As well this strikes me as odd. I almost never have any soreness in my calf muscles. It's only my quads and hamstrings that ever feel much use from riding.

If you aren't clipped in, then you might be pedaling with your toes too much and working that calf muscle too much.

How long have you been riding the 2-4 times a week and which is typical, 2 or 4 days? At 3 days a week I only feel like I'm maintaining my level. 2 days a week and I'm going backwards in my abilities on the bike. 4 days a week and I'm ready to try out the TdF!