The factory size for the 1975 coupe and convertible is: 225/70-15
All the tires should be the same size. If the other tires are in place you should be able to get the size from the other tires. If not the size should be on a plate inside the drivers side door with many other specs.
Wheels : Size 15"x5", Bolt pattern 5x4 3/4 , Back spacing 3 1/2" Tires: P205/75-R15
it is the tires
No they do not have a spare. They come standard with Goodyear run flat tires.
This depends on whether or not your wheels are staggered (the front and rear wheels are different sizes). On some years of Corvette all four wheels were the same size, and on some they weren't. For example, I can't rotate the tires on my 95 Corvette because the rear tires are wider than the ones in front.If your tires are different sizes from front to rear but wearing unevenly, an option would be to swap the tires from left to right, keeping them on the same end of the car (ex. right rear to left rear). However, it is very important to note that if your wheels or tires are unidirectional (side specific) or have an asymmetrical tread pattern (the tread changes as it moves across the tire), you won't be able to swap your tires.Also, moving tires from one side to another isn't generally considered rotation. After all, the point of rotating tires and keeping them on the same side of the car is due to the fact that tires develop wear patterns based on your suspension and alignment.Check the tire size for your year Corvette. If all of your tires are the same size, you can rotate them. If they are different sizes but you feel that uneven wear needs to be addressed, consult a mechanic you trust to discuss options.
The 1969 Chevrolet Corvette was offered with P205/75/15 tires. These wheel can have a larger fitment of 225/75/15 on the same wheel. Kumho still makes tires in the 205 size, and if you are looking for originality restoration companies may offer replications of the factory style radials. Changing the wheel size in this application will offer better handling from modern performance tire sizes, as well as much better purchasing options.
It depends on your tires. Look for the "PSI" rating on the wall of the tires.
Corvette tires can be purchased from various New York car dealerships. They can also be purchased online from various tire suppliers, such as Goodyear.
My 89 Corvette which is also a C4 recommends 35psi on all 4 tires
Let about 1/2 of the air out of the tires.
The 90 Corvette had a 350 c.i. engine
The 2009 Chevrolet Corvette has a 6.2 L base engine size.