What would be the 1/4 mile time difference between two equal cars, one with 245 front tires and one with 275 front tires? What about 60' since it'll be heavier up front with the 275?

 

I don't think there would be any noticeable difference between 245 and 275 fronts on most cars. Running higher air pressure in the fronts can reduce rolling resistance, though.

 

well my boss and i ran at the track and he has 956speed with 3.42 gears and i have a 97auto with 2.73 and he has 245/45/17 all the way around and i have 275/40/18 all the way around and i was 1 tenth quicker

 

Totally not able to compare.
You wanna know how much faster an orange rolls than an apple? Try it.

 

What are you talking about? This is definitely oranges vs. larger oranges. A wider tire will not only be heavier, but also create more friction and therefore, theoretically, slower times. I was just wondering if anyone knew how much this would affect a low 13 second street car. Since it would obviously affect a street car much less that say, a pro street dragster. Why else you think they run skinnies?

 

You've got two parts to the equation. First, there's rolling resistance. That's easy to "correct" for by raising the pressure to the point where there is only limited contact with the pavement. Second issue is rotating mass/inertia. The more the tire weighs and the farther the center of mass is from the spindle, the more energy its going to steal from the acceleration of the rear wheels as the front wheels spin up to speed.

The change in going to a wider tire, and not a larger diameter tire, would appear to be minimal. A wheel builder named Monocoque (now sold as Bogart) claimed an ET redution of 0.05 seconds with the 2 or 3 pounds saved with his wheels. Doesn't appear there's a lot of difference between a 245 and a 275. But put a true "skinny" on the front, reducing wheel+tire weight from 50# to 20# and you've saved a lot.

Not a "definitive" answer, but probably in the ball park.

 

There is more involved in the situation than different tires.

You have a larger contact patch.

IIRC, '97s are rated 10hp more than older LT1s. I don't know the specific reason why, but that could be related.

Traction might have been better in your lane.

Your boss may weigh more or less than you do. Similarly, his car may have different options than yours, creating even more weight difference.

Drivers vary. Just because Evan Smith pulled off a 12.7 or whatever in an LS1 Z28 doesn't mean anyone could do it, even in the very same car.

Cars vary. You could have two identically-equipped '97 Z28s, and run them down the same track side by side, and one might beat the other.

Last Fall, I went to the track and made 17 runs. Not counting runs where I botched the launch or a shift, or forgot to turn off traction control, my times ranged from 13.2 to 13.8. You need to make more than one run to really find out who has the faster car.

 

I think you posted in the wrong thread, lol. That's what I figured Injuneer, thanks for your expertise.

 

Nope, this is where I meant to post. Your question didn't match up with the situation, and I wanted to point that out.

Two similar cars run side-by-side down the track, and one beats another by 0.1 -- front tire width is only one of several things I'd credit for the win.

I just realized that post #3 wasn't made by the original poster.