I replaced my stock 17"s with the stock 20"s on my '02 QC - 4.7L. I was wondering if I'll need to have the computer reprogrammed so that everything works correctly, ie: speedo, gas mileage, tranny, gears,etc. Seeing as the 20"s were an option with the 4.7L in '02, I assume everything will be o.k. Just wanted to know if anyone knows anything different.

 

yes you will neeed to reprogram ur comp. speedo and odometer will be off. plus be careful trying to stop alot more weight to being stopping. I did the same thing 3 months ago and just took them off yesterday.

 

You don't have to worry about it if the tire diameter is the same as your old one.

Rim size has no effect on your speedo reading, but the tire size will.

 

Get a superchips (if they make one for yor application). They have a built in section for adjusting tire diameter. Like Mr Mojo says, if the tire overall diameter is the same, you won't have to do anything. That's how I put 305/50r20's on my stock wheels when the original ones were 275/55r20. Same diameter.