Wheel offsets explained...also, OEM offsets listed

[Chewy]

I copied and pasted this from another site to here as I was looking for a definition. Many people say that BMW wheels will bolt on to our cars but I noticed their offset tends to be 15-20 where as ours is 35-40. Looking at this definition allows me to assume that it would probably work but the wheels would be inset into the car more than the stockers. Being that the bolt pattern from a 2005 530i is the same but has a bit of a different back spacing and offset I believe (without trying) that the BMW wheels WILL fit.

To start things off, I’d like to get a few definitions out of the way.

The offset of a wheel is the distance from its hub mounting surface to the centerline of the wheel and for some ungodly reason is usually measured in mm. the offset can be one of three types.



Zero offset - the hub mounting surface is even with the center line of the wheel.

Positive offset - the hub mounting surface is toward the front or wheel side of the wheel.

Negative offset - the hub mounting surface is toward the back or brake side of the wheels center line.

Backspacing of a wheel is the distance from the hub mounting surface to the rear outer most edge of the wheel.

Front spacing is a term not used too often, but is a term I like when discussing a wheels ability to tuck. It is the distance from the hub mounting surface to the front outer most edge of the wheel.

As an example I’m going to use a wheel that is 20x8.5 with a +19mm offset as this seems to be a pretty common size.

The first thing you have to understand is that actual wheel width is about 1 inch wider than stated, so a wheel that is 20x8.5 in actuality measures 9.50 inches wide. That being said the center line of the wheel, +0.00mm offset, is the same as 4.75in backspacing/front spacing.

9.50in/ 2 = 4.75

Now to get the offset from metric to a more understandable unit of measure (inches), we are going to divide it by 25.4. This number is a constant as there are 25.4 mm in an inch.

19mm/25.4 = 0.7480314in

For practical reasons, we’ll round up to 0.75in. Since we already established that our center line is 4.75, and we are dealing with a positive offset, we are going to add 0.75 in to 4.75 to give us a wheel backspacing of 5.50 inches. This in turn will allow us to figure up the wheel front spacing by simply subtracting the wheel backspacing from the overall wheel width giving us 4.00 inches.



To find to total backspacing/ front spacing, we are going to apply the same principle we did to find wheel backspacing/ front spacing.

The new center line of the tire/ wheel combo is 5.05. we found this by dividing 10.1 by 2. Again we are dealing with a positive offset, so you add the 1.25 offset to the center line to get a total backspacing of 6.3 in.

(10.1/ 2) + 1.25 = 6.3 in

This will let us find our total front spacing by subtracting the backspacing from the tire width.

10.1 – 6.3 = 3.8 in

Since the 3.8 inch total front spacing is less than 4, you should have no problems tucking this wheel/ tire combo. You can of course get around the 4 inch limit by rolling or trimming your fenders.

*note – you should take measurements when possible. these numbers are close, but not necessarily exact

[99-LS1-SS]

I found a good wheel offset calculator that should help people with any questions relating to offset.

http://www.1010tires.com/WheelOffsetCalculator.asp

[GeorgeInNePa]

From another thread.

So, found the details.

OEM HSV sizes are:

Fronts - 19 x 8", 5 x 120, +48

Rears - 19 x 9.5", 5 x 120, +57

[-Ray-]

Thanks to LDV60, I think we know what offsets to use now.

[Chooch]

So knowing the offsets, and looking at our sister car from the UK Vauxhaul VXR8 which comes with these tires standard , 245/40 R 19 front and 275/35 R 19 rear , if we go with the above offsets, should clear with aftermarket wheels. my car has not been lowered so all being said, should be a straight bolt on with no clearance issues? Just want to be sure as I am getting my summer wish list of SUmmer RIms and tires and CAI funds ready

[99-LS1-SS]

Will a 5 x 4.75" wheel fit on our 5 x 120mm lug pattern?

[GeorgeInNePa]

Will a 5 x 4.75" wheel fit on our 5 x 120mm lug pattern?

5x4.75" is 5x120.65mm. It will fit. The 17" Fbody wheels we are using for DRs are 5x4.75". The 18" Vette wheels that Panther 2 is using are 5x4.75" pattern.

[99-LS1-SS]

Cool! I was looking at a set of Vette wheels.

[f117rt]

??????
If you can't, they are 2008 Caddy CTS wheels.
Had to add Pontiac logos of course!
Bolted right on, even using stock lug nuts.
Got them from EBAY for $200 (all 4!!)

[Saginaw748]

I hear you on the ebay wheels, those are tempting. I'm leaning more towards the BMW take-offs, or 'knock-offs'. I don't want to go larger than 19', and there are some hella deals on ebay....

..problem is, I don't want to be the guinea pig!

example - http://cgi.ebay.com/ebaymotors/BMW-1...Q5fAccessories

Another I kinda like - http://cgi.ebay.com/ebaymotors/19-wh...Q5fAccessories

It all comes down to the offset. It's just hard to 'imagine' how it will look. I know it would be more inset than ours, but...