Need some help with backspacing measurements please.

[OldJimmy57]

I am going to order a set of Mickey Thompson HR-2 wheels 20x16's and they offer offsets from -1 to -56. I am using a Ford Explorer 8.8 that measures 59.5 from mounting point to mounting point. And the rear fenders are 73.5 inches from inside lip to inside lip. I know I need to leave 3/4 of an inch clearance by the fender lip and by the frame. So what i am needing is to know the backspacing I think. Also what would be the widest tire we could get away with in the front?

[Spackle100]

This might help http://www.srbymichael.com/help/front-spacing.pdf

[mr48chev]

Somewhere there is a chart for the inflated height and I----I sectional width of tires and there is probably one that includes the rim width.

My handy dandy little cell phone calculator says you are going to have about 5-1/2 inches to work with beyond the wheel mounting surface of the hubs/axles. This might work if you are a bit better figuring it out than I am. http://www.1010tires.com/tiresizecalculator.asp

http://www.tirerack.com/wheels/tech/...jsp?techid=101

This might be better in explaining wheel offsets.
http://www.wheelandtiredesigns.com/tech.php

[DransportGarage]

Please tell us the width of the chassis assembly (i.e., from where the tire would first hit [on the inside] on the right to where the tire would first hit on the left). Note that the tire might hit the frame, the leaf spring, or something else.

I would also measure in on both sides, from the mounting face to the interference point, to be sure they're close to being the same. (It's not a bad idea to measure from the mounting face to the fender lip on both sides too.)

[OldJimmy57]

From the inside fender lip to the frame 19 5/8" I cut off the leaf springs and decided I am gonna try the 67-72 rear trailing arm suspension.

[63 & 64 Bowties]

I don't know what your budget is, but this is a really nifty tool:
http://www.speedwaymotors.com/Percys...rite,6761.html
It's the only 100% fool-proof way to know for sure that I know of.
You could always sell it after you use it.

[DransportGarage]

Here's a drawing for you (pdf. Sorry it's not to scale). Maybe you can send this to your supplier and let him decide on the backspace.

I'm concerned that your rim's inside bead-to-bead dimension is 16" and your fender lip-to-frame dimension is 19-5/8". That leaves only 1-13/16" on each side from the INSIDE of the bead for the tire bulge. Then there's cornering, and distortion at WOT, assuming a perfectly accurate backspace from the manufacturer and an identical clearance on both sides...

Since I don't know the width of the bead I can't accurately calculate the backspace.