Compact convertible car seats can be useful if you have a very small car or if you have several young children close in age. With updated recommendations to keep children in a car seat for until they weigh 80 pounds, it's not out of the question for a family to have two or three children who need to be in a car seat at the same time. The drawback to a compact fit is that the seats often don't meet the NHTSA's recommendations for upper weight ratings.
Convertible car seats are more compact front-to-back when forward-facing, so families with smaller cars may find it more practical to start with an infant seat and move their child into a forward-facing convertible car seat after the child has reached the upper weight rating for the infant seat. Those with multiple children may find a combination of infant, toddler and booster seats a better fit. See our companion reports on infant car seats and booster seats for reviews and recommendations.
Three compact convertible car seats stand out for their crash test ratings: The Diono RadianRXT (*Est. $340) and the Combi Coccoro (*Est. $200) get high ratings in one independent test. The inexpensive Cosco Scenera (*Est. $55) scores higher than the top-of-the-line models. The Scenera is fully reviewed in Best Convertible Car Seats under $150.
The RadianRXT has the best overall safety features in the compact category, with a solid steel frame for increased protection without increased bulk. Its comprehensive side-impact protection stabilizes the head in the event of a crash. The Combi features side impact protection and a stabilizing top tether that keeps the seat from moving from side to side or forward to backward in the rear-facing position. The RadianRXT can be tethered from the front when the seat is rear-facing to prevent the seat from tipping and to prevent side-to-side movement.
The Combi Coccoro (*Est. $200) gets good reviews for ease of installation because of its smaller size and lighter frame. Both the Combi Coccoro and the RadianRXT offer high-end convenience features like push-button connectors that anchor the seat to the car, and the Combi Coccoro has seatbelt lock-offs to ensure a tight fit with seatbelt-only installation. With the RadianRXT, parents complain about more challenging installation, particularly with older cars without LATCH anchors. The RadianRXT has a lower center of gravity overall and relatively narrow path for the anchoring tethers and the seatbelt, which can make it difficult to route the straps and to tighten them, particularly in the rear-facing position.
Both the RadianRXT and the Coccoro require rethreading to adjust harness height and to remove the seat cover for washing, but harness tension is adjustable from the front.
Where the compact models differ significantly is in their height/weight ratings. The RadianRXT offers exceptionally high weight ratings for convertible car seats in general and for the compact car seat category in particular. The RadianRXT's 3-in-1 design transforms this seat from a rear-facing seat with a 45-pound weight rating to a front-facing car seat with an 80-pound weight limit to a seatbelt positioning booster seat with a 120-pound weight limit, maxing out at 57 inches. The Combi Coccoro, by contrast, has a weight rating of 33 pounds rear-facing and 40 pounds front-facing, which means children may outgrow it before they reach the recommended height/weight ratings.
The Diono RadianRXT is able to achieve these higher weight ratings while sharing the Coccoro's narrow, 17-inch width, thanks to its a steel frame, which allows for a narrower build without sacrificing protection. Both of these 17-inch wide seats fit three seats across in one row in most sedans. However, the Radian is a much longer car seat in the rear-facing position. So parents with extremely compact cars should measure carefully before relying on the Radian as a rear-facing seat. By contrast, reviewers find that the Coccoro fits well, even very small compacts.
The Combi Coccoro and the Diono RadianRXT have infant positioners for a better fit for very small infants. The Radian has a 3-position crotch adjustment, but the Coccoro does not have an adjustable crotch strap. The RadianRXT is uniquely able to accommodate taller and older children; the Coccoro is unique in being able to carry a 3-pound infant safely.
Toddlers are well accustomed to riding in five-point harnesses, but as they get older and see more friends moving into belt-positioning booster seats, some may protest against remaining in a car seat. Due to its lower profile design, the Diono RadianRXT looks somewhat less like a car seat. Kids may balk less at a seat that blends in better with the car and looks less babyish overall.
Comfort is assured with any of these seats. They feature plush padding and easy to wash seats. The Radian RXT comes with one cup holder and can be outfitted with up to four more (*Est. $10). There are additional accessories available as well, including a seat protector to keep spills and accidents from soaking into the seat foam (*Est. $10), and a travel bag (*Est. $30). For parents who travel, the Diono folds flat and comes with a carry strap, but at 23 pounds, it is considered heavy by most reviewers.
In the world of the top car seat companies, customer service tends to be excellent, and most manufacturers are very good at responding to issues. In the case of two of these compact car seats, there are a couple of notable customer service issues worth mentioning. A few years ago, Combi was plagued by complaints of a rear flip issue with the Coccoro, and they fixed the problem on subsequent models. Because of this, it is important to verify that you are purchasing a recent model of the Coccoro seat. If you have an older model of the Coccoro, you can contact Combi for an attachment that will allow you to tether the seat.
Diono, makers of the RadianRXT, has a crash exchange program. If you are in an accident with your child in the car seat, they will send you a new seat in exchange for being able to examine the affected seat. There are limitations and it's at their discretion, but still, it's an idea that may be worth expanding.
The Diono RadianRXT offers one of the safest rides in one of the smallest packages without sacrificing comfort or convenience. It's pricey and it's not the easiest to install, but many parents don't seem to care. The car seat is a top seller on most major retail websites with some of the highest user ratings. Owners overwhelmingly say that they purchased more of these seats to accommodate other children, or that they will turn to this seat again when they need another.