wheel backspacing
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Trailering
Joined: Oct 2014
Posts: 18
Likes: 6
From: Iowa
wheel backspacing
Hi All,
Maybe I'm over simplifying this backspacing issue. I have tubbed my 59 F100. Regular 9 inch rearend, Leaf springs, From my leaf springs to my fender well I have 15 inches of space. From my Leafspring to the face of my drum brake where the wheel is mounted is 9 inches. That makes 6 inches from the drum brake cover to the fender well. Ive bought 12 in wide tires and with the 9 inches of space lets take off two inches for tire clearance . It seems that a wheel with 6 inches of backspace should work fine. Or am I missing something?
Thanks
Maybe I'm over simplifying this backspacing issue. I have tubbed my 59 F100. Regular 9 inch rearend, Leaf springs, From my leaf springs to my fender well I have 15 inches of space. From my Leafspring to the face of my drum brake where the wheel is mounted is 9 inches. That makes 6 inches from the drum brake cover to the fender well. Ive bought 12 in wide tires and with the 9 inches of space lets take off two inches for tire clearance . It seems that a wheel with 6 inches of backspace should work fine. Or am I missing something?
Thanks
Lead Driver
Joined: Sep 2003
Posts: 7,013
Likes: 205
From: SoCal
If the tire is really 12" wide, that means you have 3" of clearance, which has to be split between the outside (to the fender lip) and inside (to the leaf spring). Splitting that evenly is 1.5" on each side, which means you want the tire (and therefore, wheel) center line to be in the middle of that 15" space between the leaf spring and fender, or 7.5" from either side.
If the brake mounting face is 9" from the leaf spring, you want a wheel with 1.5" positive offset (mounting face outboard of the wheel center) in order to center the tire/wheel in the available space.
Having just the backspace measurement of a wheel is insufficient; you also need its width.
EG, if you use a 10" wide wheel with a 1.5" positive offset, then its backspace would be 10"/2 + 1.5" + 0.5 (for rim thickness) = 7". The tire would stick out about 1/2" past the rim on each side.
If the brake mounting face is 9" from the leaf spring, you want a wheel with 1.5" positive offset (mounting face outboard of the wheel center) in order to center the tire/wheel in the available space.
Having just the backspace measurement of a wheel is insufficient; you also need its width.
EG, if you use a 10" wide wheel with a 1.5" positive offset, then its backspace would be 10"/2 + 1.5" + 0.5 (for rim thickness) = 7". The tire would stick out about 1/2" past the rim on each side.
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