Britax Marathon 70 G3 Review & Video Demo

Britax Marathon 70 G3 Customer Rating: 487/511 – 95%

Britax Marathon 70 G3 Review

Britax Marathon 70 G3 – Azalea

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  • Rear-facing: 5 to 40 pounds
  • Forward-facing:  up to 70 pounds and 49″ tall
  • SafeCell Technology in base – Compress in the event of a crash, minimizing forward rotation and lowering center of gravity
  • Integrated steel bars strengthen the connection between vehicle and seat
  • Energy absorbing versa-tether anchors the seat and vehicle
  • Side Impact Protection – Rigid seat with deep side walls and EPP foam shell
  • NEW – EZ-Buckle System – keeps the harness buckle from falling back into the seat.
  • Reclines in both forward and rear-facing positions
  • High-density comfort foam seat
  • Plush cover set with matching belly pad – removes easily for cleaning
  • Tangle-free five point harness
  • 10 Harness height adjustments – with quick-adjust which allows you to adjust without disassembling the car seat
  • 2 buckle positions
  • Infant Positioning Insert – Perfect for giving smaller infants a snug fit (SOLD SEPARATELY)
  • Premium Lower LATCH connectors
  • Built-in lock-offs for seat belt installation
  • Anti-slip contoured base grips and protects seat – provides tight installation
  • Holders keep harness straps at bay while loading and unloading your child
  • Comes with a One-Year Limited Warranty

Britax Marathon 70 G3 Review

In case you’re wondering, the Britax Marathon 70 G3 is the new and improved version. They haven’t changed much, in fact I do believe the only real change was the addition of the EZ Buckle System. Other than that it’s the same seat.


Britax Marathon 70 G3 -Review  Safety FeaturesObviously, Safety is probably the number one advantage to the Britax Marathon 70 G3, or any other Britax Car Seat for that matter. That’s the number one reason why Britax is such a trusted brand. They are the leaders in car seat safety, as you can see by the never-ending list of safety features listed above. If you want a more detailed description of any of the above saftey features, refer to this article: Britax Safety Features Explained.

Easy Installation – The Britax Marathon 70 G3 installs incredibly easy. It offers both LATCH and seat belt installation.  Most vehicles will allow you to use the LATCH system up to at least 40 pounds, some allow you to use it up to around 48 pounds. It’s important to check your vehicle owner’s manual first before installing. Once you’ve reached that LATCH limit you must then reinstall the Britax Marathon 70 using the seat belts.

Soft Cover and No-Rethread Harness – The seat cover on the Britax Marathon 70 G3 is extra soft, and it can be removed easily without having to take the whole thing apart. Same goes with the harness. It’s called quick-adjust, and basically it’s a handle on the front of the seat above the headrest. You squeeze and move it up or down to readjust the harness and headrest. Beats the heck out of re-threading!

The Britax Marthon 70 G3 offers a 40 pound maximum weight limit for rear-facing. That follows NHTSA’s recommendations to keep your child rear-facing for as long as possible. Same with the 70 pound max weight for the forward-facing harness. Of course, chances are your child will probably out-grow the seat height first before the weight capacity, but that’s just par for the course with convertible car seats.

Here are a few other pro’s most commonly listed.

  • EZ-Buckle system – Keeps the buckle from flipping back into the seat when getting your child in and out. No more digging!!
  • Push-button release on LATCH, makes it super easy to un-install
  • Anti-slip contoured base that protects your seat
  • Harness holders keep the straps out of your way when you’re loading and unloading your child, especially helpful when using it rear-facing
  • Seat belt lock-offs – no need for those annoying little clips
  • 3-position recline – 2 positions are for forward-facing, and one is for rear-facing. This helps achieve that 45 degree angle recommended for rear-facing infants.


I like to go through the customer feedback with a fine toothed comb, looking for any common complaints that stick out.

Britax Marathon 70 G3 Review- Chili PepperThe thing is, the Britax Marathon 70 G3 had very little complaints. In fact 196 out of 205 reviewers rated it 4 or 5 stars, with 5 being the most. That’s a 96% customer satisfaction rating! Even the old Britax Marathon 70 had a 91% rating. So, keep that in mind as you read through the common complaints listed below.

As I said above, chances are your child will outgrow the seat height before the seat weight. The Britax Marathon 70 G3 offers a max height of 49 inches, which is definitely not the most, but it’s not the least either. There are a couple other convertible car seats out there with taller seats, like the Radian RXT which offers a seat height of 57 inches, or the Safety 1st Complete Air 65 that offers 52 inches. The things is, the Britax Marathon 70 G3 may not get you all the way up to 70 pounds, but it will get you close, and it will get you there safely.

Britax Marathon 70 G3 - Seat Belt Lock-offs

Lock-offs for both Forward and Rear-facing Installations

Installing the Britax Marathon 70 G3 using the seat belt is a bit more complicated, especially if you’re using the integrated seat belt lock-offs. You actually have to lock the seat belt in while there’s still slack, then pull the remaining slack out through the already locked, seat belt lock-off. I know that’s confusing but I don’t know how else to explain it. has an excellent video you can watch that demonstrates this feature. Check it out here.

The Britax Marathon 70 G3 is 18.5 inches wide, so ya, it takes up some space. The best spot seems to be in the center of the back seat. If you have a smaller car, you may have to readjust seating if you plan on putting it behind the driver or passenger seats.


The Britax Marathon 70 G3 is SAFE, Convenient, Easy to Install, and Comfortable. It’s also the MOST popular Britax Convertible Car Seat currently on the market, and it has the highest customer satisfaction rating. It’s also the number one Best Seller on Amazon. I definitely recommend it!

Where to Buy:

Still undecided? Watch the video demo below, or read through some of the Customer Reviews on Amazon.

Video Demonstration:

Get the Britax Marathon 70 G3 @ Amazon – Best Price

Comparison Reviews:

Britax Marathon 70 Vs. Britax Boulevard 70

Britax Marathon 70 Vs. Safety 1st Complete Air

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Best Convertible Car Seats – If you’re looking for the best convertible car seats with the best features, best reviews, and the best prices, then look no further.

Best Car Seats – From the best infant car seats and the best convertible car seats, to the best booster seats.

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