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Britax Marathon 70 Review

*Est. $290
August 2012
by ConsumerSearch
Britax Marathon 70

Britax Marathon 70 Review

  • New safety technologies
  • One-handed, harness-height adjuster
  • High weight ratings
  • Cover removes for cleaning
  • Big and bulky

Part of Britax's "new generation" of car seats, the Marathon 70 (*Est. $290) improves upon the renowned Marathon Classic with higher weight ratings, new usability features and improved safety features. In the words of BabyGizmo's editorial team, "[i]t just keeps getting better."

Takes child safety a step further

The new Marathon 70 includes a base design with cells that compress in a crash, significantly lowering the child's center of gravity and reducing his or her forward thrust. Integrated steel bars strengthen the connection to the vehicle and reduce forward flexing in the seat, also minimizing the forward thrust of the child. Deep, rigid sides with energy-absorbing foam provide side impact protection for the child's head and chest. Energy-absorbing tethers stabilize the car seat from the top in both the forward and the rear-facing positions, reducing the motion of the seat and reducing the crash impact. Finally, the Marathon's thick and sturdy five-point harness is equipped with chest pads that keep the top restraint of the harness in place over the child's chest, ensuring that the harness provides maximum restraint.

An intuitive design for ease of use

One reviewer describes the Britax Marathon 70's manual as "simple and straightforward." Parents and reviewers alike praise its no-rethread harness height adjuster that allows you to change the harness height from the front with a simple one-handed move while the seat is installed. The Marathon 70 has thick, nontangling harness straps and a long, 8-inch, two-position crotch strap, making it easier to secure larger children. The seat installs easily with push-button, seatbelt-style attachments that you can connect from above to the car's anchors without digging in between the seats. The Marathon 70 is also equipped with lock off fasteners that keep the seat belt tight around the seat when latch connectors are being used. Finally, the Marathon cover removes easily, in one piece while the seat is installed, for washing. The cover is sturdy and will endure repeat washings.

Simple luxury for comfortable riding

Both parents and reviewers comment on the plush feel of the Marathon 70 seat. The entire chassis is lined with high-quality foam that provides energy absorption in a crash and softer cushioning for children. The seat is deeper and roomier than in the Marathon Classic, and the protective side wings provide a resting point for sleepy heads. The Marathon 70 offers rear and forward facing recline positions to keep kids comfortable. It will also take your child from infancy to childhood with a rear-facing weight rating of 40 pounds and a forward-facing weight rating of 70 pounds. An attachable cup holder and a travel cart for airport use can be purchased separately. The only criticism of the Marathon 70 is that its larger size makes it harder to fit in smaller vehicles or when more than one car seat is used.

Britax stands behind its products

No complaints about Britax service were found in our research of the Marathon 70. The Britax website offers comprehensive installation instructions for all car seat models, but you must know the date of manufacture to access the information. All Britax car seats carry a one year warranty against defects in materials and workmanship with proof of purchase. Like most car seats, the seat expires and should not be used after seven years.

The bottom line

The Marathon 70 gets our Best Reviewed rating because it offers the advantage of the capacity for years of use with quality components that will hold up over time as well as safety features that exceed safety standards. Britax car seats are the only convertible car seats that that have a tether that works in both the front and rear-facing positions. However, the Marathon 70 is big, so if you have a small car, need to move the seat frequently or need to fit more than one car seat in one row of seating, you may prefer a less bulky car seat.

Where to Buy Britax Marathon 70
Britax Marathon 70-G3 Convertible Car Seat, Onyx

 (301 reviews)
Buy new: $289.99 $264.99   12 Used & new from $224.00

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EtsyEtsy rated 3.87 (23 reviews)23 store reviewsIn Stock. $99.99

Our Sources: Britax Car Seat Reviews


This review covers safety, best price, comfort, ease of adjustments, ease of installation, dimensions, customer reviews, washing seat covers and pros/cons with detailed photos. This blog also offers comparative reviews of the Marathon 70 and other car seats, including the Graco MyRide 65.

Review: Britax Marathon 70 Review, Editors of


This thorough review is well illustrated with photos of children of various ages sitting in the seat both forward- and rear-facing. The author says the Britax Marathon 70 has a roomier seat with more room in the crotch area than the older Marathon, and the Marathon 70 takes up less room rear-facing. Installation with LATCH is a breeze, but she does have problems with the seat's built-in seat belt lock-offs.

Review: Britax Marathon 70 Review -- Part I, Kecia Healy, July 6, 2010

3. National Highway Traffic Safety Administration

The Britax Marathon 70 earns 4 stars out of 5 for overall ease of use in the NHTSA's tests. The Marathon is penalized for poor labels, receives 5 out of 5 stars for evaluation of instructions and securing the child, and 2 to 3 out of 5 for installation features.

Review: Child Safety Seat Ease of Use Ratings, Editors of National Highway Traffic Safety Administration, As of Aug. 2012


The Britax Marathon 70 is one of the highest-rated convertible car seats here, averaging 4.66 stars out of 5, with 80 owners posting reviews. It earns consistent praise for being safe and well cushioned. Although several reviewers point out that it's expensive, most say it's worth the price.

Review: Britax Marathon 70 Convertible Car Seat - Cowmooflage Reviews, Contributors to

5. Baby Bargains

"Baby Bargains" covers the Britax line in general and the Britax Marathon specifically. Authors Denise and Alan Fields consider performance and ease of use -- as well as the brand's track record -- to come up with their overall rating.

Review: Convertible and Forward Facing-Only Car Seats, Denise and Alan Fields, Ninth Edition, 2012


The Britax Marathon 70 makes Hollie Schultz's list of the five best convertible car seats. This review covers the seat's features at length, but it doesn't mention any testing.

Review: Britax Marathon 70 Convertible Car Seat Blue Print, Hollie Schultz


This comprehensive review details new generation features, including SafeCell technology and the inclusion of steel bars into the seat frame. It also looks at the Marathon 70's installation and harness features, and its size and weight ratings.

Review: Britax Marathon 70 Convertible Car Seat Review, Robert Glazer


The Britax Marathon 70 is one of the highest-rated convertible car seats here, with an average rating of 96 out of 100 based on 56 reviews.

Review: Britax Marathon 70 Convertible Car Seat, Contributors to


The Britax Marathon 70 receives an overall user rating of 4.5 out of 5 stars based on 88 owner reviews. Users say they love the plush comfort of the seat, the thick harness and the easy to install LATCH tethers, among other features. Many users also say they were surprised at how well the seat fits after hearing so much about how big it is.

Review: Britax Marathon 70 Convertible Car Seat, Contributors to


The Britax Marathon 70 was a finalist in's Readers' Choice Awards for best convertible car seat. Readers say they appreciate the extra safety features in the Marathon 70 and the slightly lower price than some of the other Britax models. (Note: ConsumerSearch is owned by, but the two don't share an editorial affiliation.)

Review: Untitled, March 2012


The Britax Marathon 70 is at the top of Heather Corley's list of the eight best convertible car seats. She praises its ease of use and safety features. (Note: ConsumerSearch is owned by, but the two don't share an editorial affiliation.)

Review: Top 8 Convertible Car Seats, Heather Corley

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5 picks including:, National Highway Traffic Safety Administration…

Combi Coccoro Est. $175

3 picks including:, National Highway Traffic Safety Administration…

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1 pick including:, National Highway Traffic Safety Administration…

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