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.
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.
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.
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.
Keep up with your baby's development, get the latest parenting content and receive special offers from our partners