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Britax Marathon 70 Review of Parent Friendly Convertible Seat..

Britax Marathon 70-G3 OnyxThe Marathon 70 is a convertible type of seat. It can be used rear-facing between 5 and 40 Pounds and then converts to front facing and will protect your child until reaching a maximum weight of 70 pounds.

(4.7 / 5)

The Britax Marathon 70 has now been updated and the latest model is called the Marathon G4.1.

See Latest Marathon G4.1 Designs >>

The design incorporates Britax SafeCell technology, integrated steel bars and versa-tether technology to protect your child in the event of an accident. These features act in unison to prevent your child’s head from moving forwards too fast if your vehicle is involved in a frontal collision and offer greater protection from head injury. The side walls are also lined with EPP foam to give added protection from side-impact collisions.

The advanced design of the 5-point tangle-free harness means that your child is securely restrained and the straps are easy to adjust even after months of use as they do not get tangled as in some other manufacturers models. There is a head and body cushion supplied which provides extra comfort for your child.

The Marathon 70 can be fitted in your car using either LATCH or your existing vehicle safety belts and has further been certified for use during aircraft travel.

The cover can be removed and then hand washed by using a mild detergent. The harness can also be sponge cleaned with water and a mild detergent. be with warm water and mild detergent if there are any spills that need cleaning. It is recommended though that the buckle and LATCH hardware are only cleaned using warm water.

The Marathon 70 comes in a range of different colors and designs including, Azalea, Jet Set and Waverly.

Britax Marathon 70 G3 Azalea
Britax Marathon 70-G3 Jet Set
Jet Set
Britax Marathon 70-G3 Onyx
Britax Marathon 70-G3 Waverly
Britax Marathon 70-G3 Cowmooflage


Convertible Car Seat

Used Rear Facing
Child Weight: 5 to 40 Pounds
Child Maximum Height:  49 Inches

Used Front Facing
Child Age:  1 Year Minimum
Child Weight:  20 to 70 Pounds

Weight: 19.5 Pounds
Height: 26 Inches
Width: 18.5 Inches
Depth: 21 Inches


  • Steel bars integrated into the design of the seat prevent forward flexing during a crash
  • Britax SafeCell technology designed to absorb crash forces during an accident
  • Versa Tether absorbs energy during crash by offering staged-release thereby limiting the speed of forward motion reducing the amount of crash forces reaching the child
  • Energy absorbing EPP foam used to line the side walls of the seat to cocoon child safely
  • Extra comfortable due to the forward and rear facing recline incorporated into the design
  • Cleaning is easy due to the removable covers and inserts
  • Certified for airline travel

What Parents Liked about it..

  • Thick material
  • Simply oozes quality
  • Sturdy and well-made
  • LATCH Fittings are really strong and secure
  • Can be adjusted without removing it from the car
  • Straps don’t get twisted
  • Fastens easily to airplane seats
  • Recline works well
  • Child finds seat comfortable, lots of padding

What the Parents Didn’t Like..

  • Some parents commented that it could be difficult to fit but problems were resolved after watching the manufacturers videos available on the Britax website
  • Quite a bulky seat
  • No cup holder

We liked the Marathon. It’s easy to install, especially after watching the videos available on the Britax website. The finish is excellent and it furthermore offers great value for money.

Many parents also liked this model and saw it as a great investment and they were glad that they had bought it, even after it had been in use for several months. There were also several parents who had purchased more than one seat.

It was frequently commented that the the seat felt very safe and sturdy and the degree of padding surpassed many other manufacturer’s seats. Once installed parents said that it was rock solid and they had peace of mind that their child would be protected in the event of an accident.

In view of all these facts we recommend this model if you are looking for a convertible model of seat.

Get More Information on The Britax Marathon Here

More Choices

Several other Convertible seats have been reviewed on our site, including these very good models:

The Britax Advocate is a very good model featuring the very best technology that money can buy including the ultimate in side-impact protection. This seat is suitable for a medium to large-sized car as it is quite wide and takes up quite a lot of room but is an excellent choice if you want the very best protection for your child. See Our Review

A completely different type of seat is the Safety 1st Alpha Omega Elite. This got very good ratings from most parents and will accommodate your child all the way from Birth to 100 pounds for a very reasonable price! 

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