Good morning, afternoon, evening and night,
(whenever you read this post)

I am giving up on finding wheels for this car that fit without adapters and don't look like the traditional 5 spoke everyone and their grandma torq thrust IIs.

I found a decent wheel adapter company that mills the size and bolt pattern you need specific to wheel and car, and isn't going to gorge on the price.

I'm not sure exactly how they are figuring out the measurements... maybe some one can help with that.

I found these:




KMC DIME 127
18" x 8.5"
I was gonna use a 255/35/18 in the front and a 275/35/18" in the rear Falken FK452

In that size they only come in a 5 on 115 or 4.5 pattern in a +38 offset.

I know our cars use a 5 on 4.75 or 120.7 pattern with a -11 to 0 offset
(CORRECT ME PLEASE IF I AM WRONG ON THE OFFSET RANGE)

I WAS TOLD if I have a wheel with a +38 offset and a billet adapter that is a 5-4.75 to 5-4.5 with a thickness of 1 and 1/4 inch that is would make the wheel a 0 offset but the backspace would become 6 and 1/4 (OUR CARS AGAIN CORRECT ME IF I AM WRONG THE ONLY BACKSPACE AVAILABLE IS 4.01 or 4 and 1/100th)

I was told that if I needed the backspace to be the closest to 4.01 or
4 and 1/100th I would need a 2 and 1/8 inch adapter but that would make the offset -16

I was also told that to get a -11 offset I would need a 1 and 15/16th inch adapter. but still have a backspace higher than the 4.01

The torq thrust IIs fit with no adapters 4.01 backspace with a -11 offset with 5 on 4.75, no adapter.

All of these measurements were based on a wheel having an offset of +38 to begin with. I would appreciate any input from you guys and possibly any other wheel options regardless of offset or backspace.

Thanks guys,

-Louis

 

NO body knows?

 

Why don't you call VBP and talk to Gary. They make wheel adapters and I'm sure he can help you out. I don't know about wheel offset, just backspacing.

 

+38mm offset is very close to 1.5" (actual is 1.496"). An 8.5" wheel is actually about 9.5" overall width from inner flange to outer flange (advertised wheel widths are measured from bead seat to bead seat), and backspacing is measured from the inner flange. Therefore the backspacing of an 8.5" wheel with +38mm offset is 9.5/2+1.5 = 6.25", so you'd need a 2.25" adapter to get yourself to 4" backspace.

Look here for information on wheel measurements, and there is an offset-to-backspace conversion table (your particular wheel is off the chart but you can see where it's going):

https://www.rsracing.com/tech-wheel.html

 

Thank you for the replies.

I know that I have to convert the wheels + size offset MM to inch, and get that from where it needs to be to a 0 is that I need that adapter to be that size... the backspace is where I am confused, to bring that from 6 to 4

If wheel is a +38 offset with a 6" backspace..

Using simple math 1"=25.4MM

6-4 = 2 or 50MM 50MM = 2"
38MM = 1.5 INCH

so to get the wheel to become a 0 offset with 4" backspace that means I need an adapter size of
1.5" + 2.5" = 4" adapter and to go from 5 on 4.75 to 5 on 4.5

Am I correct? Is that even safe a 4" adapter?
How safe are these billet adapters at high speeds of 60MPH and 10MPH 80MPH? Do they fail? DO lug nuts pop off? I mean the wheel isn't supposed to be on there in the first place, and 4" out plus the wheel width of 8" or 8.5" could be 12" or 12.5" thats kind of a lot. don't ya think?

The people that make the wheel adapters can;t answer specific questions... I am tremendously pissed off...
Either I put factory wheels on the car, or go with some crappy torq thrust II wheels and look the same as everyone else. No other wheel companies make off the shelf products for our cars, some 3-piece custom wheel companies won;t do it even if I supply the measurements. There has to be some company out there that makes an attractive looking wheel that fits today's modern looks, and not a crager ss knock off, or some modern twist upon that traditional 5 spoke design.
THe new corvettes on the same 5 on 4.75 bolt pattern even the 2010 model does, however the backspacing of 6" and offset of +58 doesn't help either.. Are we forgotten in the dark? Shunned to one type of wheel? WTF?

 

I called Gary at VBandP... Gary gave me some decent info, assured me they were safe, but who knows. Gary said they've only put on a few cars, and hes never used them. He wouldn't talk to me any further unless he sent me a catalog to look at and such.

 

I think you need to review the link I posted above to become familiar with wheel measurement terminology. Some of the numbers you put in your post above are impossible combinations for the wheel width you are talking about. For example, you cannot have an 8.5" wheel with 0 offset and 4" backspace; for 0 offset on an 8.5" wheel it would be 4.75" backspace, or for 4" backspace it would be -19mm offset.

Offset and backspace are tied together based on the wheel's other dimensions, they are not independent.

Adapters are safe, if used properly. Many people here run them, and in more extreme applications than just street driving.

If you want to avoid adapters, there are plenty of modern wheels out there that are direct bolt on. Do a search for in Tech/Performance and General and you should come up with some results.

 

I've been to the link you posted, I have it printed out, I found it a week ago. I know they go hand in hand. The wheels I had on the car before were 16" TT2 wheels, 8" with a -11 offset and 4.01" backspace according to AA, and tire rack.

I'm saying if I took the 8.5" wheel from the +38 offset and brought it down to 0 offset, the backspace would be about 6.25" how do I get that backspace down to 4" as I understand the C3 can only take upto a 4.5" backspace.

 

That's where the 2.25" adapter which 69autoXr mentioned comes in. Subtract the 2.25" from the 6.25", and you'll have 4.00". If you want to bring that 6.25" down to 4.50" BS, you need a 1.75" adapter.

 

I'm not sure that we're on the same page somewhere. I'm not sure what you mean when you say "if I took the 8.5" wheel from the +38 offset and brought it down to 0 offset, the backspace would be about 6.25" "

8.5" wheel +38 offset = 6.25" backspace: you'd need a 2.25" bolt on adapter to get to 4" backspace.

8.5" wheel 0 offset = 4.75" backspace you'd need a 0.75" spacer to get to 4" backspace and long studs.

 

Yeah, what he said

 

Thats what I mean,

First to bring the offset from +38 to 0.. I need a 1.5" adapter..

That makes the wheel a
0 offset with a 6.25" back space with a 1.5" adapter.

So now I need an additional 2.25" on the spacer to bring the backspace down from 6.25 to 4.0

so that means total thickness of the adapter is:

1.5 + 2.25 = 3.75"

Next what I am saying is.. If the wheel width is an 8.5" and I'm running a 3.75" adapter...

8.5 + 3.75 = 12.25" wide Isn't the max width on stock trailing arms like a 9 or 9.5" wheel?

 

I give up

 

I'll give you an "A" for effort...

 

Boss 338 with a +2 offset and a 4.5" backspace with a 5 on 4.75
in an 18x8" please tell me this will work!?

 

I'm dumb, sorry...

 

Offset - distance from the centerline of the wheel to the mounting pad surface.
Back space - Distance from inside edge of wheel to mounting pad surface.

You don't need to be conserned with getting the wheel to a 0 offset. All you are looking at doing is getting the wheel to a 4" or 4.5" backspace. Look at it this way. With the same size wheel, you have one at +38mm offset and one at 0. The one at +38mm will have a 6.25" backspace and the one at 0 offset will have a 4.75" back space. The mounting pad will have been moved 38mm (1.5") towards the back of the wheel thereby reducing the backspacing by that much.

They gave you the answer three times above. To get a 4" bs, run a 2.25" adapter. To get a 4.5" bs, run a 1.75" adapter. With the 2.25" adapter the wheel will be pushed away from the trailing arm more than with the 1.75" adapter.

This statement makes no sence:

Next what I am saying is.. If the wheel width is an 8.5" and I'm running a 3.75" adapter...

8.5 + 3.75 = 12.25" wide Isn't the max width on stock trailing arms like a 9 or 9.5" wheel?

As long as you get the backspacing correct, the wheel will not hit the trailing arm. With the same backspace, the wider the wheel is the more it will stick outside the body. If you want to run a wider wheel, but try and keep it inside the body, you will try to increase the backspacing. If you go too far, you will hit the trailing arms. That is why people run the offset trailign arms. It is so they can run wheels with more backspacing so the wheels will stay under the fenders.


I run the 3" adapters with the C4 style 16"X9.5" wheels and have been doing so for about 12 years now. I have never had any problems with the adapters, bearings, hubs or anythig else related. I don't just cruise around on them either. The car isn't street legal. I have been autocrossing the car for that long. Lets look at those since i think they are a 38mm offset also: (9.5/2) + 1.75 (38mm) = 6.50 backspace - 4" = 2.5". So, I really need a 2.5" adapter to get to a 4" backspace. I run the 3" to push the wheels out further to give me a wider track. That helps my cornering on the autocross course, but the wheels do stick outside the fenders a little. So in effect, I am running a 3.5" backspacing on my car.

Get it, got it, Good!

 

Yes! There are cars on this forum running that very same wheel. Do a search using "Boss".

I'm sorry but I have to ask this - with literally 1000s of wheels to choose from in so many different styles with such a wide price range why choose something that has to be "forced" to work?

"69autoXr" you get a big from me! Great try.

 

Those wheels work great for me - no problems. You will find you have many more tires to choose from than if you choose 16" or 17" wheels. I have 255/45-18 UHP tires on my BOSS 338's:

 

So what you are saying is that he needs a 3.75" spacer and a 1.75" adapter, right? .................j/k This thread is a fun read.