Was looking at my new tractor because all I can do is look at it at this point here in Central New York. Not even enough snow to snow-blow!!! Anyways I lifted my seat and noticed two rubber seat springs as they call them which don't look like springs at all! They just look like rubber bump stops. It looks like you can slide them in a track forward and backward. Is this an adjustment to change the stiffness of the seat. My manual has no mention of it. Do they make a coil spring you could replace the rubber one with?