The Diono Radian RXT came in second to last in our review of convertible seats. While it is about average for the ease of installation no matter what direction or method you choose, the low ease of use score will impair your daily experience enough to cause chronic frustration. In our tests, this seat failed to impress in comparison to pretty much every other option we considered. So, while it has some interesting features like fold-ability for transport and angle adjustment in forward and rear-facing positions, it also has the convoluted rethreading harness height adjustment and the lowest crash test results. These factors combined with a higher than average price make this car seat one we wouldn't recommend over the higher performing competition.
Update — April 2019
The Diono Radian RXT has been updated and is now called the Diono Radian 3RXT. This new version likely remedies the issues that caused the recall mentioned below, but still features the same heavy steel frame and cushy memory foam seat padding. It has a slightly redesigned infant insert, and a much lower price, retailing at $300. We are now linking to the new version in this review, think our info on the seat is still accurate.
Our Analysis and Test Results
Recall Notice - October 2017 Diono has issued a safety notice/recall for the Diono Radian RXT convertible car seat. This notice affects 519,052 Radian R100, Radian R120, Radian RXT, Olympia, Pacifica, and Rainier convertible and booster car seats. The recall is related to installing the seats using a vehicle lap belt only without the top tether. Installing the seats with a lap/shoulder belt with or without the top tether and installing with the LATCH anchors with or without the top tether are NOT affected by this recall. Diono is offering a free remedy kit with an updated instruction manual, an energy-absorbing pad, as well as a new chest clip, free of charge. Customers can contact Diono customer service at 1-253-256-9939.
The crash test data used in our reviews are results from sled tests designed to the same specifications as those used for the National Highway Traffic Safety Administration (NHTSA) standards. The sled tests are designed to determine if each seat meets or exceeds the Federal safety guidelines defined in FMVSS 213. The Diono does exceed the safety minimum required by law for crash testing, and therefore is considered safe. The Diono head sensor result is 820, below the Federal maximum allowed of 1000, and chest result is near 53, below the maximum allowed of 60. The other seats in this review had sensor results lower than those of the Radian.
The charts shown here include the test data for both the head and chest sensors from the dummy used in testing for the Diono (shown in black). Also shown are the crash sensor results for the product with the lowest recorded G forces for each sensor for comparison.
The Britax Allegiance head sensor has the lowest amount of G-forces recorded in its sensor out of all the seats in this review. The Clek Foonf test result data has the least amount of G-forces in the chest sensor (both shown in green).
Ease of Install - LATCH
For testing ease of installation using LATCH, the Diono performed about average with a score of 7 of 10.
Using the LATCH system is harder than the belt with this seat. We had trouble getting it tightened securely enough to the vehicle. This seat felt like more work than it should be and more work than the others. The feet on the base in the rear-facing position hit the lower anchors if not in the right position. We had a little more luck in the Subaru Outback than the Toyota Corolla, but the tether is tough to get tight enough, and you have to release and lift the seat to loosen the tether because the release gets smashed between the car and vehicle seats. Overall, testers described the Diono as awkward and hard to operate.
Ease of Install - Belt
For installation using the vehicle seat belt, the Diono earned a 7 of 10.
The photos above show the vehicle belt path of for forward-facing (above left) and rear-facing (above right) configurations for the Diono.
Installation using the vehicle belt is about the same for the Diono as the LATCH method. We still felt like the seat is strangely awkward given its narrow width and the belt path isn't the easiest to use. Some testers felt the lack of a belt lock-off makes this one a little easier as the belt threads without worrying about the lock-off mechanism. In some of the vehicles, we struggled to get this seat tight enough using the belt installation, and the tether even harder to get tight. It certainly isn't the easiest option in the group, but it isn't the most difficult either. With work and persistence, we were able to work the seat in tight enough to the vehicle seat in one car to feel comfortable that it was indeed stable. However, in another vehicle, the Subaru Outback, we struggled to get it tight with the seat belt, and we never felt it was stable enough. This lack of consistency leaves us feeling like the Diono may work well in some cars, but not all. The problem? Parents won't know how it works in their car until they purchase it.
Ease of Use
The Radian earned the lowest score in the group for ease of use with a 5 of 10.
The buckle on the Diono is the worst in the group. The button is so stiff it almost takes two hands, and we suspect if you have any structural problems in your thumbs or hands that you will need both hands. Interestingly, the chest clip is the easiest in the group and pops open immediately when you squeeze it gently. We kind of wish all the retainer clips were this easy. The tightening strap is a pull strap you can find at the bottom front edge of the seat. It is a little harder to pull than the average strap. The release button is above the strap under a Velcro fabric flap.
The harness height adjustment is a rethread style. The splitter plate is a single hook, and you will need to remove your baby from the seat and the seat from the car if it is front facing to adjust. Threading the straps is simple, but we prefer the non-rethread harness height adjustment found on some of the competition because they can be done as needed with the baby in the seat. We think parents will be more likely to ensure a properly fitting harness when it is that easy. The harness has five shoulder height options and two crotch positions.
The LATCH connectors and rear tether store in pockets near the top of the seat on the back. Neither pocket keeps the straps out of the way, and it seems like there is a lot going on or extra straps, when we know there aren't. While being able to stow the anchors out of the way isn't as critical in convertible seats as it is with infant seats so you can easily attach the carrier to the base, it is still nice not to have the clips flying around in the car.
The photos above show the unique feature of a small storage pocket that can hold medical information about the child in the seat. The pocket is part of the fabric that covers the harness release button.
The fabric for this seat can be hand or machine washed in a front loading washer, though we assume they mean a washer without a center agitator. The fabric is cold water washable and line dried or tumble dried on low temperature.
The Radian earned an average score for quality and comfort with a 6 of 10. This score is disappointing given that the seat is one of the more expensive products in the review.
At first look, the Diono has the appearance of a quality sea. The fabric is smooth and soft to the touch and feels somewhat like that found on the Chicco NexFit. While it is probably baby-friendly, it also feels very absorbent and possibly hard to clean. Some testers felt like it had the look of old broken in sweatpants, which probably isn't ideal, but might be cozy. The padding on the seat has some memory foam components. The foam is firm on the bottom of the seat with a thinner layer of softer padding over the top. On other parts of the seat, the padding is only a lightly padded seat cover. The padding grows relatively thin on other parts of the seat, and the plastic base pokes through the padding without much pressure.
The outer shell on the Radian is similar to the one found on the Clek Foonf with a mostly contained back and sides that are easy to keep clean. There are only a few spots that might prove challenging to get to on the back. The energy absorbing dense foam on the inside of the shell is the more common Expanded Polystyrene (EPS). It is more brittle and compact than the alternative Expanded Polypropylene (EPP), which does not off-gas and is somewhat more forgiving should it be accidentally dropped.
The fabric attaches to the seat shell snuggly enough to avoid looking sloppy, but the infant insert is not sturdy or stiff enough to hold itself in the proper position which makes it look like it is falling apart or overly used in comparison to the tight fitting cover. The overall fit and finish of the Diono are somewhat improved by the look of the fabric that helps it stand out in the competition, but the limp insert and strange collection of straps and clips on the back make it feel awkward and a mess. The bottom of the seat is relatively smooth and has some rubber portions to help it grip the vehicle seat better. There are no sharp edges or corners that look like they could damage the vehicle seat.
The overall weight of convertible seats comes into play if you travel frequently or live in an urban environment. The Diono weighs about 27 lbs making it one of the heavier options. The Diono gets somewhat lighter in the forward facing position at 25 lbs, but it is still heavier than most. On the upside, the seat folds in half to make it somewhat smaller to carry and store, and there is an optional carry strap you can purchase should you transport it frequently. However, we still think the hefty weight will prevent most parents from wanting to carry this seat on a regular basis or over any long distance. It is, however, narrow with a 17.5 width, but the Clek Foonf and the Evenflo Tribute LX are both narrower and score higher overall.
BabyGearLab was founded by a Pediatrician Mom with a mission to provide a reliable, independent, source of information to new parents. Our experts have tested thousands of baby and kids products to share key performance, health, and safety findings. We spend tens of thousands of dollars crash testing car seats to inform our ratings. And, we combine our review work with gobs of expert parenting advice. To assure complete independence, we buy all the products we test ourselves. No sponsored content. No ads. Just real, honest, side-by-side testing by people who care.