Fork flex: headset play?

Quoted message said:

Hello all,
while trying to check that my bike headset is OK I noticed that the
fork assembly is quite flexy. If I brake hard and rock the bike back
and forth, I feel a noticeable springy effect; the handlebars move 1-2
cm. This happens also if the wheel is turned 90 degrees.
The frame and flex are made of Columbus steel.
Is this flex normal? What could cause it?
This does not happen with the rear wheel, so I guess that the tyre and
wheel are not at fault.
I can't feel any play in the headset (or at least, no clicking sounds),
but it is also an indexed headset with a tiny crack in the lower cup...
Could this be responsible for a slight sensation of instability I feel
with the bike, especially when cornering?

Thanks,
Federico

Something is not right. I say take it to a competent bike shop and have
it taken apart and inspected. The handlebars should NOT move back and
forth like that if the HS is not loose.

Quoted message said:

Hello all,
while trying to check that my bike headset is OK I noticed that the
fork assembly is quite flexy. If I brake hard and rock the bike back
and forth, I feel a noticeable springy effect; the handlebars move 1-2
cm. This happens also if the wheel is turned 90 degrees.
The frame and flex are made of Columbus steel.
Is this flex normal? What could cause it?
This does not happen with the rear wheel, so I guess that the tyre and
wheel are not at fault.
I can't feel any play in the headset (or at least, no clicking sounds),
but it is also an indexed headset with a tiny crack in the lower cup...
Could this be responsible for a slight sensation of instability I feel
with the bike, especially when cornering?

Thanks,
Federico

Do you mean the handlebars move independently of the frame? Then there's
a problem. But, if you say there is no noticeable play in the headset,
then the handlebars and frame should move together. Forks are flexible
to a certain degree, but the brakes flex as well and contribute to the
displacement you're feeling.

But you should really replace that headset first.
-Collin

Quoted message said:

while trying to check that my bike headset is OK I noticed that the
fork assembly is quite flexy. If I brake hard and rock the bike back
and forth, I feel a noticeable springy effect; the handlebars move 1-2
cm.

I'm trying to visualize this. How are the bars moving? Do you mean that
when you pull up on one side of the bar, that side moves up and the
other side down? That could be due to flexy bars and stem. Is this a
quill stem with a long horizontal reach?

Quoted message said:

This happens also if the wheel is turned 90 degrees.

That situation would never occur while riding.

Quoted message said:

The frame and flex are made of Columbus steel.
Is this flex normal? What could cause it?

Lightweight steel tubing like Columbus SL (with traditional tube
diameters) combined with a long quill stem can feel flexy when pulling
on the bars compared to bikes with oversize tubing and 1-1/8"
threadless headsets.

Art Harris

Quoted message said:

Hello all,
while trying to check that my bike headset is OK I noticed that the
fork assembly is quite flexy. If I brake hard and rock the bike back
and forth, I feel a noticeable springy effect; the handlebars move 1-2
cm. This happens also if the wheel is turned 90 degrees.
The frame and flex are made of Columbus steel.
Is this flex normal? What could cause it?
This does not happen with the rear wheel, so I guess that the tyre and
wheel are not at fault.
I can't feel any play in the headset (or at least, no clicking
sounds), but it is also an indexed headset with a tiny crack in the
lower cup... Could this be responsible for a slight sensation of
instability I feel with the bike, especially when cornering?

The HS is indexed /and/ cracked? Why, pray tell, are you reluctant to
replace it?

(And the answer to your last question, IMO, is "yes".)

f.cozzi said:

Hello all,
while trying to check that my bike headset is OK I noticed that the
fork assembly is quite flexy. If I brake hard and rock the bike back
and forth, I feel a noticeable springy effect; the handlebars move 1-2
cm. This happens also if the wheel is turned 90 degrees.

If I understand this correctly, the bars --- along with the rest of the
bike -- move 1-2 cm as you rock it back and forth with the front brake
clamped tight. Some motion is due to the fork, at the crown, but most of
it is the tire and the brake itself. If you don't believe that, then try
to get the same motion with the fork clamped into a mount of some kind,
like a roof rack. If it still moves then, you have one heck of a flexy
fork.

Quoted message said:

could cause it? This does not happen with the rear wheel, so I guess
that the tyre and wheel are not at fault.

Well, that doesn't quite translate that well.

Quoted message said:

I can't feel any play in the
headset (or at least, no clicking sounds), but it is also an indexed
headset with a tiny crack in the lower cup...

You know, you can get a brand new headset, sans crack and "indexing", with
sealed bearings, for less than $50. Considerably less.

Quoted message said:

Could this be responsible
for a slight sensation of instability I feel with the bike, especially
when cornering?

You mean the indexing? It would have some effect, but not a whole lot.
The crack would have less effect. The tire would have a lot.

However, fork stiffness can affect handling. I recently went through an
odyssey with forks. I discovered that the original fork (threaded) had
welded itself to the stem. I ordered a new one (threadless), and in the
interim used an old steel fork. It was not as stiff as the previous one,
and the bike handled strangely. Then when the new fork arrived (thanks,
Mark), I could tell again that the handling was different, in this case
much better.

--

David L. Johnson

__o | Anyone who is capable of getting themselves made President
_`\(,_ | should on no account be allowed to do the job. -- Douglas Adams
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