How important is steel in a car seat?

Do seats that incorporate steel in the frame hold up differently in crashes?

I don't think we really know, given that most manufacturers don't release crash test data.

SKJP/Diono do release some of their data, though, and they do use steel.

They might hold up differently, but we don't know if that's necessarily better.

Some people like the idea of steel because it's so sturdy. Other people worry that steel might be TOO sturdy, and rather than absorbing crash forces, it transfers them to the kid.

Bottom line: We don't know.

Assuming money isn't an issue, I'd choose a seat with metal reinforcement over an all-plastic seat. Steel is probably the best balance of fatigue life and strength with cost and manufacturability, although certain of the light metals might be a good choice based on strength-to-weight ratio. (There's no question that the magnesium frame is part of why Foonf is going to cost so much!)

Plastics are great structural materials, but they have notable potential failure modes depending on the exact polymer used and how it is manufactured. I admit to a bias due to my job, but when I compare properties like tensile strength, hardness, flex modulus, susceptibility to environmental weathering, etc. I would prefer that my kid's car seat have a steel frame, or at least steel reinforcement.

In crash tests it may not matter; certainly unless the companies release test data there's no way to know for sure if metal reinforcement is a benefit. For certain seat and frame/reinforcement designs you may want a more compliant seat. I considered doing my master's project on materials optimization for car seat frames, but there is remarkably little published academic literature on the subject so I chose something else.

ks227 said:

I considered doing my master's project on materials optimization for car seat frames, but there is remarkably little published academic literature on the subject so I chose something else.

Click to expand...

This is a key point.

When physicians and their governing bodies make recommendations & policy, they have a body of literature on which to draw- dozens, sometimes hundreds, of studies on any given condition.

A CPST - or even an engineer - does not have this depth of information available to them. We are talking about a couple of studies, and stats from the few other countries with conditions similar enough to ours to make comparison at least slightly meaningful. Crash tests use very limited circumstances, on one style of bench, etc. We are really totally dependent on what conclusions for-profit companies come to and decide are cost effective for their products.

It would only be a deciding factor for me if I thought I might need to use it ff w/out a TT anchor. I would also opt for the steel frame radian if it was going outboard in a vehicle w/ horrible side impact ratings where I was concerned that a side crash would cause massive vehicle intrusion.