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...

Bill Curlee

THANK YOU for some excellent tech info!:

Florida99

'Now, most people will want to know the other end of the scale - in other words, how much bigger can my rear tires be than my fronts?

And the magic number is [insert drum roll here] 94.2%'

While you correct what you are saying in the next sentence, that number cannot be 94.2%. That would mean the rear tire could be just slightly less than twice the size of the front
The rears number would be something like 10% larger than the fronts, not 94%. Shouldn't have cut math that day to go out street racing

lucky131969

I think with those ratios, it's not called a car anymore....it's a tractor.

c5vetteguy

I'd like to know where the magic number of 94.2% comes from...
Stock C5 tires have a 96% front to rear ratio.

SaberD

im curious as to where these numbers came from also.

2000BSME

Wut? Interesting bs. I run same size all the way around and haven't had problem one.

xtech

If you divide the front tire diameter by the back, you will end up with a number. Usually somewhere around 0.95, or 95%. If it makes you happier, subtract that number from 100% to get a smaller, apparently more believable number.

Some cars seem to be less restrictive than others for some unknown reason - as per 2000BSME. Some seem to get freaked out over similar sizes front & rear.

From my research, you will be safe with the numbers I suggest. Not to say some others won't work - but you're on your own in that case.

Personally, I don't have the funds to be buying tires and wheels that might work. I'd rather buy ones that will work.

It would be nice to hear from other members what sizes they have found to work without incident.

c5vetteguy

Soooooooooooooooo, the 94.2% comes from where, again?

lucky131969

Try a search. It's been discussed many times over the years.

lionelhutz

It's how you wrote it. You wrote - how much bigger can the back tires be compared to the front = 94.2%

So you posted that the back tires can be 94.2% larger. 100% larger is twice the diameter so 94.2% larger is almost twice the diameter. It's the way you wrote it, that's all.

So once again, how did you come up with 94.2%?

Peter

xtech

OK I suppose it's all in how you read it. If the front tires were the same size as the rears, then they would be ratio-wise 1.00:1 , or 100% (not 100% larger). If they were what I'm referring to as 95%, then they would be .95:1. For example - if the rears were 26.5" in diameter, then the fronts would be .95 x 26.5" = 25.2" (or 25.175 to be fussy) in diameter.

If something is 95% the size of something else, then it's .95 times the size. If it's 95% bigger, then that could be a problem. At least when it comes to C5 wheel stagger, that is. You'll need some pretty big tubs to fit 95% bigger diameter tires on the back. Unless you're using hand truck wheels on the front, that is.

Just ignore the % signs and multiply (or divide) by .99 or .942 to get the minimum and maximum staggers (that will work for sure). As some other members have noted, apparently some cars can tolerate no stagger at all - but I know for a fact that some cars aren't happy with this. Maybe some GM engineer will enlighten us as to why this is.

Personally, I think that, regardless of whether it works or not, a car with no stagger would look a bit strange, as the wheelwells are different sizes.

For some road race / autocross applications, this probably isn't a big deal. But for street, I'd still stick with what the factory intended - which seems to be between .942:1 to .98:1 stagger. With no 'percent signs' to mess things up...

As far as were .942 came from, this is the most stagger that I have seen reported that has worked on more than 3 cars. I discount single car exceptions - mostly due to the "2000BSME factor" - just because it worked on one car, doesn't necessarily seem to mean that it will work on every car. I arbitrarily decided that 3 cars would be enough, as there doesn't seem to be that many people reporting their results online.

Why you would want more stagger than this I'm not sure, as the car would start to look like it had go kart wheels on the front and wagon wheels on the back if it were much more than .942.

Please note that if you religiously turn off your traction control every time you drive anywhere, you can probably run any stagger you want with no ill effects.

If you either don't want to or don't remember to turn it off at every startup, then I suggest that you go by the .942 - .98 rule. Then you won't have to worry about it.

NOTE - original post has been revised slightly to clarify any misunderstandings.

rick4grafx

Question, I am currently running 305/30/19s on the rear, and 275/35/18's on the fronts.

Can I increase my rear height to 305/40/19's without a problem? Or even 305/45/19's??

lionelhutz

Now your post is saying the fronts can be 94.2% smaller than the rears. That's some small front tires.

lucky131969

FSTFRC

Nice Corvette Lucky, do you drive it daily?

xtech

Are you really that dull, or are you just being obtuse? I said to ignore the damn % signs and multiply by .942 - or whatever other number makes you happy. You can multiply by 50 for all I care.

Is it really that difficult? Gad.

Nice tractor, by the way. If you want to run that rubber on your C5, you might want to turn off the traction control.

Just a suggestion.

vickvette

I can't believe this. how come u don't understand the percentage?
if something is 20% size of something else, it means it's 5 times smaller.
if something is 94.2% smaller, it's 94.2 centimeters of 100 centimeters.
If you have a front tire and want to know how large the rear can be, just divide it by 94.2 and multiply by 100. and u get the rear tire. don't blame others and don't give them a hard time if you don't understand the simple 2nd grade math, please.

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.

vickvette

my bad, I meant it's 94.2% of the size of the one u r looking at in this case the rear tire. Thanks Florida99. my fingers type faster than my brain works lol