Minimum weight for HBB

[voxnihili]

We have a Britax Advansafix isize as our spare car seat. I chose it as the advert highlighted it could harness until 21kg but I didn’t realise that maximum harness height was 102cm which DD (almost 3.5) has already reached.

It’s isize so doesn’t specify a minimum weight for using the seatbelt but I know that for older style seats it was 15kg. Is it safe to use a seatbelt under this weight? DD is approx 13.5 kg. She’s a good traveller so I think she’d be ok on a seatbelt.

We have a Britax Max Way plus for her main car seat but need something easier to move for our spare.

Ps - thanks to anyone who can advise.

Hi! It isn't actually safe or advised to use a seat belt for children until at the minimum of 4, usually more towards 4.5, to do with their bone development in the even of an accident.
The advansafix page on their website does state 15kg for using the belt.

It isn't letting me add a screenshot- if you go to

https://www.britax-romer.co.uk/car-seats/toddler/advansafix-i-size/9208.html

Scroll down to features, and the second to last slide is "flip and grow" where it says about being 15kg to use the belt

Thanks - I’d missed that bit. Such an annoying design of a seat as it’s now useless for us. Not really sure what our options are as don’t really want another ERF seat as need something easy to move between cars and that grandparents can easily install. I know there’s the Joie Bold but I’m not keen on that.

The i-size high back boosters have a height not a weight limit. You can also get them with an extra hook between the leg to reduce the risk of younger children submarining, e.g. this one www.britax-romer.co.uk/car-seats/highback-boosters/kidfix-i-size/9007.html .

If you decide you don't want to use a high back booster yet, the other seat I'm aware of would be the Britax Two Way Elite, which rear faces until 25 kg and forward until 18kg, and doesn't need a tether forward facing. My DC didn't outgrow it until being about 125 cm so it would give you at least a few more years. (I've only used it rear facing though, so don't know how well it fits facing forwards).

Just spotted the Britax hbb still says 15-36kg, this one doesn't have a weight limit www.besafe.com/en/product/izi-flex-fix-i-size/ , but it might be worth contacting a specialist like the In Car Safety Centre.

I'd assume the 15kg is to make sure the inertia reel on the seatbelt works properly, same reason there's a minimum weight on clip and climb. DD was pretty close to 5 before she hit 15kg, DS already is at a naughty 3 years old.

We got the Britax 2 way Elite when DD got too tall for the Cybex Sirona we had before. It's a bit of a pain to install especially when DS throws a strop and undoes it from the car!

Thanks - some ideas to look at. I’m not keen on the two way elite - discounted it when we got our max way plus (had to get that after DD became too tall for her Sirona at 2.5).

@randomsabreuse that was something like I was thinking about in terms of the seatbelt mechanism.

The advansafix won’t be a complete waste as she’ll be able to use it as her main seat once she outgrows the max way plus.

I've found car seats manufacturers very helpful when I've messaged them on Facebook. You could ask Besafe directly about their Hbb and the seatbelt mechanism for a child under 15kg? Otherwise, what about the Joie Stages as an easier to move rear facing seat, my impression is it's actually quite tall?

Your DD must be on the very thin side to be 102 cm tall and 13.5 kg, eyeballing charts in my DC red book suggests that's about 75th centile for height and 10th centile for weight. Is the weight definitely accurate, is it worth getting it checked at a health visitor weigh in?

I will contact besafe and see what they say and if they have a seat they can recommend. I’ll also contact Britax and ask about the advansafix we already have.

Her measurements are correct - she’s been the same centiles the whole way through. The ultrasound scanner picked up on her length during one of my scans and was concerned until she saw the height of DP! I’m also on the taller side but slim so she seems to be the same build as me. She needs 18-24 months for the waist in clothes but 4-5 years in length.

I thought HBB stood for home broadband 😂

If she physically fits in the harness I think I would use it anyway. Or you could look at the non i-size version, which has no height limit on the harness. If she's only 13kg then you don't need the 21kg capacity anyway.

Minimum weight to ensure the seatbelt works properly doesn't make sense or you wouldn't be able to use an infant carrier with the seatbelt - they weigh about 4kg and a newborn is about 4kg so much less than 15kg.

I believe the minimum weight is purely age based to stop people using them too early. It is better to wait until they weigh 15kg even if they are over 3 though.

Or what about the Joie Stages, used rear facing? It has a bit of a higher harness capacity but RF to 18kg.

A child must be at least 15kg to use a high backed booster with a seat belt however it is not really safe for a child to use a high backed booster before a minimum of 4 years old (but preferably closer to 6) as their pelvis is not fully developed before this age which can result in injury or them slipping under the belt in a collision. They are also generally not mature enough to sit sensibly in the seat before this age.
Could you buy a second set of tether for your britax max way plus so you could leave a set fitted in each car and then it would only take a few minutes to transfer the car seat over?

She still fits in the harness just about so we’ll carry on using it until she can’t fit any longer and then see where we are. I’ll probably get the non-isize version when she can’t fit (@BertieBotts do you know the name of the one you’re thinking of?) - she can then use the isize one as a HBB when she grows out of the MWP.

A spare set of tethers won’t solve the issue as we need more than one seat. Even if we tried to be really organised and manage with one seat, her grandparents wouldn’t manage the fitting of the seat, even with tethers already in their car.

It's just called the Advansafix 4 but the harness is the same size.

Thanks. Funnily enough I looked at that one but went with the isize as it was 21kg and wrongly assumed we’d therefore get longer out of the harness (it wasn’t clear you had to switch at 102cm). The isize was a bit of a bargain as it was half price in John Lewis so I probably purchased it quicker than I otherwise might have done and hadn’t read all of the small print.

I mean, they are exactly the same seat, so I wouldn't worry too much about it. It doesn't make logical sense that there is a height limit on one (and I don't understand why they went with the 102cm rather than the more usual 105cm) I probably wouldn't be brave enough to use the non i-size one with an over 18kg child, but going over the height limit really doesn't seem like a big deal to me. I'm not basing that on any technical info unless you count the fact that the two seats are identical.

If you want more height in a harness Joie bold if the best choice as it's huge. But as said earlier Joie stages also has a decent height limit, and can be rear facing so if you did get stuck there is always that.

With the advansafix 4, can you use the harness even with headrest fully extended? With the isize I would have to remove the harness to get the headrest to move up any more. Yea

I'd go for the Joie stages. Has a high height limit and you'll get a decent amount of time in it if she's 13.5kg. The britax two way elite or axkid move are other options depending how long you want to RF for and I think both go up to 120cm. I wouldn't put a 3.5 year old in a hbb.

No, it works the same as the i-size. The headrest is limited in height when the harness is in. Most high back boosters with harness do that, the exception is Joie ones, but I am not keen on the way they fix into the car because it's very basic. The Joie bold is ok. That uses top tether, seatbelt and Isofix so it's more secure.

Thanks. In that case we wouldn’t gain anything. I’m happy for her to use the harness above the 102cm for as long as she’ll fit her shoulders under it.