Rear end Width/Rear wheel Offset...

[ItsA68]

Call me weird, but I don't like the deeeep dish wheel look on the rear of cars....Most of the late model stuff all seems to have big offsets, and correspondingly not much dish on the rear. I have a 68 Camaro, and plan to do minitub, and DSE quadralink some day. How would the suspension handling/performance be effected if I used a rear end that was 4-6" wider than stock, with wheels that had 2-3" more offset (to the inside) on each side to keep the tires in the same position? If you're paying big bucks for forgelines, you don't want the nice centers burried deep inside the wheel, right?

Any insights appreciated.

Thanks,

~~fred francis

[pav8427]

Wider Is Better!!

[JMarsa]

In the front that set-up with yield better scrub radius, so just match the rear wheel to the front. Like the C5/C6 vette set-up.

--JMarsa

[68Formula]

Okay. You're weird.

[baz67]

In the front that set-up with yield better scrub radius, so just match the rear wheel to the front. Like the C5/C6 vette set-up.

--JMarsa

One note of caution here. Yes, having a larger positive offset will lessen the scrub radius. The problem is there can be interference with the frame when the wheel is turned. It just a matter of comprimise.

[silver69camaro]

In the front that set-up with yield better scrub radius, so just match the rear wheel to the front. Like the C5/C6 vette set-up.

--JMarsa

I'm confused. I believe the original post was referring to the rear axle, and not the front...

If you are referring to the rear, in our situation with a solid rear axle, you will actually get better results with shallow backspacing, unlike the front. The reason is because such a wheel requires a shorter axle housing, which reduces unsprung AND rotating mass. The wheel weighs the same no matter what the backspace is. Too little backspace can cause unusual bearing wear, but that usually not an issue.

Personally, I like the look of some dish, so it's a win-win situation for me.

[JMarsa]

I realize he was refering to the rear, the point I was trying to make is that it would benefit him on the front and the wheel style would match.

I'm not an engineer but my understanding of a wide versus narrow axle width was that a wide axle (while heavier) provided more leverage to the springs and pivot points and affected the spring rate choice.

--JMarsa

[ItsA68]

I'm not an engineer but my understanding of a wide versus narrow axle width was that a wide axle (while heavier) provided more leverage to the springs and pivot points and affected the spring rate choice.

--JMarsa

This is along the lines of what I was thinking...you could only eliminate 6" or so of 3" tube, and axles, so it doesn't seem to me that the weight would be a whole lot less....less for sure, but not a lot.

Other than the weight penalty, would there be any other problems?

Matt, Sincerely, thanks for your input.

Thanks,

~~fred

[ProdigyCustoms]

Lucky for you Forgeline builds a lot of high offset wheels. Where some 19 X 12s right now with 2" offset built as we speak.

[silver69camaro]

I'm not an engineer but my understanding of a wide versus narrow axle width was that a wide axle (while heavier) provided more leverage to the springs and pivot points and affected the spring rate choice.

--JMarsa

The load applied to the spring doesn't really change since the load can be considered to be applied to the center of the tire tread. In real life, the load is applied evenly across the tire tread, but it can be assumed there is a single force applied to the center. So as long as the tread width remains identical, the spring rate wouldn't change.

But what you are referring to actually relates to the bearing load like I mentioned.

[silver69camaro]

Other than the weight penalty, would there be any other problems?

~~fred

Nope!

[JMarsa]

Matt,

I've exaggerated the placement of the coil spring in this picture to illustrate my point. I believe the longer distance from Point A to Point B in the top drawing would have an affect on spring choice, maybe only 25 lbs in a performance/race car, but some affect.

If the spring was mounted closer to the wheel as in real life on a street car the affect I'm trying to emphasize would be minimal.

If this is wrong, no worries, lesson learned.

--JMarsa

[silver69camaro]

I see what you're saying and it is somewhat confusing.

Shown in the drawing, no matter what the housing length is, the force applied is to the center of the tire, and the distance between Fn and Fs is the forces in question. From Milliken's bible, finding axle rates:

Kw=(Kr*Kt)/(Kt-Kr)

Where:
Kw=Vertical axle rate or wheel center rate
Kr=ride rate
Kt=Tire rate

As you can see, we are only concerned with the force applied to the center of the wheel/tire. Imagine the wheel and axle housing as once piece, and it would be just like applying the load directly to the axle tube itself where the tread center lies. Just because the wheel bolts onto the axle two inches outboard does not change the distance beween Fn and Fs.