Tire questions..

I was wondering if anyone knew if tire size 245-45-16 would fit on a stock 2000 z28. All advice welcome thanks.

Yes, it should. But with a lower aspect ratio, the tire will be shorter than the stock tire, and your speedo will be slightly off.

Tire diameter will be 1" smaller than stock, and cause the speedo to read 4% higher than actual speed. Fender gaps will grow by 1/2".

Why?

I wanted some wider tires on the back and i want to stick with 55's or 50's in the front. I was just wondering if I needed to alter anything to get them to fit.

The stock tires on a V8 4th Gen with the Z-rated tire option (RPO "QLC") were 245/50-16. That is the correct size for your car, not 245/45-16. The "45", "50", "55" has nothing to do with the width of the tire. A "45" aspect ratio tire is no wider than a "50" or "55" aspect ratio tire. The aspect ratio is the height of the sidewall divided by the width of the tire.

For a wider tire, you would go to a 255 width, or wider, but there are no decent high performance tires any wider than 255 in the 16" diameter. That's why people run 17" wheels - so they can run wider 275/40-17, 285/40-17 or 315/35-17 tires.

If you choose to stay with the 245/45-16 you won't have to do anything to make it fit, because the diameter is so small, there will be less interference than with the stock tires.

Did your Z28 leave the factory with the "base" 235/55-16 tires?