2025 HYDRATION REGULATIONS

New DTU Regulations for Front Hydration Systems (2025)

The German Triathlon Union (DTU) updated its Sportordnung 2025 with clear limits on the size and placement of hydration systems to prevent aero fairings. Any bottle, cage, or container mounted on the front end (aerobars/handlebars) must stay within a defined imaginary box relative to the rider’s armrests.

Note this is the same reference point used for the initial sizing of your TF1, (pad stack and reach).

Specifically, front-mounted hydration setups (e.g. between-the-arms bottles) must remain:

– No more than 25 cm rearward (toward the saddle) from the elbow pad base reference (TF1 ref; reach to back of pad)

– No higher than 20 cm above the pad’s lowest point (TF1 ref; stack to pad)

– Not beyond the frontmost point of the aerobars or extensions (i.e. cannot protrude in front of your bar tips).

– At least 2 cm above the front wheel’s top (cannot extend downward too close to the wheel). Never a problem with the FAST fork!!!

These constraints (illustrated in the DTU diagram below) ensure any BTA hydration system stays within a 25 cm (fore-aft) by 20 cm (height) envelope, and clear of the wheel. The DTU also caps total front hydration volume at 2 litres, (but this is generally not a concern with standard bike bottles. Importantly, no part of the rider’s body may rest on or be covered by these hydration components) – they must purely serve as hydration, not as an aero arm shield.

DTU’s official schematic of allowed hydration system dimensions (green zone) on a triathlon bike (Any front hydration (blue bottle between the arms) must fit within 25 cm rearward (red dashed line) and 20 cm upward of the elbow pads, not extend past the aero bar tips, and stay ≥2 cm above the front wheel.

Kú TF1 Top Cap Bottle Mount – Design and Placement:

The Kú TF1 triathlon bike features a standard bottle cage mounted on the top cap of the headset (at the top of the head tube). This places a bottle between the rider’s forearms, tucked close to the head tube. In practice, the bottle sits just in front of the rider’s torso/chest, in line with or slightly above the aerobars – a location chosen to both improve aerodynamics (filling the gap between the arms) and ease drinking in the aero position. The mount uses two bolts on the steerer top cap, and a normal cycling bottle and cage. By design, this integration keeps the bottle low and centred. Essentially, the TF1’s top-cap mounted hydration is a minimal BTA system that follows the bike’s existing profile.

Because the Kú’s bottle cage is attached to the movable part of the front end (the steerer/handlebar assembly), the DTU categorizes it under the “Lenker” (handlebar) rules – not as a top-tube storage unit. (The DTU rules for top-tube mounts are different and more restrictive, but the TF1’s bottle is not on the fixed top tube; it’s on the steering assembly, so it falls under the front hydration allowances.) This distinction is important: the DTU explicitly disallows separate hydration bladders on the top tube itself and does render the current Kú bento box illegal for DTU sanctioned events.

Analysis of the TF1’s standard bottle setup against DTU’s criteria confirms it is fully legal, for all frame sizes under the 2025 rules. Even when considering a “worst-case” configuration of minimum stack and maximum reach as the pad measurement reference point, the mount stays within the DTU’s limits:

Kú TF1 with minimum stack and maximum reach applicable to all sizes

– Rearward Extension: The TF1’s bottle sits centred around the headset – well within the 25 cm allowance behind the arm pads. In practice, the back of the bottle is very close to the head tube and nowhere near 25 cm aft of the pads. Even if an athlete uses a very forward pad position (moving the pads ahead of the bottle), the bottle won’t extend 25 cm backward past the pad mount point. Measured from the elbow pad’s underside (DTU reference point), the TF1 bottle mount positions the bottle only on the front side or directly between the pads, easily satisfying the ≤25 cm rearward rule.

– Height: A standard cycling bottle on the TF1 top cap mount sits well below the 20 cm height limit above the pads. The DTU measures height from the bottom of the arm cup; In the most extreme scenario, minimum pad stack, the top of the bottle remains slightly under the 20 cm threshold. This means the TF1’s BTA bottle does not exceed the 20 cm height allowance in any size configuration. By comparison, many banned “fairing” bottles were much taller – the TF1’s setup is far more compact.

– Forward Limit: The TF1’s bottle mount is between the extensions, behind the shifters and BTA bridge. It does not stick out past the ends of the aerobars. This complies with the DTU mandate that front hydration cannot extend beyond the frontmost point of the bars. In fact, the bottle sits behind the bar tips in the airflow, so it’s comfortably within this limit.

– Front Wheel Clearance: The bottle and cage sit on top of the top tube/head tube area – nowhere near the front wheel. There is ample clearance above the wheel, easily satisfying the rule requiring ≥2 cm gap to the wheel’s top.

– Additionally, the TF1’s top cap bottle mount is made of carbon composite and a standard bottle, meeting the DTU requirement that hydration components be of unbreakable material).

– There is no aspect of the Kú system that would cover the rider’s arms or allow resting on the bottle – the arms rest on their pads beside the bottle, not on it. This means it also honours the rule that arms cannot be supported by or hidden behind the hydration system.

Conclusion and Athlete Guidance

The standard top-cap mounted bottle on the Kú TF1 is legal under the new DTU 2025 rules. The bike’s front hydration configuration was evaluated against the DTU’s precise limits (25 cm length, 20 cm height, etc.) and found to be compliant in all respects. Even in the most extreme positioning, the TF1’s between-the-arms bottle stays within the allowed envelope and thus requires no modification or special exemption for use in Germany. Athletes riding a Kú TF1 can confidently use the stock top cap bottle mount in DTU-sanctioned events, regardless of frame size or rider setup, and remain within the regulations.

All Kú TF1 owners should ensure their bottle and cage are installed as intended; the cage bolts tight to the top-cap mount.

In summary, no action is needed – the Kú TF1’s front bottle solution is “race legal” for DTU events in 2025 and beyond, providing both hydration and aerodynamic benefits without breaking any rules (DTU-Regelwerk: Klare Vorgaben für installierte Trinksysteme und aerodynamische Aufbauten – tri2b.com

Alternative solution:

Using a standard (200mm tall) cycling bottle facing rearwards, when assembled correctly, this system will naturally fall inside the DTU’s limits for front hydration. The worst-case compliant configuration has been illustrated in DTU’s guidance (see figure 1 above), and the Kú TF1’s design stays inside those boundaries. For those athletes not at maximum reach or minimum stack it may be possible to mount a taller rearward facing bottle and still respect the 250mm maximum rear ward position of the regulation. In this solution additional hydration can be added with a second forward facing bottle with the size limit being the end of the extensions or a 2 litre maximum capacity from both bottles.

Kú TF1 with 200mm tall rearward facing bottle with second forward facing bottle

Kú bottle mount extender
As of the 20^th May 2025 Kú Cycle have introduced a specifically machined bottle mount extender that, mounts to the standard cage fixings in the top cap. This extender allows a combination of two ‘mirrored’ bottles as above or, alternatively, a single large bottle depending on rider preference and hydration needs for a particular event.

Sources: The DTU Sportordnung 2025 clarifying hydration system dimensions (DTU-Regelwerk: Klare Vorgaben für installierte Trinksysteme und aerodynamische Aufbauten – tri2b.com), and analysis of the Kú TF1 standard bottle mount design. (DTU reference: Lenker-mounted hydration must be ≤25 cm back, ≤20 cm tall, not past bar tips, and ≥2 cm above front wheel (DTU-Regelwerk: Klare Vorgaben für installierte Trinksysteme und aerodynamische Aufbauten – tri2b.com).

Media Contact Kú Cycle:

Alex Bok
alex@ku-cycle.com
+31 (0) 683 033 920

About Kú Cycle
A Dutch based company with a mission to design bikes and performance solutions that will change the sport forever – the perfect fit between body and machine. We believe a rider’s position should be established independent of the bike and will therefore reposition bike fitting services from a post-purchase service to a pre-purchase service. A new production process (built-to-order) and a completely different sales model are introduced with a single objective: athlete performance delivered!