Apidura Aero Bolt-On Top Tube Module
The Apidura Aero Bolt-On Top Tube Module is a strapless, aero-optimised top tube pack that integrates with your bike's stem for competitive gravel racing. It holds 0.4 L, weighs 95 g and attaches with two M5 hex-headed bolts to top tube mounts. Developed through Computational Fluid Dynamics (CFD) analysis, it smooths airflow behind the stem; combined with the Aero Frame Module it creates an average 5 watt saving at race speed, validated through wind tunnel testing.
Why an aero top tube module – and why this one
Air flowing over the stem leaves a low-pressure pocket behind it, which causes drag. A conventional bag does not address this. The Aero Bolt-On Top Tube Module addresses it and the usual top tube bag compromises:
- It reduces drag. Transfer Panels bridge the gap between the stem and the top tube, so oncoming air glides across the front of the bike instead of getting trapped. Together with the Aero Frame Module, Apidura reports an average 5 watt saving at race speed.
- It integrates with the stem. An elastic tensioner contours to the stem and draws the Transfer Panels inwards for a gap-free, aerodynamic fit.
- The attachment is solid and minimal. A carbon plate and low-profile hex bolts create a strap-free fit, and a flexing centre channel pulls the module flush against the top tube.
- It adjusts to your frame. 64 mm bolt spacing and 5 cm of fore-aft adjustment ensure precise alignment between the module and the rear of the stem.
- It is quick to use. The magnetic opening allows quick, one-handed access, and the slim profile reduces the chance of knee rub when sprinting.
Who is it for?
- Competitive gravel racers who want to improve aerodynamic efficiency.
- Riders with top tube mounting points who prefer a strapless fit – the module is optimised for modern, flat-surface carbon top tubes and is also compatible with traditional round tube shapes.
- Riders building a full aero setup by combining it with the Aero Frame Module (Aero System Medium 300 g, Large 330 g in total, including the Frame Module).
Key features
Stem integration
Transfer Panels designed to conform to the stem for aero-optimised integration.
Quick entry
Magnetic opening allows for quick, one-handed access.
One system, your setup
Three top tube modules and two frame modules to mix and match.
Minimalist attachment
Carbon plate and low-profile hex bolts create a solid, yet minimal attachment.
Knee clearance
Slim profile reduces the chance of knee rub when sprinting.
Fore/aft adjustability
Five centimetres of adjustment for a perfect fit on any frame.
Removable padded base
Protects your gear and minimises contact with the frame.
Made from Hexagrid
Ultralight, high-strength nylon grid, laminated with TPU for a minimalist, yet structured material.
Materials & technology
- Hexagrid – an ultralight, high-strength nylon grid laminated with TPU to create a minimalist yet structured material. PFA- and PFC-free.
- HDPE – high-strength, rigid reinforcement boarding with good shape recall to avoid deformation.
- Aero optimised – active improvement of the aerodynamic performance of the bike and rider.
- Ultralight – minimal design and lightweight materials for optimal weight-performance.
- Wind tunnel tested – the Aero System is validated through wind tunnel testing, with an average 5 watt saving when the top tube and frame modules are combined.
Specifications
| 0.4 L (TSB) | |
|---|---|
| Capacity | 0.4 L |
| Storage | Single main compartment |
| Closure | Fast entry magnetic closure |
| Attachment | Two M5 hex-headed bolts anchor the module to top tube mounts (64 mm bolt spacing, 5 cm fore-aft adjustment); centre channel in the base flexes around the mounting points and pulls the module flush against the top tube; elastic tensioner contours to the stem and draws the Transfer Panels inwards |
| Structure | Full-length carbon fibre reinforcement for a rigid, strap-free fit; internal HDPE thermoplastic frame |
| Waterproofing | Seam welded – bespoke materials and RF welding create watertight seams. The materials are fully waterproof, but the magnetic closure is not |
| Visibility | Reflective graphics |
Care & maintenance
- Spot clean only – stains can be spot treated with concentrated dishwashing liquid. Abrasion is not recommended.
Frequently asked questions
How does the Aero Top Tube Module improve aerodynamics?
Air flowing over the stem creates a pocket of low-pressure air directly behind it, which causes drag. The module's Transfer Panels bridge the gap between the stem and the top tube, filling this space so oncoming air glides smoothly across the front of the bike instead of getting trapped. This reduces aerodynamic drag.
Can I use the Aero Top Tube Module with steel, titanium or other traditional round tube shapes?
Yes. The Aero Top Tube Modules are optimised for modern, flat-surface carbon top tubes but are compatible with traditional round tube shapes. The slim profile and non-slip silicone base ensure a stable fit; the bolt-on versions give a direct, locked-in mount.
How do I attach the Aero Bolt-On Top Tube Module?
The module uses two M5 hex-headed low-profile bolts that screw directly into the top tube mounting points.
About Apidura
Founded in 2013, Apidura designs bikepacking bags for long-distance and ultra-endurance riding, tested by riders on events such as the Transcontinental Race and the Tour Divide. The range is built around three families: the fully waterproof Expedition series for touring and all-weather bikepacking, the lightweight Racing series for ultra-distance racing, and the rugged Backcountry series for off-road trails.
Every Apidura product comes with a 3-year producer guarantee from the date of purchase, covering the entire product. After that, Apidura can support at-home repair or recommend a trusted repairer.
