wugak

I like the look of older cars with "deep dish" wheels. Why do all modern cars have the wheels flush with the outside of the car with like 8-9" of backspacing?

From a logical engineering perspective it seems to me that with a small backspace you could have shorter (lighter, stiffer) axles.

Why not go to the extreme and have the wheels with zero backspacing? The wheel is the same shape and weight, just essentially mounted inside out. Less stress on the lugs and studs? It would still be lighter to bump the studs up 2 sizes and cut the axles down 8" in length on each side.

Just a curiosity...

427V8

Areodynamics my man. Aerodynamics...

Ak. Mal

I think it has more to do with the positioning of the weight of the wheel and tire. Your wheels, tires and brakes are all considered unsprung weight. But they also works much like a teeter totter. The farther out the weight is, the more it takes to move it around and it has a larger affect on handling. So, by moving most of the weight inwards, (ie. flush mounted rims) it reduces the amount of multiplied weight and appears to lighten the unsprung load.

I agree with you though, I like the look of the older deep rims.

norvalwilhelm

To me the strongest wheel is one that has equal spacing front and back. The rim itself can be rolled out of light weight sheet metal and but welded to get very lightweight rims.
If you have a say 10 inch wide rim and you have the mounting in the center, 5 inch backspacing 5 inch front the wheel is balanced in the center of the load.
Take the same rim and put the mount at the extreme front or the extreme back and the loading on the rim is not centered and the forces or load on the rim goes up.
This can lead to fatigue of the rim or the spokes where it is mounted to the outer rim itself.
To have extreme offset the rim needs to get strong/heavier.
It's like you grabbing a broom by the very end and holding it striaght out in front of you . Take the same broom and grab it in a balanced center and the force on your wrist goes down.
Your axle is your wrist.

442olds

There are several things involved that determine just how much backspace a particular suspension setup requires. Things like scrub radius and king pin angle come to mind. If you'll notice that some of the newer cars with modified strut front supsensions also have the ball joints quite a ways apart. In some case like my 4th gen fbody the upper ball joint is above the tire. The spindle actually wraps around the tire to accomplish this. Backspacing, tire grip, contact patch and all be adjusted for optimal conditions sometimes this requires these severe offsets. Now if you measure the wheels on my camaro you'll notice that the backspacing is still close to center but the brake setup requires the wheels to be flush with the outside of the wheel. Packaging also plays a big factor with wheel design and shape.

WESCH

Hi

This is correct for the wheel ( rim ), but not for the axle bearings.
For the bearings, best load is equal backspacing in relation to them, so the newer design rims with the flat outside actually distribute the load more equal to the axle bearings, which are much further inboard.
Nevertheless, I also prefer the older design where you can see a large rim.

Rgds. Gunther

mrvette

Which goes right back to my ages old observation about the wheel center needs be not far from b/j centerline, or bearing centers....anything too far off that increases stress on bearings, and expecially in the REAR, that is not summfin I wanna mess wit.....

GENE

Twin_Turbo

He hit the nail right on the head, it's about modern ways of designing the geometry with the kingpin inclinations that require the pos. offset wheels to get an acceptable scrub radius. Also, most modern cars come with front wheel drive, meaning theu have "thicker" hubs on the front than our cars do, to keep the width of the suspension within reasonable limits they go for the pos. offset.

Neg. offset rocks in my book too pos. offset is for ricers

As for bearing stress, there's a drawback to both neg. & pos. offset wheels. Pos. offset have more bearing load in straight line and neg. have more load during cornering. The inner bearing is the one that sees most of the load.