📏 BTA Stack Guide: How to choose your spacers' height?

The goal of a BTA (Between The Arms) mount is to optimize aerodynamics while keeping your data in view. To avoid any interference with your face during exertion, here's the RocketTT method for calculating your ideal setup.

1️⃣ Measurement Protocol

For maximum precision, do not measure on an empty stomach.

1. Set up your bike on a Home Trainer.

2. Get into an aero position (hands on the extensions, flat back).

3. Ask someone to measure the vertical distance between the top of your cockpit (the base where the mount will be attached) and the underside of your chin/face.

💡 RocketTT Tip: Maintain a safety margin of $10$ to $20\text{ mm}$ to allow head movement without hitting the bottle.

2️⃣ Calculating the "Stack" (Cumulative Height)

To determine the necessary spacer height, you must subtract the height of the RocketTT components from your total measurement.

Here are the fixed heights of our ecosystem:

• Bottle + Standard Bottle Cage: $80\text{ mm}$

• Double Bottle Mount: $20\text{ mm}$

• Garmin Computer Mount: $10\text{ mm}$

• BTA Mount Base: $20\text{ mm}$ (average)

Total fixed components = $130\text{ mm}$

3️⃣ The Magic Formula 🧮

To get your spacer height, apply this simple calculation:

Example: If you have $160\text{ mm}$ of space under your chin: $160-130=30\text{ mm}$. You need a $30\text{ mm}$ spacer.

4️⃣ The RocketTT Trick: The Adjustment Pack

Hesitating or planning to modify your position? Don't stay fixed.

It's entirely possible to choose a shorter main spacer and complement it with our Adjustment Pack.

• Pack composition: 1 x $10\text{ mm}$ spacer + 1 x $20\text{ mm}$ spacer.

• Modularity: These spacers are stackable. You can gain $+10\text{ mm}$, $+20\text{ mm}$ or $+30\text{ mm}$ of height in a few turns of a wrench, without buying a complete new mount.

⚠️ Safety Reminder

All our spacers are made of PAHT-CF (Carbon Nylon) to ensure your setup remains rigid, even with a significant stack of spacers. Just be sure to use the corresponding stainless steel screw length (refer to our hardware guide).