You'd need a long cage rear der. Basically, a longer cage takes up more chain-slack to deal with the different amounts of excess chain when you have a wide range of gears. And your range is pretty wide. An LX derailler would have been a long cage. You can get a road long-cage (105 would be your best bet) or a mountain-group derailler such as LX.
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"c" is not a unit that measures tire width