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Question: Auto X Tire/Wheel Combo for C7 Grand Sport

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Question: Auto X Tire/Wheel Combo for C7 Grand Sport

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Old 11-19-2017, 10:31 PM
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Nitro-C5
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Default Question: Auto X Tire/Wheel Combo for C7 Grand Sport

I did Auto X for 12 years with a few of my previous vettes, so I am relatively experienced. Just got a new GS and did an event recently. Car is all around great but the stock Pilot Sport tires are the week point. Thinking about going with either a set of C6 Grand Sport Wheels or something similar and running Hoosier A7 for the track.

Questions:

This seems like a pretty logical change so am I missing anything here? Will they fit the new GS without any fitment issues? Do I need spacers? Also given the fronts are 9.5" wide are the 275mm the widest I can fit on that rim?

Basically I'm asking who in here has done this upgrade/change for the track and what is our overall opinion and would you do it again?

Thanks
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Old 11-20-2017, 03:05 PM
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Anyone?
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Old 11-20-2017, 04:33 PM
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Default Gs

It's best to take the Michelin Cup2 ZP
Or you switch to 18 "and skill with slick
305 / 650x18 and 315/680

Michelin Cup2


Michelin Slick


Cölestin
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Old 11-20-2017, 07:55 PM
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Originally Posted by Nitro-C5 View Post
I did Auto X for 12 years with a few of my previous vettes, so I am relatively experienced. Just got a new GS and did an event recently. Car is all around great but the stock Pilot Sport tires are the week point. Thinking about going with either a set of C6 Grand Sport Wheels or something similar and running Hoosier A7 for the track.

Questions:

This seems like a pretty logical change so am I missing anything here? Will they fit the new GS without any fitment issues? Do I need spacers? Also given the fronts are 9.5" wide are the 275mm the widest I can fit on that rim?

Basically I'm asking who in here has done this upgrade/change for the track and what is our overall opinion and would you do it again?

Thanks
Are you looking to autocross or take the car to the track. Autocross you have the various class rules to figure out and where you want to run the car. For the track you can go with what is lower cost and more fun over the long haul.

For the track go with a set of 18x11 wheels in the front and 18x12 in the rear. You can also use 18x13 in the rear but they will touch the upper control arm when the car is off the ground so you can't torque the lugs down until the suspension is depressed. When I run the 18x13 I also add a rear .3 inch spacer which helps move the wheels out just a bit. They still touch the uca when the car is on the lift but it only takes a small depression in the suspension to clear the uca. This makes it a little easier to torque the wheels.

In front I use Hoosier A7, R7 in a 315/30/18 size or a Pirelli 305/645/18 slick. In the rear I use a 345/35/18 Hoosier A7, R7 or a 325/660/18 Pirelli slick. All of these tires can be purchased used so you can cut consumable costs. The other option is to go with the Z07 type Cup2 tires on stock rims. All of these tires provide about the same performance although some will last longer than others.

Like my Z06 if you run in an open autocross class using the 18 inch rims with Hoosiers you will more than likely eat up the competition. It was almost effortless to run a second faster than any other Corvette at an autocross I ran with the car. I had it setup for running Watkins Glen but couldn't pass up the chance to run against some old friends the weekend before. They were people who had very fast, well sorted non stock cars and had been autocrossing for many years.

Bill
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Old 11-20-2017, 08:16 PM
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Originally Posted by Bill Dearborn View Post
Are you looking to autocross or take the car to the track. Autocross you have the various class rules to figure out and where you want to run the car. For the track you can go with what is lower cost and more fun over the long haul.

For the track go with a set of 18x11 wheels in the front and 18x12 in the rear. You can also use 18x13 in the rear but they will touch the upper control arm when the car is off the ground so you can't torque the lugs down until the suspension is depressed. When I run the 18x13 I also add a rear .3 inch spacer which helps move the wheels out just a bit. They still touch the uca when the car is on the lift but it only takes a small depression in the suspension to clear the uca. This makes it a little easier to torque the wheels.

In front I use Hoosier A7, R7 in a 315/30/18 size or a Pirelli 305/645/18 slick. In the rear I use a 345/35/18 Hoosier A7, R7 or a 325/660/18 Pirelli slick. All of these tires can be purchased used so you can cut consumable costs. The other option is to go with the Z07 type Cup2 tires on stock rims. All of these tires provide about the same performance although some will last longer than others.

Like my Z06 if you run in an open autocross class using the 18 inch rims with Hoosiers you will more than likely eat up the competition. It was almost effortless to run a second faster than any other Corvette at an autocross I ran with the car. I had it setup for running Watkins Glen but couldn't pass up the chance to run against some old friends the weekend before. They were people who had very fast, well sorted non stock cars and had been autocrossing for many years.

Bill
Bill, thanks for the detailed response. I have owned several Corvettes that I modded to race.....BUT...I am doing my very best to just use this one (atleast for the first few years) doing Auto-X ~Once per month...we will see how long that lasts

My main thing I'm looking for is something very simple and cheap that I can just change at home and drive to the track (its only about 10 miles) so I would just change into the A7 at home and drive them. I was looking at the C6 GS/Z06 wheels as I understand that would fit....but I have now heard form a few people that they will not with the offsets and the tires will rub abit. I was purposely going with 275 in the front and 325 in the rear...which are 10mm smaller then the current tires I have but at the same time I don't really want them wider as then I will definitely have rocks/pebbles thrown up onto the paint. I would think that 275 and 325 would for the most part keep that under control.

I used to run 18 all the way around but now sure if will fit over the rear brakes. Also even though I'm not on a budget per say but I want to ease into this (this time anyway) and not go out and buy expensive custom wheels where I can get OEM used for ~$800 or so and A7 scrubs cheap.
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Old 11-20-2017, 08:19 PM
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Originally Posted by Bill Dearborn View Post
Are you looking to autocross or take the car to the track. Autocross you have the various class rules to figure out and where you want to run the car. For the track you can go with what is lower cost and more fun over the long haul.



Bill
Forgot to answer your other question. My first race I ran Super Stock Class (SS)....but then did and intake, tune, headers, x-Pipe and cats...so I now run Super Street Prepared (SSP) which allows race tires. I was only 1 second off another SSP car with A7's in the last race and I ran on the stock MPSS tires. On a 1:10 sec course I have better be able to pick up a few seconds with this new combo.
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Old 11-28-2017, 07:08 AM
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OP, have have a friend here in Virginia Beach who just bought a new Z06 and he is trying to sell the Michelin Cup tires. They should fit your wheels. He had them removed yesterday. They have less than 100 Miles on them. He also has them listed in the C7 For Sale forum. If your interested, send me a PM.
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Old 07-12-2018, 03:44 AM
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Originally Posted by Nitro-C5 View Post
I did Auto X for 12 years with a few of my previous vettes, so I am relatively experienced. Just got a new GS and did an event recently. Car is all around great but the stock Pilot Sport tires are the week point. Thinking about going with either a set of C6 Grand Sport Wheels or something similar and running Hoosier A7 for the track.

Questions:

This seems like a pretty logical change so am I missing anything here? Will they fit the new GS without any fitment issues? Do I need spacers? Also given the fronts are 9.5" wide are the 275mm the widest I can fit on that rim?

Basically I'm asking who in here has done this upgrade/change for the track and what is our overall opinion and would you do it again?

Thanks
I am in a similar situation, c7 z06 with ceramic rotors though, and I am looking for the fastest autocross tires.
I have a set of c6 z06 rims, but think i read the c6 fronts will not fit the c7 z07 fronts with ceramic brakes. Could i keep my stock c7 z07 front rims and put hoosiers on that and replace the c7 z07 rear rims with the c6 z06 rear rims?

According to hoosiertire.com, these are the 19 inch a7 options:

P235/35ZR19
P315/30ZR19
P325/30ZR19
P345/30ZR19

I was thinking of putting P315/30ZR19 on the stock c7 z07 19 inch front rims, but maybe those tires are too big for those rims?.
I was thinking of putting the P345/30ZR19 on c6 z06 rear rims.

Is this my best option for the highest performance for autocross? If i cant make the a7s work, i am guessing my 2nd best option would be re71r 305's all around.

thank you




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Old 07-12-2018, 10:27 AM
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Unfortunately, there isn't that many good option for autoxing with C7Z. If you want to stay in SS, you can run Cup 2s and it works well when it's hot. It won't work well when it's cold outside.

Some people run RE71R in 305/30/19 for all corners or 285/35/19 in front. I hear they don't have any issue on traction control but I'm not sure if they turn everything off completely.

If you want to step up to CAM-S, you can run BFGs but you gotta get 18s all the way around.
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Old 07-12-2018, 12:04 PM
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Originally Posted by Takoyaki View Post
Unfortunately, there isn't that many good option for autoxing with C7Z. If you want to stay in SS, you can run Cup 2s and it works well when it's hot. It won't work well when it's cold outside.

Some people run RE71R in 305/30/19 for all corners or 285/35/19 in front. I hear they don't have any issue on traction control but I'm not sure if they turn everything off completely.

If you want to step up to CAM-S, you can run BFGs but you gotta get 18s all the way around.

Thanks! So what is the problem with using the A7's as i described, is it the fronts that would be the problem like I guessed? thanks again!
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Old 07-12-2018, 12:27 PM
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Originally Posted by z8ra View Post
Thanks! So what is the problem with using the A7's as i described, is it the fronts that would be the problem like I guessed? thanks again!
Not sure about 315/30/19s in front. Lots of people run R7s in 315/30/18s without any issue. Compare the tire size against the stock one. 295/30/19 may be a safer choice.
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