Dave-T

I have a bone stock 2015 Z51 and will most likely keep it that way. Wanted to put a set of drag radials on it for the track but wanted to keep the factory Z51 wheels. What wheel and which drag radial works best.

robz

I'd run a 245 drag radial.

Dave-T

Can you be more specific? Thanks

TorchZ51

I picked up a set of 19x10 replica Z51 wheels in black. They are an identical match to the factory wheel, just don’t have “Corvette” embossed on them. Haven’t bought tires yet, but will use either 285/35 Mickey Street SS or 305/30 Nitto NT05R. I went with 19s because the drag radials in a 19” are quite a bit less expensive than 20” size. Also a bit more side wall on the 19” tire is a good thing.

Mike Jesse

Good advice from Rob.

Hoosier 245/40/18 DR.

Don't hold me to it, but I think a C6 Z06 "FRONT" wheel may fit and clear everything. Lighter than the Racestar wheel.

bigsapper

I'd like to hear more about this!

robz

A 245 fits on a c6Z front rim which fits on a c7Z and c7 GS rear with regular brakes.

bigsapper

I'm confused now. Aren't we talking about a narrow body here?

Mike Jesse

A base C6 Stingray has an 8.5 x 18 front rim with an ET of 56 MM.
If I've done my math correctly, the tire will stick out 2 mm farther. Rim will stick out 3 mm farther. Perfect.


This should be the hot setup IMHO.

Rob can chime in with his thoughts.

bigsapper

Why would I give up a 285 on a 10.5" rim for a 245 on an 8.5" rim? Who took the the crazy pills today? Me?

smajicek

I am on the same thought as you. from 285 to 245? hmmmmm????

smajicek

I am on the same thought as you. from 285 to 245? hmmmmm????

YO-EL

Are you really gonna race the C7????!!!!!!!

Mike Jesse

Read and learn. For a stock or near stock powered C7 this works just fine.
Thanks Rob.

I copy and pasted this post from another thread for the fellas on here:

So I was able to actually test my theory of using a small drag radial on a c7 with the stock clutch.
I haven't been to a drag strip since 2014 and as mentioned above I have no experience with a c7. However, I felt that my experience in the c5 platform has provided me with enough knowledge to understand what it takes to launch a manual c7 successfully.
I had not planned to track my new c7 GS but after reading so many threads of people searching for the widest drag radial possible I felt I might have test out some theories so I could provide concrete evidence that a narrow drag radial might in fact be the best option for many c7 racers with a reasonable amount of HP.
Rewind to about 1 month ago, I was watching 2 new c7Z06 (M7) owners taking passes at the strip. The were both struggling on the launch. I was a little surprised to see that both had glazed their clutches with stock cup tires. This made me more convinced that a drag radial is just going to make this problem worse.
So eventually I caved in a bought a Hoosier drag radial and mounted in on my buddy's (Gary2004Z06) c6Z front rims and they cleared on the back of my GS despite all efforts not wanting to beat on this car.
I was able to sneak out today last minute to give them a try. I used the hour drive down to the track to get a feel for this car that I hadn't shifted over 5500rpms yet.

Test: Does a narrow drag radial, that most wouldn't even consider, have enough traction to provide a good enough launch and 60' with the stock clutch?

So here are the result. I say my theory is plausible based on only 2 passes.

2017 GS (bolt ons) ~430whp Mustang dyno
RW: 3535lbs
18" Hoosier (245 40 18) drag radials with Forgestars 18" skinnies
Atco, NJ test-n-tune

Launch 1: (first launch in years)
~4800 rpms
22.5 psi cold
touring mode
1.74 60'
perception: Some bog and stumble. A little too long on clutch and slightly too quick on throttle. Slight glaze of the clutch. Track prep was good.
On this shakedown pass the car ran 11.51 shifting around 6200/6300 if anyone cares.

Adjustments made and flushed in some fresh fluid via the "Ranger method". Fluid didn't look bad.

Launch 2:
4500rpms
25 psi warm
Sport mode
1.53 60'
perception: car felt good with a slight stumble/hop, released clutch quicker, and quick throttle squeeze. Slight glaze of the clutch.
Aborted pass due to hitting limiter on the 1-2

So there's the real world data. It's obvious to me that the small radial works and there is still more left in the 60'.

Conclusion: A narrow 245 drag radial with 25psi can hook well enough to propel a 3500lb c7 to a respectable 60'.
A wider tire would put even more strain on the stock clutch and the car in general and slow the car down IMO.

My goal is to provide knowledge through my experience to corvette drag racers so they can utilize the same parts and techniques I have without wasting valuable time and money.

bigsapper

So the context is an M7 trans?

Mike Jesse

My take away is if Rob can make that tire stick behind an M7 with mild performance upgrades, you should be able to hook it up behind an A8 with similar power output.
If I wasn't already committed to my new setup, I certainly would have tried it on a stock A8 Z06.

On a marginal track with little to no prep, might want the more forgiving wider setup.

Rob has lots of seat time with the smaller tire, and I'm listening.

383vett

Nice 60. What does "slight glaze of the clutch" mean?

Mike Jesse

I'm passing along this info from Rob.

He may chime in and add more info.

robz

Typically for drag racing you want lightweight stuff provided traction.
A smaller tire and rim combo can save a lot of weight and that's rotational mass which is even better.
So, if you can hook, it's best to go with a lightweight and narrow tire for best et and mph.
Plus having too big a tire is not only going to slow the car down it's going to put unnecessary wear/strain on the car. In addition, a smaller rim and tire is usually cheaper.

Hoosier drag radials, due to their construction(nylon belts?) are very light drag radial compared to the other quality brands.

I've always had success with smaller drag radials and was able to prove that a 245 drag radial is plenty of tire for a c7 grand sport making around 500whp @ 25 psi. In fact it was too much for the stock clutch and actually glazed it a bit.

Yes this is a stick car but the same applies for an auto car.
A stock c7 with a stock converter and ~410 whp doesn't need a wide tire. Why put unnecessary strain on the car and slow it down?
I've seen bracket racers, auto and stick, run similar tires with more hp with great success in the c5 and c6 platforms.
And, you can't compare a street tire to a quality drag radial; 2 different animals.
So, you can be open minded and make sense of all the above information and trust people who have experience, or you can believe that wider/bigger is always better and pursue fitting a 345 drag radial on the back and mini tub while you're at it.

Not so crazy,
Rob

bigsapper

Thanks! That all makes perfect sense.