Children don't complain about their legroom (or lack thereof) when they are rear facing. But, parents often want them to ahve the most legroom they can. So, I used my daughter, who was 3 years 3 months old at the time as a model. I installed many convertibles in my van. The van's seatbacks were all set to the same spot, so any variance in legroom is purely because of the carseat itself.
Safety 1st Complete Air:
Evenflo Triumph Advance:
Graco My Ride:
Sunshine Kids Radian:
The First Years True Fit Premiere: