The rolling radius of the tyre will be slightly larger and therefore your speedo will under read slightly - you will get a ratio error of 3.17% . eg, an indicated speed of 60 becomes 61.9 mph.
One of the many tyre size calulators available:-
www.tyretraders.com/Tyrecalculator/
will give you more detailed information.
Make sure there are no insurance complications by fitting different sized tyres. Is the 195/65/R15 an alternate approved size recommended by Ford for instance?
Edited by Dynamic Dave on 05/08/2008 at 19:56
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