RXT $300
R120 $260
R100 $234
Convertible Car Seat Review: Diono Radian RXT / R120 / R100

Type: Convertible (RXT converts to belt-positioning booster)

Limits:  rear-facing: 45 lbs (except for the R100, which is 40). Forward-facing: 100 or 120 lbs., depending on model. Height up to 57″. Harness use up to 80 lbs.

NHTSA ease of use rating:
R100: Rear-facing: 3 out of 5 stars. Forward-facing: 2 out of 5 stars. Booster mode: 2 out of 5 stars.

R120: Rear-facing 2 out of 5 stars. Forward-facing: 2 out of 5 stars. Booster mode: 2 out of 5 stars.

RXT: Rear-facing 2 out of 5 stars. Forward-facing: 2 out of 5 stars. Booster mode: 1 out of 5 stars.

Pros: Folds up! Works to 100/120 lbs, depending on the model. EPS foam. RXT has added side impact protection. Narrow base lets you fit three across.

Cons: Heavy weight. Biggest kids may find crotch strap too tight. Low LATCH weight limits. Low ratings on ease of use.

Comments: The Diono Radian is the company’s flagship car seat and boasts three key advantages: extended harness use (up to 80 lbs.), a narrow base and a seat that is car pool friendly—yes, they fold up!

The Radian accomplishes its folding trick by omitting the base you see on so many convertible seats—the seat actually sits along the back of the vehicle’s seat. One plus to this: the Radian’s narrow base allows for a three-across install in the back of a vehicle.

The Radian now comes in three versions: RXT, R120 and R100. All the seats feature steel alloy frames. And you can use LATCH up to 80 lbs. (65 lbs. for the R100), much higher than other seats on the market.

The RXT is the flagship and features a special trick: the harness removes so the seat can become a belt positioning booster (up to 120 lbs.). The pitch: you can use this from birth (starting at 5 lbs.), rear-facing for infants, forward-facing for toddlers with a harness that works to 80 lbs.  . . . and then in belt-positioning mode to 120 lbs. The RXT also features memory foam and side impact protection (wings that are near the top of the seat).

The R120 omits the side impact protection wings, but otherwise is much like the RXT (example: you still get the memory foam, etc.) and has the same weight limits.

The entry level R100 is more bare bones: no memory foam and the booster mode is only rated to 100 lbs.

For 2018, Diono is refreshing this line of car seats and renaming them—the R100 will become the 3R ($200). The R120 will be the 3 RX ($250) and the RXT will now be known as the 3 RXT ($300). The “3” refers to the fact that these seats fit three-across in most vehicles. As for other changes, the 2018 versions will feature a cover that wraps completely around the back of the car seat.

Also new: lower prices. The 3R and 3RX will be about $50 less than the seats they replace, despite having the same features and weight limits. The 3RXT will be the same price ($300) as the outgoing seat but features more premium fabrics.

The 2018 models will be released in July 2018.

Here’s a look at the 2018 Radian 3 RX:

Reader feedback on the Diono Radian has generally been positive. Folks love the narrow, low profile of the seats and their overall quality. Yes, you can fit three of these in a back seat in most vehicles, which is difficult with many other seats.

What’s not to like? Well, these seats are rather tall and that can make the fit rear-facing difficult in smaller vehicles. And even though these seats fold up, they are rather heavy (25+ pounds)—so lugging them around is no picnic. And ease of use is a problem: Diono bombed on the government’s ease of use ratings, earning very low scores. Consumer Reports echoed that issue, citing “fair” ease of use and rear-facing fit to vehicle. The Diono Radian ranked at the bottom of CR’s “all-in-one” seat tests. Not encouraging.

To top it off, there is a major caveat for LATCH installation for this seat: when using LATCH, the top weight limits are 35 lbs. (rear facing) and 40 lbs. forward-facing (these limits are for vehicles made after 2014). That means you’ll have to switch to a seat-belt install to hit the higher stated rates—and the seat belt installation can be a challenge, say our readers.

One reason for the ease of use ratings for these seats: the numerous installation options and features of these seats can take a while to learn.

On the plus side, the Insurance Institute for Highway Safety rates the Radian (R100, R120 and RXT) to be a “best bet” in booster mode.

Bottom line: these seats are best for folks who need a seat to fit a super-size baby—or need to put three seats across in a back seat. There are few (no?) other seats on the market that are as narrow (in the base) as the Radians. Yet the steep learning curve for this seat with all its various features and installation nuances will require patience. Rating: B-