We're currently using a Britax Expressway in our C and it works great, but I can't comment on the convertible model. If you have a BabiesRUs or The Right Start store near you, they will help you try out the carseat in your car. I'd imagine it would work without any difficulties. Good Luck!
My wife and I purchased the Britax Convertible Express and alternate the installation from her truck to my car ('01 C320). I can't speak enough about the car seat itself. As for the installation, I am a bit disappointed. The C320 appears to be a bit off-center with regard to the center seatbelt (possibly due to the fact that the center seatbelt is a shoulder belt). Anyway, the Britax seats can make use of a tether for additional stability and safety. The tie-down bolts for child restraints are actually in the center of the car (under the front edge of the back seat and on the front edge of the rear deck). When you install the seat in the center position and securely fasten the seat belt and the tether, the seat is pulled a bit to the right (as seen from someone seated in the backseat). As a result, a child is seated at a slight angle. I am able to almost eliminate this angle by very securely fastening the seatbelt and slightly tightening the car seat tether. Anyway, I can't complain too much since Mercedes is one of the only newer cars I have seen (in the US) that has the seat tethers all around (middle, left, and right) and I always have the option of installing the seat on the left or right. <br>
I hope this information helps...<br>
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