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Diono Rainier 2AX Car Seat Review – Buy or Bye?

Car seat safety is incredibly important, but with so many brands all claiming to perform small miracles, choosing a car seat can be beyond daunting. I know that’s how I felt as a first time mom, staring at all the different options.

A car seat has a very important job protecting your child from being harmed and so it’s in your whole family’s best interest to make sure that you have really done your research before purchasing a seat.

And as important as safety is, it is not the only consideration for the Diono Rainier car seat. Installation of this seat can be a bit confusing and see the NHTSA ratings below.

Bottom line: We don’t recommend this car seat primarily because it is difficult to use (although it is very safe and fits well in narrow cars). Check out the Britax Frontier instead, and see our review here.

Diono Rainier 2AX Convertible Car Seat, Black

Ratings Comparable to Other High-End Car Seats

This car seat is rated fairly high across several different shopping sites, as it should be for the price. Enough people have purchased the product from several different stores that the confidence level in the stars is pretty high.

Here are a few of the numbers for the original Diono Rainier car seat:

  • 4.6 stars, 230 reviews Google Shopping
  • 4.7 stars, 155 reviews Target
  • 4.5 stars, 489 reviews Diapers dot com
  • 4.5 stars, 306 reviews Walmart

Diono Radian 3RXT Convertible Car Seat, Red

The Diono is pretty much the Roles Royce when it comes to car seats.

They were the first brand to create a folding car seat that had a full metal frame. Diono has four different lines of car seats: the Olympia, the Pacifica, the Radian 3RXT and the brand new model, the Rainier which takes car seats to a whole new level.

It is an upgrade of the Radian 3RXT, complete with deeper walls on the side (a great plus in terms of safety) as well as a greater weight and height capacity. Children up to 50lbs can sit rear facing comfortably and forward facing up to 90lbs.

Once they are a little bit older, the Rainier 2AXT model converts into a booster seat that can support a child up to 120lbs. The regular Rainier 2AX does not convert into a booster.

Diono Rainier 2 AXT Convertible Car Seat, Blue

Let’s look at some of the key features and feedback on the Diono Rainier.

Safety Features of the Diono Rainier 2AX Car Seat

As a parent, of course, safety is the first element of a car seat that I am concerned about. It doesn’t matter how aesthetically pleasing or comfortable it is, I need to be one hundred percent certain that should I be in a car accident, my car seat of choice will keep my child safe.

Crash Tested

All Diono car seats are crash tested on a regular basis to maintain a high standard. In addition to that, all all-in-one car seats by Diono surpass Federal crash test standards which I think is pretty impressive.

One stand out difference between the Rainier and other car seats are its deep side walls, a feature that the other Diono car seats don’t have. These are crucial to protect your child against side impact in the event of an accident. These walls are also lined with EPS, an energy absorbing foam that supplies additional head and body protection.

Over and above all of this, the Diono Rainier car seat has a full steel frame and is reinforced with aluminium so that you can rest assured that your child is completely protected whilst driving.

Another nifty safety feature is the SafeStop energy-absorbing harness which helps to reduce impact on children that are seated in the forward facing position. In the unlikely event that you are in an accident, the SafeStop energy-absorbing harness creates a bungee like effect, which in turn, helps to protect your child against severe impact.

Locked Indicator

Another great addition to Rainier is the SuperLATCH. Once you have strapped your child in, you will hear a click as well as see a visible indicator that your child is indeed securely fastened into their car seat.

Diono Rainier 2AX Convertible Car Seat, Black

Suitable for All Ages

Although the Diono Rainier 2AX costs a pretty penny, you won’t need to buy another car seat for your child! Suitable from newborn, the Rainier has extended rear-facing capacity, until your child is 50lbs. After that, the 5 point harness is still perfect to use in the forward facing position until your child weighs 90lbs.

But No Booster

Here’s the only bad part though, the Rainier 2AX does not convert into a booster seat. You’ll have to get the Radian 3RXT or the Rainier 2AXT for a booster seat that is perfectly safe to use until your child weighs 120lbs. But you will certainly pay more for that longevity.


Diono really took your child’s comfort into consideration when designing the Rainier:

  • Long seat bottom makes long road trips so much better
  • 12 height positions for the adjustable head support
  • 3 buckle and 5 shoulder positions to choose from
  • Body support cushions for newborns

I think often parents forget how important neck support is in a car seat. The fact that it looks so supported in the Diono means big-time brownie points in my books!

Diono Rainier 2AX Convertible Car Seat, Black

Installation Not the Easiest

A pretty handy tool on the Diono website is that they show you exactly how to install the Diono Rainier.

Having said that though, quite a few consumers have noted that installation is fairly difficult, tedious and is not completely compatible for smaller cars.

Many have found that the angle adjuster does make it easier, although it is a separate purchase on top an already pricey car seat which is a bit off-putting. There are a number of different straps and parts depending on which weight category you are setting the seat up for and this can most definitely get confusing.

To me, this isn’t the biggest deal breaker as we keep our car seat in our car. But if you plan on using your car seat as a carrier or need to switch it between cars quite regularly, it could start to get really annoying.

Space-Saving Size

Something that is useful is the space-saving design of the car seat, this allows for most cars to be able to accommodate 2 seats with ease, a huge plus for those with more than one child in a car seat. The space-saving design also means that even with one car seat, the other passengers won’t feel squashed in the back seat.

The Rainier is also able to fold flat for traveling and is certified by the FAA.

Forward-facing Installation Video

Rear-facing Installation Video

Full Steel Frame

Now this is a bit of a good news, bad news scenario.

Let me give you the bad news first: the steel frame, reinforced by aluminum makes the Diono Rainier very heavy. So heavy that most consumers agree that this is not the ideal car seat if you are looking for something that can be carried around easily.

On the plus side however, the steel frame makes the Rainier incredibly safe and strong which in the greater scheme of things, is more important as far as I am concerned.

Diono Rainier 2AX Convertible Car Seat, Black

Maintenance and Cleaning

If your child is anything like mine, your car seat is filled with crumbs in all of the nooks and crannies and has a good few juice (I hope!) stains on it.

Although not as easy as other car seats, the Rainer’s cover and head wings cover are pretty easy to remove once you have unthreaded the harness. Diono recommends a hand wash or a front loader.

Ease of Use Ratings

Car seats sold in the United States are safe. They meet or exceed federal safety standards. The National Highway Traffic Safety Administration (NHTSA) rates each car seat on Ease of Use because injury is more likely to be caused by improper installation and usage than by the seats themselves.

The Diono Rainier car seat received an overall rating of  2 stars in both forward and rear facing mode. The Booster Car Seat received an overall rating of 1 star. 

NHTSA ease of use rating for the Diono RainierForward-Facing
Credit: NHTSA


Here’s a quick summery of the pros and cons of the Diono Rainier 2AX:


  • Safe
  • Can be used forward-facing or rear-facing
  • 10 year warranty
  • Durable due to steel frame


  • Heavy
  • Can be difficult to install
  • Bulky to carry around
  • Have to get upgraded model to get booster mode
  • Can’t fit 3 across like other Diono models

At the end of the day, if you are able to afford a Diono Rainier car seat and are looking for something that will stay put in the car, then this is a solid car seat choice. It’s safe and secure, but it has some of the lowest ratings for usability.

Upgrading to the Diono Radian 3RXT is smarter: it can fit 3 across and has the booster mode, all with similar safety and usability features. Plus, it’s more highly rated. Check out our full Radian 3RXT review.

To see the best booster car seats (and why this one didn’t make the list), read our Best Booster Seat article.

Sarah Booyens

Mother, wife and writer fueled by coffee and an insatiable desire to make parenting as easy as possible.