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Discussion Starter · #1 ·
I'm still struggling with which wheels to get, and came up with the following:

Stock:
Front: 265/40-17
265*.40=106
106/25.4=4.17"
Total (wheel+(sidewall*2)=25.34"

Rear: 295/35-18
295*.35=103.25
103.25/25.4=4.06"
Total (wheel+(sidewall*2)=26.12"

Upgrade (265 front):
Front: 265/40ZR17
265*.40=106
106/25.4=4.17"
Total (wheel+(sidewall*2)=25.34"

Rear: 315/30ZR18
315*.30=94.5
94.5/25.4=3.72"
Total (wheel+(sidewall*2)=25.44"

as you can see, the ratio of height from front to back is only .1" difference

Upgrade (275 front):
Front: 275/40ZR17
275*.40=110
110/25.4=4.33
Total (wheel+(sidewall*2)=26.66

Rear: 315/30ZR18
315*.30=94.5
94.5/25.4=3.72"
Total (wheel+(sidewall*2)=25.44"

In this case, it would appear that the front tires/wheels are larger than the rears, which would make me think that it looks funny. Anyone have any pictures to look at/comparisons to make? I know that more rubber is generally a good thing for handling, but does the size difference throw things off? Is 275/40 front and 315/30 rear a problem, or am I getting concerned over a whole lot of nothing? TIA. :cheers:
 

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Do not go with larger fronts.
AH will kick in. I know some one that did this and AH kicked in at a high speed and spun him out. Lucky for him he was in the country and he only wound up in a field.
 

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I have the 275/40/17 up front and have had no problems. This includes a 170mph romp on Sunday.

Don't hesitate to go with the bigger front tire. Maybe someone else will chime in, but like I said no problems here.
 

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z06_23_45 said:
I have the 275/40/17 up front and have had no problems. This includes a 170mph romp on Sunday.

Don't hesitate to go with the bigger front tire. Maybe someone else will chime in, but like I said no problems here.
Are you running 315s on the back which are a 1/2" shorter than the stock 295s?

I just noticed that he has the 275s listed at 26.66 in diam.
Looking on tire rack they are 25.7.
 

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Discussion Starter · #7 ·
FRC Tom said:
Are you running 315s on the back which are a 1/2" shorter than the stock 295s?

I just noticed that he has the 275s listed at 26.66 in diam.
Looking on tire rack they are 25.7.
It's possible my math is wrong, I'm still trying to learn all this. The tires are Michelin Sport PS2's. I know some folks have mentioned that a 315 isn't the same on all wheels, so I called Michelin direct and confirmed that size on the rear... I have to be honest, I have heard (on 3 different forums) so many different answers I just don't know what to believe. For every warning about traction control, I have a post saying they actually run them with no problems. I don't know which to believe. I'm almost to the point of giving up on the whole thing. :screwy:

I think I'm going to call Michelin again on Monday to follow up on the 265 vs. 275 discussion. Sigh. :bang:
 

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Discussion Starter · #8 ·
I just did the tire rack comparison, and yeah it looks like my math is wrong. According to their chart it would appear that the 275's are 25.6" in diameter while the 315's are 25.5". Given that, those numbers seem a LOT better than the numbers I came up with on my own and seem to me at least to lend credence to the argument that 275/315's will work fine...
 

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FRC Tom said:
Are you running 315s on the back which are a 1/2" shorter than the stock 295s?

I just noticed that he has the 275s listed at 26.66 in diam.
Looking on tire rack they are 25.7.

No, actually I still have 295's in the back. I didn't really pay attention to that part. My bad. :crazy:
 

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Click my Sig, and at the bottom of the page that opens up, there's a link for the tire size calculation spreadsheet. It's got some example Corvette rim/tire size combinations, and room for you to enter your own so you can do comparisons. It tells you the percent change in the "stagger" for the sizes you specify, and highlights in red if the change is above 2%, which is the "danger zone" for AH/TC issues.

I'm running 315/30-18s in the back and 285/30-18s on the front.
 

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I run 305/35-18 on the back and 275/40-17 on the front. No issues whatsoever. But I agree with the others... a 315/30-18 is shorter than stock, so there would be absolutely no reason to run anything other than the 265/40-17 on the front, IMHO.
 

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Discussion Starter · #12 ·
WA 2 FST said:
I run 305/35-18 on the back and 275/40-17 on the front. No issues whatsoever. But I agree with the others... a 315/30-18 is shorter than stock, so there would be absolutely no reason to run anything other than the 265/40-17 on the front, IMHO.
What manufacturer? When I put 305/35-18 in at tire rack, I get no matching tires.
 

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prospero63 said:
I just did the tire rack comparison, and yeah it looks like my math is wrong. According to their chart it would appear that the 275's are 25.6" in diameter while the 315's are 25.5". Given that, those numbers seem a LOT better than the numbers I came up with on my own and seem to me at least to lend credence to the argument that 275/315's will work fine...
Prospero63,

I have seen this on several Z06's and the owners had no complaints. It seems to work fine and is the way I was going next time as well. You will have to jump in and try it or stick with stock sizes for the sure thing.

Nice pissing contest you have going on over at CF.
 

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Discussion Starter · #16 ·
dwjZ06 said:
Prospero63,

I have seen this on several Z06's and the owners had no complaints. It seems to work fine and is the way I was going next time as well. You will have to jump in and try it or stick with stock sizes for the sure thing.

Nice pissing contest you have going on over at CF.
Heh, yeah that one wasn't my fault though. You should see the PM's Chuck (or whatever, no solofast the other one) sent me. To be honest, I'm a little disconcerted about the information I've received. It seems to come down to two camps:

1) People who actually run the tires and say it works fine
2) People who don't run the tires, never ran the tires, but say it won't work

Unfortunately, I really don't feel like I'm any better informed than I was when I started (well, I now know how sizes are calculated and can do that in my sleep, but...). I'm probably going to call Michelin tomorrow and barring them saying "no, bad idea" I'm going to go with the 275/315 combination and see how it works. If it sucks, I'll be the first to post about it. If they work great, I'll be sure to post that too in hopes that others don't have as much pain with this as I have.
 

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On my ZO6 I run 275/40/17 on the front, 305/35/18's on the rear BFG KDW's front DR"s on the rear no problems
 

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prospero63 said:
What manufacturer? When I put 305/35-18 in at tire rack, I get no matching tires.
Not available through Tirerack!

Nitto 555R2's;

305/35/18 & 275/40/17

Used them at the Fest for Nashville HPDE, AutoX, Maker's Mark, and the Drags. Worked great !!!

Steve
 

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prospero63 said:
Heh, yeah that one wasn't my fault though. You should see the PM's Chuck (or whatever, no solofast the other one) sent me. To be honest, I'm a little disconcerted about the information I've received. It seems to come down to two camps:

1) People who actually run the tires and say it works fine
2) People who don't run the tires, never ran the tires, but say it won't work

Unfortunately, I really don't feel like I'm any better informed than I was when I started (well, I now know how sizes are calculated and can do that in my sleep, but...). I'm probably going to call Michelin tomorrow and barring them saying "no, bad idea" I'm going to go with the 275/315 combination and see how it works. If it sucks, I'll be the first to post about it. If they work great, I'll be sure to post that too in hopes that others don't have as much pain with this as I have.
I don't think there is any question at all that it will fit on the stock wheels. The only question is if you will get any rub or traction control/active handling issues. I have not heard of any from the guys I have talked to that run them, but they do not race on these tires either. As said earlier as long as you stay very close to the stock OD you should not have problems. Shoot me a pm if you go this route and how it all works fits. Don
 

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Discussion Starter · #20 ·
dwjZ06 said:
I don't think there is any question at all that it will fit on the stock wheels. The only question is if you will get any rub or traction control/active handling issues. I have not heard of any from the guys I have talked to that run them, but they do not race on these tires either. As said earlier as long as you stay very close to the stock OD you should not have problems. Shoot me a pm if you go this route and how it all works fits. Don
Will do. Just to clarify, I don't race my Z06. Still owe too much on it to risk the insurance loss :mah: I will drive... agressive from time to time (open Texas back country roads), but those are few and far between (and seem to get fewer and farther...). I'll definately post the results for the forum. I appreciate all the advice I got (and in particular am impressed that unlike on other forums, this thread didn't become a pissing contest). :z:
 
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