Well, this is still a short'ish version, and I'm not sure any of us could give a 100% technical long version because there seems to be some things we don't fully know...
Height limits - it seems that this one is up for debate. Evenflo simply states 1" above head as a height guideline. Radian is currently reviewing the height limit. CMVSS regulations basically state a height guideline must be labelled, but it doesn't specify how it's to be labelled.
30lb rf'ing limit - this breaks down to a difference in testing methods. CMVSS regulations stipulate the construction of the crash test bench, and our crash test bench is different than the NHTSA crash bench used for FMVSS testing. Speculatively, maybe the seats perform differently on the 2 benches. It also seems that CMVSS testing is being done with Hybrid II dummies while FMVSS testing is being done with Hybrid III dummies. The Hybrid II toddler dummy weighs 1lb less than the Hybrid III. There's also been some mention of the desire for standardization between seats, but there is nothing in the regulations preventing a manufacturer from certifying a seat up to 35lbs rf'ing.
Ff'ing weight limit - Our new MA's and Radians' have 65lb ff'ing limits. TC (transport Canada,) issued an order almost a year ago now allowing the increase in limits. All MA's manufactured since Sept 07 have had the 65lb limit. Our 65lb limit seats are being tested using the FMVSS crash bench specifications, but they have to be tested with the top tether and meet top tether head excursion requirements.
From the sounds of it, there is currently a review underway of CMVSS regulations and how they can be aligned in such a way that manufacturers won't incur much extra expense in certifying a seat to CMVSS standards. Given the speed of bureaucracy though, I really couldn't give a time line, nor do I have any idea what those changes are going to entail. I suspect one of them will be moving to the NHTSA prescribed crash test bench assembly, but that's just speculation on my part.
We do have some differences in standards now - ours were recently updated to require some form of energy absorbing material in any area that can be contacted by the head of a child during a collision. Not all seats are compliant with that yet and I'm not sure how long manufacturers have to update their seats when a change takes place like that.
Our seats all have to be top tethered, and that's partly the reason why we have some seats here with higher weight limits than what the seat is labelled to in the US - our Evenflo combination seats all go to 47lbs here whereas in the US they only go to 40lbs. Evenflo states that there is a structural difference, but I'm not sure about that. It could be a different in testing processes, or it could be that the seat doesn't meet FMVSS non-tethered head excursion standards at the higher weight, so perhaps in the US they can only label to the weight that meets both the tethered & the untethered head excursion requirements.
It's really not such a weird question. :thumbsup: The opposite question is often brought up as to why US seats have higher limits and more selection. There seems to be the desire on TC's part to smooth the process for manufacturers to get their seats certified in Canada, and there is also an increasing number of seats becoming available in Canada. Some are being released even close to the same time as the American counterparts.
Anyways, those are my thoughts in a not so short version, but I'm sure there's a much longer and more technical version out there that I just don't know about.
