How to Determine the correct tire size for new wheels on a C5 and C5 Z06.



I have been seeing a bunch of folks asking questions about what sized tires to go with their rims.
They are also asking if there Active Handling, and Traction control will have issues.

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Upsizing your wheels to 18/18, or 18/19, or 19/19, or 19/20 ... etc...:

First off, I would like to say that your Rim size has NOTHING to do with the stagger that GM built into these cars.
You "do not have" to upgrade to a 18/19 combo, or 19/20 combo.
You can upgrade to 18/18 or a 19/19 combo with no issues.
The TIRE sizes are what maintains the built in stagger from GM.
As long as you choose the correct tire size then you will NOT have issues with Traction control or Active Handling.

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The "Corvette Staggerd" look works 2 different ways.....:

Going with a 17/18, 18/19, or 19/20 wheel setup will give you a look that the wheels are staggered in size from front to rear.
- FYI... The front tire will have a larger side wall than the rear tire sidewall in this situation.


Going with a 18/18, 19/19, or 20/20 wheel setup will give you a look that the tire sidewall is staggered in size from front to rear.
- FYI... The rear tire will have a larger side wall than the front tire sidewall in this situation.


This is where you get to choose the "look" you want to go with.


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Check out this great little wheel/tire calculator I have been using for years.

---> Click Here for Wheel/Tire Calculator <---


If you input the original tire you have now, and input the proposed size you want to go with, it will output the differences.

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Stock C5 and C5 Z06 Tire Sizes to use in calculator:

Using the original size of your tires (see below).
Use the above calculator and do the math.
If you up size your tires, you want to make sure you up size the front and rear the same amount (or as close as possible).
That way you avoid the computer seeing a mismatch in tire speed between the front and rear tires.
Thus eliminating Active handling, and Traction control issues.


Stock C5 (97-04):
Front
Rim size = 17x8.5" rim
Tire Size = 245/45/17
Diameter = 25.7"
Rear
Rim Size = 18x9.5"
Tire Size = 275/40/18
Diameter = 26.7"


Stock C5 Z06 (01-04):
Front
Rim size = 17x9.5" rim
Tire Size = 265/40/17
Diameter = 25.4"
Rear
Rim Size = 18x10.5"
Tire Size = 295/35/18
Diameter = 26.1"


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This is the general rule of thumb you want to follow.

Stock C5 rear tire diameter is 1.0" larger than the front tire.
Stock Z06 rear tire diameter is 0.7" larger than the front tire.

Notice that I'm talking about "TIRES" above and not RIMS.

You can go with any size "rims" you want. Just be sure to try to keep the rear tire larger in diameter than the front by at least the values above.
Issues with Traction control and Active handling only seem to arise when your rear diameter is close to or smaller than the front diameter.

Try not to venture too far away from the stock diameter in general.
--> If you go with a smaller diameter tire (compared to stock) they will look small in the wheel well.
--> If you go with a larger diameter tire (compared to stock) they will really fill out the wheel well and look great...but, you run the risk of the tire hitting the fender liner when turning with an oversized front tire.

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Here is an example of what I did when I upgraded to a 19/19 combo.

I have had no issues with traction control, or active handling since I got this combo.

Using the calculator above I calculated up sizing my front and rear tires to a size that kept me very close
to my stock tire diameter, AND made sure that both tires increased/decreased the same amount.

Front
Stock Z06 = 265/40/17 = Diameter 25.4"
Proposed = 275/30/19 = Diameter 25.6"

Rear
Stock Z06 = 295/35/18 = Diameter 26.1"
Proposed = 305/30/19 = Diameter 26.3"

So with my proposed new tire setup:
Front --> Increased the Diameter by only 0.2"
Rear --> Increased the Diameter by only 0.2"

As you can see above (for my situation), both proposed tires are barely larger in diameter than my stock Z06 setup.
The most important thing is that they both increased the same amount.
I maintained a larger rear tire diameter of 0.7" compared to my front tire.
That’s the key to keep the traction control, and active handling in check.

With a larger rear tire my speedometer will not be reading 100% accurate.
In my situation when my speedometer is reading 60mph, I will actually be going 60.4mph.
There is NO need to make a change to the computer for a change this small.

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With all that being said.... MOST C5 owners (Coupe/Vert/Z06) tend to go with the following tire sizes.

For a 18/19 Wheel Combo
Front - 275/35/18 (or 265/35/18)
Rear - 305/30/19

For a 19/19 Wheel Combo
Front - 275/30/19
Rear - 305/30/19

The above sizes have proven time after time to NOT cause any issues with the C5 computer.
The above sizes work great on Coupes, Convertables, and Z06's with no issues.


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C5 Wheel Offset information

C5 (Coupe/Vert)(1997-2004):
Front 17x8.5", 58mm offset = 7.03" backspace
Rear 18x9.5", 65mm offset = 7.81" backspace

C5 Z06 (2001-2004)
Front 17x9.5", 54mm offset = 7.38" backspace
Rear 18x10.5", 58mm offset = 8.03" backspace


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I also recommend that you verify the calculator values by going to the tire manufactures web site
to verify the sizes this calculator spits out for the specific tire you plan to purchase.
Just to be sure...

If something does not make sense above feel free to ask.

Hope this helps!
Mark
MSilverZ06@gmail.com