Convertible car seats

Diono Rainier

Diono Rainier

Best forParents looking for a convertible car seat that has an expandable seat for a growing child’s comfort

Top BenefitsSuitable for kids up to 120 lbs., steel frame, side-impact protection, narrow space-saving design

ConsiderationsHeavy, rethreading required to adjust height of harness shoulder straps, may not fit in all vehicles at the infant recline angle

Bottom lineThe Diono Rainier is a cozy ride for kids thanks to extra-long leg support, plus it’s packed with safety features like a full steel frame, aluminum-reinforced sides, energy-absorbing EPS foam, an energy-absorbing harness and the option to use the tether with rear-facing installations.


ca.diono.comCAD $429.99


  • SuperLATCH connectors for easy installation
  • Machine-washable and dryer-safe seat cover
  • Cup holder


There are lots of convertible car seats out there promising to keep kids simultaneously safe and comfy, so how can parents narrow it down? Reputation is a good place to start, and the Diono Rainier has a great one. With its deep side walls and memory-foam padding, your child will sink comfortably into this plush, yet sturdy car seat (it has a full-steel frame). The Diono Rainier features SuperLATCH connectors to make proper install a cinch and an angling base for rear-facing that easily detaches when it's time to switch the seat to forward-facing. For travelling families, the Diono’s slim width and ability to fold flat make it more portable than most convertible car seats—though it is on the heavy side. Bonus features include a cup holder and machine-washable seat covers.

Like all the car seats we tested, the Diono Rainier has been crash-tested by the manufacturer and approved for use in Canada by Transport Canada and Health Canada. Given the rigorous testing that car seats go through to get approved, we focused our assessment on the car seat’s ease of installation and use, value for cost, quality of materials and overall comfort. 


Installing car seats can be a challenge for some and a breeze for others, so we recommend approaching the installation with time and patience. Having an assistant—for back-up or moral support—never hurts either. The manual, which in this case is loaded with detailed images, descriptions and checklists, will guide you through the process and help ensure everything is safe and secure. Instructional stickers conveniently located on the side of this car seat also help, although they're not colour-coded (a feature on some car seats that distinguishes between rear-facing and forward-facing belt paths to eliminate the chance of guesswork). The UAS connectors, stored at the back of the seat, are easy to remove thanks to a stay-open release button—no need to press and hold.

Threading the UAS strap through the rear-facing pathway without allowing it to twist can be a little finicky, and it's easy to scratch your hands on the hard plastic parts of the frame. But with that done, it's pretty easy to attach the SuperLATCH connectors to the UAS anchors in your vehicle. The next step, tightening the UAS belt, is typically the toughest part of installing a car seat, but our editors and parent testers had no trouble securing the Radian to the point that it didn't move an inch when tugged in any direction at the belt path. (Tip: Putting your weight into the seat with a hand or knee while pulling on the strap will help you get a tighter fit.) When you need to remove the car seat from your vehicle, detaching the UAS connectors is a breeze thanks to the stay-open release button on the UAS clips.

To achieve a safe recline angle, the Diono Radian rXT has a detachable base, which is secured with a metal lock, and the curved foot of this base slides in between the back rest and seat cushion for a secure fit. Diono does not allow the use of a rolled towel or pool noodle to adjust the angle, so if you can’t get the angle right with the detachable base, the car seat is incompatible with your vehicle. It’s worth noting that Diono offers a foam angle adjuster, but it can only be used in the more upright rear-facing position, once your child has complete head control and can sit unassisted. The benefit of the angle adjuster is it can give you a bit more clearance between the car seat and the front row seat—super helpful as the Rainier is one of the taller car seats on the market. When your toddler’s forward-facing car seat days roll around, the detachable base needs to be removed. You can adjust the forward-facing recline by pulling an adjustment bar (located under the seat) upwards to lower or raise the seat bottom.

Take a look at your vehicle's manual before you buy a car seat. Some manufacturers have dos and don'ts for car seat installation that conflict with the installation instructions for some car seats. The seat you're eyeing could even be completely incompatible with your vehicle—and you don't want to find that out after you've made a pricey non-refundable purchase.

Overall, installing the Diono Rainier using the vehicle’s seat belt it a bit challenging. Although the belt path is clearly labelled, there’s not an easy sightline, and it takes some coordination to get the vehicle's belt fed through properly without twisting it. (Twists add stress to the belt, which can compromise the belt's strength in a crash.) Tightening the seat belt to secure a car seat is always a challenge, but it can be tricky with Diono car seats because the belt path is fairly low on the base and the vehicle's buckle can get in the way of a tight fit. With some vehicles, you can twist the vehicle's belt buckle so that it doesn't interfere with the belt path on the car seat, but some car manufacturers prohibit this. (It's important to check your vehicle's manual.) Our parent tester who installed this car seat with her vehicle's seatbelt found installation easy, but it's really going to depend on the compatibility with your vehicle and your strength.

Most new vehicles come with a seat-belt locking mechanism to help you secure the belt once you’ve gotten it tight enough. If your vehicle doesn't come equipped with an automatic locking retractor, you'll need to get a locking clip to prevent the seatbelt from loosening after you've secured it.

This car seat was relatively easy to install. I still had an expert look over the job for me to ensure it was properly installed; a few minor tweaks were needed, but overall I did a good job on my own." —Michelle, mom of one


During your child’s forward-facing car seat and booster seat years, the top tether has to be secured. And, unlike most car seats, you can also use the tether for added security in the Diono Rainier's rear-facing installations. Consult your vehicle’s manual to help you locate the appropriate anchors point. Before positioning the car seat, it’s best to remove the top tether from the storage hook on the back of the car seat and fully extend the strap so you have enough length to reach your vehicle’s tether anchor. Although the tether's clip is a tad stiff, it was easy to attach, tighten and detach for both our editors and parent testers.


The Diono Rainier isn’t the tallest car seat we tested in the lab, but at a height of 28 inches, it still required moving the passenger seat forward a lot to accommodate the rear-facing installation during our testing, and most parents who tried it out for us had to do this as well. On the plus side, the 18-inch width makes the Rainier one of the more narrow convertible car seats we've tested—in fact, one mom said that with two of the car seats in the back, her kids didn’t look the least bit squished.

At 31.3 pounds, the Diono Rainier is no lightweight—but that's understandable given it's steel alloy frame. The weight does, however, mean it's a car seat that's best for families who only plan to install it in one vehicle.

machine-washable, this one is also dryer-safe—a rarity among car seat covers that you'll come to appreciate the first time your kid vomits or has a diaper blowout. It's worth noting that some parent testers found it was a bit of a struggle to remove the cover, while editors found reattaching it was a little tricky.
My daughter is comfortable in this car seat, and I like the steel frame—it makes me feel like she's very safe." —Jennifer L., mom of two

When it comes to comfort, it's hard to beat the Diono Rainier’s memory foam padding and soft fabric. An infant insert offers extra padding to keep babes snug in their seat, and our parent testers who used it felt their wee ones were secure, well-supported, and comfortable. The headrest height has an adjustable range of about four inches, while the expandable sides and 16-inch-deep seat allows for customized comfort with proper leg support as your kid grows. The car seat also has a single cup holder and our parent testers gave it a thumbs up—though proper install (signalled by an audible “click”) wasn't terribly simple. Additionally, one of our testers said their daughter was able to remove it on her own, which could make for a messy car ride.
Diono has a solid reputation for safety, and it's easy to see why: The Rainier has a steel frame and deep, aluminum-reinforced side walls, energy absorbing EPS foam and side impact protection, rear-facing tether capability, an energy absorbing harness feature for forward-facing kids under 40 lbs., and more. All of our parent testers felt their kids were safe and secure in the Diono Rainier, and they gave it very good ratings for quality and ease of use, and a good rating for value. None would hesitate to recommend the Rainier to other parents or parents-to-be. Our editors, meanwhile, were impressed with the energy-absorbing foam padding, the seat's narrow width, and the convenience of the stay-open release button on the UAS connectors. All the safety and convenient features put together makes the Diono Rainier a great option if you're in the market for a convertible car seat.
It's important to try before you buy. As we found in our testing, there are all sorts of incompatibility issues between vehicles and car seats. The belt path could be too low, the tether might hang loose or a car seat's height might interfere with the vehicle's front seats. Or it just might be challenging for you to lift your kid into and out of a particular seat. Ask retailers if you can try installing the floor model in your vehicle to see if it's a good fit. And when you're buying a new vehicle, be sure to take your car seat to see if it'll work—or be prepared to shell out for a new car seat if you love the car.

Tech Specs

    33.3 lbs.
    Width: 18 in.
    Height: 28.5 in.
    Seat depth: 16 in.
    Rear-facing: 5-50 lbs., 30-44 in.
    Forward-facing: 22-65 lbs., 30-57 in.
    Booster: 50-120 lbs., 40-57 in.
    5-point harness
    12-position adjustable headrest
    8.25-in. to 17-in. shoulder strap range—rethreading required
    4- to 7.5-in. crotch buckle range
    Steel frame
    Foam harness pads and memory foam seat
    Side-impact protection pads
    Infant head pillow and body support
This article was originally published on Apr 13, 2018

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