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March 15, 2026 00:45
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light-research.md
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This is a solved problem in the bike industry — every major component maker now offers an internal cable routing (ICR) system through the headset. Since you're designing the Omera frame from scratch, you can pick the approach that works best.
How It Works
All systems share the same core idea: a slotted compression ring sits inside the head tube between the steerer tube and the upper bearing. Cables/hoses pass through the gap between the steerer and the head tube wall, bypassing the bearing entirely. enduro-mtb
The Three Approaches
Oversized upper bearing (industry standard)
Use a 1½" (52mm) upper headset cup with a standard 1⅛" steerer. The ~12mm gap between the steerer and the cup gives plenty of room for brake hoses, the H1E light wire, and antenna coax to pass through. This is what most modern road and gravel frames use. Your head tube just needs a 44mm bore at the top. forum.customframeforum
Semi-integrated (simplest for a custom build)
Use a standard 1⅛" headset with a slotted top cover from brands like Prestine or FIRST Components. The cables exit from under the stem, pass through slots in the top cover/spacers, and drop into the head tube. No proprietary stem needed — you use any stem you want. [prestine.com](https://www.prestine.com.tw/internal-cable-routing)
Fully integrated (cleanest look, most restrictive)
One-piece bar/stem combos (ENVE In-Route, FSA ACR, Deda DCR) where cables disappear entirely inside the bar and exit directly into the headset. Looks incredible but locks you into a specific ecosystem and makes maintenance painful. firstcomponents
What Makes Sense for Omera
The oversized upper bearing approach is the move:
- Head tube design: Weld it to accept a 44mm upper cup (IS52 or ZS56 standard) and a standard lower. Prestine and others sell these off the shelf. prestine.com
- Cable path: Brake hoses + H1E wire + antenna coax exit the handlebar, wrap under the stem, pass through the slotted top cover, and drop into the gap between the steerer and the 52mm cup.
- Inside the head tube: Everything continues down and exits through a 22–35mm access hole at the HT/DT junction into the down tube. [forum.customframeforum](https://forum.customframeforum.com/t/internal-hidden-cable-stems-headsets-and-forks-resource/2473)
- Brake hoses split off to the fork (front) and chainstay (rear) at the head tube junction, while the electrical wires continue into the DT.
The Full Routing Bundle
Everything going through the headset in one pass:
| Wire/Hose | From | To |
|---|---|---|
| Front brake hose | Handlebar lever | Fork / front caliper |
| Rear brake hose | Handlebar lever | Down tube → chainstay → rear caliper |
| H1E light DC wire | Handlebar | DT electronics (KT light output) |
| Antenna coax (U.FL) | Plastic top cap | DT electronics (BT/GPS module) |
Plastic Top Cap + Antenna
This still works perfectly with the oversized bearing approach. The top cap sits above everything. Replace the standard aluminum top cap with your 3D-printed plastic cap containing the GPS/BT antenna. The slotted compression ring and cable routing happen below it, inside the headset — they don't interact with the top cap at all. prestine.com
So your top cap stack becomes:
[Plastic antenna cap] ← GPS/BT radome, coax exits downward
[Stem] ← clamps steerer
[Slotted spacer(s)] ← brake hoses + wires pass through slots
[Slotted compression ring] ← sits in the 52mm upper cup
[Upper bearing] ← standard sealed cartridge
The key frame design detail: make the HT/DT junction hole at least 22mm diameter so all four lines (2 brake hoses + light wire + coax) can pass through without kinking. forum.customframeforum
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This is a brilliant idea and it works perfectly from an RF physics standpoint. Aluminum blocks GPS/BT signals completely, but plastic (ABS, polycarbonate, nylon) is fully RF-transparent. A plastic top cap becomes an antenna window.eabel+1
Why the Top Cap Is the Ideal Antenna Location
GPS needs sky visibility — the top cap faces straight up, unobstructed. Best possible position on the entire bike.
Bluetooth needs line-of-sight to a phone in your pocket — top of the steerer, above the frame tubes, is great.
The steerer tube is a metal cylinder that would kill signal if you buried the antenna inside it. But with a plastic cap on top, the antenna sits right at the opening, radiating outward.eevblog+1
What Already Exists
There are already AirTag headset top cap mounts — they use a machined aluminum base with a plastic or polycarbonate cover on top, specifically because the AirTag needs to transmit BT through the cap. SpyBike made a dedicated GPS tracker that lived entirely inside a top cap. So the concept is proven.aliexpress+1[youtube]
How to Do It for Omera
Your electronics module (BT + GPS radio) lives inside the DT. Run a thin coax or antenna feed wire up through the same path as the H1E light cable:
Inside the top cap, mount a small dual-band ceramic patch antenna (GPS L1 + BT 2.4GHz — these are ~15×15mm, a few dollars each). The plastic cap acts as the radome.
For the cap itself:
3D print in ABS or PETG — both are RF-transparent and weather-resistant[eabel]
Match the diameter to standard 1⅛" (28.6mm steerer, ~31.8mm OD cap)
Make it thick enough to hide the antenna inside (8–10mm tall)
Add a small channel for the coax to exit downward into the steerer
Design Considerations
The aluminum steerer tube actually helps here — it acts as a ground plane and shield below the antenna, which can improve the upward radiation pattern for GPS. You get shielding from frame noise below and a clear sky window above.[data-alliance]
This is honestly a cleaner solution than the plastic console on the DT you were considering for the antenna. The top cap is the highest, most exposed point on the bike — ideal for both GPS and BT. And since you're already routing the H1E light wire through the steerer, adding a thin coax alongside it is trivial.
Why the Top Cap Is the Ideal Antenna Location
What Already Exists
There are already AirTag headset top cap mounts — they use a machined aluminum base with a plastic or polycarbonate cover on top, specifically because the AirTag needs to transmit BT through the cap. SpyBike made a dedicated GPS tracker that lived entirely inside a top cap. So the concept is proven. aliexpress
How to Do It for Omera
Your electronics module (BT + GPS radio) lives inside the DT. Run a thin coax or antenna feed wire up through the same path as the H1E light cable:
Inside the top cap, mount a small dual-band ceramic patch antenna (GPS L1 + BT 2.4GHz — these are ~15×15mm, a few dollars each). The plastic cap acts as the radome.
For the cap itself:
Design Considerations
The aluminum steerer tube actually helps here — it acts as a ground plane and shield below the antenna, which can improve the upward radiation pattern for GPS. You get shielding from frame noise below and a clear sky window above. [data-alliance](https://www.data-alliance.net/blog/antennas-mounted-on-metal-enclosures-guidance)
This is honestly a cleaner solution than the plastic console on the DT you were considering for the antenna. The top cap is the highest, most exposed point on the bike — ideal for both GPS and BT. And since you're already routing the H1E light wire through the steerer, adding a thin coax alongside it is trivial.