Technical Out side rolling diameters???

[mr2807]

Hi there!
I currently have the punto GT wheels on my sporting 16V which have some 185/65/R14's on.I am going to be getting some 16s with 195/45/R16's on...
Will this slow me down or not as it is a less rolling diameter but a greater width???and if it does slow it down how much??

also what effect will it have on my speedo????
many thanks look forward to hearing from anyone?!?!?!

 

[custard]

http://www.performancetyresdirect.co.uk/converter/converter.html

 

[mr2807]

what about the alterations in speed/acceleration???