Why are 3 and 4 piece rims better?

Wouldnt a 1 piece rim be better because its a solid piece? I don't get why higher end cars have expensive 2-4 piece rims.

 

The advantage of a multi piece wheel is that each part can be made using an optimal process.

The center section of the wheel is forged, and this provides substantially higher strength to weight than a cast material.

The rim is usualy spun from a tube, and again it can be made thinner because the tube material is stronger than the typical casting.

Three and four piece wheels can be stronger and lighter than a one piece casting. The disadvantages are sealing the pieces, and transferring the loads to the center section, which does add weight, but if done correctly they are lighter than a casting of similar strength.

 

Hello very good points, plus you can customize offsets and widths easier.

 

And, IMHO, they look better!
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Typically, the 3 piece wheels aren't lighter than a similar one piece wheel, and not necessarily stronger either - forged is forged, to make a huge generalization. However, you have much more flexibility to adjust width and offset/backspacing and to create staggered sizing easily, so for the manufacturer it allows them to offer many more size/offset combinations for much less than with one piece wheels.

 

For street cars, it's ALL about marketing the "Racing Look". They typically are heavier than a one piece, especially forged, wheel. All of those neat-o fasteners weigh something, even in Ti.

In racing, the flexibility in offsets provided by picking your halves (as normv and GordonC noted) could tune handling. These days, once that's established, notice that most teams have a bunch of single-piece units made, thanks to CNC being everywhere.
Alternately, when a rim (proper use here - it's NOT the whole f'n wheel, yo!!) is damaged, it can be swapped out without tossing out the entire wheel.
A "good" end-result of this is that eventually, you'll kill a center, and you can make a neat table out of two of the wider halves and a thick piece of glass.

 

They aren't superior they are garbage, hence why you don't see them in racing.

Okay, maybe not garbage but they are not superior.