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  • Britax Marathon 70 Convertible Car Seat, Onyx (Prior Model)
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Britax Marathon 70 Convertible Car Seat, Onyx (Prior Model)

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  • Safe cell technology features safe cells 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 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, 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
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Product Description

The Britax Marathon 70 convertible car seat is designed for children rear facing from 5 to 40 pounds and forward facing from 1 year and 20 lbs up to 70 pounds. The Marathon 70 achieves revolutionary head safety through the use of Britax SafeCell Technology, integrated steel bars, and versa-tether that work together to minimize head excursion and reduce the risk of head injury during a frontal impact. The Marathon 70 also incorporates Britax side impact protection, offers a no-rethread and quick-adjust five-point harness, multiple buckle and recline adjustments, and an easy access cover and access to belt paths from the front of the seat. A head and body pillow is provided for comfort.

Product Information

Technical Details
Item Weight18 pounds
Product Dimensions21 x 18.5 x 26 inches
Item model numberE9BB11A
Minimum weight recommendation5 Pounds
Maximum weight recommendation70 Pounds
Batteries requiredNo
Additional Information
Best Sellers Rank #40,819 in Baby (See top 100)
Shipping Weight22.4 pounds
ShippingCurrently, item can be shipped only within the U.S. and to APO/FPO addresses. For APO/FPO shipments, please check with the manufacturer regarding warranty and support issues.
Warranty & Support

Product Warranty: For warranty information about this product, please click here
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Customer Questions & Answers

Customer Reviews

Very safe and easy to install..
Mandy Tomecko
My most favorite feature is how easy it is to adjust the strap height by moving the back up and down.
Angela Harvey
This car seat had very high rating and I am completely satisfied with it.
Amazon Customer

Most Helpful Customer Reviews

83 of 87 people found the following review helpful By -- on December 13, 2011
Verified Purchase
I just had this car seat installed RF in my VW GTI and it fits perfectly fine with room for someone to sit in the front seat. I had looked all over the internet for this info but could not find it so I was concerned I would have to return the seat for lack of space. Pleasantly surprised I didn't have to!. Also, I had it professionally installed but I was there as it was done and it looked like a breeze (RF with the latch system).
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103 of 110 people found the following review helpful By Ed Mind on June 3, 2012
We bought this car seat because our baby outgrew his infant car seat. We installed it rear-facing and placed our baby in it and was absolutely shocked by how little leg space there is. My 17 month old baby is in the 60th percentile for length/height, so he is not too tall and his legs are no unusual length, but his knees have to bend at least 45 degrees because they hit the seat of our car and his legs look very uncomfortably scrunched up when we place him in the seat. There is no way we can have him ride in this car seat like that! I guess that all the positive reviews is for the safety aspect of the seat, or the front-facing use, or maybe some paid reviewers, because I cannot imagine any child being comfortable in this seat rear-facing unless they are still very small or have REALLY short legs. This seat would probably be fine forward facing, since it is room in the seat part and well cushioned but PLEASE test out the chair in your car with your child in it before buying. We tested the seat at the store to make sure it fit in our car, but we didn't think of testing the child in it too, big mistake! We are returning this seat ASAP.

NOTE: I just read that the Britax Marathon 70 was rated #1 in having the most toxic chemicals, so consider this before buying.

UPDATE: Upon further research, I've found that most convertible carseats in the rear-facing position offer little leg space for toddlers and that it is "normal" for kids' legs to bend or rest on top of the back of the seat in which the carseat is on. Rear-facing is still safest for kids under 40 lbs. However, some carseats do offer more leg space than others. We are continuing or search for the right one....
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73 of 83 people found the following review helpful By Melissa Kitchen on January 16, 2012
I seen there were 2 One Star reviews. I also went into research mode.
According to the HealthStuff.com site, YES, this car seat is considered HIGH on the Toxicity Chart.

And no, I'm not concerned.

It states that there is a large measure of Bromine in the clips on this safety seat.
I looked up what that is used for, and why it's such a big deal.
You know what I found? Bromine is used as a Flame Retardant. You see the importance?

Think about being in an accident, the car in raging hot with flames. You are scared for your child's life, not sure if you can get him/her out quickly.
Then you take into consideration, there is Bromine on the clips so they DON'T MELT in the extreme heat.
Therefor, you un-clip and free your child easily and are away from the vehicle in an instant!

See what I did there? I don't wish that on ANYONE... But doesn't it make sense?
Besides, how many of you see your children chewing on something and getting poisoned by something that's resistant to extreme heat like fire?

This is a worth while seat for the price, and ease of mind.
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7 of 7 people found the following review helpful By P. G. Reynolds on April 19, 2012
Verified Purchase
I've had and tried several kinds/brands of convertible car seats and this is by far the best and easiest to install and use. I have a 2009 Toyota Highlander and this fits very well with the latch system. It's a rock solid fit. I have the tether attached down where the driver seat bolts to the floor of the vehicle (Britax recommends that you use the tether in the rear facing mode as well as front facing and they provide a rear facing tether attachment that you can use to wrap around anything that is bolted to the vehicle frame.)

Why I love this seat:
The seat is VERY easy to install with the latch system and almost as easy with a seat belt. Each latch strap has its own buckle. I installed it rear-facing with the latch in about 5 minutes. (That doesn't include the time it took me to read the manual though - which EVERYONE should do prior to installing any carseat).
The seat has 3 different recline settings for a more custom fit in your vehicle - since backseats aren't all at the same angle. This is an awesome feature.
My daughter's head doesn't droop when she sleeps because I can install this at an angle that keeps it tilted back enough - lots of other convertible seats were too upright when rear-facing.
You can easily adjust the height of the shoulder straps on the back of the carseat by lifting a lever - while the carseat is in the car and while the baby is in the seat.
You can adjust the tightness of the harness with the strap on the front of the carseat while the kid is in the seat - very nice, convenient, and easy.
The rubber guards on the harness make it easy to keep the straps where they are supposed to be and help keep the chest buckle in place.
This seat is very cushy - much softer and more padding than all the others we have owned or used.
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