A-head stem cap question

[Call Me Bob]

I think this should work, but want to ask in case I'm missing something obvious.

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.

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. 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?

Thanks if you can help.

Bob
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[Pete Biggs]

Call me Bob wrote:
> 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!).

> 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........

> 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

 

[James Annan]

Call me Bob wrote:
> 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

 

[Tony W]

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

 

[Pete Biggs]

Tony W wrote:
> 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.......

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

> 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

 

[W K]

"Pete Biggs" <pLime{remove_fruit}@biggs.tc> wrote in message
news:[email protected]...
> Call me Bob wrote:

> > 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]

> 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).

 

[Thomas Letherby]

In message <[email protected]>, Taywood <[email protected]> writes
>
>> 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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[Huw Pritchard]

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

> 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.

> 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.

> 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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[Tony W]

"Pete Biggs" <pLime{remove_fruit}@biggs.tc> wrote in message
news:[email protected]...
> Tony W wrote:
> > 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.
>
> > On my bike this plastic thingy is broken so it is now a c ring of about 300 degrees.
> /snip
> > 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.

> > 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

 

[Pete Biggs]

W K wrote:

>>> 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:
http://www.parktool.com/repair_help/howfix_headthreadless.shtml (I'm quite new to threadless myself
and this info made it all clear to me)

> 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.

> 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.

> 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.

> 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

 

[Pete Biggs]

Tony W wrote:

>> 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

 

[Call Me Bob]

On Wed, 15 Jan 2003 11:25:18 +0000, Thomas Letherby <[email protected]> wrote:

>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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[Tony W]

"Pete Biggs" <pLime{remove_fruit}@biggs.tc> wrote in message
news:[email protected]...
> 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

 

[Call Me Bob]

On Mon, 13 Jan 2003 06:10:51 -0000, "Pete Biggs" <pLime{remove_fruit}@biggs.tc> wrote:

>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.

>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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[Call Me Bob]

On Mon, 13 Jan 2003 17:52:43 +0900, James Annan <[email protected]> wrote:

>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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[Thomas Letherby]

In message <[email protected]>, Call me Bob <[email protected]> writes
>On Mon, 13 Jan 2003 17:52:43 +0900, James Annan <[email protected]> wrote:
>
>>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.
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Thomas Letherby Remove NOSPAM to reply.

 

[Taywood]

> 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