When a child is over 40 pounds is it okay to start using lap and shoulder belt with high backed booster?

Or are there car seats for children over 40 pounds with harnesses (that fit)? I have seen the ones with harnesses that can be for children up to 100 pounds but at 40 pounds the harness is supposed to stop being used and the belt is supposed to secure the child. Any help is much appreciated!

3 Answers

  • 6 years ago
    Favorite Answer

    I will first describes what a booster seat does.

    A booster seat is a seat that sits on the vehicle's seat and the child is buckled in with the lap/shoulder seat belt. It is designed to lift a child up so that the adult seat belt fits across their body correctly, so that the lap belt is on the hips, not the stomach. The shoulder belt should be positioned on the child's collar bone. A child can only be protected if they sit up straight and back into the seat. A child is not mature enough for a booster if they play with the seat belt or will unbuckle, lean over to tease a sibling or pick up a dropped toy. Three year old children never, ever belong in booster seats, even if they meet the minimum size requirements: http://www.jrn.com/ktnv/news/187038601.html

    This is because three year olds do not have the bone development required to take the force of a lap/shoulder. Their bones are flexible as they contain a lot of cartilage, which could potentially cause the child to slide underneath the lap belt during the crash (injuring organs) even if it was properly position before the crash. The crotch strap on harnessed seat will prevent a child from sliding under the lap belt and injuring their internal organs. Age 4 is the bare minimum to put a child in a booster regarding physical bone development.

    Most children do not have enough impulse control for a booster until they are between 5 to 7 years old.

    Not all booster seats are doing their job, which is positioning the seat belt properly. If the lap belt is on the child's abdomen for any reason, it will sink in and injure the child's inner organs. The Insurance Institute for Hghway Safety (IIHS) rates how well a booster seat positions the seat belt across different seat belt configurations. "Best bets" are highly likely to position both the lap/shoulder seat belt on the "average" 6 year old's body. "Good bets" are likely to position the lap belt as good as "best bets", but the shoulder belt fit may be off. Seats that are on the "not recommended" list or "check fit" generally make very, very bad booster seats. Here are their ratings. You can explore your seat by brand: http://www.iihs.org/iihs/ratings/child-boosters

    Consequences of poor seat belt fit shown here (video is about not using a booster, but poor seat belt fit applies to booster seat use too): http://www.boosttil8.org/

    Remember that a child needs to meet *all* the requirements as stated in the manual regarding the booster seat. A relative of mine is almost 5 years old and is still to short for a booster seat even if she is 39 1/2" tall and meets the standing head-to-toe minimum height regarding a booster on the market. She does not meet the other requirements. I asked her to sit in her older sister's booster without coaching her how to sit and the fit was terrible because her knees don't bend anywhere at the edge and she was slouching down. Her bum to knee length is too short (by about 2-3 inches) before they will bend at the edge of the booster seat. She is also too immature for a booster anyways.

    The American Academy of Pediatrics (AAP) recommends that children ride in a car seat with a harness for as long as possible. This is because a properly used car seat with the harness is always safer than a properly used booster seat. The National Highway Traffic Safety Administration (NHTSA) recommends that children ride in the harness for as long as possible, even until age 7: http://www.safercar.gov/parents/RightSeat.htm

    Using the top tether on a harnessed seat is one reason that makes it safer than a booster seat. The top tether is a strap that connects the top back part of the car seat to an anchor in the vehicle. Takes less than 10 seconds to connect and will reduce the chance of head injuries because it reduces head excursion by 4 to 6 inches!

    Most harness car seats are outgrown by height before weight, when the child's shoulders are parallel to the top most harness slots. All forward facing car seats require that the harness straps be positioned at or slightly above the child's shoulders and is extremely important to do so. If the harness straps were coming from below a forward facing child's shoulders, the child's spine will compress in a crash leading to spinal cord injuries. Selecting a car seat that can adjust in the slot height (18 inches from bum to shoulder) will keep a child in a harness longer.

    All of the options below have 18" top slots besides the Britax Frontier 90, which has about 20 inch top harness slots.

    Just to be clear, no car seat on the market has a harness weight limit of 100 lbs (unless if you are counting special needs car seats). That is the booster seat weight limit. Most car seats with the harnesses can be used up to 40 to 70 lbs and then have a different booster size limit.

    However, if you use the top tether and install with the vehicle's seat belt with the Britax Frontier 90, it will go up to the full 90 lbs. (But most children will outgrow the seat by the 20 inch bum to shoulder height).

    Harmony Defender 360~ $100 at Walmart and converts to a great booster

    Evenflo Maestro (only goes up to 50 lbs though) ($80 from amazon).

    Evenflo SecureKid 300 or 400

    Graco Nautilus

    Recaro Prosport

    Britax Frontier 90

    All of the above seats will convert to boosters in the future. Technically speaking, the Maestro does have a booster mode function; however, it is outgrown when the shoulder belt guide is parallel to the top of the child's shoulders, so kids will outgrow booster mode function at the exact same time they outgrow the harness mode by height. It will be unusable because of this.

    Another frugal option is the Evenflo SureRide. This does not convert to a booster seat at all as it is a convertible car seat that can be used rear facing and forward facing. It has 19 inch top harness slots and goes 65 lbs forward facing. The only major problem with this seat is that Evenflo made the harness length so short that kids will outgrow the seat by harness length before they max out the generous size limits. Put your child in the display model and see how much room they have left to loosen the harness for growing room. If you have a younger child that would still be rear facing in 1-2 years (when your oldest is around age 6), then it might be an option.

    Any more questions about harnessed seats or booster seats or child passenger safety in general? Ask them on this forum: http://www.car-seat.org/

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  • Bobbi
    Lv 7
    6 years ago

    We have the Evenflo Triumph 65, the booster works to 65 pounds forward-facing, 40 pounds rear facing. I would not go by weight of child, but age.

    By around age 5-6, their bones are stronger and can withstand a car crash in a high back booster vs a 3 year old who is 40 pounds in that high back booster. If it all possible, keep in a harness as long as possible.

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  • Anonymous
    6 years ago

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