Headset dead spot?

Quoted message said:

jim beam said:

you're a blathering freakin' idiot utterly clueless of
extremely well and abundantly documented facts that any "engineering
professor" should know. all you do is shoot your mouth, completely
unable to add the smallest quantum of value. other than entertaining
with your uselessness of course. give up your day job krygowski. every
check you cash is the commission of fraud.

Seems like every time I post web links that prove you're wrong, you
lapse into another childish tantrum.

funny. and ironic because it seems every time /i/ post something that
might help fill a little of the huge cognizance gaps in your meager
grasp of engineering basics, you don't read them!

Quoted message said:

We've gone through this many
times - for example, when you claimed no bike components are castings.

thixo-forming has a completely different microstructure to casting.
that's why thixo-forming is not /called/ casting! idiot.

Quoted message said:

You tell others to do your work, use Google to find photos to prove
you right. Why won't _you_ use Google to learn a little, before
arguing yourself into a corner? If you didn't have to defend such
obvious mistakes, maybe you could be more civil.

see above. and i'd be civil to someone that wasn't a fraud. and i
wouldn't be /able/ to point out that you're an idiot if you weren't one.

Quoted message said:

Google "false brinell." Read a few links. Or stop in at any
engineering library and start learning about bearings.

if only /you/ would do that, maybe you'd have some idea of what you
didn't know.

[only a complete idiot could try to lecture from a position of utter
ignorance and complain when they get it wrong. and yet again, your post
is completely free of any technical content.]

still just me said:

jim beam said:

as for grinding paste, yes, it will work for a while, but it has a risk
of eroding the seat post [because there will be small movement and thus
abrasion] and it could subsequently fatigue and break.

I think it's highly unlikely that using valve grinding paste
(typically around 500 grit) will lead to any sort of a failure. Those
are very, very minor. People run with scratches way deeper than that
on their posts from frame imperfections for years and years and years
and never have a failure.

it's not the grit size, it's the erosion.

Quoted message said:

For the OP, I still wouldn't use a compound with that kind of grit
factor to fix your seat post situation.

jim beam said:

Ben C wrote:

[...]

Quoted message said:

Quoted message said:

Yes but the distinction here is important. Do you get those indents from
a single big thump or overload, or are they gradually eaten away by some
kind of corrosion/fretting process?

The practical side of this is that a headset that's too loose I would
expect to be more prone to true brinelling, one that's too tight more
prone to the false kind.

other way about.

I figure that if there's some up and down travel in the headset because
it's loose the bearings get a bigger knock when you hit a bump.

I think it's because if they're loose they're less protected by ability
of the tyre and fork to slow down the impact.

Suppose the front wheel is crashing back down to earth after a bump.
While it's in mid-air, the fork drops a bit because the headset is loose
and so there's a small gap between the bearings and the races. The tyre
hits the ground first and perhaps bounces up a bit but in any case the
bearings collide with the races directly.

If you plot force against time at the bearing for the impact I think you
get the same area for tight and loose headsets (total change of momentum
the same), but a shorter fatter shape with lower maximum force for the
tight headset. So perhaps less risk of true brinelling.

I think tight headsets are more likely to promote false brinelling
because if they're too tight they may prevent the balls rolling around
and the grease circulating.

On the other hand, increasing pre-load increases total load when you hit
a given bump, so I can see that too-tight could also promote true
brinelling.

And I suppose too loose could promote false brinelling if it meant all
the grease leaked out.

Ben C said:

jim beam said:

Ben C wrote:

[...]

Quoted message said:

Quoted message said:

Yes but the distinction here is important. Do you get those indents from
a single big thump or overload, or are they gradually eaten away by some
kind of corrosion/fretting process?

The practical side of this is that a headset that's too loose I would
expect to be more prone to true brinelling, one that's too tight more
prone to the false kind.

other way about.

I figure that if there's some up and down travel in the headset because
it's loose the bearings get a bigger knock when you hit a bump.

I think it's because if they're loose they're less protected by ability
of the tyre and fork to slow down the impact.

Suppose the front wheel is crashing back down to earth after a bump.
While it's in mid-air, the fork drops a bit because the headset is loose
and so there's a small gap between the bearings and the races. The tyre
hits the ground first and perhaps bounces up a bit but in any case the
bearings collide with the races directly.

If you plot force against time at the bearing for the impact I think you
get the same area for tight and loose headsets (total change of momentum
the same), but a shorter fatter shape with lower maximum force for the
tight headset. So perhaps less risk of true brinelling.

I think tight headsets are more likely to promote false brinelling
because if they're too tight they may prevent the balls rolling around
and the grease circulating.

On the other hand, increasing pre-load increases total load when you hit
a given bump, so I can see that too-tight could also promote true
brinelling.

And I suppose too loose could promote false brinelling if it meant all
the grease leaked out.

Following up to myself here, but I think from the other posts that
too-loose promotes false brinelling because it allows the balls to
vibrate?

That's why you pre-load in the first place, but hopefully not by too
much.

Ben C said:

Ben C said:

jim beam said:

Ben C wrote:

[...]

Quoted message said:

> Yes but the distinction here is important. Do you get those indents from
> a single big thump or overload, or are they gradually eaten away by some
> kind of corrosion/fretting process?
>
> The practical side of this is that a headset that's too loose I would
> expect to be more prone to true brinelling, one that's too tight more
> prone to the false kind.
other way about.

I figure that if there's some up and down travel in the headset because
it's loose the bearings get a bigger knock when you hit a bump.

I think it's because if they're loose they're less protected by ability
of the tyre and fork to slow down the impact.

Suppose the front wheel is crashing back down to earth after a bump.
While it's in mid-air, the fork drops a bit because the headset is loose
and so there's a small gap between the bearings and the races. The tyre
hits the ground first and perhaps bounces up a bit but in any case the
bearings collide with the races directly.

If you plot force against time at the bearing for the impact I think you
get the same area for tight and loose headsets (total change of momentum
the same), but a shorter fatter shape with lower maximum force for the
tight headset. So perhaps less risk of true brinelling.

I think tight headsets are more likely to promote false brinelling
because if they're too tight they may prevent the balls rolling around
and the grease circulating.

On the other hand, increasing pre-load increases total load when you hit
a given bump, so I can see that too-tight could also promote true
brinelling.

And I suppose too loose could promote false brinelling if it meant all
the grease leaked out.

Following up to myself here, but I think from the other posts that
too-loose promotes false brinelling because it allows the balls to
vibrate?

That's why you pre-load in the first place, but hopefully not by too
much.

that's right. you need a degree of preload, to stop the sliding in
false brinelling, but as you say, too much means you reduce the load
bearing capacity that would lead to true brinelling.

don't get too side-tracked on the "no grease" theory - it's a little
out-dated as it fails to explain why otherwise identical bearings in
oxygen-free environments don't false brinell. it also ignores the fact
that any bearing that's not rotating fast enough will not
hydrodynamically separate, and thus there will be full metal-to-metal
contact, complete with asperity welding. and bearings operate for
decades in this state with no apparent problems.

Hugh Fenton said:

"Teh bike guy" <[email hidden]> wrote in message
news:[email hidden]...

Quoted message said:

This is common and easy to fix, just squirt some toothpaste (whitening
formulations work best) into the headset and ride around for a few miles,
it will become all smooth again, after that you can flush with water and
add grease.

On a vaguely similar topic.........

I've an old aluminium CADEX ALM1 where the (lubricated) seatpost keeps
slipping down slowly........ No, the clamp IS correctly adjusted AND the
seat tube isn't squeezed closed...but it still happens unless I overtension
the quick release (and I DO need one of these owing to the riding I do.)

A friend suggested that valve grinding paste would solve my
problem.........an inert grit to prevent movement embedded in a lubricant to
prevent seizure......

Comments??????

Hugh Fenton

First thing I would try is to lube the QR cam and, if it's the removable
collar type, lube between the collar and frame tube. Sometimes friction
in these places limits the clamping force.

On Tue, 08 Apr 2008 12:54:34 GMT, Peter Cole <[email hidden]>

may have said:

Hugh Fenton said:

"Teh bike guy" <[email hidden]> wrote in message
news:[email hidden]...

Quoted message said:

This is common and easy to fix, just squirt some toothpaste (whitening
formulations work best) into the headset and ride around for a few miles,
it will become all smooth again, after that you can flush with water and
add grease.

On a vaguely similar topic.........

I've an old aluminium CADEX ALM1 where the (lubricated) seatpost keeps
slipping down slowly........ No, the clamp IS correctly adjusted AND the
seat tube isn't squeezed closed...but it still happens unless I overtension
the quick release (and I DO need one of these owing to the riding I do.)

A friend suggested that valve grinding paste would solve my
problem.........an inert grit to prevent movement embedded in a lubricant to
prevent seizure......

Comments??????

Hugh Fenton

First thing I would try is to lube the QR cam and, if it's the removable
collar type, lube between the collar and frame tube. Sometimes friction
in these places limits the clamping force.

Also, a detail I'd forgotten; if the split in the tube is not lined up
with the split in the camp, the grease mentioned becomes absolutely
essential.

--
My email address is antispammed; pull WEEDS if replying via e-mail.
Typoes are not a bug, they're a feature.
Words processed in a facility that contains nuts.

Hugh Fenton said:

I've an old aluminium CADEX ALM1 where the (lubricated) seatpost keeps
slipping down slowly........ No, the clamp IS correctly adjusted AND the
seat tube isn't squeezed closed...but it still happens unless I overtension
the quick release (and I DO need one of these owing to the riding I do.)

A friend suggested that valve grinding paste would solve my
problem.........an inert grit to prevent movement embedded in a lubricant to
prevent seizure......

Comments??????

Some cheap headset races are only case-hardened; using grinding compound
to smooth pits in such a race will remove the hardening.

--

John ([email hidden])