Will the 20x11 Z06 Motorsport wheel stick out past the fenderwheel? I am about to pull the trigger on the 19x9.5 and 20x11 tomorrow. It was recommended to use 285/30/20 and 265/30/19. Can you go bigger on the rears?

 

I had the 20x11's with 305/25/20s and they fit perfect. Wish I wouldn't have sold them. post your email and I will see If I can find some pics of mine and send them your way.

 

Cool thanks.

james@topazappraisal.com

 

Can you send me pics too if you find them? I have the 19x9.5's and 20x11's, but i havent bought tires yet. I am considering the continental conti sport contact 2. what brand tires did you have? TIA.

Tim
TSL812@aol.com

 

I have the same wheels with conti sport contact2 tires and 275 at the front and 305 at the rear.
They fit perfect.

 

I been thinking of buying just a pair of 20's for the rear, have 18 on front already.Can you send me pics? Do you know what your back spacings are?

 

I been thinking of buying just a pair of 20's for the rear, have 18 on front already.Can you send me pics? Do you know what your back spacings are?

 

Sorry fellas, I forgot I had to reformat my PC a couple weeks ago and the pics are gone. I got my 20/19 combo from Nate at CorvetteGarage so you might want to call him about the backspacing. The rear wheels fit perfect, that was one of the things I was concerned about also before I got them, I hate it when the wheel sticks out past the fender. The continental tires were the only ones I could find in the 305/25/20 size for the back.

 

Definately do not get the 285's on the rear.

I just got my 20\11 and 19\9.5's and the 285 was thinner than the 11 inch rim.
If I would have mounted them the rim would stick out farther than the tire. Ghetto....

I went with the Conti's 305-25-20 and 275-30-19.
They fit perfect. They are flush to the body of the car.
If I could do it over I would have gotten 315's for the rear... but 305's are fine...

Kid

 

I have the 20x11 wheels on mine with the Conti 305/25/20 tire. They are a little thin for my tastes (not enough sidewall). When I burn through these rears (which should be fast the way that I drive) I am thinking about going to the 295/40/20 size. There's much more tire selection in that size and it would definitely offer more sidewall than the 305/25 would. The only thing is I am unsure of fitment -- I may have to raise my otherwise lowered Vette to get things to fit without rubbing.

 

I was thinking about the 295/40/20 size also, but in the wheels section, I was told I would have problems. DIYNOOB, if you go with this size, will you stay with the same front? Anyone else using this size rear? I am not currently lowered either. I have the Z51 package and was just going to go as low as the bolts will take it, which I assume is about an inch.

 

Going with this size tire "40" will cause problems with you traction control and active handling. You want to keep the tire dimension as close to stock as possible.
With a 20" rim the lower profile tires is about the same height as the stock tire size.
A 20" with a "40" on it will definately be a problem.

 

I thought as long as you maintain the 1" dif. fornt to rear you were cool with the active handling.

 

I thought as long as you maintain the 1" dif. front to rear you were cool with the active handling.

 

You can reprogram your tire size in LS1Edit. I'm not sure if that's only for the speedo or if it also helps AH.

How can you be so certain that going from 305/25/20 to 295/40/20 will cause a problem?

 

[QUOTE=diynoob]You can reprogram your tire size in LS1Edit. I'm not sure if that's only for the speedo or if it also helps AH.

Ugh - here we go again. I learned the hard way on this one.

LS1 edit will not touch a TC/AH issue as the edit program only deals with the PCM. The TC/AH system has its own computer that talks with the PCM but as best I know, no one is able to get at the TC/AH brain to adjust anything.
Tire size parameters seem to be a year dependant thing, as Cheby will go in and change computer settings from year to year. Seems that most guys have to maintain that 1" variance in height, but other guys have gone way less and not had an issue.
I can only assume that GM has locked out the TC/AH 'puter for liability reasons and no one has cracked the code or even which year VS which tire size formula. This issue has kicked some dealer's ***** as well. Looks like GM is not giving up this data to anyone.

 

Thanks for the info pinot, this is good to know. Does the TC/AH issue occur when there is too much difference in tire size or not enough difference in tire size?

 

Not enough.

I am the Brainiac who installed tires that are taller in front than in the back! TC just loves this................. Sometimes for fun I take my car,using F1's, out in the rain with TC/AH off just to pratice my skidpad technique.
Oh well, I could just replace tires with proper size of GS D3's, but wait ...............they're not made in Zo6 sizes.

I am just silly enough to hope that someone will find a work around for this.

Pinot

 

Here's a copy of my post on "Tire Help" elsewhere in this forum:

<The tread should be approximately an inch wider than the wheel. 245 divided by 25.4mm is 9.64" on a stock 8.5" rim. Likewise a 275 is 10.83" on a 9.5 inch rim. If you're going to use Z06 rims you need at least the stock Z06 tire sizes. You can go that far without any adverse affects but you won't be getting optimum performance. You can use the Z06 tire sizes on your coupe without any problems to your speedometer too. According to my calculations the Z06 rear tire is less than 2% smaller diameter. This means that when your speedometer reads 50, you'll really be going 49, or 98 when it says 100 etc.

Tire sizes are numbered in millimeters. A 275/40 is 275mm wide. The 40 means the height is 40% of the width. In this case, 275/25.4 is 10.83" wide x .40 is 4.33" tall x 2 + 18" rim = a tire diameter of 26.66". The Z06 is 295/25.4 =11.61" x .35 = 4.06" tall x 2 + 18" rim = a tire diameter of 26.13". Finally 26.13/26.66 = .98012 - 1 = 1.988%>

Therefore a 295/40/20 ends up being almost 10% or 3" taller than the stock tire. You may have problems fitting it in the wheel well and in my opinion will not only screw with your speedometer but probably your active handling and traction control as well.

 

What is the best place to find the 305-25-20? Tire Rack? Hoping to get mine this weekend.

Tim