Toque

Everyone:

All of this information is available on my web site.
www.ToqueZ06.com

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.
- The front tire will have a larger side wall than the rear.

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.
- The rear tire will have a fatter side wall which gives it a more muscular look.

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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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!
Toque
MsilverZ06@yahoo.com

Dave68

Great info, Toque!

I might also add that you can significantly increase the weight of each wheel by upsizing if you don't pay attention to wheel weights. Going forged will often keep the weight down but I've seen many cars with giant (cast) wheels that cause the car's performance to suffer greatly. I'm talking about a much harsher ride, poorer acceleration and longer stopping distances.

And if you live in an area that has bad streets (potholes everywhere), think twice about swapping in lower profile tires. The shorter sidewalls flex less and transmit more kickback to your backside.

As always, do your homework and there should be fewer surprises.

road pilot

Alot of good info.........
Those that run a rear air duct ie C-5 ZO-6 should check
clearence of larger rear tires or you will have rubbing
issues. The duct can be adjusted.

Toque

Very true Dave.
Thats good info for people to know.

Toque

FYRARMS

...only if you do not properly size the tires. A rule of thumb when dropping sidewall profiles by 5% (say, a 35-series profile front to a 30-series profile rear) is to make sure your tire widths are at least 40mm wider in the rear (say, a 265mm tire front and a 305mm tire rear). That will keep the front and rear tire sidewalls about the same height.

Johnson 92

Mr31FlavorsVette

Great info, still a little confusing, but definitely helps. Toque, love your wheels, exactly what I want when I replace mine!

mgmcaleer

I used Toque's info when choosing the size tires for my C5. Just put them on yesterday.

Mike

Toque

Id have to look into this... I have never seen a "properly sized" setup with the same size sidewall front/rear on 17/18, 18/19, 19/20 setups. To meet the required diameter stagger front/rear i have always noticed that the front side wall is larger.

The stock Z06 setup for example is 265/40/17, and rear 295/35/18. The front tire sidewall is HUGE compared to the back. I have seen many 18/19 setups with 265/35/18, 305/30/19, or 275/35/18, 305/30/19. These are properly sized setups for 18/19 wheels and the front tire also has a larger sidewall than the rear.

Toque

madmatt9471

Very nice and well done buddy!

This should and will help many a new Corvette owner!

Bookmark it for quick reference once the newbie question is brought up -

Thanks,Matt

madmatt9471

Very nice and well done buddy!

This should and will help many a new Corvette owner!

Bookmark it for quick reference once the newbie question is brought up -

Thanks,Matt

FYRARMS

Just basic math, really. The sidewall height is based off the profile-to-width ratio. A 35-series profile means the sidewall height is 35% of the tread width. The wider the tire, the taller the profile. If the sidewall height is too short, just run a wider tire. Easy! Tire widths vary from brand to brand, though, so you need to keep tabs on that.

Toque

I completely understand where your coming from, and yea I always recommend going to the MFG for specific data on what tire you plan to purchase based off your research.

Example on 2x common 18/19 setups:

Front 265/35/18 - Diameter 25.3" - Sidewall 3.7"
Rear 305/30/19 - Diameter 26.3" - Sidewall 3.6"

Front 275/35/18 - Diameter 25.6" - Sidewall 3.8"
Rear 305/30/19 - Diameter 26.3" - Sidewall 3.6"

The above are very common sizes people choose when going to a 18/19 setup. They will not have any active handling issues at all since the stagger is between 1" and 0.7". The sidewall is just slightly larger in the front. The overall diameter of front and rear tires are still very close to stock.

You can't just add width to a tire without doing the math though. You always have to keep the required stagger in mind that GM engineered into our car's. Its also best to try to stay close to the original overall diameter of your tires so as not to have any fender rubbing issues in the front, or speedo issues from the rear tire being too far away from OEM size.

Thanks for bringing this up though. I think it gets people thinking about different aspects of tires they may not have thought of before. It pays to educate yourself before choosing big $$ tires for our cars. I can't tell you how many times I have seen car's on the forum with wrong sized tires that look horrible (too small), or complain about active handling issues after new tires.

Toque

Spreader

I've always used this link. Simple yet effective.

Miata Tire Calculator - Not Just For Miatas!

Toque

Yea that's a decent tire calculator too. I used to use that one a lot. THe one in my link in post #1 gives you much more comparison data though.

Thanks for the extra info !
Toque

FYRARMS

Agreed 100%. Nobody does their homework, and most wheel/tire "experts" are just vendors slinging products without really knowing what they are doing. Owners should educate themselves a little before making such an expensive investment!

My new setup will be done soon. 19x9.5 front 20x11.5 rear with 265/30R19 front 325/25R20 rears. No flares, no rubbing, no active handling issues. Just a lot of testing and proper offset selection...

Vetteman Jack

Outstanding info - saved it for reference.

StatmanRN

Should be a sticky.

Toque

TTT..... A lot of questions about this lately...


Toque

TXGS507

You guy's stop feeding Toque's EGO.... What does he know about nice wheels, tires...

JK Mark....