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Product Information

Britax Marathon 70 Convertible Car Seat- Onyx

 

With so much of baby’s day-to-day adventures spent in a car seat, he needs a seat that’s built for comfort and safety! The Britax Marathon 70 Convertible Car Seat has everything both you and baby are looking for. From safety features like side impact protection to comfort features like high density comfort foam, baby will look forward to taking that ride to grandma’s house!
 
Why You’ll Love It: It’s a car seat standout with tons of safety features!
 
Features
  • “SafeCell” technology, designed to compress in a crash
  • Side impact protection
  • Tangle-free, 5-point harness
  • Quick-adjust harness
  • Easy-remove cover
  • Rear and forward-facing recline
  • Lower LATCH connectors
  • Anti-slip, contoured base
  • Convenient harness holders
  • High density comfort foam provides extra layer of padding
 
Age/Height/Weight Limits
  • Rear-facing: From 5 to 40 lbs.
  • Forward-facing: At least 1 year and 20 lbs.; up to 70 lbs.
  • Standing height: Up to 49 in.
 
NOTE: The LATCH connectors for this car seat are stored under the cover near the back of the seat.

 

Product Notes

View All Britax Marathon 70 View All Britax View All Car Seats

Britax Marathon 70 Convertible Car Seat- Onyx

542 reviews
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  • Britax Marathon 70 Convertible Car Seat- Onyx
  • Britax Marathon 70 Convertible Car Seat- Onyx
  • $289.99
  • Discontinued by vendor
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Review Snapshot

REVIEW SNAPSHOT®

by PowerReviews
BritaxMarathon 70 Convertible Car Seat- Onyx
 
4.7

(based on 18 reviews)

94%

of respondents would recommend this to a friend.

Pros

  • Comfortable (15)
  • Durable (15)
  • Easy to adjust (14)
  • Safe (14)
  • Stylish (14)

Cons

    Best Uses

    • Toddler (13)
    • Infants (10)
      • Reviewer Profile:
      • First time parent (9), Parent of two or more children (5)

    Reviewed by 18 customers

    Sort by

    Displaying reviews 1-15

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    5.0

    BEST CAR SEAT EVER!!!

    By RogersGrl

    from Rancho Cucamonga

    About Me First Time Parent

    See all my reviews

    Pros

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

    Cons

      Best Uses

      • Toddlers

      Comments about Marathon 70 Convertible Car Seat- Onyx:

      THIS CAR SEAT IS EASY TO INSTALL, COMFORTABLE FOR ALL CHILDREN, AND VERY EASY TO REMOVE. ORIGINALLY, I BOUGHT AN INFANT CAR SEAT FOR MY SON, AND WHEN HE TURNED 8 MONTHS HE NO LONGER FIT IN IT. I LOOKED VERY CAREFULLY AT DIFFERENT CAR SEATS AND REVIEWS IN STORES AND ONLINE. I ENDED UP RUNNING INTO A FRIEND WHO USED THIS CAR SEAT AND SHE SAID IT WAS WORTH EVERY PENNY. I WENT OUT AND BOUGHT ONE AND IT IS WORTH EVERY PENNY. IT IS CLEAR THIS COMPANY HAS 3 MAJOR FACTORS ON THEIR MIND: SAFETY, COMFORT, AND DURABILITY. I BOUGHT MY CAR SEAT IN DEC OF 2010, AND IT IS STILL IN BRAND NEW CONDITION!

      Comment on this review

       
      5.0

      L-O-V-E THIS CAR SEAT!!!

      By Aubrey's Momma

      from Fort Bragg, NC

      About Me First Time Parent

      See all my reviews

      Pros

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

      Cons

        Best Uses

        • Infants
        • Toddlers

        Comments about Marathon 70 Car Seat - Cowmooflage:

        This car seat is AMAZING. I am so glad I spent the extra money and bought it! I had originally bought the Safety 1st car seat, and all I will say about that one is that I did not like it and had to return it. I did so much research and asking around for the best possible car seat and the Britax Marathon was perfect! It is soooo comfortable, just like a baby lazy-boy! LOL.... the cow print is so adorable and so gender neutral so I'm very glad I went with it. It reclines (unlike a lot of other car seats), and it's just perfect. I haven't had any problems with it, and my daughter is very comfortable and happy :)

        Comment on this review

         
        4.0

        Bulky but secure and comfortable

        By Vanessa

        from Glendale, CA

        About Me First Time Parent

        See all my reviews

        Pros

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

        Cons

        • Bulky

        Best Uses

        • Toddlers

        Comments about Marathon 70 Car Seat - Cowmooflage:

        I have a mid size sedan and this seat just barely fits in the rear facing position. It is not very easy to get my LO in and out of the car but I am hoping that will change once she meets the weight requirements to sit front facing. That said, the seat was easy to install and the straps adjust well. The fur can get a little hot for LO when it's warm outside, but she is snug and happy riding around.

        Comment on this review

         
        5.0

        GREAT CUSTOMER SERVICE

        By Satisfied Mom

        from Rock Hill, SC

        About Me First Time Parent

        Pros

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

        Cons

          Best Uses

          • Infants
          • Toddlers

          Comments about Marathon 70 Convertible Car Seat-Waverly:

          Product is pretty easy to install. We love the fabric and look of the car seat. It is perfect for our 10 month old and will allow him to grow into it.
          We had a tear on our seat when we received it, so I immediately emailed customer service. Within hours, I had a response saying they would send a new cover if available, or replace the entire car seat. Great customer service and I would highly recommend this sight and seat to friends.

          Comment on this review

           
          5.0

          So easy to adjust - love it

          By cat7510

          from NJ

          About Me Parent of Two or More Children

          Pros

          • Comfortable
          • Easy to Adjust
          • Sturdy
          • Stylish

          Cons

          • Hard to cary around
          • Heavy

          Best Uses

          • Toddlers

          Comments about Marathon 70 Car Seat - Cowmooflage:

          We have this seat for two years now and we love it. Very easy to adjust straps so everytime I am buckling my son I can adjust it depending on what he is wearing that day to make belts tighter or looser. We also used it on the plane but it is too heavy to travel with and there was nothing to hold it by which made our trip on the airport very difficult. However I highly recommend it for a car.

          Comment on this review

           
          5.0

          Love Love Love it

          By jones mom of 3

          from wyoming

          About Me Parent of Two or More Children

          See all my reviews

          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 Car Seat - Cowmooflage:

            I love this seat. we have 2 of them and wouldn't have anything else. My oldest started hating the carriers when she was about 3 months old. So we switched her over without any concerns for her size. It fit her perfecly.

            Comment on this review

            (0 of 2 customers found this review helpful)

             
            2.0

            I would not buy again

            By Dave the dad

            from Cohasset, MA

            About Me Parent of Multiples (Twins etc)

            Pros

              Cons

              • Difficult To Adjust

              Best Uses

                Comments about Marathon 70 Convertible Car Seat- Onyx:

                Purchased two Marathon 70 car seats for my twin daughters. After using Peg Perago infant seats, the Britax seat adjustments were clearly inferior. The chest/shoulder restraining straps jam frequently. The straps twist and jam behind the seat and the seat must be removed to clear the jam so the shoulder straps can again be adjusted properly. In addition, it is very difficult to adjust or release the bottom straps holding the car seat to the vehicle seat hooks. This becomes more problematic since we have to remove the seat frequently to unjam the shoulder straps. The red release button on the bottom strap is pretty much disfunctional. Easy to tighten, very difficult to loosen. Very disappointed in the quality of the product and ease of use.

                Comment on this review

                 
                4.0

                He seems much more content at stoplights

                By New Mom

                from Radcliff, KY

                About Me First Time Parent

                See all my reviews

                Pros

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

                Cons

                  Best Uses

                  • Infants
                  • Toddlers

                  Comments about Marathon 70 Car Seat - Cowmooflage:

                  We love this car seat and our little baby boy seems a whole lot happier since we've started using this instead of the temporary infant-only car seat we'd gotten (which we'd only gotten really because we weren't super comfortable with whether he'd fit in this one when he was a tiny NB - the only downside, I'd say). We did buy a head positioner for him (started using this Britax car seat when our son was 3 months old) but with that he fits like it was made just for him.

                  One mistake we did make was buying the Britax infant positioner - even with this his head would flop down when he was too tiny, so we didn't end up using it. Oh well, lessons learned.

                  Really glad we decided on this brand/model - oh and it fits in my 2009 Toyota Corolla easily rear-facing in the center of the backseat. If we were to have another child though, we'd probably have to either rethink the seat or get a bigger car.

                  Comment on this review

                   
                  5.0

                  Amazing Car Seat!

                  By Natalie

                  from St Louis, MO

                  About Me First Time Parent

                  Pros

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

                  Cons

                    Best Uses

                    • Toddlers

                    Comments about Marathon 70 Convertible Car Seat-Waverly:

                    Super comfortable car seat! My baby 14 month in love with this car seat! I'll recomended this car seat to all my friedns. Lil bit expensive, but it cost every penny you're pay for it!

                    Comment on this review

                    (1 of 1 customers found this review helpful)

                     
                    5.0

                    Stop looking, this is the best!!!

                    By Ruby and Pearl's Momma

                    from Texas

                    About Me Parent of Multiples (Twins etc)

                    Pros

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

                    Cons

                      Best Uses

                      • Toddlers

                      Comments about Marathon 70 Car Seat - Cowmooflage:

                      Love this car seat!! My folks bought these for our 15 month old twin girls. We had Graco infant seats prior. Britax is the BEST!! Durable, secure, comfortable and great design! I immediately feel in love with the cow print...after my folks ordered I got a little nervous about the white fabric and kids. Luckily when we opened the boxes we found they have a tan color mixed in as well. For added security I sprayed all of the fabric surfaces with scotch guard. So far SO great!!! The one downfall, they are cumbersome to install...but I left that up to my hubby ;)

                      Comment on this review

                      (0 of 1 customers found this review helpful)

                       
                      5.0

                      LOVE LOVE LOVE THIS CARSEAT

                      By ON THE GO MOM

                      from SALEM, OREGON

                      About Me First Time Parent

                      Pros

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

                      Cons

                      • Bulky

                      Best Uses

                      • Infants
                      • Toddlers

                      Comments about Marathon 70 Convertible Car Seat- Onyx:

                      THIS IS THE BEST CAR SEAT. A MUST!

                      Comment on this review

                      (10 of 11 customers found this review helpful)

                       
                      5.0

                      This carseat saved my daughter's life

                      By MaddiesMommy1

                      from Carrollton, IL

                      About Me First Time Parent

                      Pros

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

                      Cons

                      • Heavy

                      Best Uses

                      • Infants
                      • Toddlers

                      Comments about Marathon 70 Car Seat - Cowmooflage:

                      My husband and daughter were in a car accident on 12/6/2011, and this car seat saved my 1 year old daughter's life. They were hit while at a complete stop on the highway by a SUV going 55mph. Luckily, no one was hurt in the accident and my daughter was not even phased by the impact because of the sturdy build of her Britax Marathon. If it hadn't been for this seat, she very well could have been hurt or killed...I will never again buy any seat other than Britax for my kids! I would reccomend this to everyone, it is GREAT!

                      Comment on this review

                      (1 of 1 customers found this review helpful)

                       
                      5.0

                      Perfect!

                      By Amanda S

                      from Albertville, AL

                      About Me Parent of Two or More Children

                      Verified Reviewer

                      Pros

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

                      Cons

                        Best Uses

                        • Infants
                        • Toddlers

                        Comments about Marathon 70 Car Seat - Cowmooflage:

                        This seat is perfect! I have no complaints!

                        Comment on this review

                        (6 of 7 customers found this review helpful)

                         
                        5.0

                        Love It!!

                        By Love Britax

                        from PBG, FL

                        About Me Parent of Two or More Children

                        See all my reviews

                        Pros

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

                        Cons

                          Best Uses

                          • Infants
                          • Toddlers

                          Comments about Marathon 70 Car Seat - Cowmooflage:

                          This is the best car seat out there. I tried Sunshine Kids booster seat and I am so upset. I love Britax and I am now getting a Britax booster seat. My daughter is very tall and lean. She started using this car seat at 8 or 9 months. We used it rear facing until 15 months because she is so tall. It works well both ways. I feel very safe with her in it. It is easy to take out and clean, it is not too heavy but very sturdy.

                          Comment on this review

                          (8 of 9 customers found this review helpful)

                           
                          5.0

                          Great Carseat!

                          By Christine

                          from New Jersey

                          About Me Parent of Two or More Children

                          Verified Buyer

                          Pros

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

                          Cons

                            Best Uses

                            • Infants
                            • Newborn

                            Comments about Marathon 70 Convertible Car Seat- Blueprint:

                            We love this carseat. It is very safe yet super comfortable and stylish. We have the blueprint pattern. Our 10 month old son seems very happy in it.

                            Comment on this review

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