Fat kid is child abuse (unless medical condition) and the young bike needs to be rated for the weight otherwise it’s also child abuse (/jk). But older bikes usually have steel wheels while younger bikes have aluminium bikes, so the weight capacity is larger with older bikes (not that it matters for kids though, but it does matter when having someone on your luggage carrier).
What about fat kids on young bikes?
Fat kid is child abuse (unless medical condition) and the young bike needs to be rated for the weight otherwise it’s also child abuse (/jk). But older bikes usually have steel wheels while younger bikes have aluminium bikes, so the weight capacity is larger with older bikes (not that it matters for kids though, but it does matter when having someone on your luggage carrier).