The seats mentioned in this article are all discontinued. Our review of the 2018 radian looks at a more recent version of the seat.
The Diono Radian is a popular choice among convertible car seats, and for good reason; it has great extended rear facing capabilities and the narrow, low profile makes it an excellent solution for 3-across or tight spaces.
This seat was subject to a recall in late 2017.
CSFTL Quick Stats
Rear facing weight range: 5-45 pounds- Rear facing height range: less than 44 inches tall
- Forward facing weight range: 20-65 pounds (Note: versions of this seat manufactured prior to September 2017 had a different maximum weight limit. Seats made after September 2017 have a 65 pound weight limit.)
- Forward facing height range: less than 57 inches tall
- High back booster weight range: 50-120 pounds
- High back booster height range: less than 57 inches tall
- Shell height: 25″
- Lowest harness position: 9″
- Highest harness position: 17.5″ (Diono allows use of the seat until ears are over the shell)
- Expiration: 8 years harness, 10 years booster
- 3 crotch buckle positions
- Push button lower anchor connectors
- Narrow enough for 3-across
- IIHS Best Bet for all Radian models
Diono Radian R100
Radian R100 (Discontinued)
- Rear facing 5-40 pounds
- Forward facing 20-65 pounds (Note: versions of this seat manufactured prior to September 2017 had a different maximum weight limit.)
- Booster 50-100 pounds
- Does not include a cupholder, infant insert, memory foam, or headwings.
Diono Radian R120
Radian R120 (Discontinued)
- Rear facing 5-45 pounds
- Forward facing 20-65 pounds (Note: versions of this seat manufactured prior to September 2017 had a different maximum weight limit.)
- Booster 50-120 pounds
- Includes a cupholder, infant insert and memory foam in the seat cushion.
Diono Radian RXT
Radian RXT (Discontinued)
- Rear facing 5-45 pounds
- Forward facing 20-65 pounds (Note: versions of this seat manufactured prior to September 2017 had a different maximum weight limit.)
- Booster 50-120 pounds
- Includes a cupholder, infant insert and memory foam in the seat cushion.
- Has headwings.
Diono Radian GXT
Radian GXT 
- Rear facing 5-45 pounds
- Forward facing 20-80 pounds
- Booster 50-120 pounds
- Includes two cupholders, infant insert, and memory foam in the seat cushion.
- Has headwings
- Includes stain resistant fabric and waterproof undermat.
Diono Radian RXT rear facing seat belt installation
Usage
The rear facing capacity of the Radian is one of its biggest draws. The ideal is for kids to remain rear facing until 3-4 years of age, and the RXT allows rear facing up to 45 pounds, 44 inches tall, or the child’s head 1.5″ from the top of the 25″ shell. It will easily accommodate most kids until they are of a safe forward facing age.
Diono Radian RXT 9 months, 2 years, 3.5 years
Our 9 month, 2 year old, and 3.5 year old testers all fit great rear facing in the Radian. The manual directs users to adjust the headwings so the bottom is level with the jawline once the child is on the 3rd slots. As illustrated, our 9 month old wasn’t quite ready for the headwings to come down, so the manual directs they should be left in the uppermost position.
One downfall of the rear facing Radian is that it takes up a large amount of front to back real estate in the vehicle. To combat this, Diono created the Angle Adjuster
Diono Radian RXT rear facing tether
The Radian allows for the top tether to be used in rear facing mode. To do so, use the attached d-ring to create a tether point. Wrap the d-ring around a fixed metal part of the vehicle, such as the rail of the front passenger or driver’s seat, and attach the top tether strap. If a frontal location cannot be located, the Radian does allow tethering to the seat it is installed on. Rear facing tethering is not a requirement, but Diono does recommend it. Many vehicle manufacturers do not allow rear face tethering so please verify your vehicle allows this before attaching the tether.
Fit to Child
Harness Mode
The Radian advertises that it is a “birth to booster” convertible car seat. We know that choosing a convertible seat for a newborn can be a challenge, so how does the Radian stack up for a newborn?
Diono Radian RXT- 3 weeks old, 8lbs, 21 inches
Newborn
At 8 pounds and 21 inches, this 3 week old fit nicely. It’s important to note that this is a Radian R120 with the infant insert, and the seat also has Diono’s 33″ harness straps (standard straps are 38″, shorter straps are available separately) in order to get a secure fit on such a small baby. Adjusted to an angle appropriate for a newborn, the Radian does take up a significant amount of front to back space, which may not work in many small to mid-size vehicles. While the Radian is rated from 5 pounds, it would not be likely to provide a safe fit for a premature or small newborn.
Diono Radian RXT- 3.5 year
Preschooler
Our 3.5 year old tester tried out the Radian both rear and forward facing. As you can see, she found it horribly uncomfortable forward facing!
With 17.5″ top harness slots and an 80 pound weight limit, the RXT will get most kids to 5-6 years old forward facing in harnessed mode.
Diono Radian RXT SafeStop
Forward Facing
If the child is forward facing and under 40 pounds, the Safe Stop must be installed on the harness.
Effective 12/04/2014 Diono requires that the recline foot is extended for all forward facing children who weigh over 25 pounds.
Diono Radian RXT- 7 years old, 52 pounds, 50 inches in booster mode
Booster Mode
The Radian also has a booster function, with some limitations. The RXT booster limits are 50-120 pounds, however, the child must also have their ears contained within the top of the shell. Our 7 year old tester is only about an inch before his shoulders bump up against the headwings, at which point he will no longer be comfortable in the seat. We know that big kids need boosters until age 10-12, so the Radian definitely will not be the last seat that he needs.
The Radian RXT did provide an excellent seat belt fit: positioning the lap belt low on the hips, touching the tops of the thighs, and the shoulder belt even across the torso. Received an IIHS Best Bet rating for 2013.
The Radian R100 and R120 did not achieve the same rating in booster mode, due to the different shoulder belt guide. While it positions the lap belt correctly, it completely fails to fit the shoulder belt correctly. These versions of the Radian should not be considered useable in booster mode unless the occupant is tall enough to otherwise achieve a good shoulder belt fit. Note: children will be about to outgrow the seat by virtue of the ears exceeding the head rest when this happens.
To prevent the seat from becoming a projectile in a crash, the Radian can be secured with lower anchors and/or top tether when used in booster mode.
Installation
Diono Radian RXT installed rear facing with seat belt with twisted female buckle
Installation of the Radian can be a bit tricky. Rear facing, the belt sits very low in relation to the vehicle seat. The result is that often the latchplate falls right on the edge of the belt path, putting a lot of stress on the latchplate as well as making it extremely difficult to achieve an installation with less than 1″ of movement. Most vehicle manufacturers allow the buckle stalk to be twisted up to three times to shorten it. The bottom left picture shows the latchplate once the buckle stalk has been twisted, sitting below the edge of the belt path.
Diono Radian RXT forward facing installation with seat belt
Forward facing installation can be a challenge as well for similar reasons. The back edge of the belt path sits very close to the vehicle seat back, which can make for a difficult angle to tighten the seat belt. One handy trick to tighten a forward facing installation is to open the velcro slits in the cover to access the seat belt in order to pull it tight.
Diono Radian RXT forward facing tether
Remember to attach the top tether when installing forward facing!
Diono Radian SuperLATCH
The Radian can also be installed using lower anchors. The limit for the use of lower anchors will be found on stickers on the side of newer seats. For seats made before 2014, consult the manual that came with your seat as well as your vehicle’s manual; CSFTL always recommends taking into consideration the LATCH weight limit set by your vehicle manufacturer, which may be lower.
3 across with an 8 month old, 4 month old, and 2.5 year old in Diono Radians in a 2006 Honda CRV.
Diono Radian RXT can be folded for travel or storage
Three Across
The Radian is especially handy for 3-across situations because of its narrow profile. It’s also fantastic for travel because it folds for travel, and a carry strap can be purchased to carry the seat as a backpack. The low profile also allows the child to use the tray table when installed on the airplane.
can be purchased to carry the seat as a backpack. The low profile also allows the child to use the tray table when installed on the airplane.Pros
- Narrow
- Low profile makes it great for 3-across situations
- High rear facing weight limit (R120 and RXT)
- Push button lower anchor connectors
- Allows for tethering rear facing (if the vehicle allows it)
Cons
- Can be difficult to install
- often requires the angle adjuster to avoid taking up a large amount of front to back space
- Booster mode is not very functional because of the 50 lb minimum weight limit and the short belt guides
- Booster mode is outgrown at the same time as the harness mode
- Impractical to very poor fit in booster mode
Overall Thoughts
The Diono Radian has a lot of great features including folding for travel, being narrow for three across, and high rear facing limits. It may not work in every situation, especially rear facing before the child can sit unassisted or for a newborn, but will be a good choice for many.
Is the Radian the right seat for your Little? You can find it on Amazon.com!
Diono provided the cobalt Radian RXT used in this review, but we were not otherwise compensated; opinions are all our own!
