New Wheels for 110, smaller external diameter?

As some modular wheels and tyres came up for sale local to me at the "right price" I bought them not thinking about external diameter.
Now I have swapped the wheels over I have noticed that due to tyre profile the external diameter is about two inches smaller. Does this mean the car will be even slower and the speedo will over read?

To be honest I think I prefer the original steel wheels now but need to save up now to replace the cracked tyres!!!!

Stick the tyres off the modulars onto your rims, still to small a diameter but will keep you going for not to much money