I bought some new tires yesterday. I swapped the stock 275/55/20 pirelli's for 275/65/20 toyo open country at II's. Since I went from a 32" tire to a 34" tire obviously the speedo and odometer are off. What do I do about getting this reprogrammed? Can the dealer reprogram it for the new tire size or are the oem sizes the only option?

 

OEM sizes are only option through dealer. Other than that you will have to get a programmer

 

Faced the same dilemma when I upsized tires. Find yourself a good ol' fashioned Speedometer Shop.
In n' out while you wait !

 

Haven't heard of speedometer shops. How do they operate?

 

The 34.1" diameter (275/65x20) is close to that of the Raptor's 34.4" (315/70x17).

Meaning: The dealership can use their IDS to set the RPM (Revolutions Per Mile) to that of the Raptor - 607

IDS ( IntegratedDiagnosticSystem ) - Standard, OEM Tire Size (PCM) = ...

 

Check : dicksspeedotach.com
Their site explains their work.

 

Awesome I will look into that

 

Hopefully my shop will do this to

 

No go according to the dealer. They say the raptor has a different computer for programming the speedo and that they can only adjust the tire sizes up to 5% each way. Since my truck has the 20" wheels the largest they can program it for is the stock tire size that came on my truck

 

They are lying to you, they can read your pcm and select from quite a few tires sizes, I already looked at that field when I just changed my tires.