ROBERT AXLE PROJECT · US-machined thru-axle adapters

A Robert Axle Project thru-axle for kid, dog and cargo trailers in M12×1.0 × 217–229 mm (with spacers: 217/229 mm).

Robert Axle Project Thru-Axle | Kid Trailer | M12×1.0 × 217–229 mm (with spacers: 217/229 mm) (Syntace)

A Robert Axle Project thru-axle for kid, dog and cargo trailers. It replaces your bike's stock rear thru-axle with one that carries a bolt-on eyelet for the trailer hitch, so you can tow a kid / cargo trailer from a modern thru-axle bike.

Spec: 12 mm diameter, M12×1.0 thread, 217–229 mm (with spacers: 217/229 mm) long. Machined in USA — Bend, Oregon, in 7075 aluminium with stainless-steel ends. Backed by RAP's lifetime warranty.

The M10×1 threaded stud on the stainless end accepts any standard trailer hitch — the one your Croozer, Thule Chariot, Burley, Weehoo or Wike came with. Installed or removed with a 5 mm Allen key.

Highlights

M12×1.0 × 217–229 mm (with spacers: 217/229 mm) — Direct-fit thru-axle spec
Trailer-ready — Bolt-on eyelet accepts your trailer hitch
7075 aluminium & stainless — Hard-anodised axle shaft, stainless-steel ends
Five-minute swap — Fits with the Allen key you already own
Made in USA — Machined and tested in Bend, Oregon
Lifetime warranty — Backed by Robert Axle Project

At a glance

Best for — Towing a Croozer, Thule, Burley or similar trailer from a thru-axle bike
Ideal rider — Parents or cargo cyclists towing on a thru-axle bike

Full specification

Axle diameter — 12 mm
Thread pitch — M12×1.0
Axle length — 217–229 mm (with spacers: 217/229 mm)
Material — 7075 aluminium axle shaft with stainless steel ends
Made in — USA — Bend, Oregon
Warranty — Lifetime — Robert Axle Project
Compatible brands — Aevon, Burley, Chariot, Croozer, InStep, Thule, Weehoo, Wike
Named-fit bikes — Syntace

Pro tip

If you own a modern mountain, gravel, road or e-bike from around 2018 onwards, you probably have a thru-axle rather than a quick-release. A thru-axle looks like a solid rod that threads directly into the frame — no lever, no skewer. The RAP axle replaces that rod with a matching one that has a bolt-on eyelet for the trailer hitch. Five minutes with the Allen key that came with your bike, and you're done.

This axle ships with spacer options that change the effective thread-engagement length. Compare the length range on the box to your existing axle before you install — pick the spacer that matches.

What's in the box

Robert Axle Project thru-axle — Machined 7075 aluminium shaft with stainless-steel ends
Spacer(s) — To match multiple thread-engagement lengths
Instructions — Simple install with a 5 mm Allen key

Will it fit

Fits bikes with a 12 mm thru-axle, M12×1.0 thread, 217–229 mm (with spacers: 217/229 mm) long. Check your bike manufacturer's spec sheet, or unscrew your existing rear axle and read the markings on it. Robert Axle Project keeps a bike-lookup guide at robertaxleproject.com that lists common bikes and their axle specs.

Fits kid trailers and cargo trailers that use a hitch-and-nut mount — Croozer (Click & Crooz), Thule Chariot, Burley, Weehoo, Wike, Aevon, InStep and similar. The RAP axle replaces your rear wheel axle and provides an M10×1 threaded stud that accepts the standard trailer hitch.

Named-fit bikes on the source page: Syntace.

Not sure if it fits? Email fit@hitchabike.co.uk with your bike make, model and year — we'll match you to the right axle. Robert Axle Project and Croozer both make thru-axle solutions for trailer-hauling; either is a valid answer depending on your axle spec.

Quick answer

A Robert Axle Project thru-axle for kid, dog and cargo trailers in M12×1.0 × 217–229 mm (with spacers: 217/229 mm). Replaces your bike's rear thru-axle so you can tow a trailer from a thru-axle bike. Made in USA — Bend, Oregon, lifetime warranty. £86.95.

Fast facts

Thread: M12×1.0
Diameter: 12 mm
Length: 217–229 mm (with spacers: 217/229 mm)
Material: 7075 aluminium axle shaft with stainless steel ends
Made in: USA — Bend, Oregon
Warranty: Lifetime (RAP)
SKU: 44412
Named-fit bikes: Syntace

Choose if

Your bike has a 12 mm rear thru-axle with a M12×1.0 thread and you want to tow a Croozer, Thule, Burley or similar kid/dog/cargo trailer.
You want a lifetime-warranty, made-in-USA axle from the company that pioneered thru-axle trailer solutions.
You already own a Croozer, Thule Chariot, Burley or similar hitch-mount trailer and need the axle to attach it to a thru-axle bike.

Not ideal if

Your bike has a quick-release rear axle (a lever-and-skewer setup) — you don't need a thru-axle. Use the Croozer Universal Click & Crooz Round Axle Hitch (/products/croozer-universal-click-crooz-round-axle-hitch-for-kid-kid-plus) or the standard hitch your trailer came with.
Your rear axle is not M12×1.0 — the axle must match. Check first, or email fit@hitchabike.co.uk.
You want a Croozer-native thru-axle solution — the Croozer Click & Crooz thru-axle adapter is a valid alternative if we stock one that matches your axle spec.

FAQ

How do I know if this axle fits my bike?

Check your bike manufacturer's spec sheet for rear-axle diameter, thread pitch and total length. Or unscrew your existing rear axle and read the markings. Or email fit@hitchabike.co.uk with your bike make, model and year.

Is the trailer hitch included?

No. The hitch is what comes with your trailer (BOB skewer, Croozer Click & Crooz, Thule ball hitch, etc.). This axle just gives that hitch a mounting point on your bike.

What tool do I need to install it?

A 5 mm Allen key — the same one you likely already carry.

Is there a warranty?

Yes — Robert Axle Project offer a lifetime warranty on their axles and adapters.

Where is it made?

Machined and tested in Bend, Oregon, USA.

Does this work with my Croozer?

Yes — Croozer's standard trailer hitch mounts to the M10×1 threaded stud on the stainless-steel end of the RAP axle. Works with the Kid, Yuuna, Dog and Cargo Croozer lines that use the Click & Crooz hitch system.