I went out and bought a set of the 16" Formula rims. I had the 15" factory. I have been told by my girlfriend that my speedo is 5 MPH fast. The tires look like they were the same size. What do I need to do to correct the speedo problem? Is my speedo even off? Thanks for the help.

 

Really the diameter of the rim doesn't change anything, it is the diameter of the rubber itself that will throw off the speedo. What size tires where on the 15" rims????

 

also ...the stat is called the outside rolling diameter. tire makers give this stat out when asked at the dealer you are buy it from. you can have two tires ....same dimention .....different outside rolling diamter

good luck

 

They both are factory tires that came with the bird. The 15" had 215/65R15, 245/50R16. I met a guy that was getting rid of his 16" Formula rims and tires for $100.

 

245/50R16's are 25.6 inches tall, while the 215/65R15's are 26 inches tall. The speedo will show faster than you are actually going, but it won't be much. When the speedo shows 60 you are actually going more like 59.

 

Thank you for the info, I was told that at 75 mph, I was only doing 70 by my girlfriend. She has all the stock stuff on her truck, but it is a ford.... LOL I was just wondering if it was something I should check out. Thanks again.