So when I went from my old 245's to a set of 285s, my speedometer changed to being about 7 mph faster than I was actually going. I didn't mind it, but when I switched to a set of 35's now all of the sudden I my speedometer is saying I'm going 20 mph over what I am actually doing. Any idea on how I re-calibrate my speedometer if I can? I have a 1997 F-150, short bed, ext. cab, 4.6L V8, automatic transmission, 4x4.

EDIT: I have a traditional speedometer, not a digital one.
EDIT: This does not matter the speed either, sitting at 0 mph it says im doing about 20.

 

Pretty sure on the 97 the speedo was mechanical / cable driven and not PCM controlled so even with a tuner, wouldnt be able to change that.

 

If you have a cable then you need t o get a differnt gear for the tranny end. if it is wired then you need a tunner.

 

How do I see if I do?

 

Go to fordparts.com and look up your truck and serch speedometer cable. if that comes up no parts found then yours is electronic.

 

You have a mechincal speedo cable.
With 35" tires is should not be 20 off. Mine is 7 off with 35s. 97 4x4

 

I'm new to electronic speedos, can you provide the cliffs notes on your tuners? Is there a budget version for a guy that just wants to recalibrate the speedo and doesn't really need to mess with HP gains?

 

If you have analog odometer a tuner will not correct the mph.

 

Looks like he has an 01 from anouther post of his.

 

Did a serch on ebay and it looks like you would be cheeper to just co to a speedometer shop. The cheapest tunners are close to 4 bills.