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Official 6-Lug Re-drill Thread: Now in the USRM!


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ok so i understand what back spacing is, but what is offset? and what do you have to look for when picking out a set of wheels to make sure that they wont interfere with brake components?

 

so what im asking is what do i look for to make sure that the surface the lugz go through or the spokes dont rub on the caliper's. ive seen it happen in other custom situations

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IMO Offset is another word for Backspacing. (At least thats what I go by) As long as you go bigger then 13", nothing will interfere with the brake system, Calipers, Rotors and or Drums will all clear.

 

Width will be the only issue, may hit the Spring perch or Strut body, Possible rubbing on Tierod end. But you can run a pretty wide tire on these.

 

Incorrect. Offset is the distance from the centerline of the rim of the wheel, to the wheel mounting surface(The surface up against the wheel hub/brake drum when it's mounted.) It's negative when it's closer to the outside lip, and positive when it's closer to the inside.

 

EXAMPLE:

My 14x6 Pug alloys have 4.5" of backspace. The centerline of the 6" wheel is 3" across. 3"-4.5"= -1.5" This implies that they also have 1.5" of negative offset.

 

The "real" formula for calculating offset is as follows:

 

(Wheel width/2)-(Backspace)=Offset

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Incorrect. Offset is the distance from the centerline of the rim of the wheel, to the wheel mounting surface(The surface up against the wheel hub/brake drum when it's mounted.) It's negative when it's closer to the outside lip, and positive when it's closer to the inside.

 

EXAMPLE:

My 14x6 Pug alloys have 4.5" of backspace. The centerline of the 6" wheel is 3" across. 3"-4.5"= -1.5" This implies that they also have 1.5" of negative offset.

 

The "real" formula for calculating offset is as follows:

 

(Wheel width/2)-(Backspace)=Offset

 

Nice work buddy....

 

You're such a sexual intellectual.....

(effinknowitall) :-p

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so effectivly is back spacing really just offset + other half of the rim. i get it i just dont understand why they need both measurements

 

Yup pretty much. You can get the other number, no matter which one you have. I usually see backspace always measured in inches though, while offset can be either inches or mm.

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so if i put a skinny tire on a wide wheel it wont fit, and if i put a wide tire on a skinny wheel it will bubble.

 

If you put a skinny tire on a wider wheel, it willl bow or pull out the sides, a tire shop will not mount a tire that is to much narrower then the rim, as it is a lot of stress on the bead.

 

You can mount a wider tire on a less wide rim, it will protect the bead lip more if offroading (I see this all the time on offroaders)

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As you can see here, the wheel bead is sunken into the tire more, so there is more rubber sidewall to protect the rim from rocks ect.

 

Subaru026.jpg

 

Also like this, the wheel is a 15x7 but it is a 10.5" wide tire. You can also run a 12" wide on the same 15x7 wheel.

 

2011_1216AG.jpg

 

2012_0325AE.jpg

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It's also a royal pain in the butt trying to mount a tire that's considerably thinner than the rim.

After dealing with that a few times while working at a garage, I started refusing to do it.

It was a lot of VW crowd wanting sidewall stretch... sigh...

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