A-head stem cap question

Call me Bob said:

About to install a computer on my new bike (Cateye Mity 3). I want to route the cabling as neatly
as possible and so the plan is to use a stem kit to mount it centrally on the A-head stem. I
intend to pass the fork sensor down through the inside of the fork, past the star fangled nut and
neatly down the inside of the fork to where it will
live.

Blimey Charlie, that an ingenious idea!! So the sensor will /stay/ in the fork and it'll be close
enough to the wheel to be triggered by the magnet without rattling out of position (or making a
noise)? Very neat, but wouldn't it be a pain when needing to remove fork (for headset service, etc)?
- Perhaps fitting a mini inline plug and socket to the cable could help there. Or will the cable
just be passed through and sensor will be fitted to outside of fork as normal? Throught what hole,
etc? (Obviously, I'm a bit puzzled!).

Quoted message said:

I've checked the sensor assembly and it gently comes apart enough to get it past the star fangled
nut so I won't have to mess with that. However, I need to have the cable pass through the stem cap
if this is to work. This means I have to put a small cut in it.

Checking Sheldon's site tells me that once the stem is properly fitted (bolted tightly etc) then
the stem cap and star fangled nut serve no real function and take no stress.

That's right, you could even ride safely without it if you wanted to. But it does have to press down
hard on the stem/spacer while adjusting headset........

Quoted message said:

So, there's no reason why I can't hacksaw a small slot in the plastic stem cap to pass my comp
cable through is there?

Should be ok if it's still strong enough for headset adjustment. I expect it would be but I'm not
sure. Could always get another cap if it fails.

I thought my Mity 3 looked quite cool (mounted at bottom of fat carbon forks) but.... Hmm,
maybe? :-)

~PB

Call me Bob said:

So, there's no reason why I can't hacksaw a small slot in the plastic stem cap to pass my comp
cable through is there?

The obvious thing to do if you are remotely worried is to use another whole cap for the tightening
of the stem and once the stem is fitted swap for the slotted one. But I can't imagine this is really
necessary.

James

The bottom bearing in the stem seems to be protected by a plastic doughnut thingy (note the
technical precise language applied here!).

On my bike this plastic thingy is broken so it is now a c ring of about 300 degrees.

I suspect it was broken when the head set came loose on a pretty dramatic and bumpy down hill.
Tightening everything up (and doing some more long bumpy downhills) seems to have everything working
OK -- except, of course, more dirt is getting into the bearing.

Are these thingies easily obtained? Will my LBS (a good one) have one? Should it be repaced ASAP or
can I continue to play on the bike for a while without doing serious damage?

T

Tony W said:

The bottom bearing in the stem seems to be protected by a plastic doughnut thingy (note the
technical precise language applied here!).

I'm assuming this is a seal in the headset, and not some external boot thing or other.......

Quoted message said:

On my bike this plastic thingy is broken so it is now a c ring of about 300 degrees.

/snip

Quoted message said:

Are these thingies easily obtained? Will my LBS (a good one) have one?

Different headsets can have different bits. The shop maybe able to order one or find something
suitable in their junk collection.

Quoted message said:

Should it be repaced ASAP or can I continue to play on the bike for a while without doing
serious damage?

I would replace ASAP. The headset may not be able to be properly adjusted and stable without it and
may suddenly get worse if the remaining bit of seal disintegrates further, and dirt & muck will get
in (although lack of sealing wouldn't necessarily cause wear-problems for some time. Some headsets
have no/minimal seals).

~PB

"Pete Biggs" <[email hidden]> wrote in message
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Quoted message said:

Call me Bob wrote:

Quoted message said:

Quoted message said:

Checking Sheldon's site tells me that once the stem is properly fitted (bolted tightly etc) then
the stem cap and star fangled nut serve no real function and take no stress.

[can see that on a quick look- but not the extra info]

Quoted message said:

That's right, you could even ride safely without it if you wanted to. But it does have to press
down hard on the stem/spacer while adjusting headset........

Quick Q. Is it easy to just take out spacers below the stem and shove them on top?

As in, loosen things off, swap over carefully leaving fork where it is. Then, tighten the stem cap
(how tight?), then the main stem bolts.

Also - what actually determines how tight the bearings are? is it just the position of the stem (as
set initially by the stem cap).

In message <[email hidden]>, Taywood <[email hidden]> writes

Quoted message said:

Quoted message said:

Don't think anyone's mentioned this, but you could replace your star fangled nut and top cap
assembly with a BMX one. Some of these use a fatter hollow bolt to allow the front brake cable to
pass down the steerer tube. Otherwise what you plan should be fine, this could possibly be a
'neater' solution.

Good stuff thanks and welcome back Thomas

Only just getting the time back to read all the newsgroups I'm subscribed to again. Moved branches
at Cycle Surgery to Camden. other than that it's business as usual 🙂. As before, I'm more than
happy to contact suppliers for info for people. 😄

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Thomas Letherby Remove NOSPAM to reply.

On Mon, 13 Jan 2003 11:44:20 +0000, W K did issue forth:

Quoted message said:

Quick Q. Is it easy to just take out spacers below the stem and shove them on top?

Yup. Provided the top bolt is long enough to reach the star fangled nut then you should be fine.

Quoted message said:

As in, loosen things off, swap over carefully leaving fork where it is. Then, tighten the stem cap
(how tight?), then the main stem bolts.

That's the bunny.

Quoted message said:

Also - what actually determines how tight the bearings are? is it just the position of the stem
(as set initially by the stem cap).

Bingo. The top bolt determines how much preload is put on the bearings by pulling the stem down onto
everything else. After that the stem bolts hold everything in place.

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"Pete Biggs" <[email hidden]> wrote in message
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Quoted message said:

Tony W said:

The bottom bearing in the stem seems to be protected by a plastic doughnut thingy (note the
technical precise language applied here!).

I'm assuming this is a seal in the headset, and not some external boot thing or other.......

Its a hard plastic profiled anulus. My guess is that it is there to keep crud out though I think it
would not bee too good at keeping water out. I didn't describe it as a 'seal' as that would be a
little OTT.

Quoted message said:

Quoted message said:

On my bike this plastic thingy is broken so it is now a c ring of about 300 degrees.

/snip

Quoted message said:

Are these thingies easily obtained? Will my LBS (a good one) have one?

Different headsets can have different bits. The shop maybe able to order one or find something
suitable in their junk collection.

This is a standard A-head 1 1/8th stem.

Quoted message said:

Quoted message said:

Should it be repaced ASAP or can I continue to play on the bike for a while without doing
serious damage?

I would replace ASAP. The headset may not be able to be properly adjusted and stable without it
and may suddenly get worse if the remaining bit of seal disintegrates further, and dirt & muck
will get in (although lack of sealing wouldn't necessarily cause wear-problems for some time. Some
headsets have no/minimal seals).

Thanks -- you confirmed my suspicions. I'll drop by my (not so local) LBS.

T

W K said:

Quoted message said:

Quoted message said:

Checking Sheldon's site tells me that once the stem is properly fitted (bolted tightly etc) then
the stem cap and star fangled nut serve no real function and take no stress.

[can see that on a quick look- but not the extra info]

I recommend these for aheadset instructions:
parktool.comhowfix headthreadless.shtmlOpen ↗ (I'm quite new to threadless myself
and this info made it all clear to me)

Quoted message said:

Quick Q. Is it easy to just take out spacers below the stem and shove them on top?

Yes, except I found it impractical to have the stem with just one 2mm spacer on top, but 5mm+ is
fine. You will also need to make sure stem is aligned with front wheel (which I find an annoying job
to eyeball). Cable lengths can limit height if short.

Quoted message said:

As in, loosen things off, swap over carefully leaving fork where it
is.

Yes. If front brake is caliper type, removing (and letting dangle) might make swap-over easier.

Quoted message said:

Then, tighten the stem cap (how tight?), then the main stem bolts.

Not very tight at all to begin with. It's a "feel" thing that requires repeated operations. First,
press the stem gently down by hand then tighten top bolt until it feels as if it's just doing
something plus 1/4 turn more. Tighten main stem bolts (evenly), test headset as you would do a
conventional one (rocking bike with front brake on, etc). If play, undo stem bolts, tighten top bolt
just a little bit, etc, repeat until done.

Quoted message said:

Also - what actually determines how tight the bearings are? is it just the position of the stem
(as set initially by the stem cap).

Yes.

~PB

Tony W said:

Quoted message said:

I'm assuming this is a seal in the headset, and not some external boot thing or other.......

Its a hard plastic profiled anulus. My guess is that it is there to keep crud out though I think
it would not bee too good at keeping water out. I didn't describe it as a 'seal' as that would be
a little OTT.

I'm not 100% sure I've identified the part - but I reckon the advice I gave is still appropriate if
any part of the headset or stem is broken.

The parts known as "seals" in headsets are usually hard rings less than 1mm thick. They are supposed
to keep some water as well as crud out. They're not made very close fitting or soft because that
would add too much friction. (As it happens, I've found my Stronglight O'Light top race runs much
smoother with the relatively tight seal removed).

If the part is several mm high and fits ontop of the top part of the headset, then it's a spacer
that comes with the headset or has been added, and the LBS should have a suitable spare in stock.

Sorry about the vagueness/confusion.

~PB

Thomas Letherby said:

Don't think anyone's mentioned this, but you could replace your star fangled nut and top cap
assembly with a BMX one. Some of these use a fatter hollow bolt to allow the front brake cable to
pass down the steerer tube.

That's interesting, I didn't know that. I'll have a look at one next time I'm passing a BMX'y
LBS. Cheers.

Bob
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"Pete Biggs" <[email hidden]> wrote in message
"]news:[email hidden]...

Quoted message said:

Tony W wrote:

I'm not 100% sure I've identified the part - but I reckon the advice I gave is still appropriate
if any part of the headset or stem is broken.

The parts known as "seals" in headsets are usually hard rings less than 1mm thick. They are
supposed to keep some water as well as crud out. They're not made very close fitting or soft
because that would add too much friction. (As it happens, I've found my Stronglight O'Light top
race runs much smoother with the relatively tight seal removed).

If the part is several mm high and fits ontop of the top part of the headset, then it's a spacer
that comes with the headset or has been added, and the LBS should have a suitable spare in stock.

Sorry about the vagueness/confusion.

Pete

Thanks for the advice. I think it is a 'seal'. It is certainly not a 'spacer'. I'll get the LBS to
check it out.

T

Pete Biggs said:

Blimey Charlie, that an ingenious idea!! So the sensor will /stay/ in the fork and it'll be
close enough to the wheel to be triggered by the magnet without rattling out of position (or
making a noise)?

No, not quite that ingenious. The sensor is fitted to the fork blade in the normal way. The only
tricksy bit is mounting the computer unit on the stem, then running the cable down through the
inside of the steerer tube, past the star fangled nut and out the bottom. From there the cable runs
down the inside (but not /inside/ if you know what I mean) of the fork blade to where the sensor is
sited. It doesn't save much clutter but it's neater than coiling the wire down brake cables etc.

Quoted message said:

That's right, you could even ride safely without it if you wanted to. But it does have to press
down hard on the stem/spacer while adjusting headset........

Right oh, thanks for that.

Bob
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James Annan said:

The obvious thing to do if you are remotely worried is to use another whole cap for the tightening
of the stem and once the stem is fitted swap for the slotted one. But I can't imagine this is
really necessary.

I figured I might do that but I only needed to put a small notch in the cap so no spare required.

Thanks.

Bob
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In message <[email hidden]>, Call me Bob <[email hidden]> writes

Quoted message said:

James Annan said:

The obvious thing to do if you are remotely worried is to use another whole cap for the tightening
of the stem and once the stem is fitted swap for the slotted one. But I can't imagine this is
really necessary.

I figured I might do that but I only needed to put a small notch in the cap so no spare required.

Don't think anyone's mentioned this, but you could replace your star fangled nut and top cap
assembly with a BMX one. Some of these use a fatter hollow bolt to allow the front brake cable to
pass down the steerer tube. Otherwise what you plan should be fine, this could possibly be a
'neater' solution.
--
Thomas Letherby Remove NOSPAM to reply.

Quoted message said:

Don't think anyone's mentioned this, but you could replace your star fangled nut and top cap
assembly with a BMX one. Some of these use a fatter hollow bolt to allow the front brake cable to
pass down the steerer tube. Otherwise what you plan should be fine, this could possibly be a
'neater' solution.

Good stuff thanks and welcome back Thomas Mike