17 inch to 20 inch wheels

I have a 2016 Express with 17 inch wheels. I have a opportunity to get a set of 20 inch wheels that were an option on this truck. What will I have to do so the the speedometer and odometer will work properly?

Thanks
Raul

Absolutely nothing so long as the tire is the same outside diameter.
It isn't the rim but the tire height that would effect the speedo...

Sorry, I should have mentioned that the 20 inch tire is a lot taller than a 17 inch tire.

Raul

Are you sure they are a lot different? I changed the 17's to 20's on my 15 and there wasn't a big difference in circumference. The speed went from reading 2% slow to reading about 1% fast. When it is showing 60MPH the truck is actually doing about 61MPH according to radar anyway.

It is easy for someone with a real scan tool to reprogram it. I am not talking the little code readers but a real scanner like my mac mentor or snap on solus or the one the dealer has. If you were in my neck of the woods I wouldn't even charge for it because it's so easy.

OK so we are looking at a tire diameter change, (29 or 32 or 40?) it doesn't really matter...

You can reprogram as stated above, or do it the way I do....

Put the new wheels & tires on and have a friend with a cell phone follow you. They can then make sure you are traveling a specific speed. Test it on the highway and in the city at slower speeds.
Now it's just math.
The speedo is "X" m.p.h. off.
Not as precise as the above but will give you real world accuracy.
Drive accordingly.

the problem doing it that way is you have to figure a percentage off not just X MPH as it will be different at every speed. Its good math excercise for your brain though.

Good stuff.
Didn't know that.
Hurts my brain thinking about it.