drag radials

[Fheckro]

HI all

My name is Fred Heckroth and I work for MARC (Michelin Americas Research Company)
I am a mechanical engineer and design tires for Michelin. While I have only been there for 3 years, I can tell you there is an immense amount of effort, math, testing, and technology that goes into designing a tire. In short the process is mind boggling. I could not begin to address it here.

While I will admit I don't know much about the Goodyear (or any other company's) "drag radial"... there are some things that about tire design that are universal.
 
I am sure --->  as your distance traveled on drag radials increases, you margin of safety decreases...significantly.

My opinion---> while you might get away with it 10 , 100, 1000 times, eventually you will find the limit.

Question---> why go there?

Fred

[revolutionary]

What vehicle were you guys running?

White 96 Firebird # 9614 in B/FALT

I had hoped to see you guys run but my friend said there was an engine problem Sat or Sun?

[revolutionary]

HI all

My name is Fred Heckroth and I work for MARC (Michelin Americas Research Company)
I am a mechanical engineer and design tires for Michelin. While I have only been there for 3 years, I can tell you there is an immense amount of effort, math, testing, and technology that goes into designing a tire. In short the process is mind boggling. I could not begin to address it here.
While I will admit I don't know much about the Goodyear (or any other company's) "drag radial"... there are some things that about tire design that are universal.
 Fred

Fred Thanks for coming aboard. Apparently the big issue is sidewall strength during a spin. Do you have any data that would help regarding sidewall ply thickness/strength for various tires? What does Michelin have to offer in a tire that would be compatable with land speed racing and how many side plies? I am absolutely not opposed to using other tires but I'd like to know the reasons why. Looking at some posts it seems like the only tires that should be run at Bville are MT or Goodyear LSR specific tires and I get that but there are a good 80 percent or more people who dont run those there and are going 200-250 pretty regularly. Again they are using REGULAR front runners and not LSR specific tires (I looked at a lot of tires in line). Hopefully you can let me know why those are better than DR's in the 200-250mph range.

[thundersalt]

HI all

My name is Fred Heckroth and I work for MARC (Michelin Americas Research Company)
I am a mechanical engineer and design tires for Michelin. While I have only been there for 3 years, I can tell you there is an immense amount of effort, math, testing, and technology that goes into designing a tire. In short the process is mind boggling. I could not begin to address it here.
While I will admit I don't know much about the Goodyear (or any other company's) "drag radial"... there are some things that about tire design that are universal.
 Fred

Fred Thanks for coming aboard. Apparently the big issue is sidewall strength during a spin. Do you have any data that would help regarding sidewall ply thickness/strength for various tires? What does Michelin have to offer in a tire that would be compatable with land speed racing and how many side plies? I am absolutely not opposed to using other tires but I'd like to know the reasons why. Looking at some posts it seems like the only tires that should be run at Bville are MT or Goodyear LSR specific tires and I get that but there are a good 80 percent or more people who dont run those there and are going 200-250 pretty regularly. Again they are using REGULAR front runners and not LSR specific tires (I looked at a lot of tires in line). Hopefully you can let me know why those are better than DR's in the 200-250mph range.

Did you look at the "D" compound number on the Frontrunners? I would bet that most of the Frountrunners you looked at were LSR tires.
http://www.racegoodyear.com/tires/pdf/drag_front_runner.pdf
Check out this pdf on Frontrunners. LSR tires at bottom

[saltfever]

I have to agree with Mr. Revolutionary that many run non-LSR tires although the number might not be as high as 80%. Here is a picture of the front tires of a car that is in impound every year. Every record is over 200 MPH. I wanted to know what tires they were running. So I took a pic to take home and look up the number. That Front Runner tire costs $149 and has no load rating! I know the car and it is most likely generating about 500-600 lbs of down force on the front end at record speeds. A similar LSR tire costs $499 and is rated at 1,700 lbs load. The engine builder told me the car runs titanium con rods. I don't get it. . . expensive rods but cheap rubber?  But in all fairness . . . failures of the drag front runners are relative rare. And maybe less that LSR tires that get destroyed by FOD. So far SCTA doesn't consider the drag tire an issue.

[saltfever]

Reading the complete thread there seem to be some misunderstanding. There are two kinds of Good Year front runners. One is a drag tire and the other LSR. They are both made in the same mold! They look exactly alike and you cannot tell them apart unless you look at the 4 digit hardness number. They are made for two different environments and obviously their cost is different.

I took the picture to show you as much of the "Front Runner" logo as I could but still get in the 4 digit number. This is an LSR tire and costs $499. The same drag tire costs $139. SCTA allows the use of the drag tire but I wouldn't run it. YMMV

[saltfever]

Sorry about the serial postings. 

I remember talking to a streamliner driver at SEMA quite a few years ago. He was extremely proud of how he got a hold of some surplus (but new) Lear Jet tires. He wanted them because they were small diameter. His thinking was what could be better than something made for a jet aircraft. I tried to explain how he was using something exactly opposite of its design function! Aircraft land at high speed but the tires are at their lightest loading. (carrier landings are excused). As the plane slows the load increases as the wing looses lift. LSR is completely opposite. The lightest load is at low speed (the start, etc) and load increases (aero down-force) as the speed increases. He promptly shredded both front tires the next year. After that SCTA changed the rule book requiring a 45 day approval for non-rated tires.

Think about it. Drag racing is exactly opposite the LSR environment. The front tires carry almost no load due to weight transfer. Then high load for about 5 seconds (chute deployment)! Load decreases as speed decreases. LSR is completely opposite. Load increases (aero down-force) as speed increases and lasts for 2-3 minutes! LSR cars are heavier than a drag car.

Other than centrifugal force, Heat is what kills tires. Load x Speed x time is what creates heat. LSR is the worst environment. Do you really want to use a drag design completely opposite its intended use?

[racergeo]

  I have run regular front runners over 270 mph and others have run them up to 300. The trick to making a regular drag race front runner work at high speed is to cut or grind most of the rubber off the tread and especially on the edges. The difference in the land speed front runner is it has 6 plys and several more wires in the bead. Then they removed over 50% of the tread especially from the shoulders. The tires weigh virtually the same. The 24" front runner is what funny cars run and is very stiff in the casing as they create a lot of down force at high speed. I actually have a picture of a well known streamliner that has the #D2981 front runners on it. When I asked about it he said the important thing was removing the rubber and increasing the load capacity with a lot air pressure. This was before the Mickeys became available. I have since change to the LSR tires and would recommend them to anyone over 250.

[revolutionary]

I was definitely looking at the compound. All LSR tires start their compound wit '22__'. Anything else is a drag tire.

[Fheckro]

I hear a lot of speculating.

First of all there are many factors that determine tire strength, speed and traction. It takes a new engineer about a year and a half to come up to speed with all that is involved in tire design so it is near impossible for me to impart it all here.

The rubber compound number (at least for Michelin, BFG, Uniroyal and a few others I work with) pertains to the tread surface only, and has nothing to do with the rest of the tire.  I am confidant that this is universal throughout the industry.The tread rubber is no deeper than the lowest groove,(just the outer layer for a slick). It does not give any indication of speed capability. period

When you talk about a tire's speed rating it is largely a function of its internal construction. There are about 5 or 10 different rubber components and numerous non rubber components in the average street tire. For speed... the construction elements that mater the most are the construction elements just under the tread. But wait there's more! speed alone is not what you are looking at when you read the speed/load rating. All parts of a tire are interconnected and work together, so you cant stop there. when a tire is rated it is rated at a certain load at a certain speed. As the tire rolls it flexes. Flexing causes heat. The side wall must carry that heat and be able to dissipate it faster than it is being generated.

So:

A drag radial's  "design concern" is with traction, off the line, and relatively nothing else! Heat build up is a real concern.

An aircraft tire is concerned with high speed with enormous load. The Lear jet tires were designed to carry an aircraft that weighs something like 12500 lbs at speeds close to LSR. Your car probably weighs far less and so heat build up should not be a concern. But these tires have extremely heavy construction so top speed becomes a concern.

Increasing the air pressure will reduce flexing and therefore reduce heat build up, but does nothing for stresses generated by high speed (probably aggravates it).

Shaving off tread will reduce the weight of the tread sculpture therefore lessening the internal stresses generated by speed, but does nothing to address heat build up(probably aggravates it).

Sidewall plys, bead rings, and special belt packages effect tire performance in numerous ways, to speculate if a certain tire is applicable for a purpose outside of  it's design intent based on "Ply rating" or "belt package" or "bead ring" is just that...speculation. without data and testing there is no way to know.

There are no street tire applications that I could recommend. That being said, a "Z" rated tire, especially a Michelin or BFG (and i say this not because I work for Michelin but because there is a marked difference between Micelin/BFG high performance tire construction and Goodyear or any of the others), would I think be a better choice than drag radial or aircraft tires.  Keep in mind that if you exceed the rated speed of any tire you are in uncharted waters. But the internal construction of these tires is probably closest to what you are looking for (you already know this I'm sure).

I am not familiar with Frontrunners construction so i will have to research. Bear with me... I'm old but I'm slow. It might take a while but I'll get back to you.

Well I've probably said too much. If I were going to put my butt in a car that goes 200mph + on a regular basis I would probably wait till i could afford LSR or similar type tires. It's your life.

Fred

[racergeo]

 The streamliner I mentioned went over 350 mph with the the non land speed tires. There have been times in the not to distant past when land speed tire availability dried up. The practice of removing all but a little bit of the tread eliminated the problem of high centrifugal force throwing chunks of rubber off the tire resulting in failure.

[saltfever]

(Snip . . .)
An aircraft tire is concerned with high speed with enormous load. The Lear jet tires were designed to carry an aircraft that weighs something like 12500 lbs at speeds close to LSR. Your car probably weighs far less and so heat build up should not be a concern. But these tires have extremely heavy construction so top speed becomes a concern.

The highest speed the tire will ever see is at lift-off or landing. (about 110-125mph for the Lear). That is 2x-3x slower than LSR use. But in general, at the tire's highest rated speed the load is ZERO! In both cases the wing is carrying all of the load! On the takeoff roll the wing produces lift and removes weight from the tire. On landing, assuming 500ft/min decent and reasonable flair, the wing is carrying most of the load when the wheels hit and load increases only as speed decreases. We have all felt some bad landings that seemed like 3 Gs. The reality is that the oleo struts absorb most of that and typical landings are less than 1G. Compare that to LSR when the load only increases as the speed increases.

There are many Lear variants with various takeoff weights. Landing speeds can be 110-125 MPH. I'm generalizing here only to keep the point simple. There are also 4 main tires on a Lear. So divide AC weight by 4. Now compare that environment to LSR. Just when the Lear tire typically sees no load and max speed, the LSR car is increasing load and increasing speed! Just the opposite of design intent. Not a good plan. 

If I were going to put my butt in a car that goes 200mph + on a regular basis I would probably wait till i could afford LSR or similar type tires. It's your life.
Fred

I couldn’t agree with you more. 

[Fheckro]

Hi Saltfever,

I don’t want to debate the inner workings of a Lear but I think you are missing the point.

The Lear 25 weights 12000 lbs, the 60 weighs something like 17000. Divide that by 4 and its 3 to 4 thousand pounds per tire. The momentum of landing is much greater than you think. Remember F= ma. If you want to calculate the load figure the time it takes for the strut to absorb the impact (1 sec). The shock strut travel (12 inches) and the rate of decent on touch down (20fpm).   Remember the tire must withstand the maximum touch down rate the aircraft is designed for ( and if its designed for me it is going to have to be stout). When 4 thousand pounds is decelerated from 20 fpm to 0 any way you look at it that tire is going to take a beating. Throw in a tail wind and a short runway and you are getting to the design intent.

On a good day a Lear45 touches down at 130kts = 149mph  but that is not the max it is designed for. There is always the chance of a zero flap landing which can up the speed generously.

The load transfer on takeoff is as you say but not as gradual as you think. A jet maintains some positive ground contact in the event of engine failure to maintain directional control (until V1 speed).

We don’t design, and the government won’t certify, parts that are designed to never exceed normal usage. We design for worst case scenario. Aircraft tires must withstand extreme loading/beating.

 
Fred

[jdincau]

http://www.landracing.com/forum/index.php/topic,8282.0.html

[saltfever]

Hi Fred and thanks for the continuing discussion. Yep, I agree . . . the purpose of my response was not to debate the characteristics of the Lear. As I said there are a bazillion flavors of the AC type and I was generalizing. Also, to keep things simple I left out information. But to support your point even further the landing gear system on all aircraft must meet G load factors. AFAIK, on general aviation, all parts of the system must accept 3Gs without failure. That means the tires must take not only the weight you mention, but 3x that weight! I am aware of the tremendous loads they must survive. However, that is not my point. The invisible load you are missing is centrifugal force. As you know, it increases as the square of the speed! In LSR, OEM VR or ZR tires are approved up to 200mph. So I thought we were discussing the use of a Lear tire over 200 mph and speeds far beyond that. You have already mentioned the incredible mass and multiple plies these tires have. So if your Lear is rated for 150mph and you run it at 300 mph the force is 4x its design and all that mass is working against you! The tires I saw shredded failed in the low 300 mph range.

We are both in agreement . . . neither one of us would run them .