head tube aren't parallel.
>
> The crown race and the two fixed head tube races are all showing
> "normal" wear in an arc about 270 degrees or so around the
> circumference, oriented toward the front of the bike, with no or
> virtually no wear in the remaining 90 degrees or so at the rear of the
> races.
>
> Even though this is an old bike I'm guessing it saw very, very limited
> riding miles, so maybe what I'm seeing is an artifact of that?
>
> On the other hand, this wear pattern suggests to me that a cross
> section of the head tube in the plane of the bike is in the shape of
> an isosceles trapezoid, with the long side of the trapezoid oriented
> toward the front of the bike.

It's possible, easily checked by machining the faces with a Campagnolo
mill.
Did you check the steerer with a straightedge?
--
Andrew Muzi
www.yellowjersey.org
Open every day since 1 April, 1971

 

[TomYoung]

On Feb 26, 11:06 am, A Muzi <[email protected]> wrote:
> TomYoung wrote:
> > I'm taking apart a 1985 Trek I recently purchased and I'm wondering if
> > the uneven wear pattern I'm seeing on the headset fixed races is
> > telling me the ends of the head tube aren't parallel.
>
> > The crown race and the two fixed head tube races are all showing
> > "normal" wear in an arc about 270 degrees or so around the
> > circumference, oriented toward the front of the bike, with no or
> > virtually no wear in the remaining 90 degrees or so at the rear of the
> > races.
>
> > Even though this is an old bike I'm guessing it saw very, very limited
> > riding miles, so maybe what I'm seeing is an artifact of that?
>
> > On the other hand, this wear pattern suggests to me that a cross
> > section of the head tube in the plane of the bike is in the shape of
> > an isosceles trapezoid, with the long side of the trapezoid oriented
> > toward the front of the bike.
>
> It's possible, easily checked by machining the faces with a Campagnolo
> mill.
> Did you check the steerer with a straightedge?
> --
> Andrew Muziwww.yellowjersey.org
> Open every day since 1 April, 1971

You're suggesting that maybe the steerer tube itself is bent?

I hadn't thought about that possibility. I'll check it out.

Thanks.

 

[TomYoung]

On Feb 26, 8:25 am, TomYoung <[email protected]> wrote:
> Hi all:
>
> I'm taking apart a 1985 Trek I recently purchased and I'm wondering if
> the uneven wear pattern I'm seeing on the headset fixed races is
> telling me the ends of the head tube aren't parallel.
>
> The crown race and the two fixed head tube races are all showing
> "normal" wear in an arc about 270 degrees or so around the
> circumference, oriented toward the front of the bike, with no or
> virtually no wear in the remaining 90 degrees or so at the rear of the
> races.
>
> Even though this is an old bike I'm guessing it saw very, very limited
> riding miles, so maybe what I'm seeing is an artifact of that?
>
> On the other hand, this wear pattern suggests to me that a cross
> section of the head tube in the plane of the bike is in the shape of
> an isosceles trapezoid, with the long side of the trapezoid oriented
> toward the front of the bike.
>
> Thoughts?
>
> TIA.
>
> Tom Young

In looking much more carefully at the races in the head tube it looked
to me like the races might not have been pressed in completely. I
could get a fingernail into the seam line between the races and the
head tube, and I don't think that should be the case. I got out the
(home-made) head tube bearing press and got about 360 degrees turn -
or a bit more - of the wrench before meeting considerable resistance,
and now the seams are closed up to the point where I can no longer get
a fingernail in there.

I think I'll go ahead and assemble the headset and look at it again
after a 1,000 miles or so and see if the wear has equalized around the
circumference of the races. If not, it 's too the shop.

Tom Young

 

[sergio]

On Feb 27, 3:34 am, TomYoung <[email protected]> wrote:
> In looking much more carefully at the races in the head tube it looked
> to me like the races might not have been pressed in completely.

Possible albeit unlikely in such an aged assembly.
Better credible that the machining was not perfect to start with and
that the head set pieces simply could not be pressed and be inserted
correctly.
No matter what, you should better take the frameset to an adequately
equippped shop.

As a side note, I would be very surprised if the head tube were bent
as Andrew seems to suggest.
It being so short, even upon a bad collision it is the horizontal and
the sloping tubes that usually get bent.

Sergio
Pisa

 

[sergio]

On Feb 26, 8:06 pm, A Muzi <[email protected]> wrote:
> Did you check the steerer with a straightedge?

By the way, Andrew, if that is the case wouldn't you still have to
reface the steerer tube?

Sergio
Pisa

 

[A Muzi]

> TomYoung <[email protected]> wrote:
>> In looking much more carefully at the races in the head tube it looked
>> to me like the races might not have been pressed in completely.

sergio wrote:
> Possible albeit unlikely in such an aged assembly.
> Better credible that the machining was not perfect to start with and
> that the head set pieces simply could not be pressed and be inserted
> correctly.
> No matter what, you should better take the frameset to an adequately
> equippped shop.
>
> As a side note, I would be very surprised if the head tube were bent
> as Andrew seems to suggest.
> It being so short, even upon a bad collision it is the horizontal and
> the sloping tubes that usually get bent.

Sorry if I was unclear.
He should remove the fork and check the steerer (cannotto forcella?)
with a straightedge. They can bend in relatively minor crashes.

Yes, as you note, it's possible the cups are merely askew in the frame.
--
Andrew Muzi
www.yellowjersey.org
Open every day since 1 April, 1971

 

[A Muzi]

> A Muzi <[email protected]> wrote:
>> Did you check the steerer with a straightedge?

sergio wrote:
> By the way, Andrew, if that is the case wouldn't you still have to
> reface the steerer tube?

Yes, we would anyway once the fork is out and aligned.
--
Andrew Muzi
www.yellowjersey.org
Open every day since 1 April, 1971

 

[datakoll]

breathe deep relax.
take the bike apart, box and label parts, clean everything and examine
for wear before it falls apart outside DeMoine. Paint the inside with
rusto if steel tubing.
get the tubes, head and BB refaced, dropouts checked down at the LBS.
odds are, never done in '85 so do it now.

BUTbutbut, the narrow wide race paths are probabbbly from lack of
maintenance: bearings were never periodocally relubed, the grease (or
beef tallow like that's uh 23 years ago) absolved, evaped, the races
wore out as bearings went thru the Brandtian bearing cycle, round not
so round round not so round, forcing the race metal to one side from
lube lack.

you know about using a machete for removing the crown race? after
propane heat/smoke. tap tap 180 degrees and nung slides off. brush,
dose with PC blaster, razor out seam debris. MORE BLASTER SOAK.

odds are the assembly will not go back together and run again without
fresh races and bearings. Why? doesn't show any affinity for
assembling in reverse order. nada.

 

[A Muzi]

datakoll wrote:
> breathe deep relax.
> take the bike apart, box and label parts, clean everything and examine
> for wear before it falls apart outside DeMoine. Paint the inside with
> rusto if steel tubing.
> get the tubes, head and BB refaced, dropouts checked down at the LBS.
> odds are, never done in '85 so do it now.
>
> BUTbutbut, the narrow wide race paths are probabbbly from lack of
> maintenance: bearings were never periodocally relubed, the grease (or
> beef tallow like that's uh 23 years ago) absolved, evaped, the races
> wore out as bearings went thru the Brandtian bearing cycle, round not
> so round round not so round, forcing the race metal to one side from
> lube lack.
>
> you know about using a machete for removing the crown race? after
> propane heat/smoke. tap tap 180 degrees and nung slides off. brush,
> dose with PC blaster, razor out seam debris. MORE BLASTER SOAK.
>
> odds are the assembly will not go back together and run again without
> fresh races and bearings. Why? doesn't show any affinity for
> assembling in reverse order. nada.

Campagnolo machete? Park? Army surplus?
--
Andrew Muzi
www.yellowjersey.org
Open every day since 1 April, 1971

 

[sergio]

On 27 Feb, 23:48, datakoll <[email protected]> wrote:
> you know about using a machete for removing the crown race? after
> propane heat/smoke.

No need to risk a fire alarm.

Insert the fork horizontally in between the jaws of a (solid) vice,
the protruding race against the flat sides of the jaws. With buffer in
between, tighten barely enough to hold the fork against its weight.
Interpose a block of hard wood amd give the end of the fork tube a
good blow with no less than a bricklayer hammer.
The fork will separate and slip along the jaws.

Never failed, in my basement.

Sergio
Pisa

 

[datakoll]

the motha load:

https://www.wescooutfitters.com/c-428-knives-accessories.aspx

I bought the mid range standard spanish pig sticker for $14 excellent
value, cut firewood, dig excrement holes, open cans when the can
opener is...cut meat offen ur leg....
painted hiViz yellow you will probabbble leave my area pronto.

butbutbut WalMart machete is the one for crown race removal. tap dull
side with tuba4 or...

if yawl remove the race and clean the fork real nice, the LBS will
treat you better than otherwise when yawl ask the LBS to turn or burn
the new race on. One shop said the fork needed turning, Palm Beach
said no, the race gets rammed on. depends.

 

[Werehatrack]

On Tue, 26 Feb 2008 08:25:55 -0800 (PST), TomYoung <[email protected]>
may have said:

>Hi all:
>
>I'm taking apart a 1985 Trek I recently purchased and I'm wondering if
>the uneven wear pattern I'm seeing on the headset fixed races is
>telling me the ends of the head tube aren't parallel.
>
>The crown race and the two fixed head tube races are all showing
>"normal" wear in an arc about 270 degrees or so around the
>circumference, oriented toward the front of the bike, with no or
>virtually no wear in the remaining 90 degrees or so at the rear of the
>races.
>
>Even though this is an old bike I'm guessing it saw very, very limited
>riding miles, so maybe what I'm seeing is an artifact of that?
>
>On the other hand, this wear pattern suggests to me that a cross
>section of the head tube in the plane of the bike is in the shape of
>an isosceles trapezoid, with the long side of the trapezoid oriented
>toward the front of the bike.
>
>Thoughts?

You could be right, but considering the way that a headset operates
(at low speed, with most of the load borne by the lower bearing, and
some radial thrust inevitably present which generally tries to push
the lower bearing against the front of the head tube and the upper
bearing towards the rear unless you're braking), it's only the upper
end of the tube which seems likely to be off spec...and unless the
headset has had a habit of loosening and requiring readjustment, I'd
be very tempted to leave it alone.

If the rider habitually positions his hands and leans forward in a
manner that pushes on the bars, then the wear pattern may mean
precisely nothing.

As long as the steerer functions smoothly and doesn't require frequent
fiddling, it's probably good enough.

One other note; I've spotted a couple of aluminum frames in the past
year whose head tubes appeared to have shrunk slightly adjacent to the
top and down tube welds; an '85 Trek is probably steel, though, which
shouldn't display that tendency to any marked degree. On the ones I
spotted, the deformed tubes did not produce any performance problem,
so I didn't try to "fix" it.

That's just my two cents' worth. Do what you feel is warranted.


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