The OEM tire size for the C5 Coupe is 245/45-17 front and 275/40-18 rear.

In the past I have fitted tires one size wider and one size lower aspect for a slightly bigger footprint on other cars.

Is this appropriate on the Corvette or is best to stick with the standard tire sizes.

I drive a 2004 Coupe with automatic and factory magnesium wheels.

Thanks in advance.

Cheers

 

You can absolutely run 255/40/17 and 285/35/18 - those are the exact sizes I would run on stock wheels. Check out the Sumitomo HTR ZIII for a good CHEAP tire.

You gain a little bit more rubber and a little bit of a performance bump due to the smaller OD of the tires. Your ride height and consequently center of gravity will go down about 3/8" and your effective gear ratio goes up a bit too, roughly like going from a 3.15 to a 3.22.

C5's have a lot of space for both bigger or smaller tires, I'd guess you could safely run anything from around 24 to 28 inches in overall diameter and you can fit up to 315mm widths front and rear. Just don't run taller tires in the front than the back and you should be OK.

 

You can go bigger on the stock rims. I went 10mm wider and kept the same aspect ratio. The speedometer is pretty close. If you go to the smaller aspect ratio they should fit also and the speedometer will be a little further off.

The sizes for both are shown below along with the expected speedometer errors.
Fronts
245/45/17 = 25.7"
255/40/17 = 25.0"
255/45/17 = 26.1"

Rears
275/40/18 = 26.7" Speedo reads 60
285/35/18 = 25.9" Speedo reads 58.2
285/40/18 = 27.0" Speedo reads 60.7


Just keep the stagger like 8VETTE7 suggested and you will be fine.

Good luck.

 

Or just buy the right size tires and avoid the problems listed above

 

How boring is that.....?

 

Even with a lowered car you can still get bigger tires.

I originally had 265/35/18 front
295/35/18 rear...on a 2000 coupe

These will fit just fine on your 2004.

 

I don't know too much about comprehensive insurance policies outside of Australia, but we have to use the tire size listed by the manufacturer or risk having our policy declared null and void. Not every company is the same and some do allow slight variance from the OEM sizes.

It's just easier for me to go with the OEM sizes and not risk having the insurance company tell me that I changed the vehicle design/handling and therefore I am not covered in case of an accident.