The Britax Marathon G3 Vs. G4 Convertible Car Seats

The Britax Marathon G3 and G4 car seats are two models of convertible car seat manufactured by Britax which are not only the safest and most dependable models of car seats today, but these are also appealing to the eye and stylish, making them even more popular than they already are. The G3 and G4 model car seats are related, the G4 obviously born after the G3. While both are very popular, there are some changes that Britax has made in the G4’s manufacture. The following will break down details of the 2 models, giving you an understanding of changes Britax has made to the Marathon model.

Britax Marathon 70 Vs. Marathon G4 2014

Britax Marathon 70 G3

Marathon 70 G3

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Rating: 4.7/5
Type: Convertible Car Seat
Rear and Forward Facing: YES
Certified for Aircraft Travel: YES
Latch: YES
5 Point Harness: YES
Front Adjusters: YES
Adjustable Head Support: YES
Washable Fabric: YES
Multiple buckle and recline positions: YES
Weight: 19.5 lbs
Max Weight: 70 Pounds
Dimensions: 29.5 x 19.3 x 18.5"
Easy to adjust.
Easy to clean.
Most comfortable and durable.
Safety and easy to install.

Britax Marathon G4

Marathon G4

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Rating: 4.7/5
Type: Convertible Car Seat
Rear and Forward Facing: YES
Certified for Aircraft Travel: YES
Latch: YES
5 Point Harness: YES
Front Adjusters: NO
Adjustable Head Support: YES
Washable Fabric: NO
Multiple buckle and recline positions: YES
Weight: 19.5 lbs
Max Weight: 65 Pounds
Dimensions: 18.5W x 26H x 21D IN
Most safe and easy to install
Lightweight and stylish
Easy to adjust.
Sturdy and comfortable.
Difficult to clean.

The Britax Marathon G3

The Britax Marathon G3 has been a favorite due to its Safe Cell Technology feature, as well as the fact that it is a rear and front facing car seat. This will actually cause compression to occur in the event of an accident, reversing the child’s rotation and lowing the center of gravity. The seat was engineered for strength and safety through the use of steel bars for stability. Their use prevented the “flinging” of the child that would potentially occur on impact.

This unit is assembled in the United States and is Certified for Air Travel. It features holders which assist in keeping the harness out of the way when placing the child in the seat, and the harness features “lock-offs” which provides for a very secure fit when the child is in the seat. It is adjustable to the size of the child, making sure the seating is snug, and the belt connections are simple for adults to use with the least amount of struggle in latching and un-latching. Adjustments are made simple as well, eliminating potential strap twisting and knotting.

Britax Marathon G3

Britax Marathon 70-G3 Convertible Car Seat

The seat’s upholstery is removable for easy washing, and is simple to put back onto the seat unit itself. It features inner padding as well, for the utmost comfort while the child is in the seat, as well as assisting in the snugness of fit, for the surest safety. This seat does have a 70 lb. weight limit, but features to individual buckle settings to accommodate the child up to that weight limit.

Specs for the Britax Marathon Convertible Car Seat G3 include the accommodating of children as follows:

Rear facing: children 5 to 40 lbs.

Front Facing: 1 year of age; 20 to 70 lbs.

Height: 49″ or less

Seated Shoulder Height:

  • rear: 9-16.75″
  • front: 12-16.75″

Weight of Unit: 19.5 lbs


  • 18.5″ w x 26″h x 21″d
  • seating height: 23.5″

Other dimensional details are given with further research into the Britax Marathon 70-G3. The most recent version of this model, the Britax G4, is the next generation of the Britax Marathon convertible car seat models and is much the same in design and engineering principle, however, Britax has added a few differences to improve on appearance, safety, durability, and dependability. The following is some information regarding the Britax Marathon G4 and some of the features that may differ, if even slightly, from the Britax G3.

The Britax Marathon G4

Now, the basics of the Britax Marathon G4 as compared to the G3 have stayed the same in many respects. This is still a high-quality, durable, and extremely safe car seat which should be the number one option when shopping for an item of such importance. With that being said, the Marathon G4 by Britax has added extras that are in place with both the parent and the child in mind. While the cost is a bit higher, consumers are adamant that it is well worth it to make the purchase. Beside the features and specifications listed above regarding the G3, which apply to the G4 in most aspects, here are some of the new added features that make the purchase of the G4 worth every cent.

Britax Marathon Cowmooflage

Britax Marathon G4 Convertible Car Seat, Cowmooflage

  • The G4 features a 65 lb. weight limit rather than 70, as with the G3. Most feel the 5 lb. difference should not have taken place, but it has occurred due to legal standards that have been set.
  • There is a new insert designed for the G4 model seat. This insert is for infants up to 22 lbs. Because of this insert, be aware what seat you are purchasing for infant use, as this seat will grow with the child with the removal of the insert.
  • Various colors and designs allow the consumer to choose according to basic decor or personality preference.

Bottom Line

As far as specifications for the G4 model, they remain consistent with those of the G3, which is quite sufficient in itself. The added extras of the Britax Convertible Car Seat G4 model have been implemented to provide continuity of use for a longer period of time. The product quality and characteristics are basically the same, and the Britax Marathon G3 and G4 Convertible Car Seats remain one of the best automobile safety options for children today. Grab Yours Now!

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Britax Marathon
Convertible Car Seat
5 / 5 stars