Proper car seat installation is essential to safety. Follow these steps to help ensure your child's car seat is as safe as possible.


First Steps Checklist

Send in the registration card that came attached to the car seat or register online.

Upon removing your car seat from the box, unfold your seat.

  • Check to be sure the area is clear of debris
  • Remove body support and infant head support cushions
  • Check that your seat is in the unfolded locked position

Read the manual including all the warnings in the safety section of your manual. Get to know the parts, pieces, and accessories to your car seat.

Determine the seating position of your child.

  • Will your child be rear-facing or forward-facing?

Determine how you will be installing your seat. (See pages 10-11)

  • LATCH or Seat belt installation
  • Top-Tether
  • Booster
  • Safe Stop® *Diono Only. Please Note: Do not discard Safe Stop® as you may need this piece later during your child’s development.

Be familiar with the steps in how to properly secure your child in your seat. (See pages 21-29)

  • Proper harness height and max child weights.
  • Harness buckle location and installation.
  • Side Impact and head support
  • Infant support cushions

Properly secure your seat in your car.

  • Double check your work.
  • Did you do a car seat stability check? A checklist is provided at the end of this section.


Seat Belts

There are two ways a seat belt locks for a car seat installation:

1. Switching to locking mode by pulling the shoulder portion of the seat belt all the way out until it clicks and a ratcheting sound is heard. As the webbing feeds back into the “housing” unit, it will not be able to come out until the webbing is spooled all the way back in.

If the installation is not tight after following the user manual with a lap shoulder belt installation:

  • Be sure the bottom of the car seat is adjusted to the open position.
  • Twist down the buckle stalk 1-3 full turns and then repeat instructions
  • Unbuckle the seat belt and allow the shoulder webbing to spool back into the housing unit 1-2 clicks and then re-buckle the seat in. Having a second person will make this easier.
  • Try another seating position.


The seat belt locks at the latch plate (the metal part that is inserted into the buckle). Once all the slack is pulled out and tighten down on the seat, there is a part within the cover that cinches down on the webbing and holds it in place. Sometimes the latch plate might have to be rotated one half turn into the buckle to keep the belt from slipping loose.


Bracing is when the top or back of a rear-facing car seat touches the back of the vehicle seat that is in front of the car seat. A rear-facing Diono car seat can touch the vehicle seat in front of it as long as it does not lift the bottom of the car seat off of the vehicle seat.

Most newer vehicles have advanced airbag sensors in the front passenger and driver’s seat and anything touching the back of the seat can affect the performance of those sensors. Also, storing things in a seat-back pocket that weigh more than a pound or two can also affect the sensors. Storing things under the seat can also affect the sensors. Information on this subject will most likely be found in the SRS/Airbag section of your vehicle manual. If in doubt, call your vehicle manufacturer and ask if they allow anything to touch the back of the driver’s seat or front passenger seat.

If your car is too small or your front passenger/driver needs to move the vehicle seat back, purchasing the optional Angle Adjuster will help raise the Diono convertible seat more upright to give them more room. The Angle Adjuster keeps the Diono car seat from touching/bracing against the back of the seat. Only use the optional Angle Adjuster for children who can sit up unassisted and/or have full head control.

Proper Fit in Booster Mode

Booster mode in our convertible line begins when your child meets ALL of the following criteria:

  • Shoulders reach the 4th harness slot
  • At least 22.7kg (50 lbs).
  • At least 101.6cm (40 inches) tall.

A level of maturity should be greatly considered before using the convertible in booster mode. A child who cannot sit properly positioned for the entire ride is safer in a 5-point harness.

Proper Fit in Booster Mode:

The lap portion of the seat belt should fit low on the child’s pelvic bones and high on the thighs, much like on an adult. The shoulder portion should lay flat on the center of the child’s collar bone.

Function in Booster Mode:

Booster mode should allow for the shoulder belt to fully retract so it always lays flat against the child’s collar bone. Vehicle design may vary on position of seat belt anchoring, D-ring position and/or belt system flow direction. Vehicle seat design may dictate where all of these components exist. It is not possible for every belt positioning booster seat to function properly in every single make and model of vehicle on the market, just as every harnessed car seat may not install properly in every vehicle.

Booster mode should allow for the shoulder belt to move freely (retract) so that it always lays flat against the child’s collar bone.

If you are currently experiencing a seat belt that will not retract properly on your child in booster mode, please try the following:

  • Install the seat in a different seating position OR
  • Continue to use the car seat in harness mode OR
  • Contact Customer Service at 866-954-9786 in Canada or 855-463-4666 in the U.S.

Vehicle seat design and location of a seat belt may dictate if a seat belt can move freely in and out of a booster seat belt guide. It may not always be possible for every belt positioning booster seat, or every car seat for that matter, to function properly in every vehicle on the market.


We do not allow over-hang of any of our car seats. While there are car seats which follow an 80/20 rule, all Diono brand car seats are to fit with the bottom of the car seat making 100% contact with the vehicle seat. If you feel you have extenuating circumstances, please send a photo of your installed seat and our engineering team will evaluate your particular situation.

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