The weight saving from having lightweight wheel is UNSPRUNG WEIGHT which is different from the regular weight on the car. The less unsprung weight, the less ROTATIONAL force needed to move the wheels/tires which give traction to bring the car forward. Since less rotational force is needed, it requires less power or torque to move. Hence, it gives the following benefits:
1. Smoother and slightly faster acceleration.
2. Smoother and shorter stopping distance.
3. Better fuel economy.

Now that is the theory. In reality, I can confirm this as well through my own experience. I also want to add smoother and more accurate steering feel as well.

I believe someone have done an experiment and document it here http://www.carcraft.com/projectbuild...ls_comparison/

What is unsprung weight? https://answers.yahoo.com/question/i...=1006012500665

 

We sell replacement wheels, it's not a problem, as long as we have it in stock we will sell it.

As far as cracked wheels, most of them are covered under warranty, even if we see signs of slight impact.

Remember, it's not a forged wheel, so at a hard impact, the wheels tend to get a hairline crack on the inside barrel rather than bending

This is the case with a lot of OEM BMW wheels and many other cast wheel manufactures as well.

We just happen to cover this most the time

It's at our discretion of course, but most the time it's covered unless it seems like a major impact.

 

I have the perfect rims for you! Check miro wheels type 398. The one that looks like the te37. They have 18 with mild width