Baby Car Seats: Britax Marathon G4 Convertible Car Seat, Onyx

Baby Car Seats: Britax Marathon G4 Convertible Car Seat, Onyx
From Britax USA

Product Description

Baby Car Seats: Britax Marathon Convertible Car Seat
Britax Marathon Convertible Car Seat

Packed with comfort and safety features, the Britax Marathon convertible car seat is constructed to provide head safety through the use of Britax SafeCell Technology in the base, integrated steel bars, and energy absorbing Versa-Tether that work together to minimize head excursion and reduce the risk of head injury during a frontal impact. It offers a no-rethread and quick-adjust five-point harness and EZ-Buckle system for convenience when harnessing your child, and an easy-remove cover for quick clean-ups that also allows access to the belt paths from the front of the seat. The Marathon accommodates children rear facing from 5 to 40 pounds and forward facing from 20 to 65 pounds.

Head Safety Technologies for Advanced Protection

The base of the Marathon includes SafeCell Technology comprised of SafeCells, an engineered material designed to compress in a crash. This compression lowers the center of gravity to counteract forward rotation of the seat, helping to minimize the risk of head injury during a collision. Located in the sides of the seat shell, integrated steel bars strengthen the connection to the vehicle and prevent forward flexing of the seat during a crash to reduce the risk of head injury.In the event of a sudden stop, the Energy-Absorbing Versa-Tether strap restricts forward movement and reduces crash forces with patented staged-release webbing and a two-point attachment. This webbing securely anchors the top of your child seat to your vehicle in either rear- or forward-facing positions.

Baby Car Seats: Britax Marathon G4 Convertible Car Seat, Onyx
No-Rethread Harness System and Comfort Features

The tangle-free, five-point harness allows for multiple height positions and can be adjusted without dismantling the harness or removing the car seat from the vehicle. Two buckle positions provide a snug, comfortable fit as your child grows. The seat's harness holders prevent the straps from getting in the way when you're putting your child in the seat, while the EZ-Buckle system maintains the harness buckle in a forward position to prevent your child from sitting on it when first entering the seat. Rear- and forward-facing recline options, as well as high-density foam cushioning, help your child relax on the journey. And the plush cover comes with matching comfort pads and an infant positioning pillow to keep children of all ages comfortable and secure. Product Information: The Britax Marathon is assembled in the USA and has a seven-year life. What's in the Box: Britax Marathon Convertible Car Seat, removable cover, comfort pads, infant positioning pillow, and user guide.

Base with SafeCell Technology
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Base with SafeCell Technology

The seat is designed to keep your child safe and secure in a crash by compressing and significantly lowering the center of gravity, reducing the forward movement of the car seat.

Side Impact Protection
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Side Impact Protection System Diverts Crash Forces

The Britax Side Impact Protection system includes a rigid shell with deep side walls lined with energy-absorbing EPP foam to contain your child’s head and body and divert crash force energy while creating a barrier against possible intruding objects. This system also protects your child’s head and chest.

User-Friendly Features for Easy Installation
User-Friendly Features for Easy Installation

The Marathon takes the guesswork out of installing your car seat thanks to a range of convenience features. An anti-slip, contoured base grips and protects the vehicle seat. Premium lower Latch connectors make for a quick, simple, and tight installation, while the push-button allows you to easily uninstall the car seat. And easy-to-access, built-in lock-offs provide a secure installation when using the vehicle lap and shoulder belt.

Premium LATCH Installation
Premium Latch Installation

Provides an audible click and an easy-pull strap to simplify installation as well as a push-button design for easy removal.

Integrated Steel Bars
Integrated Steel Bars

Strengthen the connection to the vehicle and reduce forward flexing of the child seat during a crash.

Energy-Absorbing Versa-Tether
Energy-Absorbing Versa-Tether

Features a staged-release tether webbing to slow the forward movement, reducing the crash forces reaching the child, and a two-point attachment to minimize forward rotation while anchoring the top of the child seat.

Product Details

  • Amazon Sales Rank: #246 in Baby Product
  • Size: one size
  • Color: Onyx
  • Brand: Britax USA
  • Model: E9LQ91A
  • Number of items: 1
  • Dimensions: 26.00" h x 18.50" w x 21.00" l, 19.50 pounds


  • Base with safecell technology features safecells designed to compress in a crash, significantly lowering the center of gravity and counteracting the forward rotation of the child seat which normally propels the child toward the front seat
  • Harness ultra guard system (HUGS) provides resistance to forward movement in the event of a crash
  • Side impact protection comprised of deep side walls lined with energy absorbing EPP foam distributes crash forces, shields from vehicle intrusion, and contains the head, neck and body
  • Tangle free, five point harness distributes crash forces across the strongest parts of the body and provides a secure fit
  • Premium lower latch connectors for a quick and simple installation featuring a push button for easy release

Customer Reviews

Most helpful customer reviews

144 of 147 people found the following review helpful.
5Differences in Britax car seats. 

This is how to choose which Britax car seat will work for you. It can be confusing but small differences matter.
Older seats have the numbers 55 and 70 which indicates maximum weight of the child, CS means Click and Safe snug harness indicator.

G4 is new line, accommodates seats up to 65 lb instead of 70lb.

From the simplest to the most advanced the new G3 models go:
Roundabout and Highway(up to 55 lb), Marathon, Boulevard, Pavilion and Advocate (all up to 65). First two are the base models with lower child weight and I would only consider the Marathon, Boulevard, Pavilion or Advocate.

Marathon has all of the features that the rest of the car seats have except for:
- true side impact protection (Marathon has Side impact protection, this the inside cushion around child's head, models above have extra head protection),
- super thick chest pads that are supposed to minimize forward movement during a crash, Marathon has a different version than the above models have, still ok though,
- Click& Safe indicator, you can hear the click in the other models, when kid is strapped correctly, I can hear several clicks before I can say my son is safely strapped, after every click I can check the pads on his chest to make sure they are not too loose and keep adjusting (also Boulevard misses that option).

The Advocate goes further and has a bulky addition in the head area for more safety, but it was too bulky for my VW. This the only difference between the Advocate and Pavilion.

Overall I rate the this car seat 5 stars. No complaints:
- baby likes it, looks comfortable and the middle position is perfect to sit and watch the world through the window and take a nap without his head hanging down,
- easy to remove the seat cover ( minus only hand wash, no dryer),
- approved for air travel,
- made in the USA ("with global components"),
- they don't feel cheap, I compared different brands in the store and liked Britax the most,
- seat is very secure, there is no movement like I had some with my Chicco Keyfit 30 infant car sear (minimal) but this is a separate base and seat,
- my son was never sweaty after a car ride,
- easy to install but I wouldn't want to switch the car seat between 2 cars, would buy another one,
- I use it for my 3 year old and he is comfortable in it, we use it in a daddy's car, for my car he rides in a booster seat that he LOVES (big boy thing;); my 1 year old would fit perfectly in it too rear facing, I have Pavilion for her).

To simplify the models it goes like this:
Marathon (no click&safe, thinner chest pads, no inside head cushion),
Boulevard (no click&safe, thick chest pads, inside head cushion),
Pavilion and Advocate has click&safe, thicker chest pads, head cushion),
Advocate extra head protection.

There are small differences in a price, all of the car seats are good. I used them for last 2 years and love them. Good construction, fabric and happy kids. For me the best option would be Pavilion but like I said I've used both a Marathon and Boulevard with no complaints. I used to have an older version with click and safe and liked it but now I don't even pay attention that nothing clicks, I still use my fingers to see how much space my kids have around their chests.

Also the Britax website is very helpful in explaining all the features of the car seats.

Older versions (CS, 70, G3) are worth considering if the price is good, it looks like Britax offers new models every year, but on their website it says that car seats are good for 6-9 years from the manufacturing date (depends on the model).

18 of 20 people found the following review helpful.
5Plush features 

Prior to this we've been using Graco car seats. The first difference I noticed with the Britax is that the fabric details are real plush and comfy. Britax has carefully designed the little details like the shoulder pads, butt pad, head rest, etc. to make them very ergonomic. This is a one piece unit that will accommodate larger babies, so there are no extra bases available for the other car. It took me about an hour to figure out how to install it because it has so many different configurations. We absolutely love this car seat design because Britax put so much attention to all the little details and creature comforts.

6 of 6 people found the following review helpful.
4Good convertible car seat; some definite flaws 

I am not a self-styled car seat expert like so many reviewers here on Amazon...I just knew Britax has a good reputation for quality and safety, and liked their B-SAFE infant seat well enough. Britax convertible seats also are all built on the same shell, which fits perfectly in my little Toyota Corolla, another concern of mine.
I liked the Marathon specifically because it was more easily adjustable without removing from the car, and I didn't feel like the added safety features of the more expensive models were necessary. That being said, I have a few (nit-picky) concerns:

1. It was VERY difficult to install in my car. Again, I have a Toyota Corolla so it is small; maybe that makes a difference. But my husband had to unbolt the front seats in order to anchor it to the floor. This makes me concerned if I ever find I need to move it to another car in an emergency or take a cab while traveling.
2. The latch to loosen the straps is EXTREMELY awkward to reach. I have to twist my hand around backwards, reach in really far, and rather painfully contort and push my finger up against the latch for as long as I can sustain it to pull the straps loose with my other hand. I wish I could post a picture of just how awkwardly I must twist my body and hand to accomplish this!
3. One thing that appealed to me about this carseat was the twist-free straps and velcro on the sides to make loading the baby in much faster. But the velcro does not really work; it's not in the correct spot to hold up the straps high enough to make a difference. And the straps can definitely get twisted. So that, combined with the above, means strapping my baby in the carseat is not really much easier or quicker than it was in the B-SAFE.

I know these are minor inconveniences that don't really impact the safety of the carseat. But I would hope Britax corrects these flaws in their next update!

EDIT: This review does not give me the "Amazon verified purchase" stamp, even though it was purchased as a gift for me from my Amazon wish list, which you can see.

See all 23 customer reviews...

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