Beating the dead wheel horse

[FuriousGT]

Based on my current funds I'm probably a long way from buying wheels but I like to be prepared so I'm in search of knowledge. I am a total math goober so I am having a hard time wrapping my brain around offset, backspace, etc. I have read every post on the topic I could find; I'm not asking without researching first. I also downloaded the EXCEL wheel calculator which was posted in one of the threads. I just don't get it.

I'm in the same position as kndlindsey postee about in 2006. I like the disc wheels and whatever you call the wheels with the holes in them (see links). I've done a lot of looking around and I don't like any 4x100 pattern wheels. I have found some wheels with a 4x4.25 pattern that I like. This means the use of an adapter which starts with a minimum thickness of 1" and goes up based on need. Keep this in mind.

Here are the wheels I am looking at:
Cragar 3204625 - Cragar Quick Trick I Wheels – SummitRacing.com
Center Line Wheels 054603442 - Center Line Wheels Auto Drag Wheels – SummitRacing.com
If for some reason the links don't work just go to summitracing.com and search based on the numbers in the above URLs.

The question is, as many have asked, will either of these work, factoring in the need for the adapter which is at least 1" thick? To help may brain understand this, will the 1" adapter create negative or positive offset?

Thanks!

[BQS4]

Try using this wheel sizing chart, it's interactive and may well give you your answer.
http://www.bigcustomwheels.com/info_specs.jsp

[blancojp]

Originally Posted by FuriousGT Based on my current funds I'm probably a long way from buying wheels but I like to be prepared so I'm in search of knowledge. I am a total math goober so I am having a hard time wrapping my brain around offset, backspace, etc. I have read every post on the topic I could find; I'm not asking without researching first. I also downloaded the EXCEL wheel calculator which was posted in one of the threads. I just don't get it. I'm in the same position as kndlindsey postee about in 2006. I like the disc wheels and whatever you call the wheels with the holes in them (see links). I've done a lot of looking around and I don't like any 4x100 pattern wheels. I have found some wheels with a 4x4.25 pattern that I like. This means the use of an adapter which starts with a minimum thickness of 1" and goes up based on need. Keep this in mind. Here are the wheels I am looking at: Cragar 3204625 - Cragar Quick Trick I Wheels – SummitRacing.com Center Line Wheels 054603442 - Center Line Wheels Auto Drag Wheels – SummitRacing.com If for some reason the links don't work just go to summitracing.com and search based on the numbers in the above URLs. The question is, as many have asked, will either of these work, factoring in the need for the adapter which is at least 1" thick? To help may brain understand this, will the 1" adapter create negative or positive offset? Thanks!

None of the two wheels you have in the links will work on a GT. Not because of offset but because they are both made for a 5-lug hub.

If you want this style of wheel, there is a company that builds them with the 4x100 pattern and any offset you like. For a GT, an offset of 0 to +10 will work just fine without adapters on a 6" wide wheel. A front wheel drive wheel with a +35-45mm offset will require a 25mm spacer to center the wheel in the cavity.

If you are strapped for cash, find Saturn 4-lug wheels.

[RallyBob]

This might help with the definitions.

Wheel Tech - Offset

[FuriousGT]

The wheels come in a variety of lug patterns and numbers. The pictures are of 5-lug wheels but the ones I'm looking at are 4x4 1/2.

I'd be interesting it the company that builds these style wheels. I'd much rather not have to use an adapter.

I did see the tool on bigcustomwheels.com. So I can accurately compare I have been searching around the forum for the original wheel size for the GT but have not found it. Weren't they 13 x 5.5? I have also see the original offset posted as 40-something and as 25mm. What is it really?

[RallyBob]

Originally Posted by FuriousGT So I can accurately compare I have been searching around the forum for the original wheel size for the GT but have not found it. Weren't they 13 x 5.5? I have also see the original offset posted as 40-something and as 25mm. What is it really?

Original GT wheels are 13 x 5". Only the 1975 Manta and Ascona had 5.5" wide wheels in the US. Backspace on the stock GT wheels is (+/-) 4", offset is 25 mm.

Have you considered redrilling the rear axles and front hubs to accept the 4 x 4.25" bolt pattern?

Alternatively, the first wheel option you show is very similar to circle-track racing wheels that are commonly available in many custom sizes. That includes any offset and bolt pattern, so you could have them made in 4 x 100 mm.

[FuriousGT]

I must be defective. I've been searching for custom wheel manufacturers and I can't find any. Custom wheel searches come up with the usual plethora of resellers, not places that actually build the wheels. Anyone know of specific shops that will build customs as RallyBob and blancojp mentioned?

[GTJIM]

'Off-set is the most important measurement - for our Opels this is about 25mm (known as ET25).

If the offset of the wheel is not correct for the car, the handling can be adversely affected. Instead of the front wheel turning correctly around its centre line the wheel turns along a small arc that makes it move back and forward as it turns. This is what causes it to 'hit' the inner guard - where a correctly offset wheel of the same width would not.

For the offset to stay the same while you added width, the additional width must be split evenly between the inside and outside. This limits the overall width before the tyre 'hits' the inner guard because as the wheel is made wider the tyre inner side moves towards the inner guard.

Off-set can be varied about +-10 and remain acceptable - that is from ET15 to ET35 for Opels ... though plus or minus 5 (ET20 to ET30) is better ... and having it correct is FAR BETTER! No liability expressed or implied

Just 'centering the wheel' in the wheel well is a recipe for disaster - looks good but can have fatal effects on steering and higher speed handing.

The problem being with the GT is that built upon the Kadett chassis the wheels 'look' like they are too far inwards and the big temptation is to move them outward to 'look' right. Resist that temptation!

Best to get the off-set right.

See this post: http://www.opelgt.com/forums/122503-post10.html

and: http://www.opelgt.com/forums/122535-post15.html

..then I will say no more!