the IT city, the I.T. Baby


Britax Marathon 70-G3 Convertible Car Seat review

Britax Marathon 70-G3 Convertible Car SeatThe Britax Marathon 70-G3 Convertible Car Seat in cowprint cover is what we’ve got in ITMama’s car now to handle baby M, and it works pretty well as we call her Moo quite a bit.

Much like the Britax B-Agile Stroller review we’ve been doing, this piece is expected to be updated on a somewhat regular basis as the product is actually used.  You can see updates at the bottom as we run into things or new things pop up. Last update 10/21/14.

As such, many things may change from subsection to subsection. This starts with baby M about five months old when we installed the seat in the rear-facing position.

Britax Marathon 70-G3 Convertible Car Seat

The 70-G3 is a rear and forward facing seat with enough ways to secure it in a vehicle that the chances are that it won’t work are pretty slim. It’s a sturdy and well put-together compact piece of equipment, and unlike most car seats I’ve run across (truth be told, not a ton,) it feels solid.

It features a five-point safety harness, and active cowmooflage on select models for use in hiding a baby in a herd of cattle.

It can be secured via belts, latch system, and anchors as well as a couple of other things I didn’t think to memorize before writing this.

Britax Marathon 70-G3 Convertible Car Seat unboxing

Britax Marathon 70-G3 Convertible Car Seat boxThe package arrived on my doorstep by a deliver driver who thought that making it so I couldn’t open my door to get out of my house was a good thing. But enough about that. It showed up in a very well marked Britax box.

It was one of the least painful unboxingings of any baby product I’ve had, which is good because the amount of frustration that came later (which I’ll give you the guide to get around,) would have probably tipped me to the brink.

The box opens up easily and you can basically lay it down and pull the seat out if you don’t have the strength to dead lift it, although it is pretty light.

One piece of plastic covers the seat, and there are some manuals which I forget if they were attached to the seat or free floating in the box.

Britax Marathon 70-G3 Convertible Car Seat in box Britax Marathon 70-G3 Convertible Car Seat in plastic Britax Marathon 70-G3 Convertible Car Seat in plastic


Britax Marathon 70-G3 Convertible Car Seat out of box Britax Marathon 70-G3 Convertible Car Seat out of box Britax Marathon 70-G3 Convertible Car Seat out of box


We ended up using the box that it came in for a recycling bin as we were once again low on space due to baby. I’d have preferred to keep it around a bit, but no space is left in the house.

Britax Marathon 70-G3 Convertible Car Seat dry run

We decided to put baby M in the car seat while it was in the house so that we’d know what we were getting into when we had to do it at an angle. The results were mixed and I decided I would just have to try it live as something didn’t seem right or real about it being free floating.

Maggie hated it with a passion and protested, as we’ve learned she does with anything she has to get in or out of. Not sure on that.

The dry run was ruled inconclusive and a real run was set for the next day.

Britax Marathon 70-G3 Convertible Car Seat installation

There are tons of ways to install this, we chose the latch system as ITMama’s car supports it. A short amount of poking around found me both latch points and I was able to install the seat in no time.

Unfortunately it was tilted all to hell and the release didn’t seem to want to let me tilt it and I ended up pulling it out again to figure out what I was doing wrong. I have no idea what I was doing wrong because it tilted properly the instant I had it undone.

Two installations of the thing using latch took about five minutes. The hardest part was tightening up the belts properly, and that was not a strength issue, it was a belt-moving issue.

If I’d known the right amount to pull them back in before I put the seat in, would not have had an issue.

Baby’s first ride

I put Maggie in from the side as intended, it went pretty badly. She was screaming and fussing and of course the belts were not the right length any more and I couldn’t get the internal harness release to let them out. Basically a bad first run at the thing, but not the fault of the Britax car seat.

Upon getting her into the seat with shoulders tight and legs strapped down properly I noticed there was a whole lot of space between her belly and the belts. The only points of snug contact on M were her shoulders and her legs.

The chest strap sort of touched the top of her chest, but then left enough space for a small pillow by her belly. We couldn’t see any reason that it appeared unsafe, but I did a little research on that and that’s how the videos on the Britax site show them in action, so snug shoulders, snug legs, that’s about it for a rear-facing baby.

She evidently liked the seat enough to not complain and to fall asleep in it, so we’re calling it a success.

Subsequent rides have been fine.

Britax Marathon 70-G3 Convertible Car Seat considerations

Some things we had not considered when switching to the car seat included that our baby monitor mirrors were pretty much useless now as the seat back was in the way, and there is no mechanism to secure a dangling toy for a baby.

On the plus side, there’s about 5-6 more inches that the front car seat can move back and a bit more horizontal space available to passengers as well.


  • While probably sturdy enough to support elephants, the latch/unlatch mechanism feels plasticy and cheap
  • Unlatching a cranky baby is a bit of a pain

Things for the future

We have not had to clean the car seat yet, nor have we had the seat in the front facing position or anchored it in any way other than the latch system. When these come about or anything new pops up it will be updated.

More pictures to come.

Britax Marathon 70-G3 in action

Maggie in the moo seat Maggie in the moo seat

Other reviews

Holding a 4.6 out of 5 star average on Babies R Us

4.7 out of 5 star average on Amazon after 630 reviews

4.6 stars on Rightstart (different cover however)


Available from Amazon for $201.98 with free shipping. Also the lowest price I can locate with Google, but if you find it for lower feel free to leave a comment.


1/3/14 four months use in

The seat has served pretty well, the only thing we’ve had to adjust are the straps so far as when Maggie is wearing a jacket or coat she doesn’t fit. Had a run-in with another car seat for about a week and a half while visiting relatives over Christmas and have decided this seat is premium in comparison.

Maggie’s nearly nine months now, does not appear she’s going to grow out of the seat in the next few months.

Have had no reason to clean the seat as of yet, so still don’t know how that is going to work.

6/9/14 nine months in

So far we’ve still not had any reason to clean the seat. Maybe we do now that there’s been a sandbox-related dirty baby in it, but it’s been pretty easy to wipe off. Somehow one of the rubber guards managed to get completely turned around, but other than that nothing all that odd has gone on with the seat.

I’ll say it’s gotten progressively harder to get a cooperating infant in the seat in a 2006 Honda Civic though. It’s not that she’s not cooperating, it’s that every time she’s seated she’s somehow at a different angle and we have to adjust the whole thing again.

8/1/14 eleven months in

Maggie sleeping in the Britax Marathon 70-G3 Convertible Car Seat
Maggie drooling on the chest strap release mechanism.

The seat still chugs on. Anything that it’s gotten on it we’ve been able to wipe off. The only serious concern that has popped up is the plastic chest buckle is next-to-unlockable when a sleeping baby drools all over it.

Basically it’s a slicked up drooled on lock that can be extremely hard to open. I don’t have a solution (yet at least,) and I can’t say there are other better chest locks available, but I do slightly worry about what if there were an accident and I had to fumble to get that top strap lock open.

Pinch to release doesn’t work too well when it’s greased up with baby spit.

10/21/14 cleaning at thirteen months

Had to clean it finally, here’s the link to how. Not a particularly easy experience and involves a lot of trying to figure out what comes next in this puzzle.

4.5 / 5 stars     

Paul King

Paul King lives in Nashville Tennessee with his wife, two daughters and cats. He writes for Pocketables, theITBaby, and is an IT consultant along with doing tech support for a film production company.