Isofix confusion - is there still an 18kg weight limit

[tabitha8]

Does anyone know the answer to this? There used to be a weight limit for Isofix of 18kg. DS will soon need a new car seat (he's 6 but small for his age). I'm confused by it all.
Many thanks!!

Yes, in general a Group 1 ISOFIX seat (forward or rear facing with a 5-point harness) will have an 18kg weight limit. There are a couple of new rear facing seats which are isofix but have a higher limit, the Nuna Rebel is one. They have a higher limit because the seat itself has been made lighter (there is a maximum total weight that isofix can take, therefore if you make the seat lighter the child in it can be heavier!). I don't know of any forward facing isofix Group 1 seats that have a higher weight limit, I imagine the issue with forward facing is the strength of the harness - in a crash it has to take the whole weight of the child, so it's different to a forward facing seat where the harness is only required to hold the child when the car rebounds after the crash (so there is less force put on the harness).

There are lots of isofix high backed boosters that go up to 36kgs, but that's because the isofix is only holding the seat in place, the seatbelt takes the force of the child's weight.

I've just remembered the Britax Advansafix, which is isofix and forward facing with a 5-point harness up to 25kgs. But your car need to have a top tether point for the isofix too, and you also need to seatbelt it in too as well as having it attached to the isofix!

Aha, all is clear! I'll check my car about the top tether point thing.
They really are covering all bases, aren't they? Isofix, adult belt and top tether.
I'll have a look at that Britax. Many thanks!!

I've just re-read my post, clearly I meant "different to a rearfacing seat when talking about harness strength. Doh!