There is a
link in
one of the Wheel & Tire FAQs which shows the speedo changes resulting from plus-sizing tires.
Members have
reported fitting Goodyear Eagle F1 GS-D3 in both 215/40-17 and 215/45-17 sizes. Click below to see the change in speedo readings:

205/45-17 vs 215/40-17

205/45-17 vs 215/45-17