Originally Posted by Florida99

Perhaps some should read what they write and think about it just for a second before posting. 'if something is 94.2% smaller, it's 94.2 centimeters of 100 centimeters' First of all what is with the cm? Secondly, if something is 94.2% smaller than something else it is NOT : 94.2 of 100. That answer would be 5.8% of the original

Let's try it this way. I have a 100' tall building. You have a building that is 94.2% smaller than mine. Do you still think yours is 94.2 of 100? No, of course not. Yours is 5.8' or 5.8% or the original size.

Originally Posted by Bill Dearborn

I think it depends on the individual EBCM to some degree. While tracking my two C5s (a 97 and an 03Z) I used 25.3 inch diameter tires front and rear. This did not disturb the TC on either car. I usually turned it off when heading onto the track but sometimes forgot and would do several laps before I realized I had forgotten it. Other people running the same tires could not get away with that. As soon as they started moving the system would activate.

I also ran the 18x10.5 Z06 rims on front and rear with no issues other than rubbing my DRM brake ducts. I ran the same tire size on all these rims so I could rotate tires front to rear and side to side to even out wear.

Bill

Originally Posted by xtech

For all of you guys/gals that have a different concept than that of the General of what tires you think should be on your vehicle ...

As you are probably (or should be) aware of, MOST C5's (and C6's) require a 'stagger' in tire diameters from front to rear.

After much research (and personal experience) I have found that the MINIMUM stagger before tripping the TCS/AHS is .99. That means that the front tires can be .99 of the diameter of the rear tires, and you'll still be OK.

PLEASE NOTE that this is AFTER tire wear, and assumes that you've totally decimated the rear tires (down to below the tread bars), but still like the concept of going around corners, so you've installed brand new tires on the front.

Not a great idea, but fun in the rain. Just don't drive over about 60MPH (in the rain) unless your insurance is paid up.

Now, assuming you've installed brand new tires on the back too, your minimum stagger must be .98. You might run into some TCS/AHS issues if you run the rears down to the tread bars in this situation, so you'd be better with .975.

Now, most people will want to know the other end of the scale - how much smaller can my front tires be than my rears?

And the magic number is .942 x the diameter of the rears.

You can either multiply the diameter of the rear tires by .942 to get the my RECOMMENDED diameter of the fronts, or divide the front diameter by .942 to get the maximum diameter of the rears.

SO - you CAN run 345-30-19's on the back with 275-35-18's on the front without issues. This is at the upper limits however, and you may run into issues if you trash the front tires and then put on brand new rear ones.

If you want to max out, I would recommend that you go with either the stock C6 Z06 sizes of 325-30-19 / 275-35-18 or a max of 335-30-19 / 275-35-18's.

Of course to do this will require either Lingenfelter mini-tubs and custom wheels or L5 or ACS or ... rear fenders with stock C6 Z06 wheels. L5 rear fenders with stock C6 Z06 (19x12) wheels need 5/8" hub-centric spacers to look absolutely correct, but they're OK without them.

I would go the fender route, as you can just bolt them on without trashing your car, and that route is way cheaper too, as you can use stock wheels / tire sizes.

If you don't want to do either, you can run stock 18x9.5" rims all way around with 265-35-18's or 275-35-18's on the front (this will clear C6 Z51 brakes with any style rim, or C6 Z06 brakes with STOCK ALUMINUM C5 skinny/flat spokes ONLY - barely - with a 1/4" spacer) and either 295-35-18's or 285-40-18's or 275-40-18's on the back.

I haven't tried fitting the C5 Z06 rear rims on the front, but I doubt they would work very well, if at all.

275-35-18's on stock 9.5" (rear) rims fit on the front and look great with no rubbing issues at all.

Running 295's on 9.5" rims is technically not quite right, but I won't tell anyone if you don't.

Hope you're not too "tired" after reading all of this...

Originally Posted by arrie

First vette owner and newbie here....for the completely ignorant (me) and not to beat a dead horse, I get the ratio thing, but am wondering how to interpret the 285/40/18 thing. I assume the "18" is width? I can only assume the "40" is diameter? What is the 285 and correct my incorrect assumptions please. I need new tires, did want to bump up a size but I don't even know what is on there....I assume stock C6 wheels and tires???? Any layman's info would be greatly appreciated (sorry all, Im in a wicked learning curve but want to learn....)

Originally Posted by 65GGvert

Simplify the whole thing and make your rear tires 1" larger in diameter than the front. Or no more than 1 1/2" nor less than 1/2". Then you don't have to have a slide rule or calculator to buy tires.