so my truck goes tomorow to get the 2'' autopsring installed along with new 20'' oem wheels with new 33'' goodyear silent armour tires. is it necesary to go get the computer recalibrated for the taller tires? ive read other threads where they said that ford dealers cant calibrate it unless its a stock tire option.

 

It's not necessary. Your speedomoter will be off a few mph, but if it bothers you you can easily recalibrate it yourself with a tuner.

 

should look sweet man, great tire and the stock 20's are sweet! Speedo won't be off big enough to really matter, but yes you can always spend some cash and get it corrected and get better performance with the tuner. The dealer can correct it close enough, I did it with my 285's and my speedo is exact when I compare speedo with my GPS.

 

My speedo reads almost 2 mph fast at 70mph with OEM 20's and stock Pirelli's by my Garmin GPS.

Going from a 32" tire to a 33" tire is a 2% difference in tire size (+/- depending on actual size). I figure when I switch to 33's my truck will be about 4.x mph slow when indicating 70.

 

I am not sure what size your stock tires are, but if you have the 255/70/17's like I had and switched to 305/60/20 Goodyear Silent Armour Tires your speedo would read 60 mph but you would be doing 66.5

go to http://www.miata.net/garage/tirecalc.html and you can enter the tires that you currently have if they aren't 255's

 

Here's another good: Tire calculator

 

Maybe so, but it will vary with speed fluctuation.

Anyhow...

Ford can recalibrate tires up to 33" but not greater. The "stock tire option" song-tune is horse dung! Weather they want to or not is a whole nother story.

My dealership - Bill Talley - were more than happy to do mine.... but I ended up getting 35" put on.

If you don't want to fork out the dollars for a tuner, THIS is what you may want.

Google it for a little saving off SC's advertised price.

Good luck.

 

Got it covered, thanks.