5x120mm vs 5x4.75" wheel bolt pattern

Which is the GTO, or are they the same?

I know that 5x120mm is the BMW spec and that most of the wheel peddlers distiguish between the two and will often label the 5x4.75" as 5x120.65mm. Did Holden/GM actually change to 5x120mm or is it just a case of semantics?

tyvm,
Tom

I wonder if they aren't the same 5x4.75" that GM has used for decades and just called 5x120mm because AU is metric.

Tom

I called tires plus this morning and they said that you can't interchange the 5x4.75 for the 5x120 even though they are extremely close.

see my post in "nice wheels"

Went to ROH site

5x4.72-5x120mm
5x4.75-5x120.65mm

Hope this helps.

I know all of that. I'm just trying to find out what the GTO actually has, 5x120mm BMW spec, or 5x4.75" that has "mistakenly" been called 5x120mm.

Tom

I checked today 5x4.75 is actually 5x120.65 mm
be carful when selecting Rims

Quote: Originally Posted by Holeshot... I checked today 5x4.75 is actually 5x120.65 mm be carful when selecting Rims

True. The question is does the 0.025" make a real difference or not. Some tire/wheel dealers say yes, others no.

Reality check here. Some some dealers are saying that you take an inch. divide it into 40 equal parts. Add one of these 1/40th of an inch parts to the spacing and everything now doesn't fit? Now I am not an expert but I have changed a few tires in my time. It seems like there is a little more slop then 1/40th of an inch when I put the wheels back on. I would like to understand what the downside is on 1/40th of an inch.

I would imagine that AT BEST it will depend on the lug nut style. But even with conicals, it would seem that some buggering of the seat will occur when torquing down steel nuts on an aluminum wheel.

I can't seem to make this clear, it is not an issue of crossing one to the other, but rather determining which the GTO actually utilizes. I have seen both specs given, and even from the same poster. I've seen it posted that GM and Holden are the same: 5x120mm, but we KNOW that GM (pre-GTO at least) is 5x120.65mm/5x4.75". Apparently, this is just too confusing for the average Joe.

Tom

My gut tells me the 5x 120 is correct. The GTO originates in a metric country so this would lead me to believe the thought that it is the same as BMW. Hey Aussies, how about a little help? What is the Monaro?

I agree with tminer, The Lug nuts will not seat properly. Could eventually destroy Your nice new Wheels and inadvertnly Screw up other things such as throw your axle out of ballance, wear bearrinr prematurely and send errors to the ABS system .

I've checked 4 different places and got four different answers, I've currently got a call into GM engineering for the specs. Nobody can tell me for sure what the correct size is and I've yet to get a "true" expert to tell me for sure if they won't interchange. This really sucks, I'd really like some better wheels and I have money burning a hole in my pocket! (I've never had to work so hard to spend $2000 in my life)

see the "Aussie Monaro" thread.

Quote: Originally Posted by cjlannoy... I've checked 4 different places and got four different answers, I've currently got a call into GM engineering for the specs. Nobody can tell me for sure what the correct size is and I've yet to get a "true" expert to tell me for sure if they won't interchange. This really sucks, I'd really like some better wheels and I have money burning a hole in my pocket! (I've never had to work so hard to spend $2000 in my life)

If your pocket gets too hot, let me know. I'll be glad to takke that 2K off your hands.

for a nice set of tires and wheels its all yours

Quote: Originally Posted by cjlannoy... I've checked 4 different places and got four different answers, I've currently got a call into GM engineering for the specs. Nobody can tell me for sure what the correct size is and I've yet to get a "true" expert to tell me for sure if they won't interchange. This really sucks, I'd really like some better wheels and I have money burning a hole in my pocket! (I've never had to work so hard to spend $2000 in my life)

I don't know how accurate / factual this is - -

o Listen up aftermarket wheel manufacturers! The 2004 GTO lug spacing is not a traditional American size so existing aftermarket wheels for GM cars won't fit.

Source:

http://www.highperformancepontiac.co...pon_yellowgto/

I saw this on another site:

The kind people at Pontiac asked that I post the following info to me on the GTO's wheels.

The GTO hub has a 5x120.00mm bolt circle diameter.
The offset is 48 mm for both 17-inch and 18-inch wheels.
The GTO wheels have 8.0 inch wide rims.

Yea, Pontiac sent me the same info ... Howie has posted the wheel details for quite some time. That is why I did not repost it.

Quote: Originally Posted by miamio... I saw this on another site: The kind people at Pontiac asked that I post the following info to me on the GTO's wheels. The GTO hub has a 5x120.00mm bolt circle diameter. The offset is 48 mm for both 17-inch and 18-inch wheels. The GTO wheels have 8.0 inch wide rims.

Thank you sir!

Tom

Quote: Originally Posted by DevilYellow... Yea, Pontiac sent me the same info ... Howie has posted the wheel details for quite some time. That is why I did not repost it.

Yea, I'd seen his post but there was no reference to the source. There have been many different posts on various boards and several wheel dealers have the pattern listed but all seemed to split about 50/50 between the two patterns. Kind of hard to know whom to trust.

Tom

Quote: Originally Posted by miamio... I saw this on another site: The kind people at Pontiac asked that I post the following info to me on the GTO's wheels. The GTO hub has a 5x120.00mm bolt circle diameter. The offset is 48 mm for both 17-inch and 18-inch wheels. The GTO wheels have 8.0 inch wide rims.

Are we sure about the 48mm offset? That is only 1.89" if my math is not failing me. It sure looks like more than that.

That is the centerline offset, but the two "halves" will be twice that different in size. It works out to about 6" backspacing. There isn't a direct correlation because of the way the two specs are measured (0 offset on an 8" wheel isn't 4" backspacing).

HTH,
Tom

Quote: Originally Posted by tminer... Yea, I'd seen his post but there was no reference to the source. There have been many different posts on various boards and several wheel dealers have the pattern listed but all seemed to split about 50/50 between the two patterns. Kind of hard to know whom to trust. Tom

We actually did wheel & tire test fitting. Beside if you takes off any wheel from your GTO and look on the inside it'll give you the factory wheel specs.

17x8 with 48mm backspacing

Arrowhead Performance has the correct wheel specs to fit a 9" wide wheel on the back and use a 275 series tire. Up front you are limited to a 8" wide wheel and a 245 series tire.

Feel free to contact me for more info.

I thought this might be interesting because I know at least I thought that back spacing and offset were the same thing, (turns out I was wrong) see below:

Q: What is wheel backspace?
A: Backspace is the distance from the back edge of the rim to the mounting surface on the hub.


Q: What is wheel offset?
A: Offset is the distance from the wheel centerline to the mounting surface. Positive offset is when the mounting surface is outside the centerline. Negative offset is when the mounting surface is inside the centerline.

Yep, and what makes 0 offset not equal to 4" backspace on an 8" wheel is that the center line and mounting surface (same for 0 offset) are 4" from the inside of the back lip but backspace is measured from the outside of the rear lip.

Backspace is width/2 in mm (in x 25.4) + offset + 6 and then divide by 25.4 to get inches.

Offset is backspace - 1/4" - width/2 and then multiply by 25.4 to get mm.

Our 8" wheels with 48mm offset should be 6 & 1/8" backspace.

The 6mm and 1/4" represent the lip width and are just typical values.

HTH,
Tom

Edited 6 & 1/4 to 6 & 1/8. Calc'd 6.125, and blew the conversion.

There has been much discussion about whether a 5 x 4.75" pattern/wheel will interchange with the GTO's 5 x 120mm specs. For what it's worth, American Racing (www.americanracing.com) just updated their website with 2004 GTO Applications. Only 2 or 3 wheels, but all are listed as 5 x 4.75."

Received a call from a trusted friend in the aftermarket wheel business. Word from American Racing and Weld is that they won't be tooling up for GTO wheels. 18K units per year doesn't translate into enough sales to make production worthwhile.

Still can't figure out why ARE lists a few wheels (4.75") on their web-site. This recent addition conflicts with quite a bit of other info. Specifically, liability issues associated with using 4.75" wheels on 120mm hubs.

Another tire and wheel company has fitted wheels and tires and claims that the bolt pattern is 5x4.75 standard GM pattern. Geez more confusion.

I'm going to do my own testing this weekend. I have some 17" Boyd wheels from a Camaro. I will test fit those and post back here.