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Routing computer wires down stem?

Old 01-09-21, 12:00 PM
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Steel1
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Routing computer wires down stem?

Has anyone seen people route the bike computer wires down thru fork steerer tube? On this bike, the stem has a groove ground along entire length, including the wedge at bottom. The wheel speed sensor wire was routed down along the groove and exited at bottom of fork. There is the obvious question about degrading structural integrity. I judged it OK, as groove is lengthwise, and ride as is. I admit it was a clean looking install, but defaced the stem 😟 I guess this was modified in the mid 80ís.

Unfortunately, some water got in there and made its way down outside of steerer tube to lower bearing and caused some rust on balls. Its hard to see the path water would take to outside of steerer tube past threads. Maybe it can sneak down the vertical slot for washer key. And its not like I sprayed lots of water there... Anyway, I put loose balls in bottom and re-used the caged balls at top. I made mistake when I consulted Park tool website for which way the cage should face. I believe it was wrong for this headset (Tange Levin). Should have balls UP!

I have already posted about rear brake cable on this particular bike routing on drive side. I stubbornly choose to keep it ďstockĒ, as this is the way I got it and also depicted in original catalog. I know many would complain about that, but it works fine for me 😀





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Old 01-09-21, 12:21 PM
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Originally Posted by Steel1 View Post
There is the obvious question about degrading structural integrity...Unfortunately, some water got in there
Not sure if you're asking for an opinion, but I'll give you one anyways.

Hard no, for the two reasons you state.

That slot is a stress riser in a critical structural point on the bike.

You've already stated that it works fine for you, so my post is hopefully a warning so that other's won't do the same.
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Old 01-09-21, 12:26 PM
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Looks sketchy to me.

In years past, I always wound the wire around the front brake housing, using tiny zip ties at top and bottom to prevent unwinding. Worked for me, and looked pretty clean, too.

I personally would not trust an old stem with DIY mods.
Pretty creative thinking, though!
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Old 01-09-21, 01:18 PM
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personally, I wouldn't use a stem with a slot like that.
Who knows how safe it may or may not be, but if I die doing something stupid, it had better be for a more worthwhile cause.

As far as constructive comments, I would suggest the use of the traditional method where the wires are wrapped around the brake cable. Clean, efficient, and nobody gets hurt.



If that seems too safe, then I would suggest a cast stem that has a hollow quill and extension. I used to have an AVA stem like this.....




I suspect you could drill a hole (for the wires) in the steel expander cone without any structural concerns.
The caveat is that this sort of stem is not very strong or stiff. I got rid of it because I just didn't trust it.
These often fail to use a stress relieving hole at the top of the slots in the bottom of the quill. There are cases where this causes cracks in the quill, causing the stem to no longer be secured in the fork.
Not good.
You could file or drill a rounded end at the top of the slot, though, which should mitigate this failure mode.

Steve in Peoria
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Old 01-09-21, 02:02 PM
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Have a stem the the previous owner drilled & had countersunk a hole through the underside of the stem for a cmptr wire to go through the Steerer Tube. Clean job...!

I did not use it though. Being one that does not like wires running around outside the bike, I've run mine through the fork. PITA, but I like it & have done it to all my bikes. All older Avocet Cyclometers

You need to be able to solder & have some new clips to reattach to the wires. Use a thin/stiff wire to capture the wire, then pull cmptr wire out through the hole.

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Old 01-09-21, 02:07 PM
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Bicycling Magazine (I think) ran a tutorial on how to do this in the 80s, which, Iím not proud to say, I followed. You would drill a hole in the side of your stem, file a groove in the expander wedge, then route the wire through the fork (!) via holes drilled under the crown and in the fork leg. Yeah, I didnít know about stress risers then. Anyway, I and the bike survived, but I wouldnít do it again. Still have the bike, and had the holes filled during restoration.


Hole for routing cyclometer wire through fork.
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Old 01-09-21, 02:24 PM
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Originally Posted by ManekiNico View Post
Bicycling Magazine (I think) ran a tutorial on how to do this in the 80s, which, Iím not proud to say, I followed. You would drill a hole in the side of your stem, file a groove in the expander wedge, then route the wire through the fork (!) via holes drilled under the crown and in the fork leg. Yeah, I didnít know about stress risers then. Anyway, I and the bike survived, but I wouldnít do it again. Still have the bike, and had the holes filled during restoration.


Hole for routing cyclometer wire through fork.
A concentric hole is relatively strong. I mean, peeps have drilled out crank rings, crank arms & such w/o fail for years (ask drillium dude). The forks where Iíve slightly enlarged the weep holes have shown no signs of wear or fatigue going on 30 yrs...
I could see in a stem done wrong as problematic though...?
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Old 01-09-21, 02:33 PM
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I wouldn't have a problem with drilling a hole. Three of my bikes and several friends' bikes have stems drilled for various reasons (bells, cable stops, etc). I believe Jan got Nitto on the record saying it was ok in some issue of Bicycle Quarterly. The slot? ehhh.

As for the bottom bearings, it is far more likely that they got rusty due to water and dirt kicked up by the front wheel, than from water ingress down the stem.
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Old 01-09-21, 04:07 PM
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Thanks for all the good replies. Always helpful to get outside opinions.

BTW if I wasnít clear, I got the bike like this and removed the old wires. I didnít do the mod myself. I can look for a replacement stem.

Think I can save the original tape? I don't think it has sticky adhesive, does it?
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Old 01-09-21, 05:37 PM
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I do enough to my bikes now, this would cause them to leave.
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Old 01-09-21, 06:13 PM
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Originally Posted by Steel1 View Post
Thanks for all the good replies. Always helpful to get outside opinions.

BTW if I wasnít clear, I got the bike like this and removed the old wires. I didnít do the mod myself. I can look for a replacement stem.

Think I can save the original tape? I don't think it has sticky adhesive, does it?
From the picture it looks like Benotto tape, which does not have adhesive, but can be brittle. Worth a try. Benotto tape retains the shape of the original installation, so (in theory) can be re-installed in the same direction of the original orientation.
NOS Benotto tape can still be found if the original tape breaks, or one can use clear tape to splice, in a pinch.
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Old 01-09-21, 07:00 PM
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First off, I’m glad to learn that I’m not the only one still using “wired” bike computers! Not all of my bikes have computers but those that do ALL have the “wired” type. I imagine that someday I may get one of the wireless types. For the ones without a computer, I use a Garmin eTrex Legend. I came across 4 bike mount kits on clearance at Gander Mountain so I’m set.
Back to the OP’s topic . I guess I never thought of running the wire down thru the steerer tube but it seems like more work than it’s worth (even without the potential structural issues)! I too, generally have used the “traditional” method of wrapping the wire around the front brake housing and then down along the fork. Zip ties make things look tidy .
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Old 01-10-21, 02:17 AM
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This is a hollow quill stem bolt, made for BMX bikes. It's meant to pass through the front brake cable, all the way down through the steerer tube and then routed upside down to the side-pull caliper brake. That way you can spin the handlebar 360 degree around with no hindrance.
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