How will you go faster?

[n2omike]

Yes. On a well prepped surface, the radials ARE that much better.

Tire performance is another bag of worms.
A tire is a gear, an air spring that changes with pressure, and comes with various compounds that change with temperature.

A lot of time and money has been spent testing tires. And the job is far from finished.

Radials also offer less rolling resistance.
Most cars MPH better with radials.
Radials feel much more stable than slicks going down track.
Radials need to dead hook.

Slicks work better on marginal surfaces.
Slicks recover better if they start to spin.

If traction is not an issue, the vast majority of cars will be quicker/faster on radials.

'Radial Prep' is a real term. It is a term referring to a 'fly paper' track that Radial cars can set records on.
Many cars on slicks have a hard time on tracks with this amount of prep, as the track in set up to Dead Hook... with a radial... even with super high hp cars. (Tire shake/wadding up, chatter, etc)

[skinny z]

Yes. On a well prepped surface, the radials ARE that much better.

Tire performance is another bag of worms.
A tire is a gear, an air spring that changes with pressure, and comes with various compounds that change with temperature.

A lot of time and money has been spent testing tires. And the job is far from finished.

Radials also offer less rolling resistance.
Most cars MPH better with radials.
Radials feel much more stable than slicks going down track.
Radials need to dead hook.

Slicks work better on marginal surfaces.
Slicks recover better if they start to spin.

If traction is not an issue, the vast majority of cars will be quicker/faster on radials.

'Radial Prep' is a real term. It is a term referring to a 'fly paper' track that Radial cars can set records on.
Many cars on slicks have a hard time on tracks with this amount of prep, as the track in set up to Dead Hook... with a radial... even with super high hp cars. (Tire shake/wadding up, chatter, etc)

It will be nice if this is the case as another move for next season is to replace the very old ET Streets with new MT drag radials.
Given the information above, I can only hope that the track prep is good enough on test and tune nights. There are some heavy hitters there but it's a crapshoot as to whether they glue the track or not.

[frnkeore]

The way I look at it, in any type of racing, is that you need to optimize the amount of power you have available, in the distance you run, that includes a lap, in closed circuits.

In drag racing you need to over rev, 3 to ~600 rpm at the stripe so, it's all about gearing and C/F. Run the biggest (width & dia), stickious tire that the rules allow or that will fit in the wheel well. What ever trans you use, gear the final drive, to over rev at the light.

A progressively geared trans helps, too. As speed increases, air resistance, in creases by 8X, when you double the speed. It's really noticeable, above, about 80 mph. At lower mph, you have lots of gear reduction that creates tq so, a wider 1-2 shift, isn't as important as the hp/tq curve for the 3-4 shift.

If you are tire limited and have to much tq for the tire, then it's up to the driver to learn how to peddle it, for best results.

[1980RS]

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

Erland
We have to consider the effects of all gears used.

The posted results were determined using a specific vehicle torque curve, gear sets,
rear end ratio, weight, air density, aero and rolling resistance.

It did not include the effects of a torque converter. The results are for relative comparison and
not expected to be completely accurate.

A tire size is a gear, and a smaller tire is a shorter gear. But too short is not helpful. Neither is a gear
that is too tall.

But if you make a lot more torque you will need less rear gear.

[289nate]

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

Erland
We have to consider the effects of all gears used.

The posted results were determined using a specific vehicle torque curve, gear sets,
rear end ratio, weight, air density, aero and rolling resistance.

It did not include the effects of a torque converter. The results are for relative comparison and
not expected to be completely accurate.

A tire size is a gear, and a smaller tire is a shorter gear. But too short is not helpful. Neither is a gear
that is too tall.

But if you make a lot more torque you will need less rear gear.

No. It still depends on the power band of the engine. Assuming everything hooks up and goes right. With an automatic the converter and transmission have to work right too. Having said that, your typical “torque build” will be operating at a lower rpm range.

[steve cowan]

I think torque is still important if your rpm limit is fixed at X limit.
You still have to have a certain number on torque to make the desired hp.
Even past peak torque/VE when torque goes down it is still relative I believe.

[Bigchief632]

I think torque is still important if your rpm limit is fixed at X limit.
You still have to have a certain number on torque to make the desired hp.
Even past peak torque/VE when torque goes down it is still relative I believe.

Yes, I'd agree. But, you have to look at what RPM the TQ is being made at. Meaning, at 5250, it crosses over. TQ is relative. If you make 4000hp at 900 rpm like a locomotive diesel engine, peak TQ is like 50,000 ftlbs. If you make 4000hp at 9000, you make obviously a lot less TQ. But if you put a locomotive engine in a race car, assuming it wasn't so heavy, the 9000 rpm engine would lap the 900 engine so many times, you'd lose count. But try to pull something, obviously it's a different story.

[prairiehotrodder]

Yes. On a well prepped surface, the radials ARE that much better.

Tire performance is another bag of worms.
A tire is a gear, an air spring that changes with pressure, and comes with various compounds that change with temperature.

A lot of time and money has been spent testing tires. And the job is far from finished.

Radials also offer less rolling resistance.
Most cars MPH better with radials.
Radials feel much more stable than slicks going down track.
Radials need to dead hook.

Slicks work better on marginal surfaces.
Slicks recover better if they start to spin.

If traction is not an issue, the vast majority of cars will be quicker/faster on radials.

'Radial Prep' is a real term. It is a term referring to a 'fly paper' track that Radial cars can set records on.
Many cars on slicks have a hard time on tracks with this amount of prep, as the track in set up to Dead Hook... with a radial... even with super high hp cars. (Tire shake/wadding up, chatter, etc)

my car is not real consistent traction wise with a Hoosier 29 x 10 slick. I messaged hoosier just a few days ago and they said it will be even worse with a radial. The Bias slicks are more forgiving is what they said. I do find it amazing what some guys are doing on radials with way more power and way faster cars than mine. Is it the track prep that allows that ? Or what ?

[steve cowan]

I think torque is still important if your rpm limit is fixed at X limit.
You still have to have a certain number on torque to make the desired hp.
Even past peak torque/VE when torque goes down it is still relative I believe.

Yes, I'd agree. But, you have to look at what RPM the TQ is being made at. Meaning, at 5250, it crosses over. TQ is relative. If you make 4000hp at 900 rpm like a locomotive diesel engine, peak TQ is like 50,000 ftlbs. If you make 4000hp at 9000, you make obviously a lot less TQ. But if you put a locomotive engine in a race car, assuming it wasn't so heavy, the 9000 rpm engine would lap the 900 engine so many times, you'd lose count. But try to pull something, obviously it's a different story.

I hear what you are saying,
I will use my tow truck engine as an example-
Torque = HP X 5252/ RPM
570 HP X 5252 = 2993640/6600RPM.
453 FT/LBS @ 6600rpm.
I might of strayed off course but without that Torque number at that peak hp rpm it would not make that hp.
Adjust Torque number up or down at that rpm will change hp number as well.
I was looking at Bob's (1980RS) reference.
"Quote"
But if you make more Torque you will need less rear gear.
I think it is relative if rpm limit is fixed.

[n2omike]

my car is not real consistent traction wise with a Hoosier 29 x 10 slick. I messaged hoosier just a few days ago and they said it will be even worse with a radial. The Bias slicks are more forgiving is what they said. I do find it amazing what some guys are doing on radials with way more power and way faster cars than mine. Is it the track prep that allows that ? Or what ?

Top level events with the fastest cars will have a true 'radial prep'. These cars have suspensions and power management designed to DEAD HOOK the tire. The car is designed to absorb the power without spinning the tire. They will have TONS of rear separation built into the car. Some with leaf springs are even built with VERTICAL rear sliders in place of the shackles. The cars are insanely fast on a true radial prep. Proper chassis setup and power management is key.

In the world of Super Stock and similar n/a cars like most here are familiar with, everything is done in the name of efficiency. Completely different ball game than higher level power adder cars. With those, it's ALL about power management.

As for Drag Radials on regular street/race cars... They are ORDERS OF MAGNITUDE better than standard radials. I can floor my car from a roll in 1st gear n/a and it won't even spin. With standard radials, floor it in 3rd gear (stick car) and go over a little rise in the road, and it will smoke the tires and take you for a very scary ride. After only a couple rides with the new engine on standard tires, a set of DR's was a mandatory safety item for street driving. This being said, yes... it will hook in 1st gear, but shifting to 2nd breaks them loose and it spins all the way through that gear. It's still digging pretty well and not out of control, but you can tell they don't absorb shock loads like a slick. They still make the car FUN to drive again!

Slicks are definitely more forgiving when it comes to traction and varying surface prep. Slicks will work where DR's will not. However, if you can make your car work with a DR (dead hook), it will be quicker/faster.

One more thing about DR's. They do NOT absorb shock like a slick. The tires are a lot heavier built and stiffer. It's what makes them not work well with shock loads. Their lack of 'give' also makes them hard on drivetrain parts. Some people start breaking parts after switching to DR's.

[frnkeore]

You have to remember that hp is only about the rate that a engine produces tq. Tq rules, it what moves the car, not hp! Not necessarily max tq but, the rate that it falls off. When the tq falls off, faster than gear ratio can multiply it, you loose hp. Hp is a formula but, tq is what actually moves the car. Hp works, because of gear reduction.

The hp concept, was how FAST a horse could lift 660 lb. The time frame they used was one second. In other words, how FAST you can create tq and not the tq, itself. But, you can not have hp w/o tq.

A way to look at it is: Say a F1 engine makes only 200 lb/ft of tq, with a 213 ci engine @ 20,000 rpm, that's 762 hp BUT, you can not use it @ that rpm so, you have to gear it down, to were the engine rpm, will get the wheel rpm, to the speed you need (gear reduction).

So, that engine needs a final drive of 7/1, to get 212 mph, with 25" tires. 7 x 200 = 1400 lb/ft of tq. Again, tq is what got the car there.

If a street/strip car, has 400 lb/ft @ 6000, that's 457 hp. Geared at 4.11, with 28" tires, that's 1644 lb/ft tq and 122 mph. This, geared to wheel rpm, still equals 457 hp.

If this engine has 502 lb/ft of tq, at 4200, with the same 4.11 gear, it has 2063 lb/ft tq, at the wheels. Hp for that tq @ that, wheel rpm is 401.

The above is minus parasitic lose, of course.

When tuning a engine, you need to look for ways to decrease the tq drop off, or increase average tq, between max tq & max hp rpms or at least between your widest shift splits. That's why peaky engines won't do as well.

I'm not sure I've explained it well but, those are my thoughts on it.

[David Redszus]

A very important factor concerning drag tires (be it radial or bias) is their friction
coefficient, or Mu value.

Assume a tire with a Mu of 1.2 G, on a car that weighs 3600 lbs.
Given a specific set up (gear, tire dia, etc) that remains unchanged,
the car pulls 1.192G and runs 3.575s at 60 ft.

Now lets take the lead out and bring the weight down to 3300 lbs.
It will spin the tires at 1.2 G, but still run 3.405s at 60 ft.

But if we fit a set of tires with a Mu of 1.4 G, the car will pull 1.30 G,
and run 3.370s at 60 ft.

It seems to make sense to gear to the grip limit of the tire, at least in 1st gear.
The tire grip limit, is a function tire Mu and road surface Mu.

[n2omike]

A very important factor concerning drag tires (be it radial or bias) is their friction
coefficient, or Mu value.

Assume a tire with a Mu of 1.2 G, on a car that weighs 3600 lbs.
Given a specific set up (gear, tire dia, etc) that remains unchanged,
the car pulls 1.192G and runs 3.575s at 60 ft.

Now lets take the lead out and bring the weight down to 3300 lbs.
It will spin the tires at 1.2 G, but still run 3.405s at 60 ft.

But if we fit a set of tires with a Mu of 1.4 G, the car will pull 1.30 G,
and run 3.370s at 60 ft.

It seems to make sense to gear to the grip limit of the tire, at least in 1st gear.
The tire grip limit, is a function tire Mu and road surface Mu.

This is WAY oversimplified.
LOTS of dynamic, constantly changing forces involved... not only in how different types of tire construction react, but also how they work with various suspensions and power delivery. One cannot simplify a tire's properties down to a simple Mu value for its coefficient of friction. Plus, you can't just max out Mu. Different surfaces require a different adhesion vs. cohesion.

And of course, pushing the tire to it's limit and setting the chassis to get everything the tire has to offer is the entire point of drag racing.

[ClassAct]

You have to remember that hp is only about the rate that a engine produces tq. Tq rules, it what moves the car, not hp! Not necessarily max tq but, the rate that it falls off. When the tq falls off, faster than gear ratio can multiply it, you loose hp. Hp is a formula but, tq is what actually moves the car. Hp works, because of gear reduction.

The hp concept, was how FAST a horse could lift 660 lb. The time frame they used was one second. In other words, how FAST you can create tq and not the tq, itself. But, you can not have hp w/o tq.

A way to look at it is: Say a F1 engine makes only 200 lb/ft of tq, with a 213 ci engine @ 20,000 rpm, that's 762 hp BUT, you can not use it @ that rpm so, you have to gear it down, to were the engine rpm, will get the wheel rpm, to the speed you need (gear reduction).

So, that engine needs a final drive of 7/1, to get 212 mph, with 25" tires. 7 x 200 = 1400 lb/ft of tq. Again, tq is what got the car there.

If a street/strip car, has 400 lb/ft @ 6000, that's 457 hp. Geared at 4.11, with 28" tires, that's 1644 lb/ft tq and 122 mph. This, geared to wheel rpm, still equals 457 hp.

If this engine has 502 lb/ft of tq, at 4200, with the same 4.11 gear, it has 2063 lb/ft tq, at the wheels. Hp for that tq @ that, wheel rpm is 401.

The above is minus parasitic lose, of course.

When tuning a engine, you need to look for ways to decrease the tq drop off, or increase average tq, between max tq & max hp rpms or at least between your widest shift splits. That's why peaky engines won't do as well.

I'm not sure I've explained it well but, those are my thoughts on it.

Geesus. How can we be on this forum and not know that horsepower moves the car.

[skinny z]

All right. A question.
First a screenshot of the calculation.

122 MPH.jpg

So, let's say my engine will make peak power at 6000. Estimates are: 450 lb-ft TQ (4000), 470 HP (6000 RPM). It also carries sufficiently for 500 RPM over speed (essentially flat to 6500).
If the car hooks as it should (say dead hook with a drag radial or whatever it takes with a DOT slick) and the converter flashes to 4000 (TQ peak) and has good shift recovery (evidence indicates minimum RPM after the launch to be about 5000) is it reasonable to expect that MPH?

I've got all of the ingredients in the above calculation but it seems incredibly out of reach.