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Car Seat Fit Guide: All-in-one car seats

Car Seat Fit Guide: All-in-one car seats

Car Seats
Ready for the road? Make sure to check for these common car seat fitting mistakes and learn these top tips for safe travels

We’ve put together these top tips to be used as a way of refreshing your memory before traveling, but before we take a look at our top tips, let’s remember that the number #1 rule when it comes to car seat fitting and installation is to read the manual first. Understanding your car seat is crucial when it comes to the safety of your passenger, and everything that you need to know will be detailed in your manual.

Use these top tips to achieve the perfect fit with your all-in-one convertible and booster seats. We’ve worked with our very own CPST to highlight the key areas often overlooked by parents and caregivers, which are easily avoidable. Learning how to easily spot these mistakes will help you provide the safest travel for your Very Important Passenger, so let’s take a look!

Chest Clip

This should be positioned at armpit level. We often see chest clips in the wrong position, which means they won’t operate as they should in an accident. Chest clips are a pre-crash positioning device designed to keep the harness positioned in the right place. A chest clip that is too high causes risk of injury to the child’s neck whereas too low means that the harness could slip off their shoulders. Note that it is also common for the chest clip to slide down and/or break in the event of a crash. This is because its purpose is not to restrain your child, but to simply position the harness properly on their shoulders by pulling the straps inward and tight. It is a myth to think that the chest clip will keep your passenger restrained in a collision…that is what the harness straps do! 

Harness Straps

Now that we’ve established the importance of harness straps, let’s learn how to properly position them. Note that this is different for rear-facing and forward-facing travel, so you may need to revisit your manual or this guide when it’s time to switch modes.


When your child is travelling in the rear-facing position, the harness straps should be positioned at or below their shoulders.


Time to switch? For Diono convertible seats the harness straps should now be positioned above the shoulders when forward-facing. Some brands say “at or above” so make sure and read your car seat manual.


Designed to provide additional side impact protection for your kiddo, the positioning of the headwings should not be overlooked. For Diono convertible seats, the headwings should be positioned so the bottoms are about even with your child’s jaw. Other brands may differ so check your car seat manual.

Pinch Test

The Pinch Test will tell you if the five-point harness is properly tightened. Here’s how it works: Once you’ve buckled and tightened the harness, try to pinch the webbing with your thumb and finger at the collar bone. If you can pinch any of the webbing between your fingers, it’s too loose. If you can’t pinch any webbing then the harness is properly tightened. It’s super simple and only takes a few seconds to check. It’s also one of the most important things to check prior to starting your journey.

Why All These Rules?

Crash testing is done with a test dummy properly positioned and harnessed in the seat, and the car seat properly installed. The safety performance of your seat can only be replicated if your child is also properly positioned and harnessed in their car seat, and the seat properly installed in your vehicle. All of these “rules” are derived from testing and then written in your car seat manual. This is why it’s so important to read, read, read your manual!