Our Sour UDH: Universal…but actually practical

We didn’t want to just “put a UDH on the bike.”
We wanted one that works with our frame philosophy, with real‑world setups, and especially with gear systems like Tailfin, which so many Sour riders use.

So we re‑designed the entire interface with a few… let’s call them unusual but incredibly useful decisions.

1. M12x1 thread: Because swapping to Transmission shouldn’t require new hardware

Most UDH setups use mixed axle standards.
We decided: Nope. Let’s keep it simple.

Our dropout uses a straight M12x1 thread, the same used by SRAM Transmission axles.
Meaning:

No new axle needed when upgrading
No adapters
No “which axle does my frame need?” confusion
Just install the new derailleur and ride

A tiny detail, but a huge quality‑of‑life improvement.

2. The UDH bolt with a 12 mm hex — Tailfin‑ready out of the box

The standard UDH bolt uses a small Allen size.
We made ours a lot more… industrial.

We built the UDH bolt directly around a 12 mm hex interface, so Tailfin thru‑axles can sit perfectly, solidly, and without the usual adapter drama.

And because we know not everyone carries a 12 mm tool in their jersey pocket, we include a small 6 mm adapter — so you can still tighten or loosen it with the tools you already have.

It sounds odd, but once you’ve mounted Tailfin in under 10 seconds, you’ll understand why we did it.

3. A 17 mm outer wrench interface: For the “oh no, my axle is stuck” moments

Every bikepacker knows the feeling:
You’ve overtightened your axle. It’s wet. It’s muddy. Tailfin is clamped on. And now nothing moves.

So we added a feature we’ve honestly never seen on any other UDH bolt:

A 17 mm outer wrench flat.

This means you can:

Grab it with a standard open‑ended wrench
Or even pliers
And free the axle without dismantling half your luggage system

A small “emergency escape hatch” that suddenly feels like the smartest idea ever when you’re stuck on a mountain pass with cold fingers and zero leverage.

Material: 7075 T6 Aluminum anodized

Tailfin Compatible UDH

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