Convertible Car Seat review: Britax MarathonPrice$272

Type: Convertible seat.

Limits: 5 to 40 lbs. rear facing, 20 to 65 lbs. forward facing, 49” tall.

NHTSA ease of use rating: Rear facing: Four stars out of five. Forward facing: Five stars out of five. (Rating is for ClickTight version.)

Pros: Affordable, no rethread harness, easy to use. Good safety ratings.

Cons: Other Britax models have more side impact protection.

Comments: The Britax Marathon is the brand’s best-selling seat and it’s no wonder: this model was one of the first to work to 65 lbs. with a harness. Since its release, Britax has done a series of Marathon spin-offs that add side impact protection (Boulevard, Advocate). Despite being more old school, the Marathon is still worthy of consideration. And at a price in the mid $200’s, the Marathon is some $50-$100 less than the Britax Boulevard and Advocate.

What’s so great about the Marathon? Yes, it works to 65 lbs., but there are many seats on the market that work to that spec. Britax’s secret sauce is the seat’s ease of use—from installation to adjusting the harness, the Marathon is a winner. The emphasis on safety is impressive: steel bar construction, “SafeCell” technology in the base to absorb crash impacts, and built-in seat belt lock-offs.

The “ClickTight” refers to the car seat’s base that pops open to allow for easier installation with a safety belt. The base also has a multi-position recline, matching a feature seen on the Chicco NextFit.

So, what’s not to like about the Marathon? Well, first, this is a big seat. At 23.5” tall (the seat back), it may not fit into smaller cars, especially when in rear facing mode. The Marathon is also a beast at nearly 30 lbs.—you won’t be moving this seat from vehicle to vehicle without the help of a standby Sumo wrestler.

A few readers knocked the Marathon’s harness adjuster button on the front of the seat as a “crumb catcher.” And when installed rear-facing, it can be hard to reach the recline lever, says some readers. (The Chicco NextFit, for example, has a more accessible recline lever).

And if you are concerned about side impact collisions, the Marathon only has what Britax calls its basic side impact protection. The more expensive Britax Boulevard and Advocate add additional protection in the form of headwings and cushions. Those seats’ cushions have both fans and detractors—the safety benefit is obvious, but some kiddos don’t like the wings/cushions around their heads, limiting vision and movement.

One subtle note: even though the Marathon, Boulevard and Advocate are each rated to 65 lbs, the Boulevard and Advocate have two additional harness positions—this enables parents to use the seat longer with bigger toddlers. Hence, one drawback to the Marathon is your child may outgrow the seat by height before they approach anywhere near 65 lbs.

On the plus side, Consumer Reports latest car seat survey saw the Marathon land at the #2 slot out of 32 seats tested; the Marathon’s crash test rating was a “better” on the three-point scale (basic, better, best). (For the curious, the #1 seat was the Chicco NextFit.)

New in 2017, Britax debuted a version of the Marathon with an anti-rebound bar, cleverly called the Marathon ARB at $296. An anti-rebound bar provides an additional level of crash protection by preventing a seat from “rebounding” off the back of the vehicle seat. If you can afford this upgrade, we’d recommend it.

Bottom line: we ended up picked the Britax Boulevard as our top pick for convertible seats, thanks to the additional side impact protection. That said, the Marathon is still an excellent seat. And yes, Marathon does have some side impact protection (deep side walls) and that might be enough protection . . .  depending on your vehicle. If your car has rear side curtain air bags (more common on newer vehicles) and you can install a seat in the middle position of the back seat, then the Marathon may be all you need. If your vehicle lacks rear side curtain air bags, then the Boulevard or Advocate may be worth the safety upgrade.

Reader feedback on this seat has been very positive, with fans citing its ease of use and installation. All in all, we recommend the Britax Marathon.

Rating: A