How will you go faster?

[F-BIRD'88]

Uuum, no, lol. What comes first? The chicken or the egg? I reread what you said. Yes, if you cut .001 off your 60ft, it'll be .002 off your et. Half a tenth, is a tenth, etc etc. Go get your stack of time slips, err uhh, if you have any, and you'll see.

I have been drag racing for some 40+ years.

Then you know how the timing system works? Correct

me, yes. ,why?

[mt-engines]

Dick Miller, this guy isn't a nobody.

How many books has Warren Johnson written?

[David Redszus]

Dick Miller, this guy isn't a nobody.

How many books has Warren Johnson written?

What books has Warren Johnson read?

[David Redszus]

According to info in a book "How to hook and launch", a tenth at the 60' translates to nearly 3 tenths at the stripe.

To test the concept, I compared the same car but with different diameter rear tires.
The torque curve and gears were the same.

Tire size.........24".........25".........26"
Time 60ft.......3.501.......3.955......4.587s
Speed 60ft......40.66......39.10......37.27mph
G force 60ft....1.173.......1.125......1.080g
Time 1/4........9.013.......8.321......9.080s

The smallest tire (like a shorter gear) increased the G force, increased mph, with best 60 ft time.
But it did not produce the best quarter ET.

The largest tire (like a taller gear) reduced the G force, reduced mph, with worst 60 ft time.
It also did not produce the best quarter ET.

It becomes apparent that simple observations produce inaccurate results and that the
whole problem is more complicated than what meets the distant eye.

[digger]

According to info in a book "How to hook and launch", a tenth at the 60' translates to nearly 3 tenths at the stripe.

To test the concept, I compared the same car but with different diameter rear tires.
The torque curve and gears were the same.

Tire size.........24".........25".........26"
Time 60ft.......3.501.......3.955......4.587s
Speed 60ft......40.66......39.10......37.27mph
G force 60ft....1.173.......1.125......1.080g
Time 1/4........9.013.......8.321......9.080s

The smallest tire (like a shorter gear) increased the G force, increased mph, with best 60 ft time.
But it did not produce the best quarter ET.

The largest tire (like a taller gear) reduced the G force, reduced mph, with worst 60 ft time.
It also did not produce the best quarter ET.

It becomes apparent that simple observations produce inaccurate results and that the
whole problem is more complicated than what meets the distant eye.

David, the context is no actual changes other than the driver manages to launch it better producing a better 60ft

[In-Tech]

To test the concept, I compared the same car but with different diameter rear tires.
The torque curve and gears were the same.

Tire size.........24".........25".........26"
Time 60ft.......3.501.......3.955......4.587s
Speed 60ft......40.66......39.10......37.27mph
G force 60ft....1.173.......1.125......1.080g
Time 1/4........9.013.......8.321......9.080s

The smallest tire (like a shorter gear) increased the G force, increased mph, with best 60 ft time.
But it did not produce the best quarter ET.

The largest tire (like a taller gear) reduced the G force, reduced mph, with worst 60 ft time.
It also did not produce the best quarter ET.

It becomes apparent that simple observations produce inaccurate results and that the
whole problem is more complicated than what meets the distant eye.

Hi David,
Just following along but there is a huge discrepancy going on with the 25" tire "equation", no way a 1" tire change is worth 7 tenths compared to another inch tire change either direction unless that tire had almost no weight nor air resistance. In the boats, the prop diameter/pitch is the tire/gear and the gear is the gear, that's a whole 'nother conversation and still relative and super important. Sorry to diverge the thread into some boat stuff.

[Ishiftem]

I think all rules of thumb such as 100 pounds = a tenth, 4% increase in hp per point of compression, etc are all bullshit. Taking 100 pounds off a 4000 pound car won’t be the same as a 2000 pound car. A hundredth off the 60’ won’t equal the same gain on a 14 second car as it does on a pro mod in the 1/4. And the list goes on and on. It’s all application specific. For instance, what ever the variance in my 60’ is what my 1/4 time varies. I think the rules of thumb should be left to the bench racers along with stories of how they won thousands betting their passengers they couldn’t grab a Franklin off the dash in their 3/4 race cam equipped Camaro.

[Erland Cox]

How can a car with a 60 foot above 3.5 seconds be in the 9.s?

Erland.

[In-Tech]

I was never that slow, but when I used to race motorcycles with my El Camino, it was a given...if you didn't get me out of the hole, you were fackin beatin like you were on the brakes

[Rick!]

All these "what-if" can be tested in Quarter Pro, which came in the ST bundle a few years ago.
All the "air" related factors can be calculated using the "Motorsports Standard Atmosphere" and using the Correction Factor.
It's basically a modified version of J1349. A proper weather station is requisite to selecting your dial/timers, etc.
From the 660 on, it's all HP and aero, and hardly anyone works on aero. A typical 240" dragster is an aero brick with a wing and a few to several hundredths faster without one.
The convertor is one of the most effective means to go quicker. Launching on the torque peak is not essential nor the best way to 60ft.
Choosing the drop back rpm at shift is a better way to manage hp under the curve. Too low of drop back will lead to excessive slip on the big end.
It's nearly always easier to build in more power than it is to work on the other parts of the performance equation; mass (inertia resistance), rolling resistance, drag, etc.
In my brother's racing, it's all about how well you can go fast, meaning repeatability to within a handful of thousandths of ET. That, double O RT's and some luck bring home some cash.

[ChopperScott]

First time at the track with a new combo, my car ran 10.30’s. After addressing the carb, gear ratio (tire size), 4-link adjustment, coil-overs, launch control and shift point, the car is running 9.80’s. I think I can squeeze more out of it. Next two on the list are an air pan for cool air under the cowl, and improving aero. I will install a front spoiler, and remove the center section of the 3-piece rear spoiler.

[Stan Weiss]

Results from my simulations. Only change was tire size

Stan

30" tire
60 Foot ET = 1.6083
330 Foot ET = 4.6336
1/8 Mile ET = 7.2474
1/8 Mile MPH = 94.0067
1000 Foot ET = 9.5354
1/4 Mile ET = 11.4905
1/4 Mile MPH = 115.5863

28" tire
60 Foot ET = 1.5706
330 Foot ET = 4.5850
1/8 Mile ET = 7.1941
1/8 Mile MPH = 93.4902
1000 Foot ET = 9.4868
1/4 Mile ET = 11.4370
1/4 Mile MPH = 116.0249

26" tire
60 Foot ET = 1.5334
330 Foot ET = 4.5377
1/8 Mile ET = 7.1495
1/8 Mile MPH = 93.2735
1000 Foot ET = 9.4397
1/4 Mile ET = 11.3809
1/4 Mile MPH = 116.6076

24" tire hit Rev Limit before 1320 feet that shows most in 1/4 MPH
60 Foot ET = 1.4965
330 Foot ET = 4.4921
1/8 Mile ET = 7.1100
1/8 Mile MPH = 93.3690
1000 Foot ET = 9.3908
1/4 Mile ET = 11.3245
1/4 Mile MPH = 116.7470

[Mike Laws]

Stan,

Can you implement a gear change compensation for each size tire? The performance difference would increase even more with the smaller tires.

[rebelrouser]

Results from my simulations. Only change was tire size

Stan

30" tire
60 Foot ET = 1.6083
330 Foot ET = 4.6336
1/8 Mile ET = 7.2474
1/8 Mile MPH = 94.0067
1000 Foot ET = 9.5354
1/4 Mile ET = 11.4905
1/4 Mile MPH = 115.5863

28" tire
60 Foot ET = 1.5706
330 Foot ET = 4.5850
1/8 Mile ET = 7.1941
1/8 Mile MPH = 93.4902
1000 Foot ET = 9.4868
1/4 Mile ET = 11.4370
1/4 Mile MPH = 116.0249

26" tire
60 Foot ET = 1.5334
330 Foot ET = 4.5377
1/8 Mile ET = 7.1495
1/8 Mile MPH = 93.2735
1000 Foot ET = 9.4397
1/4 Mile ET = 11.3809
1/4 Mile MPH = 116.6076

24" tire hit Rev Limit before 1320 feet that shows most in 1/4 MPH
60 Foot ET = 1.4965
330 Foot ET = 4.4921
1/8 Mile ET = 7.1100
1/8 Mile MPH = 93.3690
1000 Foot ET = 9.3908
1/4 Mile ET = 11.3245
1/4 Mile MPH = 116.7470

Your simulations look reasonable. But if you are actually wanting to test just the diameter of the tire, shouldn't the gear ratio be changes to make the final to the tires ratio the same for all the tests? By changing tire size, you are changing gear ratio as well as the rolling distance of the tire. It is a little harder to pull a taller tire, so that extra loading can also affect how long the stator stays in torque multiplication phase. So, to really test a tire diameter change a manual trans would also have less variables.

[dannobee]

Mike's right, you need to "change" the rear gear to compensate for the taller tire. We all know that a taller tire acts like a taller gear, but that was not the point. We want to see if having a larger tire contact patch will help the car hook harder and lower the et, all else equal. The only way to do that is to compensate for the taller tire by changing to a lower rear gear.

Regarding rolling resistance: I started out drag racing years ago, then went circle track racing. Although miles apart, sometimes you end up in the same place. My well respected Super Stock friend asked me to help out fixing his bump steer (knowing that circle track guys are religious about setting bump steer). Got the bump steer down to within 0.010" and did a 4 wheel alignment on our latest greatest unit at work. Not only did the 60 ft improve, he said the car was now rock solid stable all the way down the track. No more sawing on the wheel as it went down the track. After the two Stock Eliminator guys across the street saw me fixing the bump steer on the Super Stocker, they were now on the bandwagon and wanted to know how to fix it without anyone knowing. There is 60ft improvement in just fixing the bump steer.

Funny thing was that both the less experienced drag racers and circle track racers ask the same question to the other type of racer, "Why do you need to check bump steer on a drag (circle track) car??" It's important in ALL forms of racing.