Aren't the trucks with 20's transmissions working more than one with 17s? I'm not at all saying the truck can't handle 35s. I believe if the transmission went out, Ford would look at the 35s to deny the claim. On a truck with factory 20s and 34" tires Ford can't say anything cause that's how they built it. Does this double standard make any sense?

 

This is where it gets touchy. Warranty issues, as most know, can be a pain in the back side. As long as what you do to the truck, can also be compared to a stock truck, you shouldn't have a warranty issue as they would have a hard time proving that you were operating outside the normal parameters of the truck. Let the flame fest begin on that.

But, just the size of the wheels themselves doesn't work the tranny any harder. Yes the rotating mass of the bigger wheels is usually greater, but definitely not enough to effect the performance of the truck. More weigh is added by large tires with more rubber, steel, nylon and / or kevlar than is added by the larger wheels. Plus the 20" wheels usually have a lower profile to the tire, which again to no real extent, would help the weigh issue.

If you are driving something with a 5R110, you defintiely aren't hurting it with 20" rims.

This is one of the reasons that a gear change is so important when going with larger tires. The part of the driveline that catches hell, excuse me, is the tranny as I mentioned earlier.

 

Sorry for the confusion.

I meant the larger tire sizes (34.25") associated with the factory 20" wheels. Not the increased rotating mass of the 20" wheels.

BTW, every pound of rotating mass one adds to a vehicle has the same effect of 15 static pounds. This and the (nominal) decrease in overall gearing is why correct equivalent gears are so important.

Next week we'll talk about rolling resistance!

 

Ahhhh, physics and auto shop. I like it!