New all-in-one child seats see the versatile category expand

When you look at our updated Ratings for all-in-one car seats, it is notable that the once-tiny category has expanded from three to eight models. This "growth" wasn't due to an influx of new models, but rather a change to old ones, with four all-in-one models from Diono–formerly Sunshine Kids.

When Sunshine Kids announced a change in their company name to Diono a couple years ago, they also announced that a number of their models would be changing from convertible models (both rear- and forward-facing use with a harness) to all-in-one models that now also include a booster mode. What were the Sunshine Kids Radian 65SL and 80SL are now the Diono Radian R100 and R120. What was the Radial XTSL is now transformed to the Diono Radian RXT and GTX models.

For us that meant adding tests to evaluate those seats in their new booster modes in dynamic simulated crash tests, ease-of-use, and how well they provide lap and shoulder belt fit on a child-sized dummy in a number of vehicles, as well as drawing on their previous performance as convertible seats.

All of our likes and dislikes from the convertible assessments still stand, but one pair—the Diono Radian R100 and R120—performed better overall as booster seats. This was due mainly to a difference in the shoulder belt guide between those and the Radian RXT and GTX models. The R100 and R120 include shoulder belt guides that are easy to see and use, plus they allow the shoulder belt portion of the vehicle belt to slide easily through them. As booster-aged kids are typically between 5 and 10 years old, we expect them to be moving as the vehicle belt is not locked. As part of our evaluation on booster fit, we move our dummy forward and side-to-side to see if the belts stay in place. We expect based on those tests that the openness of the guide in these models will let the belt move freely with a child and then retract back to a good belt position when they sit back.

That expectation is not the same for the Diono RXT and GTX models. The shoulder belt guide in those models is more difficult to see and to put the belt into for starters. But when we moved our dummy around, the shoulder belt folded and "pinched" in that guide. That in turn prevented the belt from retracting back as it should, allowing a significant amount of slack to develop in the belt. In a crash, the added slack and additional forward motion are a bad thing, as it can mean a higher potential for injury from impact into some surface within the vehicle or from the crash forces.

Pluses from all four of the Diono models are that they have high weight limits: 45 lbs. for rear-facing kids, 80 lbs. for forward-facing harnessed children, and 120 lbs. as a booster. These high limits make them a good option for larger kids or as an alternative to booster seats for older cars that may only have a lap belt. These seats are also rather narrow, making them a "go-to" seat for parents that need to put three seats across. Minuses are that they are still heavy and long, which can make them more difficult to fit, particularly in a small car. And they are still considered to be on the pricey side running between $184 and $287.

See our full Ratings on all-in-one car seats, and convertible, infant, and booster seats.

—Jennifer Stockburger