How to figure backspacing? HELP

looking · 11-08-2007, 01:20 PM

Looking in to some new wheels along with some other mods. What kind of backspacing is best for the new 08' Titan CC Pro4x? An what is all of this stuff when I am looking at wheels?

18x9, 6 on 5.5(I know the Titans run this bolt pattern)
Bolt PatternBack Spacing = 5.18 in.(What is the difference in backspacing)
Offset = 30 mm.(how do you determine offset)
Hub Bore = 100.5(what in the world is Hub Bore)
Finish = Chrome

Thanks
Frank

**gr8titan** · 11-09-2007, 07:04 PM

Offset is defined as the distance of the "mounting surface of the HUB"
form the "imaginary centerline" of the wheel width.
Here's some illustration to assist you how to figure out "offset" you need or want.
Good Luck

rgregory1965 · 11-09-2007, 07:14 PM

Quote:

Originally Posted by gr8titan

Offset is defined as the distance of the "mounting surface of the HUB"
form the "imaginary centerline" of the wheel width.
Here's some illustration to assist you how to figure out "offset" you need or want.
Good Luck

Thats great...I have been struggling with that also....but what is the pos and neg limits for the stock titan setup, with out hitting and rubbing.

Thanks

**gr8titan** · 11-09-2007, 08:03 PM

Quote:

Originally Posted by rgregory1965

Thats great...I have been struggling with that also....but what is the pos and neg limits for the stock titan setup, with out hitting and rubbing.

Thanks

The offset is always dependent on the "width" of the rim you plan to use.
In my particular size of wheel (20x9) the offset is (+) 18MM. This is the distance from the imaginary center line to the mounting surface of the wheel HUB. So you can imagine that a narrower or wider wheel with the same offset of 18MM will not clear the chassis and fenders the same way as the 9" wide wheel with 18mm offset

NorCal 4x4 · 11-09-2007, 11:53 PM

Backspacing is what matters, and offset is used to find it.
On '04-'07 Titans the SE and LE rims have 5.5" backspacing, and the XE and Off Road pkg. have 5.375" backspacing. Getting a rim with much more than 5.5" b.s. and the tire will rub the steering knuckle/spindles. Get much less backspacing, (like 4.5"), and/or wide rims, and you will likely rub inside the front fenders when you turn the steering wheel.

To find backspacing when you know the rim width and offset:
Rim width plus 1", divided by 2, plus positive or negative offset. For example:
(9" + 1" ) / 2 this is the centerline + 30mm = 6.18" backspacing.
The information in post #1 is either incorrect or from two different wheels, because 5.18" b.s. was listed.

What website is is from? I'd be cautious buying from them.

A 9" rim is really 10" wide because the lips aren't included in the advertised width.

**gr8titan** · 11-10-2007, 05:38 AM

NorCal4x4 posted above what I failed to explain. It will help to know the OEM backspacing as the OEM 5.5 inch will clear the knuckles and spindles without problem.

Moreover, most wheel manufacturers advertise their offset in millimeter (mm) so divide this number by 25.4 to convert to inches then add this number (in inches) to your imaginary centerline (rim width + 1" divide by 2) and you have the backspacing in inches. Try to stay as close to OEM backspacing as possible.

In my particular case, the backspacing of my 20x9 wheel is +18mm (+0.7 inch).
Adding this positive number (0.7) in inches to centerline of 5 inches ( 9" wide + 1" divide by 2) and I have a 5.7 inch backspacing which is close to the OEM wheel.

However, rubbing issues does not end here. If you decide to install unusually too wide or too tall tires, rubbing will be caused by the tires at this point. Then you would need a lift kit to change the geometrical relation of the wheel/tire combo to the chassis/suspension components.
Just my 0.02 Good Luck.

looking · 11-12-2007, 08:43 AM

I have an 08 Pro4x with 18" rims(dont know width) and am looking at the XD795 Hoss Black rims. They offer an 18x9 with the following 3 sizes-

Offset
a.18
b.18
c.30

Backspacing
a.5.70
b.5.70
c.5.18

Hub Bore(what is hub bore)
a.108
b.78.1
c.100.5

I would like to keep the wheels tucked as much as possible.

Thanks
Frank

TravisDTD · 11-12-2007, 09:24 AM

There is a lot of clearance under our trucks.

Here is the offset limits for an 18x9 wheel for your Pro-4x titan, other models will be very close if not the exact same.

Offset range +6 to 56mm to keep your wheels within the fenders. (I personally would run a 18mm offset) lower sets the wheel out and higher sets the wheel in. (note if you push either end of the spectrum too much you will have to be more accurate with the tire size you choose so your tire will fit correctly without rubbing.

[18mm offset with a 285mm width tire is an awesome fit]

I have attached a diagram for a hub description. The hub helps center your wheel so when you bolt it on it is perfectly in the center. If your wheels hub diameter does not match your vehicles you might have vibration problems. Our titans have a 77.8mm hub size. Hub size is determined by measuring the diameter of the hub.