I am fairly new to this. If I change my wheels from the original 20's to OEM 17's do I have to recalibrate my computer in order to get the correct speed reading?

Thanks

 

You don't have to but it will be off a little bit. When i went from 20" to 22" i was
told to do that but what is a mile or two.

 

depends. the rim size won't really affect it, its the tire size you need to worry about. Lets say you have a 33x12.5x20 tire on if you change to 17" rims but stay with a 33" tire, it wont change, but if you change to a different size tire then you will need the speedometer calibrated.

 

Also be aware that the handling characteristics are going to change as well since you will have more sidewall flex.

 

what did you do with the 20's?

 

The speedo calibration all depends on total tire diameter. If you get 17" tires that have the exact same diameter as your 20" tires, the speedo will be correct. Otherwise the dealership can change the tire size on your computer in 10 min.

 

Gentlemen:
I thank you for all your help, all the info is great, thank you very much.

Asfar as the 20's, I still have the 20" chrome clad wheels. They are inmaculate. One of the reason I am going to 17's is because of the wider choice in tires (but what do I know) I found a gentleman that is selling his 17 OEM alloywheels (which are immaculate) and I like them as well.
So here is another questions then... Will a see a change on my MPG? I do drive like a grandma in the city and hardly ever drive my truck unless I am going fishing (Colorado Mountain Passess) or towing my TT to some god forsaken place.... (mountain and ighway driving is differen for me).

 

As stated, tire dia affects it, not rim dia. I usally look for tire Revolutions Per Mile when shopping and try to get the ones that much my existing as much as possible.

 

Just buy a Superchips and then you can adjust if neccesary and you'll also have some performance gains

 

As far as your gas mileage is concerned, a number of factors have a direct relation to your mpg assuming your driving stays the same. The one thing that has the greatest impact on gas mileage is WEIGHT! If your 20" rims AND tires weighs 40lbs each (160lbs total in rotational mass) and by going to 17's you run a taller, wider, and more aggressive tire that now weighs in at 60lbs each (240lbs total), then yes, the extra 80lbs the engine now has to turn is going to have an effect. Most dont consider the effect of weight to their vehicle.

To put it in perspective, lets say you can run 500 feet in 20 seconds. Now put an extra 80lbs on your back, can you still make the dash in the same amount of time? Of course not, you got some heavy sh*t on your back slowing you down! :-)

Before selling your 20's, get a weight on one of them, and then weigh your 17" combo. If its the same or less, you are good to go. If its more, run a different tire.

-Mike