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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.
Last edited by robz; Nov 12, 2017 at 06:58 PM.
I picked the Hoosier 315/30R18 as the starting point for my A8 Z06.
The stock 335/25R20 will dead hook with enough heat put into them from the burnout. The tire won't last long doing it though.
I hope the Hoosier will dead hook with a quick burnout and a higher PSI.
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.
I am trying to create a decent high 1.7's 60 foot on the OE 285 30 20 pilot super sport with 25 psi warm and cannot get there. BTW, your tire size is 25.7 inches tall, that's 1 inch shorter than my OE size of 26.7 inches , providing a little gear ratio advantage. 1 Inch short is about 100 rpm higher in any gear. Also 11.50 pass in a base, Z51, or GS fantastic, with skinnies and some small bolt on mods.
Last edited by BJ67; Nov 12, 2017 at 07:36 PM.
I am trying to create a decent high 1.7's 60 foot on the OE 285 30 20 pilot super sport with 25 psi warm and cannot get there. BTW, your tire size is 25.7 inches tall, that's 1 inch shorter than my OE size of 26.7 inches , providing a little gear ratio advantage. 1 Inch short is about 100 rpm higher in any gear. Also 11.50 pass in a base, Z51, or GS fantastic, with skinnies and some small bolt on mods.
This can often hurt your et downtrack or sometimes end your pass.
Last edited by BJ67; Nov 12, 2017 at 08:13 PM.
























