Front Chainring

[johnnyt]

For my wife's ss I bought a surly 1+1 rear wheel and put on it a shimano 18 tooth freewheel. It seems that the spacing between the teeth is different then that of the standard mtb chain and chainrings since the old mtb chain does not fit the freewheel. Do I now need to buy a differnt size chain and front chainring ? If so how what size and where should I get it from to be sure I get the right size/spacing?

Thanks!