halokiller

I'm planning on shifting my 6 speed c5 with stock 3.42 gears and a 416 stroker at 6800-7000rpm and was wondering if it is more efficient to run a 28" tire and run to the top of 3rd gear or run a 26" tire and shift into 4th right before the traps. Will I lose a lot on the 60' because of my stock gearing with the 28" tires?

C5 Pete

My vote is to run the 26" tire.

Drewstein

If you're sure you can make it through in 3rd then run the 28" tire. You shouldn't loose 60' because you'll have more traction and you can make up for it in launch RPM.

smokinstorm

If you shifting is really bad, go with the 28" tall tire so you don't have to make that extra shift. If not, the effective gear ratio change and slightly lighter weight from the 26" will be beneficial.

GARY2004Z06

You would be best served with a 26" tire to maintain your current effective gear ratio. The correct tire will provide you with a better 60' and get you to your powerband quicker. (26s can produce 1.4 60s with your current gearing.) In the future, you should strongly consider a gear swap. Our cars with a 4.10 ring and pinion perform exceedingly well in a N/A setup. This is with both 26" and 28" tires. Tire height would be dictated by trap speed and rpm.

Drewstein

I've done 1.4s with 3.25 gearing on 28s and a friend of mine does 1.3s with 30" tires on f-bodys with 3.42s. Gearing != 60' without considering power.

OP, what's your current power and splits at the track? Maybe we can stop guessing and help you a little more.

halokiller

The car is currently making 450rwhp with a small cam 416 stroker, shorty headers, and a FAST 78mm intake. I am building it right now with a larger cam, long tube headers, and a fast 102 setup and hoping for around 500rwhp. I've never had it at the track yet because I need to buy drag radials first so I was contemplating 28" tires instead of spending the money twice

GARY2004Z06

I am just trying to compare apples to apples for the OP based on experience. All of the N/A Vettes with manual transmissions that we have ran or help design have benefited from a gear change. It gives you torque multiplication off of the line and will place you in a better rpm range at the end.

GARY2004Z06

A DR is much harder on parts than a bias ply tire with a manual trans. If you plan on street driving, then a DR with some tread (grooves) is a good choice but if you wish maximize your 60' and minimize the potential for breakage, a bias ply tire is the better way to go. Great 60's can be done with both tires; however, DRs can tend to wheelhop more when aggressive. With our setup, I attempted to use a 295/50R16 DR. This is a 28" tall tire which has great traction but is very stiff. Out of 7 passes, we broke (2) CV axles. We went back to other proven combinations.
Here are different combos that work:

315/35R17 Hoosier DR
1.44

255/50R16 Hoosier DR
1.45

26x12x16 Bias Ply M&H Slick
Three consecutive passes made with 1.41, 1.35, 1.38 60's, respectively.

26x11.50x16 Bias Ply MT ET Street
Pass #3- 1.40

28x11.50x16 Bias Ply Hoosier QTP
1.38

halokiller

Thanks for the response! Will the Hoosier dr be less violent on the driveline than other radials?

GARY2004Z06

Not really. Hoosiers do have a thinner sidewall but are extremely sticky. On a very tight track, they tend to hit hard when attempting to rotate the earth.

smokinstorm

The Hoosier drag radials are also extremely light which helps with both ET and MPH. And yes, they're sticky.

Turbo-Geist

Nice, job on documenting all of those different tires for drag racing. It very obvious to see how much better the car accelerates and carries forward momentum off the line using the bias ply tires. What clutch and flywheel is in the car Gary?

GARY2004Z06

Thanks. We try to provide real world results to help out where we can.
We have ran the RPS BC2 with an aluminum flywheel from the start once we began the mod process. It has seen some R&D along the way to enhance its already great performance. A new iteration is in the works for the most recent round of mods.

wotbluez06

What does it take to fit a 28"tall slick on a c6z ? Close to stock ride height. 28/10/17 Hoosier on a 17x11 wheel. How much will that tire grow at 145mph.

Gxpz06

Captain huff and Gary are experts and successful so I agree yet for slower shifters like myself and with M12 trans at that power level actually staying at top of 3rd would benefit ; I lose 3 tenths shifting into 4th in my set up and my self ; this will actually edge out for bracket racing especially in warmer days ; in lower elevatiom lower DA for personal best I would lean towards smaller tire and let 4th spread;

If it's mm6 trans and you can shift well into 4th( these 2 things go hand in hand with powerband/shift point) then 26" tire for sure ; assuming shift point at 7000

Gxpz06

I too want to know

C5 Pete

Pull the liner out and a 28" slick will fit.

According to M/T tech, a 28" slick will grow to 29.5" at 150MPH.

The issue with a C6Z is the rear end gear ratio. Unless you're making a boatload of power, a 26" tire is likely best due to the gearing advantage.

Have fun with your goals!

wotbluez06

Thanks for the info. I'm at about 725whp. But 17" slick sizes are unfortunately very limited. I'll be giving them a try this season.

GARY2004Z06

I had no issues with the Hoosier 28x11.50x16 QTPs on a 10.5" wide Bogart.