Ive got a 96 coupe and recently upgraded from the stock 195/55/15 rims and tires to a new set of 245/45/17 rims and tires. About how much is this going to through the spedometer off?

 

I wasn't aware the getting bigger rims affects the speedo

 

it will only affect your speedo if the tire height is different. in your case it is affected. at 60 mph on you speedo you will actually be travelling 65.7 mph. your stock tire size is 9.5% faster than your non-stock tire size.

 

but you're making the odometer think you're putting less miles on it

 

yeah but since that is illegal, you could have a chip done up to fix the problem. hopefully, without affecting your odometer. no one has to know.

 

I have a diablosport already in is this fixing my little speedo prob?

 

not unless it is programmed to fix it, which i doubt it is. go to where you had it installed and have them reprogram it to fix the speedo.

 

if your speedo changed, it went back to where it was supposed to be. 245/45/17 is how 17" tires are stock from ford.