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Discussion Starter · #1 ·
i want to get some 18" XD Monsters for my 2006 titan SE, but am confused about offset and backspacing. can someone please explain this to me. and also what offset and backspacing do i need?
 

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hondadavi161 said:
i want to get some 18" XD Monsters for my 2006 titan SE, but am confused about offset and backspacing. can someone please explain this to me. and also what offset and backspacing do i need?
Backspacing is the distance from the rim's mounting flange surface to the back edge of the inside side of the rim, like if you laid the rim on the ground with the finished side up, and stuck a tape measure to the ground and measure up to the mounting surface. The '04 to '07 stock 18x8" SE and LE rims have a 5.5" backspacing, and the XE and Off Road package 17x7.5" rims have a 5.375" backspacing.

Offset is just used to find out what the backspacing of a rim is and are shown in millimeters. This is the distance that the mounting surface is offset from the wheel's centerline. But, the centerline, (half the rim's width) isn't 4" on an 8" rim. That's because it is a nominal 8" rim and is really 9" wide. So centerline on an 8" rim is 4.5", and centerline on a 9" rim is 5". So if you have a 9" advertised width rim, with -12mm, (about 1/2"), of offset, the backspacing will be 4.5".

The formula for backspacing is: nominal width plus 1", divided by 2 (to get centerline), then add the offset (positive or negative).
Example: (9" + 1") / 2 + (-12mm) = 4.5"
[Btw, 1" = 25.4mm]

A 4.5" backspacing means that a rim of the same width as one with a 5.5" backspacing, will stick out 1" more. If the rim is also an inch wider, it will stick out 2" more. Sticking out more is likely to cause the fender rubbing when you turn the steering wheel, but can be solved by the pinch-weld-mod, heating and reshaping the plastic fender liners, and sometimes also modifying or removing the OEM mud-flaps.

Some tires and some lifts require more clearance from the spindles, and in this case you need to have less backspacing, like 5" or 4.75".

Also, some aftermarket wheels will not clear the brake calipers, even though a different brand clears fine. Someone with the AR Thug or Cannon had this issue with the 5 3/8" b.s. version. I'd guess the 4.5" b.s. version probably clears though, since the entire wheel is further out in relation to the mounting surface. This was in a 17" wheel, but someone else recently mentioned having this issue with an 18" of some model, don't recall which brand.

In the case of the guy ordering the 17 that didn't clear, the website suggested this backspacing option for his Titan, so they should be responsible for the return shipping, but for someone just selecting a wheel, you need to make sure you know it will fit.

For anything more than stock sized tires, you will need at least a PRG leveling kit. And since it's a 9" wide rim, you need to plan on the pinch-weld-mod anyway. Unless you're into the low profile tires.

For the 18" Monsters it looks like two backspacing options, at least at 4wheelparts. The 5.7" b.s. ones will stick 2/10" closer to your steering knuckle/spindle than stock 18s. If you plan to get a CST lift and wide 35" tires, you will want the 4.53" b.s. But even some of the other lift's spindles could make contact with wider tires, since wider rims allow the tires to reach their full width potential.

The 5.7" b.s. will still stick out about an inch more than the stock 18's and are probably the better choice. But test fit locally is my advise.

You will also need lug-centric lug nuts to install them, because the bore on the Monsters I saw was about 4" and our hub is smaller. The lug-nuts will be used to center the rim on your truck. Bolt circle is 6 on 5.5" ( or 6 on 139.7mm).
 

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Discussion Starter · #3 ·
thanks for the explenation, offset and backspacing is more clear to me now. and btw, i was planning on getting the 18x9 Monsters with some street tires for now, and when i get the money get a 6" fabtech lift and 35/12.5/18 toyo open country m/t tires.:futwice:
 

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hondadavi161 said:
thanks for the explenation, offset and backspacing is more clear to me now. and btw, i was planning on getting the 18x9 Monsters with some street tires for now, and when i get the money get a 6" fabtech lift and 35/12.5/18 toyo open country m/t tires.:futwice:
You're welcome ... and :futwice: Lol

PRG says that on the stock rims there aren't issues with any of the lifts fitting 35s except the CST, and then only for a couple of tires:
All the kits can run STOCK wheels and run 35" tires (exception is the CST kit on stock wheels with 325 tires or Toyo/Nitto MT...the lugs will hit the spindle). I don’t care what any one says, we do it everyday. All the kits can use aftermarket coilovers.
But since these aftermarket rims are an inch wider than stock SE rims, the tire at the sidewall will be about 0.4" wider than it would be on the stock 8" rims, but half of that would go to the inside of the rim and half to the outside ... so if you go with the 5.71" b.s. this will also stick the rim in 0.21" more than stock, and your tires will be 0.41" closer to the spindle.

Will loosing 0.41" more of spindle clearance than the Toyo MTs on stock rims have, mean your planned Toyo MT 35s will rub on a Fabtech lift? You should contact Greg. His contact info is listed on the PRGproducts.com page.
 
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