ROCKBROS Thru-Axle Roof Bike Rack Adapter

ROCKBROS roof bike rack adapters: the missing link between your fork and your bars

You have the roof bike rack, you have the bars, you have the bike. What's missing is the right axle. These ROCKBROS aluminum adapters fill that gap perfectly: they convert a fork-clamp mount to modern thru-axle standards, from 9 x 100 mm to 20 x 110 mm. Five options, one simple step, and the fork locks onto the car roof as if the mount had been designed for it.

Why an axle adapter makes all the difference on a roof bike rack

Roof mounts with fork clamping were designed back when 9 mm quick-release was the standard. Modern bikes, however, use 12, 15, or 20 mm thru-axles. The result: a perfectly sound roof fork mount becomes unusable as soon as you change bikes. The adapter restores compatibility for the price of a single part, instead of having to buy an entirely new carrying system.

The solid-machined body has no play and does not mark the fork legs. Once tightened, the assembly does not move: that is the key to riding safely on the highway with the bike above your head.

Machined aluminum: what these ROCKBROS adapters are really worth

ROCKBROS uses aluminum rather than zamak or filled plastic: the threads withstand repeated tightening, the part does not deform under stress, and it does not rust after a winter of road salt. On a car roof bike rack, this is non-negotiable: the part that holds the fork is the only thing between your bike and the road at 130 km/h.

• Five thru-axle standards — 9 x 100, 12 x 100, 15 x 100, 15 x 110, and 20 x 110 mm.
• Machined aluminum — no play during use, no corrosion after exposure to road salt.
• Tool-free installation — the adapter installs on the mount in a few seconds.
• Compatible with road, mountain, and gravel bikes — you just need to know your axle diameter.
• Negligible weight — no impact on the load capacity of your bars.
• Immediate savings — your existing mount becomes compatible again without having to buy a complete replacement.

Identify the right diameter before ordering your adapter

The dimensions are listed on the axle itself or in the fork manual: the first number is the diameter, the second is the spacing between the legs. A modern mountain bike is generally 15 x 110 mm (Boost standard), a disc road bike 12 x 100 mm, and an older mountain bike 20 x 110 mm. If in doubt, measure with calipers rather than estimating by eye. The installation on roof bars is then carried out simply by following your mount's instructions.

Can you ride on the highway with a bike mounted on an adapter?

Yes, provided that the tightening is correct and checked before every trip. Check the torque after the first ten kilometers, then at every break: an axle that is loosening will always give a slight warning before failing. Also respect the maximum load of your bars and the speed recommended by the roof bike rack manufacturer. Compatibility should be checked before installation according to the mount model.

Your carrying equipment selected by Becquet Voiture

Roof carrying is an area where the smallest part makes all the difference. We favor manufacturers who truly machine their adapters, and we provide detailed dimensions rather than selling a "universal" part that is never truly universal. Unsure about your thru-axle standard? Our French team will help you determine it before you order.

Choose the diameter that matches your fork and get your roof bike rack back in service this weekend.

Type: Axle adapter for roof bike rack
Brand: ROCKBROS
Material: machined aluminum
Available standards: 9 x 100 mm, 12 x 100 mm, 15 x 100 mm, 15 x 110 mm, 20 x 110 mm
Use: roof mount with fork clamping
Bike compatibility: road, mountain, gravel, depending on axle standard
Sold: individually, by chosen diameter
Mounting: on existing mount, no drilling required
Maintenance: check tightening before every trip