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Britax Marathon 70-G3 - Onyx

The Marathon 70-G3 achieves revolutionary 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. The Marathon 70-G3 also incorporates Britax Side Impact Protection, offers a no-rethread and quick-adjust five-point harness, multiple buckle and recline adjustments, and an easy-remove cover that also allows access to belt paths from the front of the seat. A head and body pillow is provided for extra comfort and infant positioning.

Features:

  • Base with SafeCell Technology 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
  • Integrated Steel Bars strengthen the connection to the vehicle and reduce forward flexing of the child seat during a crash
  • Energy-Absorbing Versa-Tether features a staged-release tether webbing to slow forward movement
  • 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
  • Harness Ultra Guard System (HUGS) provides resistance to forward movement in the event of a crash
  • Plush, easy-remove cover with matching comfort pads and infant body pillow
  • Infant Positioning Insert may be necessary for small infants to achieve a snug fit (sold separately)
  • No-rethread, 5-point harness repositions the harness shoulder height without disassembling straps
  • Premium Lower LATCH Connectors for a quick and simple installation featuring a push button for easy release
  • Certified for Aircraft Travel

Manufacturer Recommended Weight/Height Limits:

  • Rear facing:From 5 to 40 pounds
  • Forward facing: From 20 to 70 pounds
  • Height:Up to 49 inches

Product Dimensions:

  • Weight:19.5 pounds
  • Depth/Width/Height:21 x 18.5 x 26 inches

• Made in the USA and Imported- USA
• 100% Polyester

Product Notes

Popularity: #5 in Car Seats
View All Britax Marathon G3 View All Britax View All Car Seats

Britax Marathon 70-G3 - Onyx

998 reviews
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$238.09 SALE

List: $289.99

Description
Price
   
Britax Marathon 70-G3 - Onyx
$238.09
Discontinued by vendor
Britax Marathon 70-G3 - Azalea
$289.99
Discontinued by vendor
Britax Marathon 70-G3 - Chili Pepper
$214.99
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Britax Marathon 70-G3 - Cowmooflage
$195.99 $289.99
Discontinued by vendor
Britax Marathon 70-G3 - Waverly
$199.99 $289.99
Discontinued by vendor
Total: $0.00
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REVIEW SNAPSHOT®

by PowerReviews
BritaxMarathon 70-G3 - Onyx
 
4.8

(based on 26 reviews)

100%

of respondents would recommend this to a friend.

Pros

  • Durable (23)
  • Safe (22)
  • Comfortable (20)
  • Easy to adjust (17)
  • Easy to install (14)

Cons

  • Heavy (7)
  • Heavy / bulky (6)
  • Hard to install (3)

Best Uses

  • Toddler (20)
  • Infants (14)
  • Newborn (3)
    • Reviewer Profile:
    • First time parent (16), Parent of two or more children (8)

Reviewed by 26 customers

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Displaying reviews 1-15

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(1 of 1 customers found this review helpful)

 
5.0

Our second Britax Car Seat...

By Christina

from Buena Park, CA

About Me Parent of Two or More Children

Verified Buyer

Pros

  • Comfortable
  • Easy to Adjust
  • Easy to Clean
  • Easy to install
  • Safe
  • Sturdy

Cons

    Best Uses

    • Newborns To Young Child

    Comments about Marathon 70-G3 - Onyx:

    My husband and I love this car seat! We already have one for our 14 month old and decided to buy another for our baby due in March. It's very sturdy, easy to adjust and my son never complains about having to be in it. My parents and In-Laws have bought less expensive car seats for their cars and even though they are easy to adjust and seem comfy, my son has been able to pull the chest clip down on both of them and get his arms out from under the belts...not exactly safe. I know Britax can be pricey, but they're worth every penny and luckily diapers.com has some great sales on them from time to time.

    Comment on this review

     
    5.0

    Highly recommend!

    By Liyah

    from Miami, FL

    About Me Parent of Two or More Children

    Pros

    • Comfortable
    • Easy to Adjust
    • Easy to Clean
    • Easy to install
    • Lightweight
    • Safe
    • Sturdy
    • Stylish

    Cons

      Best Uses

      • Infants
      • Newborn
      • Toddlers

      Comments about Marathon 70-G3 - Onyx:

      I personally love this seat (I actually have the Marathon 70, not the Marathon 70-G3 but they look and am sure they are the exact same just a different generation) , I got this car seat when my daughter was 5 months old (she had already begun to outgrow her infant seat) and boy was this the best thing I could have done for my daughter and I. Installation is super easy, and not one day since the day she was in this seat has she complained or cried that she was uncomfortable. She will now be 3 in January and still loves her seat and loves that she can even buckle herself (yes, I adjust what needs adjusting) I'm also now expecting #3 and am planning on purchasing this seat again for this baby.. it really is a money saver, you spend what you have to in the beginning so your not paying more later.. I can't imagine spending money on another infant seat, then forward facing seat then a booster later on. I'm definitely getting this for my infant and letting him use this seat for years to come :)

      Comment on this review

      (2 of 2 customers found this review helpful)

       
      5.0

      Best car seat!!

      By Goose

      from San Diego, Ca

      About Me First Time Parent

      Verified Buyer

      Pros

      • Comfortable
      • Easy to Adjust
      • Easy to Clean
      • Easy to install
      • Safe
      • Sturdy
      • Stylish

      Cons

        Best Uses

        • Infants
        • Newborn
        • Toddlers

        Comments about Marathon 70-G3 - Onyx:

        A breeze to install
        No hassle straps
        Easy to adjust height
        Simple to recline
        Comfortable for baby
        Safe and Sturdy

        Comment on this review

        (1 of 1 customers found this review helpful)

         
        5.0

        Awesome seat!

        By Angie

        from Mentor, OH

        About Me First Time Parent

        Pros

        • Comfortable
        • Easy to Adjust
        • Easy to Clean
        • Easy to install
        • Lightweight
        • Safe
        • Sturdy
        • Stylish

        Cons

          Best Uses

          • Infants
          • Newborn
          • Toddlers

          Comments about Marathon 70-G3 - Onyx:

          I purchased this seat after I returned one that I ordered online that was advertised as a convertible carseat but could not be installed rear-facing and boy am I happy with this carseat! It is so so so easy to install and is comfortable! Nothing compares to the quality of Britax seats! I'm so happy with this product and highly recommend it!

          Comment on this review

          (1 of 1 customers found this review helpful)

           
          5.0

          Britax is A-OK

          By Jules

          from La La Land, CA

          About Me First Time Parent

          Verified Buyer

          Pros

          • Attractive Design
          • Comfortable
          • Sturdy

          Cons

          • Heavy

          Best Uses

          • Toddlers

          Comments about Marathon 70-G3 - Onyx:

          This car seat is popular for a reason. Easy to install, use and my toddler doesn't hate it. Solid product.

          Comment on this review

          (0 of 1 customers found this review helpful)

           
          5.0

          Excellent

          By MamaLlama

          from Lafayette, LA

          About Me First Time Parent

          Verified Buyer

          Pros

          • Attractive Design
          • Comfortable
          • Easy to Assemble
          • Sturdy

          Cons

            Best Uses

            • Infants
            • Toddlers

            Comments about Marathon 70-G3 - Onyx:

            The Britax marathon is exactly what we were looking for. The installation was quick and easy. Our little girl loves riding in it.

            Comment on this review

            (2 of 2 customers found this review helpful)

             
            5.0

            Superior safety

            By Designerskyy

            from Pittsburgh PA

            About Me First Time Parent

            See all my reviews

            Verified Buyer

            Pros

            • Safe
            • Sturdy

            Cons

            • Bulky

            Best Uses

            • Infants
            • Toddlers

            Comments about Marathon 70-G3 - Onyx:

            I call it our 'black box', like the indestructable ones used on planes. It's fantastic.
            A little tricky the first few times getting baby in and out when rear facing. But his safety comes first, and I completely feel he's safe in this seat.

            Comment on this review

            (0 of 1 customers found this review helpful)

             
            3.0

            My child has comfort issues with Seat

            By Squilts

            from Iowa

            About Me Parent of Two or More Children

            Verified Buyer

            Pros

              Cons

              • Bulky
              • Hard to Install
              • Heavy
              • Uncomfortable

              Best Uses

              • Toddlers

              Comments about Marathon 70-G3 - Onyx:

              Bought this seat for my tall skinny 3.5 yo. I knew I wanted Britax for it's reputation for safety and comfort. I considered the Roundabout b/c I didn't want the rubber HUGS things, as I knew my daughter wouldn't like them...but she would outgrow that seat by height way before weight, so we went with Marathon. A couple things I don't like...The rubber HUGS make it too easy for her to mess with the chest clip, the belly pad on the crotch strap is annoying in that it makes it hard to get your hand around it and push the button to pop them undone. Also because of the no rethread shoulder straps, there are two back pads that overlap and my daughter hates this, in fact she rides with her arm behind her back the whole time (not safe!). If you have a picky kid this is not the seat for you.

              Comment on this review

               
              5.0

              LOVE this car seat!

              By Kara

              from PA

              About Me Parent of Two or More Children

              Verified Buyer

              Pros

              • Comfortable
              • Easy to Adjust
              • Easy to Clean
              • Easy to install
              • Safe
              • Sturdy
              • Stylish

              Cons

                Best Uses

                • Toddlers

                Comments about Marathon 70-G3 - Onyx:

                We bought this car seat for our daughter who is now 2 1/2 so decided to get the same one for our son who is still in an infant seat, but will be moving into this seat in a few months. Originally, we bought the seat for our daughter because of the good reviews and safety ratings. It is super easy to adjust for height and the material makes it easy to clean and when it is dirty, it doesn't show much. Diapers.com also had the best price by far and it was delivered to our house the next day.

                Comment on this review

                (3 of 3 customers found this review helpful)

                 
                5.0

                Love the new Britax Marathon!

                By Heather

                from Germantown, WI

                About Me Parent of Two or More Children

                Verified Buyer

                Pros

                • Easy to Adjust
                • Easy to Clean
                • Easy to install
                • Safe
                • Sturdy

                Cons

                  Best Uses

                  • Infants
                  • Toddlers

                  Comments about Marathon 70-G3 - Onyx:

                  This is our 5th Marathon carseat and this is by far the best yet! I love the new wipe clean fabric, looks like it will be easier to keep clean than the softer, older covers. Also it looks to be a bit more solid than older models with the new base technology. Lastly, love the new features regarding changing the strap locations...this is great if you are using it for two different children or even for another child to use if you're carpooling. Love everything about this new Marathon model!!! Also love the price and return policy from diapers.com, will definitely order other carseats as needed from here.

                  Comment on this review

                  (2 of 3 customers found this review helpful)

                   
                  5.0

                  Well worth the price

                  By Sahm

                  from Ny,ny

                  About Me First Time Parent

                  Pros

                  • Comfortable
                  • Easy to Adjust
                  • Safe
                  • Sturdy

                  Cons

                    Best Uses

                    • Infants
                    • Toddlers

                    Comments about Marathon 70-G3 - Onyx:

                    We bought this so our son could sit rear facing longer. We were hesitant about the price but after reading all the great reviews we decided it was worth it. We were right! This seat is comfortable and you can tell the frame is of a higher quality than other car seats. It was a pricey investment and I hope my son can use it for many years to come.

                    Comment on this review

                    (2 of 2 customers found this review helpful)

                     
                    5.0

                    Love this seat!

                    By Ali

                    from Prospect, Ky

                    About Me First Time Parent

                    Verified Buyer

                    Pros

                    • Comfortable
                    • Easy to Adjust
                    • Easy to install
                    • Safe
                    • Sturdy
                    • Stylish

                    Cons

                    • Heavy

                    Best Uses

                    • Toddlers

                    Comments about Marathon 70-G3 - Onyx:

                    We love this car seat. We bought it for our daughter right before her first birthday as soon as she outgrew her chicco infant car seat. Although it is a little heavy and bulky to install, once installed it is fantastic. I recommend watching the installation video. It made install a snap. It fits in the back seat of my SUV perfectly. Plenty of room for the people in the front seats and beside her. She's super comfy in the seat too. When she snoozes in it her head doesn't flop uncomfortably to the front or sides. It is great. Highly recommend!!!

                    Comment on this review

                    (2 of 2 customers found this review helpful)

                     
                    4.0

                    HUGE seat

                    By Jenny (first time mom)

                    from Overland Park, ks

                    About Me First Time Parent

                    See all my reviews

                    Verified Buyer

                    Pros

                    • Comfortable
                    • Easy to Adjust
                    • Easy to Clean
                    • Easy to install
                    • Safe
                    • Sturdy
                    • Stylish

                    Cons

                    • Bulky
                    • Heavy

                    Best Uses

                    • Infants
                    • Toddlers

                    Comments about Marathon 70-G3 - Onyx:

                    Easy to install with LATCH system, very big and bulky. I also have a Roundabout 55 and a Boulevard. Safety is the most important thing and this seat makes me feel confident that my daughter will be safe. It is super easy to adjust the straps, no re-threading means you don't have to take the seat out of the car. This would not be best for a small car or to take on an airplane, it is very big.

                    Comment on this review

                    (0 of 1 customers found this review helpful)

                     
                    4.0

                    Love it!

                    By Baby Q's mum

                    from Boston, MA

                    Verified Buyer

                    Comments about Marathon 70-G3 - Onyx:

                    Very easy to install! Love the fabric and my son seems to like it too. Love that it will last him until booster seat time. Very easy to get son in and out of. Definitely recommend it!

                    Comment on this review

                    (4 of 5 customers found this review helpful)

                     
                    5.0

                    LOVE this car seat

                    By ellakaybee

                    from MI

                    About Me First Time Parent

                    Verified Buyer

                    Pros

                    • Comfortable
                    • Easy to Adjust
                    • Easy to Clean
                    • Easy to install
                    • Safe
                    • Sturdy

                    Cons

                      Best Uses

                      • Infants
                      • Toddlers

                      Comments about Marathon 70-G3 - Onyx:

                      This is one of 3 convertible car seats we own and it far outshines the others. We have a budget one, a mid-range and this. I originally thought a car seat is a car seat, but now that I have experience with all 3 I would definitely recommend going for a Britax if it's in your budget.

                      What I love about it:
                      -my baby is comfortable in it and doesn't complain riding in it like her other seat
                      -plenty of cushioning
                      -high weight limits; can keep our baby rear facing longer and in a five point harness longer
                      -simple squeeze-handle to raise and lower the belt shoulder height
                      -simple lever to adjust the recline of the seat on the base
                      -bottom latch always lays forward so baby doesn't sit on it, straps velcro to sides when putting baby in, straps don't twist in latches; less fishing and finnagling = happier baby!
                      -padding under bottom latch receiver, neck padding on straps

                      This seat is much larger and heavier than others, but to me that translates to more safety and comfort. And even with the larger size, it fits just fine in our little Camry.

                      Bottom line: would definitely recommend it!

                      Comment on this review

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