What Car Seat Is Best for an Extended Harnessed Almost 4 Year Old?

We have a Britax Marathon for our three year old, and a Frontier for our 6.5 year old, she loves her Frontier! I think it seems more comfortable and sturdier than the nautlius personally. And has the highest harness limit out there! Both of my kids are big and super tall and fit them both just fine. I wouldn't personally buy a marathon since the weight limit is the same as the MyRide. But not sure of the minimums on the frontier, if he can go into that just yet! I don't even let my 6.5 year old ride in a belted booster, she still can't still completely still, there are tests online that people should really run their kids through before doing this.

IIRC the Nautilus or Frontier (which are "combination seats" - forward facing harnessed seats that can be used without the harness as belt-positioning boosters after the harness is outgrown) will have more growing room than "convertible" seats (harnessed seats that can be used rearfacing or forward facing) like the Marathon (MA) or Boulevard (BV), and since you don't need a seat that can be used rear-facing if you got a MA or BV you'd be paying for a feature you don't need . Also IME older harnessed kids prefer seats like the Nautilus or Frontier over the Marathon because the Nautilus/Frontier *look* more "boosterish" than the convertible seats. And since your child can use these seats as boosters after they outgrow the harness, they could be the last seat you need to buy. Whether the Nautilus will last him another 2 years depends on how much of his growth will be in his torso versus in his legs.

I bought Britax for my kids until they outgrew the Wizard (which I think is was an earlier Marathon) and the roundabout (for them it was them 4 & 6. I researched the car seat boards. (carseat.org) A lot of parents seemed to like the Britax and the Graco Nautilus equally. Some people had issues with the fit of the Britax. Since I didn't see the Britax in stores near me, some had issues with the fit, and it was $100 to $150 more, I chose the Nautilus. The Nautilus changes from a full harness to a back booster and then a backless booster. The quality of the cover is not as nice as Britax but for the extra money I am ok with that. My oldest is reaching the upper limit for harnessing. He is probably medium height for his age and he will be 9 the end of the September. My daughter is 7. They have never questioned being harnessed in so we will continue until the reach their height limit. At that point, I will convert the Nautilus to a booster with a back. For the money, it seems to be a good seat.

He can start using a belted booster at 4. I think maybe earlier, but honestly I was having a hard time understanding all the rules when I looked them up on the KS website. My daughter is also very tall and the only reason we've been able to keep her in her car seat all summer is b/c she wears fewer clothes and can still be buckled in safely! Thankfully her birthday is in one month and I just ordered the booster! Yay! We are ALL excited! You may know that already and are just opting for a 5 point harness, I just wasn't sure the way you worded the question. If that's the case, then I can't help you!! ;) Having tall kids can be hard...in car seats and pants! LOL! I hope you get it worked out.

I just bought two Graco Nautilus seats for my 5-1/2 year old. He is approximately 46" and 46" (sounds square) and I anticipate it fitting until he reaches the 65 lb harness limit. I am sure you know it will function as a booster (either high or low back) beyond that. Although legally your son can be in a booster, a 5 point harness is still safer.

We have a Nautilus for my 4 year old in one car and really like it but he is small for his age and should work for him for quite awhile. I am not sure how it would work with kid that is tall for his age. In our other car, we have a Sunshine kids Radian 65. He is nowhere near the height limit and should be able to stay in it longer than the Nautilus.