Does anyone have any idea what offset wheel I would
need if I upgraded from the 18 inch stock lariat wheel to
a 20 inch street wheel? I know the wheel lugs are
6X135mm. But I'm not sure what offset I would need
to upsize the rim.

'04 F-150 Lariat Screw
Loaded with sunroof

 

35 ~ 40mm

 

thanks

 

I tried fitting a set of 20" wheels that were 1 " wider rims. The stock backspacing is 5 1/2 inch and the new wheel was also 5 1/2 ". This left too much wheel hanging outside the truck and did not look good.

So the wheel shop told me that 6 1/2" was the way to go to keep the stock offset and look, unless you like the roller skate look.

So does that work out to about 165mm backspacing on a 1 inch wider wheel and 140mm backspacing on a stock width wheel?

I know you asked about offset but maybe this experience will help you.

 

Coupester touches on an important point here, that is backspacing. The stock offset is 44mm, but that in not going to be the same offset required, should you chose a larger than stock width replacement wheel. The offset range suggested by red04 likely reflects just such a difference.

Quite a number of folks seem to have a difficult time getting their minds around the whole concept of backapacing and offset, so here is a FAQ to help some of you to better understand the subject: go here.

Also worth considering IMO, is Coupester's observation on moving the wheel inboard, in order to avoid the "roller skate look". While you can move the wheel in some, there is most definitely a point at which doing so will create a 'rub' issue. Wheel stops can be increased to stop the rubbing, but it is at the cost of decreasing your turning radius. The other extreme, would be moving the wheels further outboard (think lowrider look), which has the effect of increasing stress on the hubs and other suspension components.

Certainly the tradeoffs need to be considered for your particular application. Sometimes you will end up needing to add fender flares, in order to fit truly oversized tires, and not have them stick out past the fenders.

 

Thanks for all the information. I would like a little bit wider wheel. Probably a 8.5 inch wide wheel would be good. But, I definitely don't want that "dune buggy" look with the wheel
extending way past the fenders. Does anyone know the width of
the lariat stock 18 inch wheel? Thanks again.

 

While there are many different tires speced for the new F-150, Ford only has one wheel width for all their OEM rims: 7.5". Same applies for the offset at 44mm and max wheel load capacity at 2,100 lbs (except for the 7 lug steel wheels on the HD Package equipped trucks).