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Item # E9LJ51A

Britax Marathon 70-G3 Convertible Car Seat - Onyx

Share Britax Marathon 70-G3 Convertible Car Seat - Onyx

Was $289.99
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Other Options Available:

Coordinating Items
Britax Infant Positioning Insert
Britax Kick Mat (2 Pack)
Diono Ultra Mat
Diono Stow 'n Go
Include the Britax Marathon 70-G3 Convertible Car Seat - Onyx

Product weight: 19.5 lbs
Dimensions (WxHxD): 18.5 x 26 x 21"
Rear-facing capacity: 5-40 lbs
Forward-facing capacity: 20-70lbs
Height capacity: up to 49 inches

Base with SafeCell technology helps prevent child from propelling forward in case of impact. Side Impact Protection helps minimize the risk of injury in the event of a crash.
HUGS: provides resistance to forward movement in the event of a crash. High-density comfort foam provides an extra layer of padding to gently cushion your child.

Rear-Facing: 5 – 40 lbs, a standing height of 49 inches or less and seated shoulder height of 9 – 16.75 inches. Forward-Facing: 1 year & 20, up to 70 lbs, a standing height of 49 inches or less and a seat shoulder height of 12 – 16.75 inches.

EZ-Buckle System retains the harness buckle in a forward position and prevents the child from sitting on the buckle when boarding

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.

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 bodyTangle-Free, Five-Point Harness distributes crash forces across the strongest parts of the body and provides a secure fit

Harness Ultra Guard System (HUGS™) provides resistance to forward movement in the event of a crash

  • 70-pound Weight Capacity for safety and comfort as your child grows
  • Rear and Forward Facing Recline for child comfort and positioning
  • High Density Comfort Foam provides an extra layer of padding to gently cushion your child
  • Plush, Easy-Remove Cover with matching comfort pads and infant body pillow to provide extra comfort and easy cleaning without disassembling or uninstalling the child seat
  • Easy-Remove Cover allows easy cleaning without disassembling or uninstalling the car seat
  • Two Buckle Positions for your growing child
  • Infant Positioning Insert may be necessary for small infants to achieve a snug fit of the harness around your child (sold separately)
  • Quick-Adjust, No-Rethread Harness repositions the harness shoulder height without disassembling the harness straps
  • Premium Lower LATCH Connectors for a quick and simple installation featuring a push button for easy release
  • Built-in Lock-Offs ensure a snug lap and shoulder belt installation with minimal effort
  • Anti-Slip, Contoured Base grips and protects the vehicle seat while offering optimum vehicle fit
  • Harness Holders keep harness straps pulled to the sides when placing your child in the car seat
  • Certified for Aircraft Travel
  • Made in the USA with global components

Child Weight (lbs)Rear Facing: 5 - 40
Forward Facing: 1 year and 20, up to 70
Child Standing Height (in)49 or less
Child Seated Shoulder Height (in)Rear Facing: 9 - 16.75
Forward Facing: 12 - 16.75
Product Weight (lbs)19.5
Product Dimensions (in)18.5W x 26H x 21D
Seating Compartment Height (in)23.5
Seat Area Depth / Width (in)11 / 11
Shoulder Width (in)13
Harness Slot Heights (in)8.5 / 9.5 / 10.5 / 11.5 / 12.5 / 13.5 / 14.5 / 15.5 / 16.5 / 17.5
Buckle Strap Depths (in)5 / 7.5

Item # E9LJ51A

The MARATHON™ 70-G3 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.
36 Reviews
83% (30)
14% (5)
0% (0)
3% (1)
0% (0)
97% Recommend this product (35 of 36 responses)
By Nancy
Austin, Tx
March 1, 2015
Good car seat but the seatbelt is really short.
It's comfortable and safe, but the seatbelt is short, my son is 3 and half years old now, he still sits this car seat, but the seatbelt is really short , very tight when click in.
By Sunny
March 10, 2014
The Britax Marathon 70-G3 car seat is perfect for our family. I previously owned a Marathon classic for older child and purchased this newer seat for our youngest. Great seat that lasts. Little one if comfy and I feel good knowing they will be protected. Fabric is nice, and I like how the newer models are easier to adjust height, etc.
By Jennice
Pflugerville, TX
January 2, 2014
Great seat
We still have our kid rear facing and this seat fits great in our car and is easy to install. After installing we took a 6 hour road trip and our baby slept great, so it must be comfortable. Love it.
By Faith
Mobile, AL
December 9, 2013
Good Car Seat but...
This is a good car seat, but I think there is a bit of false advertising. We bought it because I wanted a forward facing car seat that I could recline when my child fell asleep. When the seat is forward facing you can only use the first recline position. Also, you have to recline the seat prior to installation. If the seat is installed, you cannot recline the seat at all. This makes this option useless when using it in the forward facing position.
By Tina
Mundelein, IL
November 24, 2013
I trust the Britax name. I have been pleased with quality and ease to install. I feel my son is very safe.
By Craig
Cleveland, Ohio
November 11, 2013
Great Car Seat
I purchased this car seat 8 months ago as our primary car seat. (We have a cheaper carseat in a secondary vehicle) We are very happy with the purchase. Compared to our other car seat this one goes in and out of the car much quicker. The chest and lap buckles are very high quality which makes strapping in a restless 2 yr. old easy. I particularly appreciate the large cushioned flap around the lap buckle. It seems to keep the buckle in the right position so I don't have to reach under my child to find it. It also keeps me from accidently pinching her skin while buckling her up.( Which I have done with our other carseat.) Also: Assembled in the USA
North Idaho
September 19, 2013
Britax Car Seat
Lighter than others, very well made
By Jon Maciel
Conway, Arkansas
August 8, 2013
Great Car Seat
Britax has always been the choice for my children. It seems as though they just get better. Plenty of room but yet secure with all around padding to keep my 8 month old safe. Once again all my children (5) have had britax car seats anew have always trusted them to keep them safe.
ProsAll around padding, 5 point harness, tethering strap, and durability.
ConsOne con: pricey.
Best UsesTo keep your little ones safe.
By Lauren
New York
May 13, 2013
Sturdy Car Seat
Love this car seat and I love that this one works up to a larger weight limit of 70lbs. However, my Marathon which has a weight up to 65lbs for my other child has small velcro strips on the sides on the car seat which hold back the straps when the child gets in. This Marathon does not have this feature, I miss them. I would recommend they bring them back. Also my son was about 6.5lbs when we brought him home from hospital, he seemed a bit lost in the up to 65lbs marathon. But we managed. My daughter came home a little over 5lbs and really seemed lost in this car seat. We actually purchased an infant carrier style for her in order to fit her better. I don't think this car seat is a good fit for a 5lbs child.
By Meredith
United States
May 7, 2013
Great Option!
We love our new carseats. Our daughter is comfortable in her "big girl" seat and prefers this to her "baby" seat. We feel great knowing she's comfortable and most importantly safe! Albee provided great, fast, reliable service. They were the most competitively priced, and we loved the free shipping too!
By Enes
Council bluffs, Iowa
May 5, 2013
Amazing product but a lite flaw
I love this car seat and so does my 14month old son. The only thing that bothers me is the stitching is coming undone after a week of purchasing. The have covers to purchase, but are for 84.00 and I don't feel I should be buying a new one after a week of using.
ProsGreat Safety Product!!
ConsStitching came undone after a week.
By Cat
Montgomery, AL
May 5, 2013
Great item. Hard to install.
Love this car seat! It seems to be much more comfortable for my daughter than her infant seat. It took a while to install though, so if you want something that can go from car to car easily, this is probably not a good choice. We had no intentions of taking it out or moving it though so it's been perfect for what we needed!
ProsComfortable Easy to buckle and unbuckle Doesn't take up too much space on bench seat, but gives the child a lot of room
ConsHard to install
By summer
Riverside, California
May 2, 2013
albee baby rocks!
Love Albee baby. I accidentally ordered 2 Car seats and their customer service center was very helpful in removing one order. I've ordered from them before and would definitely again. Great prices and product.
By Sydney
April 23, 2013
Britax Marathon 70-G3 Convertable Car Seat - Onyz
Seems very safe. This was the 2nd car seat ordered in the last few months. The 1st 1 I was not charged any shipping & the 2nd 1 I was. Why?
By Natalie
St. Louis, MO
April 22, 2013
Great Seat.
We have no complaints. We already had one of these seats, and needed a second for our other car. Albee Baby had the best price.
By ashley
niceville florids
April 6, 2013
great seat for smaller car
The seat looks great my daughter is very comfortable in it. Also it fit very nice in my subaru impreza which was nice.
ProsLook, fit , the easy straps, goes up to 70 pounds
ConsIt took a bit to install
By Donna Sprengard
April 4, 2013
Converible Car Seat
Great car seat with high safety reviews. That is what sold me on this model. Britax has the best car seats for all around safety and price. This s the only brand our family has purchased for all 5 children. This was purchase #7 Britsx car seat.
ProsSafety rating!
By A.
March 25, 2013
We're on our third carseat, and once again we went back to this model. (Had to replace one of our two due to accident.) Super safe, cleans well, we've been able to keep little one rear facing past two in this seat.
ProsSafe, easily adjustable.
ConsBulky and heavy.
By Holly
March 21, 2013
worth the money!
I love this car seat! We purchased one about a year ago for my car (the main vehicle used) and a cheaper one of a well known brand for my husbands vehicle. We ended up getting this one for his vehicle as we hated the cheap one!! This one secures well to the vehicle and the straps dont get twisted, the two main problems of the cheap one. So glad we got this, wish we would've just spent the extra money in the first place! Fast shipping too :)
By Kelsey
Kent, WA
March 18, 2013
Great carseat!
This is a good carseat. Albee baby had the best deal for this carseat and it is a good product. Honestly, I was nervous about ordering from Albee baby, but this is the second product we have ordered from Albee baby and it was great.
Prosbest price good quality timely delivery
By Ashley
Virginia Beach
February 28, 2013
Love it, but...
I love the seat - the latch installation was super quick and easy. The only negative is I was hoping to keep my daughter rear facing until she was closer to 2, but there's no way that will happen in this seat. She's 14 months and in the 50th percentile for height and weight, but her little legs are already a bit long to be rear facing. She seems comfortable, so I'll wait a bit to turn her around, but it won't be much longer!
ProsEasy installation Great safety ratings
ConsWill have to switch to forward facing earlier than I would like
By Evie
Philadelphia, PA
February 20, 2013
Etremely fast delivery - perfect shopping experience
And the Britax Marathon 70-3g was great too. We installed it rear-facing in a 2011 Volkwagen Jetta. The carseat is very spacious for my 29 lb 13-month old son and there was still room in the backseat for myself and my mother
By Dana
Walden, new York
February 10, 2013
Love! Love! Love!
Love the car seat!! My son loves it more!!! Great price!! Got it really fast!!
ProsComfort and quality!!!
By Susan
Edison, NJ
February 4, 2013
Britax car seat
I was once again very happy with the Albee Baby shopping experience and my purchase in general. The seat arrived ahead of time so I was able to start using it immediately.
By Amanda
January 21, 2013
Fourth Britax Seat We Have Purchased.
We love Britax! We have a Parkway booster seat, a Frontier 85, and just bought this Marathon to replace our expiring Marathon. I am very impressed with the new features, the higher weight limits, and the longer lifespan of the seat. The old Marathon was very easy to install and use, and this one is a breeze! And Albee had the best price!
ProsEasy to install Easy to use High rear and forward facing weight limits Durable
By Jen S.
Waterford, MI
January 19, 2013
Love Britax and Albee Baby!
We just received this carseat yesterday and had only placed our order a few days ago. I had never shopped at Albee Baby, but I am very pleased with how quickly we received our order. We have another Britax (Roundabout 55) carseat for our daughter who has always been petite. Our son is growing so quickly that we decided we better go for the Marathon 70. I love this carseat already. He fits so nicely in it at 7 months old because of the nice insert that comes with this seat. Also, you can't tell from the picture, but the material where the child is sitting is going to be easy to wipe down. Our other Britax does not have that feature and I wish it did. We have never regretted our purchase of Britax.
ProsWipeable material Neutral color Incredibly sturdy Easy to put in vehicle
By Jami
Sacramento, CA
January 14, 2013
Safe as possible
The Britax Marathon is a fabulous and thoughtful solution to child safety in your automobile. You can't necessarily prevent every/any accident but the quality of this car seat is top notch and I know that I have provided him with a very comfortable and secure as I can make it ride. Outstanding design.
ProsThoughtful design details- outstanding quality. Head protection for side impact collision
ConsIt was tricky to sort out where to anchor the tether in my Volvo- but we found it and it lends another layer of security that gives me a great sense of peace!
By S.D. Craig
San Diego CA
December 23, 2012
Excellent Car Seat
My kids already had one exactly like this, so I purchased this one for my son-in-law's car.
By Allison
December 17, 2012
Great convertible car seat
We really love this car seat, this is the third one we've purchased (one for us, and one for each grandma). It's easy to install, and adjust, and our daughter seems very comfortable in it. I would definitely recommend this to any parent looking for a convertible car seat.
By Jeff
Shreveport, LA
December 16, 2012
Great Car Seat
This car seat was slightly more difficult to install than the previous one we had, but not by much. It fits our son really well, it is easy to lead and unload him in the seat, he seems to feel comfortable and for a baby seat it is pretty good looking. We've been very pleased with it and I would recommend it.
By Alison
December 16, 2012
Great car seat!
This is the second car seat we have purchased. I recently bought a new car and had to get the same car seat for my vehicle. My daughter is 20 months and seems to love it. It's very easy to install and the straps are super easy to use! The cup holder that's sold separately works nice.
ProsInstalling and comfort
By Lacy
Gilmer, Texas
December 16, 2012
Great Seat!
We are really enjoying this seat! My 6 month old fits perfectly and when he falls asleep the seat cradles his head really well.
By Kristina
Chicago, Illinois
December 16, 2012
Works Great!
Very happy with our purchase of the Marathon 70-G3. Our son is very tall for his age and this car seat will grow with him. Durable material that can easily be cleaned as well as a super 5-point harness. Overall great car seat!
By Liz
December 15, 2012
Great Car Seat
We purchased this car seat for my son just before his first birthday. It's currently installed rear facing in our car. The installation was very simple. Britax has videos you can watch to help guide you. The seat is very padded and my son seems very comfortable in it. I feel he is safe in this seat. The only downside is that my husband and other family members that don't put him in the seat frequently seem to have a hard time strapping him in. I also feel the straps get twisted easily, which can be annoying. Haven't yet tried the seat forward facing. The fact that you can adjust the harness height wihtout rethreading is fantastic. Overall, I'm very pleased with this purchase.
ProsEasy to install Comfortable for baby
ConsStraps twist easily
By Michelle
November 27, 2012
Great Buy
It installs easily and has a good solid feel to it. The harness is easily adjusted.
By Julie
Akron, OH
September 15, 2012
Love this car seat!
I am thrilled with my experience with Albee Baby, and the purchase of this car seat. We originally purchased a Recaro car seat. I felt I was well informed when I bought the Recaro, but since I wasn't able to see it in person before I bought it, I wasn't sure how it would fit in the car. I was very disappointed when it arrived. It did not fit well in my SUV at all, it was too high for me to see the mirror and my husband who is 6'3" could not fit in the seat in front of it. We decided to test fit the Britax at a local store, and I was amazed at how much better it fit. I does not take up any more room than the infant carrier, and I can see my son in the mirror perfectly! Albee Baby had the best price on the seat, and the Britax stroller we also purchased, and both arrived two days after placing my order. I am SO happy with my experience and purchases.
ProsComfortable Small for a convertible High safety ratings

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