Does a different offset change the look of a rim?

[MustangOwner]

What i'm asking is does the different offsets of the same rim(Cobra R for instance) change the "look" of the rim. So if you had the two next to each other and say one rim was 24mm offset and the other was 36mm offset, Would one look different then the other? Cause a 24mm offset rim would have a mouting surface further in compared to a 36mm offset rim(Both 9 inch width) which would have a mounting surface further out. I have two drawings below. Which one is how the rims are designed? Thanks.

1. Picture 1. Different offsets change the angle of the rim spokes.

View attachment 343739

2. Picture 2. Different offsets change the width of the lip. Causing it to have a deep dish appearance with the higher number offset you go.

View attachment 343741

 

[DeVus1]

The offset really doesnt change the look of the rim, rather it changes how it sits on the car. Offset is the dimension between the centerline of the wheel , and the mounting surface. Positive offset tucks the wheel closer to the car.

 

[foxmustangman]

Yeah, it just changes the distance behind the wheel design to how far back it needs to be bolted on the rotor.

 

[MustangOwner]

I'm not retarded, i know what offset is.

But the point is if a 9 inch rim has a 24mm offset and say it sits flush with the fender. Okay, now take that same 9 inch rim but have it in 36mm offset. It sits in a half inch further then the 24mm. So... that would mean the angles of the rim change. From say 45 degress to 50 degrees etc.. Or does the spokes just "slide" on the rim. Which would mean a higher offset would make it have a deep dish effect.

 

[MustangOwner]

dd

 

[9 Deuce GT]

I think I understand what you are saying, but I think you have the concept backwards. The term taht would make the most difference is backspacing. Backspacing is the distance measured on a wheel with the axle mounting surface up. Take a straight edge and lay it flat on the rim lip. Take a ruler and measure from the straight edge down to the axle mounting surface. Offset is the distance the moutnig surface is from the wheel center. Take a wheel width. like a FRPP R58 Cobra R. It is 9" wide. Ford uses a 1/2 wheel lip per side, (other rim makers may use a different figure). This makes the actual width of that wheel 10". Now divide that by 2, to get 5". The mounting surface of an R58 wheel is "offset" 24mm or .95" to the face (the side that faces outward) of the wheel. This is called positive offset. If it went toward the inside of the wheel, it would be called negative offset.

Now take an M179 wheel with it's 36mm offset. The spokes are not altered or moved to changed the angle or look of the wheel. The mounting pad surface is shaved down to achieve the extra .5" or so offset. So the backspace of this wheel would be 6.42, ( 5" for the center point of the wheel plus the bigger offset of 1.42").

 

[DeVus1]

Check this link out: http://forums.stangnet.com/showthread.php?t=716968

 

[MustangOwner]

I think I understand what you are saying, but I think you have the concept backwards. The term taht would make the most difference is backspacing. Backspacing is the distance measured on a wheel with the axle mounting surface up. Take a straight edge and lay it flat on the rim lip. Take a ruler and measure from the straight edge down to the axle mounting surface. Offset is the distance the moutnig surface is from the wheel center. Take a wheel width. like a FRPP R58 Cobra R. It is 9" wide. Ford uses a 1/2 wheel lip per side, (other rim makers may use a different figure). This makes the actual width of that wheel 10". Now divide that by 2, to get 5". The mounting surface of an R58 wheel is "offset" 24mm or .95" to the face (the side that faces outward) of the wheel. This is called positive offset. If it went toward the inside of the wheel, it would be called negative offset.

Now take an M179 wheel with it's 36mm offset. The spokes are not altered or moved to changed the angle or look of the wheel. The mounting pad surface is shaved down to achieve the extra .5" or so offset. So the backspace of this wheel would be 6.42, ( 5" for the center point of the wheel plus the bigger offset of 1.42").

Okay i never thought of that. So pretty much what your saying is that a rim(Cobra R for instance) Looks identical regardless of the offset. All they do is "shave" the mount pad thinner to achieve the different offsets correct?

 

[iwashmycar]

yep!

 

[9 Deuce GT]

Okay i never thought of that. So pretty much what your saying is that a rim(Cobra R for instance) Looks identical regardless of the offset. All they do is "shave" the mount pad thinner to achieve the different offsets correct?

That's right. What are you looking to do?

 

[just4bob50]

the mounting surface thickness of the wheel is not changed to effect offset. It is the same regardless of offset, because it is a structual part of the wheel. Offset is the position of the mounting surface relative to the center of the wheel. Back spacing is the distance from the inside of the wheel to the mounting surface. Same size wheel with 2 different offsets will move the wheel in or out relative to the fender lip.

 

[9 Deuce GT]

So then what is changed on the '95 Cobra R wheel to give it more backspace? It has to be the thickness of the mounting surface area!

The structural part of the mounting surface is the same regardless of offset, but the thickness of the overall area is less when you have a wheel with more offset.

 

[gruvee87vertgt]

SUBSCRIBING..

 

[MustangOwner]

dd

 

[9 Deuce GT]

Did you not read the posts in this thread?

 

[Repostyle]

Okay, I'll chime in here too.

The look of the wheel will be a little different to the trained eye only. The spokes and the rim will be the same, it's the location of the spokes, as a unit (which includes the mounting point) in the rim that will be different. A higher positive offset (36mm) will move the spokes and mounting surface closer to the outside edge of the rim moving the rim and tire into the fender more. A lower positive offset (24mm) will move the spokes farther from the outside edge of the rim moving the tire out in the fender creating a more "deep dish" wheel. Negitive offset is when the spokes are inside the vertical centerline of the wheel.

The centerline is not the center of the circumference of the wheel, it's determinde by the width, example: a 10" wide wheel has a centerline of 5", anything on the outside of this centerline is positive offset, negitive is just the opposite, anything on the inside of the centerline is negitive offset.

So to sum up, offset is measured from the centerline of a wheel, the smaller the number for positive offset the closer it is to the centerline creating more of a "deep dish" look which is what the trained eye would notice.

I can't see your pictures they're just red x's but I hope that helps.

I'm not retarded, i know what offset is.

But the point is if a 9 inch rim has a 24mm offset and say it sits flush with the fender. Okay, now take that same 9 inch rim but have it in 36mm offset. It sits in a half inch further then the 24mm. So... that would mean the angles of the rim change. From say 45 degress to 50 degrees etc.. Or does the spokes just "slide" on the rim. Which would mean a higher offset would make it have a deep dish effect.

The spokes "slide" and no, a lower positive offset makes for a more "Deep dish" look.

 

[Repostyle]

I think I understand what you are saying, but I think you have the concept backwards. The term taht would make the most difference is backspacing. Backspacing is the distance measured on a wheel with the axle mounting surface up. Take a straight edge and lay it flat on the rim lip. Take a ruler and measure from the straight edge down to the axle mounting surface. Offset is the distance the moutnig surface is from the wheel center. Take a wheel width. like a FRPP R58 Cobra R. It is 9" wide. Ford uses a 1/2 wheel lip per side, (other rim makers may use a different figure). This makes the actual width of that wheel 10". Now divide that by 2, to get 5". The mounting surface of an R58 wheel is "offset" 24mm or .95" to the face (the side that faces outward) of the wheel. This is called positive offset. If it went toward the inside of the wheel, it would be called negative offset.

Now take an M179 wheel with it's 36mm offset. The spokes are not altered or moved to changed the angle or look of the wheel. The mounting pad surface is shaved down to achieve the extra .5" or so offset. So the backspace of this wheel would be 6.42, ( 5" for the center point of the wheel plus the bigger offset of 1.42").

This is wrong.

Shaving would weaken the mounting surface, there is not a wheel manufacturer in the world that would want the liability of wheels breaking and falling off.

A 9" wide wheel is just that, 9", it does not matter the offset or how much "lip" there is. The visible lip is measured from the spokes out, changing the offset OR rim width changes the lip.

 

[bstrd86]

I think what 9 deuce is getting at is that there is only one casting of the wheel, the mounting pad is machined to achieve the desired offset. The holes are then drilled and the wheels strength is not affected. There are thousands of wheels made this way every day and changing the offset would not change the appearance in this case. With a multi-piece wheel there is only one center and it is welded or bolted in the rim barrel in the desired location to achieve different offsets. In this case changing the offset will affect the look of the wheel, making it look deeper or more shallow.

 

[Repostyle]

I think what 9 deuce is getting at is that there is only one casting of the wheel, the mounting pad is machined to achieve the desired offset. The holes are then drilled and the wheels strength is not affected. There are thousands of wheels made this way every day and changing the offset would not change the appearance in this case. With a multi-piece wheel there is only one center and it is welded or bolted in the rim barrel in the desired location to achieve different offsets. In this case changing the offset will affect the look of the wheel, making it look deeper or more shallow.

You're half right, you're right about the multi piece wheel, but the mounting point is NOT machined to set the offset on a single piece wheel. If it's the same style wheel, then the mounting point is the same thickness no matter the offset or width of the wheel. The offset is only determind by where it is located in the rim. Manufacturers have different "castings" for different offsets. Most wheels are one piece and they just change the settings in the machining process for the whole wheel, not just the mounting pad. Thats it.

There might be some machine shops out there that will do this for you, but if you want a wheel that isn't weakend by thinning out the mount then buy the right offset from the manufacturer.

Based on your comment, the only way to achieve a smaller positive offset would be with spacers, because you can't machine more material on. And you wouldn't be able to get a negitive offset, because you would machine the whole thing away.

This is a great pic. The outside is on the left of each wheel. The wheel on the left actually looks like neutral offset, but the more you move outward from the centerline with the mounting point the more positive offset you get, the wheel on the right is negitive offset, notice mounting pad and spokes are identical, only location matters.

 

[bstrd86]

I've seen cast wheels made, they cast a "blank" wheel that has an extra thick mounting surface without any holes in it, it is machined to the desired backspacing, the lug holes are drilled to whatever pattern, and then the wheel is gets whatever finish it's going to get on it. If you look at the mounting surface of a cast wheel it is machined. I've even ordered blank wheels before when I was in the wheel business.