1. Introduction
The CYBEX Sirona S is a convertible car seat designed for the safety and comfort of your child. It features an innovative 360° rotatable seat, allowing for quick and easy transitions between rear-facing and forward-facing positions, and simplifying child placement and removal. This manual provides detailed instructions for the proper installation, operation, and maintenance of your Sirona S car seat.

Figure 1: CYBEX Sirona S Convertible Car Seat in Manhattan Grey.
2. Safety Information and Features
The Sirona S is engineered with multiple safety features to provide superior protection for your child.
- 360° Rotatable Seat: The first convertible car seat in the U.S. to feature a 360° rotatable seat with a load leg, making switching between rear-facing and forward-facing positions quick and easy. This also simplifies getting your child in and out of the seat.
- SensorSafe™ Technology: Built into the chest clip, SensorSafe provides real-time app alerts for unsafe situations. These alerts include if a child unbuckles themselves, if the back seat is too warm or cold, if a child has been seated for too long, or if the driver accidentally leaves the child behind.
- Steel-Reinforced Frame and Anti-Rebound Design: Reduces car seat rebound movement in the event of a crash, enhancing stability and safety.
- Linear Side-Impact Protection (L.S.P.): This system absorbs up to 25% more impact in a collision when compared to the same car seat without L.S.P. extended, providing enhanced side-impact protection.
- Load Leg: Can reduce rotation in certain crashes by up to 30%, further stabilizing the car seat.

Figure 2: SensorSafe™ technology providing alerts via a mobile app.

Figure 3: Illustration of One-Hand 360° Swivel Seat, Load Leg, and Anti-Rebound Base & L.S.P. features.
3. Installation
The Sirona S is designed for easy and secure installation using your vehicle's seat belt system.
3.1. EasyLock™ Bar and One-Time Belt Installation
The EasyLock™ Bar works with your vehicle belt for simple and secure installation. This one-time belt installation secures both forward and rear-facing positions, allowing for a seamless transition between modes without re-installation.
- Position the car seat in the desired orientation (rear-facing or forward-facing) on your vehicle's seat.
- Locate the EasyLock™ Bar and follow the belt path indicators on the car seat.
- Thread your vehicle's seat belt through the designated path.
- Engage the EasyLock™ Bar to tighten the seat belt, reducing the force needed for secure installation.
- Verify the dual-level indicators to ensure the car seat is at the proper recline angle for safe use.
- Ensure the load leg is properly extended and secured to the vehicle floor.

Figure 4: Close-up of the one-time vehicle belt installation mechanism.
4. Operation
4.1. 360° Rotating Seat
The unique 360° rotating seat allows you to easily turn the car seat towards the car door for effortless loading and unloading of your child. To rotate the seat, locate the rotation release lever (refer to the car seat labels for exact location) and turn the seat to the desired position. Ensure the seat clicks securely into place before driving.

Figure 5: A parent demonstrating the ease of placing a child into the rotating car seat.
4.2. Harness and Headrest Adjustment
The Sirona S features a 12-position headrest with a no-rethread harness, allowing you to adjust the height of the shoulder straps as your child grows without the need to re-thread the harness.
- To adjust the headrest and harness height, locate the adjustment lever at the top of the headrest.
- Squeeze the lever and slide the headrest up or down to the appropriate position. The shoulder straps will adjust simultaneously.
- Ensure the shoulder straps are at or just below your child's shoulders when rear-facing, and at or just above their shoulders when forward-facing.

Figure 6: Visual representation of the 12-position adjustable headrest and Linear Side Impact Protection (L.S.P.).
4.3. SensorSafe™ App Integration
To utilize the full benefits of SensorSafe™ technology, download the SensorSafe™ mobile app on your smartphone. The chest clip syncs automatically with the app to provide instant safety alerts. Ensure your phone's Bluetooth is enabled and the app is running in the background for continuous monitoring.
5. Care and Maintenance
Proper care and maintenance will ensure the longevity and safety of your CYBEX Sirona S car seat.
- Fabric Covers: The fabric covers are 100% Polyester and are machine washable. Refer to the care label on the fabric for specific washing instructions. Use cold water and a gentle cycle. Do not bleach. Tumble dry low or hang to dry.
- Harness System: Wipe the harness straps with a damp cloth. Do not machine wash or submerge the harness straps in water, as this may weaken them.
- Plastic Parts: Clean plastic parts with a mild soap and water solution. Do not use abrasive cleaners or solvents.
- Storage: When not in use, store the car seat in a cool, dry place away from direct sunlight.
6. Troubleshooting
If you encounter issues with your CYBEX Sirona S car seat, please refer to the following common solutions:
- Car Seat Feels Loose After Installation: Ensure the EasyLock™ Bar is fully engaged and the vehicle seat belt is pulled taut. Re-check the dual-level indicators for proper recline angle. Sometimes, applying pressure to the car seat while tightening the belt can help achieve a more secure fit.
- SensorSafe™ App Not Connecting or Alerting: Verify that Bluetooth is enabled on your smartphone and the SensorSafe™ app is open or running in the background. Ensure the SensorSafe chest clip is properly buckled. Check for app updates.
- Difficulty Rotating Seat: Ensure the car seat is not under tension from the vehicle seat belt or other obstructions. The rotation release lever must be fully engaged.
- Harness Adjustment Issues: Ensure no fabric is caught in the adjustment mechanism. The headrest and harness should move smoothly when the adjustment lever is squeezed.
For further assistance, consult the official CYBEX Sirona S User Manual PDF available online or contact CYBEX customer support.
7. Specifications
| Feature | Detail |
|---|---|
| Product Dimensions | 31.3"D x 20.08"W x 22.64"H |
| Item Model Number | 519004439 |
| Target Gender | Unisex |
| Maximum Weight Recommendation | 65 Pounds |
| Minimum Height Recommendation | 17 Inches |
| Maximum Height Recommendation | 49 Inches |
| Material Type | Polyester |
| Material Composition | 100% Polyester |
| Care Instructions | Machine Washable |
| Number of Reclining Positions | 12 |
| Batteries Required | Yes (for SensorSafe) |
| Rear-Facing Minimum Child Weight | 4 Pounds |
| Forward-Facing Maximum Child Weight | 65 Pounds |
| Harness Type | 5-Point |
| Item Weight | 30.4 pounds |
| Installation Type | Seat Belt |
| Color | Manhattan Grey |
8. Warranty and Support
For detailed warranty information, please refer to the warranty card included with your product packaging or visit the official Cybex website. Keep your proof of purchase for warranty claims.
For additional support, frequently asked questions, or to download the full user manual in PDF format, please visit the Cybex Store on Amazon or their official brand website.
You can also access the User Manual (PDF) directly: Download User Manual (PDF)







