Aero BTA System Landingpage

THE NUMBERS

Average of 6W Lost by Having Two Bottles on the Frame — Up to 12W in Our Testing on 35 Athletes. That's an Average of 2.5 Minutes Lost on a 5-Hour IM Bike Split.

*AeroGain velodrome testing, Ballerup Super Arena, Denmark. 45 km/h, 0° yaw, n=35 athletes.

20W+

peak saving observed, optimal setup compared to two frame mounted bottles

median saving for the Aero BTA double-bottle mount across all 35 test athletes

>10W

added drag from two frame-mounted bottles, same 45 km/h test conditions

This isn't a single-rider wind-tunnel run. It's a population test across 35 athletes spanning a range of positions and body types. The gain runs from neutral all the way to roughly 12W depending on your position and setup, with 8W as the median outcome most riders should expect.

AeroGain's own velodrome testing — Ballerup Super Arena, Copenhagen. 35 athletes, test speeds 35–50 km/h. Error bars show two standard deviation.

THE MECHANISM

It's Not the Bottle. It's the Gap It Fills.

01 — THE DEAD AIR

In an aggressive aero position, a pocket of separated, turbulent air sits in the gap between your forearms and your chest. This is dead air — flow that has already detached from the body and is stalling instead of moving cleanly past it. Aerodynamically, it is expensive.

02 — FILLING THE GAP

Place a bottle between the arms, close to and parallel with the chest, and it fills that exact gap. Air that would otherwise separate and stall is instead guided smoothly around your whole body. The bottle stops being an obstruction and becomes part of the airflow.

Airflow schematic: frame-mounted disruption vs. between-the-arms flow attachment.

Why the Down Tube Does the Opposite

A bottle mounted on the down tube sits in a path of air that was already flowing cleanly between the legs. Putting a bottle there doesn't fill a gap — it creates a new obstruction where none existed. That's exactly why frame-mounted bottles add drag instead of removing it.

And because the bottle sits right in front of your chest, you can reach it without sitting up out of the aero position — no repeated loss of position to drink over the course of a race.

THE PRODUCT

The Aero BTA System

A front-mounted, between-the-arms hydration mount that fills the gap conventional bottle placement leaves open — engineered and velodrome-tested, not guessed at.

1.282,00 kr

Single or dual-bottle setups on the same mount

BTA Plate Width

Medium (52 to 148 mm) Wide (148 to 198 mm) Extra Wide (above 198 mm)

Angle

0° 10° 15° 20° 25° 30°

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Shop the Aero BTA System — €169.90

SETUP GUIDE

Take These Two Measurements Before You Order

Two measurements determine your exact fit: the angle of your extensions, and the width of your armpad bridge. Get both right and the bottle sits perfectly horizontal and centered between your arms.

HOW IT MOUNTS

The BTA base plate mounts underneath your existing armrest pads — it's sandwiched directly beneath the armcups, which clamp down and hold the plate firmly in place. No extra brackets, no swapping your pads: your current armcups do the clamping.

1. Match Your Spacer to Your Extension Angle

Your BTA spacer angle has to match the upward tilt of your entire mounting bracket and clip-on extensions — the whole assembly, not just the extension. Match the spacer to that angle and the bottle sits perfectly level between your arm pads.

0°

Extensions horizontal (0°) → Use the 0° spacer

20°

Extensions tilted up (20°) → Use the 20° spacer

30°

Steep extension tilt (30°) → Use the 30° spacer

Not sure of your angle? Use your phone's built-in level tool (e.g. Apple's Measure app) resting flat against your extensions to read the exact degree.

2. Measure Your Armpad Bridge Width

Measure from mounting bolt to mounting bolt across your armpad bridge.

Medium

52–148mm

Wide

148–198mm

Extra Wide

198–238mm

HOW THIS STARTED

This Started as a Bottle Stuffed Down a Race Suit

We didn't just theorise this. The aero gain was discovered by accident, used at the highest level of the sport, then banned — and the Aero BTA system is the engineered, legal successor to a technique that already proved itself.

2022

AeroGain founder Kristoffer Visti first experimented with carrying a bottle stuffed down the front of his race suit at the Danish National Championships, discovering the aero benefit by accident — not from a wind tunnel, from racing.

Later That Year

Triathlete Magnus Ditlev used the same technique at the Ironman World Championship in Kona — the same principle, now on the world's biggest triathlon stage.

Early 2024

World Triathlon and Ironman banned the in-suit technique, for safety and uniformity reasons — the aerodynamic principle wasn't in question, the method of carrying it was.

The Successor

The Aero BTA system was developed as the engineered, legal answer — same aerodynamic principle, filling the gap between the arms and chest, now properly mounted instead of stuffed into a suit.

What was once a rule-bending hack is now a properly engineered, velodrome-tested mount.

HOW IT'S BUILT

Built to Sit Exactly Where the Gap Is

Modular Spacer System

Angle-matched spacers at 0°, 10°, 15°, 20°, 25° and 30°.

The bottle sits perfectly horizontal regardless of your extension angle — most one-piece BTA mounts don't adjust at all, so the bottle sits tilted to whatever angle your bars happen to be at.

Three Width Fits

Medium (52–148mm pad-bridge width), Wide (148–198mm), Extra Wide (above 198mm).

Covers most tri-bar setups without custom fabrication or filing down parts to fit.

Integrated Nose-Cone

A shaped nose-cone leads the airflow into the arm-chest gap instead of presenting a blunt bottle face to it.

Measurably less drag than AeroGain's earlier, non-nose-cone BTA design.

Clamps to Standard Pad Bridges and Aero Bars

Mounts directly onto standard pad bridges and tri-bar systems, matte black finish.

Fits most existing tri-bar cockpits without swapping hardware.

Made and Tested in Denmark

Small-batch manufacturing, validated on a velodrome with a 32-athlete population test — not CFD-only or single-rider marketing claims.

Numbers you can trust because they weren't generated in a spreadsheet.

Single or Dual-Bottle Setups

The mount accepts one or two bottles on the same frame.

Race-day hydration without going back to a frame-mounted bottle for the second bottle.

How to mount the Aero BTA system

Tool-free reference — standard allen keys, a few minutes, no special tools.

IS THIS FOR YOU

Built for Tri-Bar Cockpits and Riders Who Measure Things

This is for you if:

You race on a dedicated TT or triathlon bike with a tri-bar cockpit and pad bridge

You already know your FTP and think in watts, not vibes

You've optimised your helmet and wheels and want the next real gain, not a marginal-gains platitude

You want a mount that adjusts to your actual extension angle instead of forcing your position to match the mount

This isn't for you if:

You ride a road bike without clip-on aero bars or a pad bridge to clamp onto

You're looking for a rear/behind-the-saddle hydration and storage system (that's a different AeroGain product, the BTS system — not this one)

You want a one-piece mount and don't care about angle-matching

If your cockpit has a pad bridge and you care about the number, this is built for exactly that setup.

COMMON QUESTIONS

Fit and Installation, Answered

The Aero BTA system clamps onto standard pad bridges and tri-bar systems, in three width fits: Medium (52–148mm pad-bridge width), Wide (148–198mm), and Extra Wide (above 198mm). Measure your pad-bridge width before ordering — see the sizing schematic above.

Yes, as long as your clip-on aero bars have a pad bridge to clamp onto, the same width and angle fits apply. It's not designed for road bikes without clip-ons.

Yes, the mount supports single or dual-bottle setups on the same frame.

The system ships with angle-matched spacers at 0°, 10°, 15°, 20°, 25°, and 30°, so you pick the spacer that matches your extension angle and the bottle sits perfectly horizontal regardless of your position.

No. It installs with standard allen keys in a few minutes — no special tools required.

AeroGain's own velodrome testing at Ballerup Super Arena, Denmark, at 45 km/h, 0° yaw, across 35 athletes — not a single-rider tunnel run or a CFD simulation. Median saving was 8W, with a range up to 12W depending on rider position and setup.

TEST DATA

The Numbers

The real aerodynamic drag data behind the BTA system's savings claim — measured across a realistic race speed range, not modeled. Every figure below is a wind-tunnel and velodrome observation, presented as-is.

6–10W

Drag cost of two 750ml bottles mounted on the frame, versus running no bottles at all.

15W

Most extreme frame-bottle penalty observed in testing — recorded at 45 km/h.

5–12W

Additional savings from relocating those same two bottles to a between-the-arms (BTA) mount.

20W+

Total potential savings when moving two bottles from the frame to BTA — the combined, real-world upside.

All figures observed across a realistic race speed range. Individual results vary with rider position, bottle size, and yaw.

Test Conditions & Methodology

Aerodynamic claims are based on AeroGain in-house testing conducted at Ballerup Super Arena velodrome, Denmark. Conditions: 45 km/h, 0° yaw, n=35 athletes across a range of riding positions and body types. Savings shown compare optimal front-bottle (Aero BTA) placement against a baseline of no BTA mount / conventional setup (no front bottle, or a frame-mounted bottle). Results ranged from neutral to approximately 12W, with a median saving of 8W across the test population. Frame-mounted bottle drag reached up to 15W in the worst tested position, with a median cost of 6W across the test population, under the same test conditions. Individual results vary by rider position, equipment, and setup.