Goodyear Tires

[Dynoroom]

Thanks for that picture Jim.

If anyone is interested here are some cutaways of Mickey Thompson 18 x 875 & 18 x 900.

[fastesthonda_jim]

So, I guess that Thompson Bonneville tires aren't the fabled 12 ply as I've always heard.  Here's two pics from 2002 World Finals showing Al Teague's "situation".  The story I'd always heard is that there are so many layers of cord that Al just cuts off the exposed threads and keeps running.  Now it looks like there's only four. 

YIKES!

Keep the ummm.... rubber side down.

Jim

[Dynoroom]

As I understand tire design (not that I do)  most failures occur at the bead. If the tread is too thick (with plys) it will expand do to centrifgal force and can fail at the bead. So the 875 Mickey is a better tire than the 900 it replaced I've been told. The threads peeling from Al's tires are the same we've seen from spinning them too much. It seems if you spin the Goodyears they will blister due to the thickness of the rubber, thats why Nish and others shave their Goodyears.

Any other points of view or input anyone?

[angryyouth]

Does anyone know why the recommended PSI for the 26" Eagle LSR tire is 50psi as opposed to the recommended 70 psi of its 25" and 28" brothers? is this a typo on the Carol Shelby website? Is 50 or 70 the correct numbers?
thanks.

[fastesthonda_jim]

Depends on how fast you want to run 'em, Angry.  When I'm planning to run over 200mph I try to never run less than about 100 psi in mine, no matter who made the tire.  Who was it, Seth Hammond or someone, who got "flats" on his lakester because not enough tire pressure caused the beads to pull away from the rim at 300+ causing a fairly hairy crash?  Scuse me if I haven't got the details exactly correct, but I have heard from a number of folks to run 'em hard.

More info anyone?

Jim

[Dynoroom]

Jim I won't argue with your tire pressure although I tend to follow the manufactures recommendations untill I find out otherwise. But like you I too tend to run more air in the Goodyears especially the 28".

As for the information on Seth, that is not believed to be the cause of his crash.

[racergeo]

   According to the Goodyear engineer I spoke to, The new landspeed tires that he changed and are built in USA, have 8 more wires in the bead as compared to the frontrunner. They are 2 more ply, 6 ply verses 4 ply and they have a bunch of rubber removed from the shoulder and over half off the tread. A frontrunner has a squared off shoulder to look like a proper front tire. My new landspeed tires are rounded like a proper landspeed tire. So they are not just a glorifyed frontrunner but a reengineered tire. He also said he wouldn't shave them as they didn't chunk off rubber past 300mph in his tests.

[fastesthonda_jim]

Interesting, racergeo.  When I look at my Eagle Landspeeds (in the picture a few posts ago) they definitely have four plys, they sorta look like they may have 6 more wires in the bead, and they are definitely NOT rounded off on the corners.  They appear to actually have extra rubber there. 

I wonder if your engineer friend did his changes fairly recently.  I bought the tire in the photo prior to speedweek in 2004.  On its sidewall is stamped 5ZOSM742 and D2111.  Maybe he and/or you can shed some light on the changes, if any, that have occurred since this particular tire was produced.

Keep the shiny side up ('cept for you, 1212)

Jim

[doug odom]

I really wish Jon could get Denis Manning to chime in on LSR tire failure. He went back to Goodyear and to Wright Patterson ( where they test all the airplane tires ) and got to see how its done. From what I learned when I talked to him.
1. The tire burst from the buildup of pressure inside the tires outer edge from the centrifugal force of the air in the tire.
2. The centrifugal force pulls the tire away from the bead and the air escapes and the tire goes flat.

Now a tire that starts out at 100# psi can have over 350#psi in it at speed. Bursting pressure at the edge of the tire where the tread meet the sidewall is about 440#psi.

Denis made his own 3 piece wheels that clamp the bead ( like beadlock type wheels ) to remove the problem of the force pulling the tire away from the bead.

Like I said, I sure wish Jon could get Denis to give us all this infomation first hand. I had never met the man until the Gas-Up Party and he was a wealth of information.

Doug Odom....in big ditch....no skunk smell on me.

[fastesthonda_jim]

Doug,

I am NO scientist, however, I listened to Dennis at the GasUp too, and the part that I don't get looks a bit like this:  Let's say there is 100 PSI in your tire.  And let's say that the volume of your tire is one cubic foot.  That means there is six cubic feet of air in your tire.  Now air "weighs" or has a "mass" of around one ounce per cubic foot (at sea level for the ng-i-neer types, okay).  Now that means there is six ounces of air in your tire.  Now I'll grant you that those little molecules have weight, and I'll also grant you that a little can mean a WHOLE LOT when the tire is spinning 4000 RPM (300 +/- MPH) but we're talking, in the case of a 26" tall tire with three inches of contact width, of 245 square inches of surface area for that six ounces to press against.

Now I will also grant you that dry air has less "weight" than Bonneville air when the salt is damp, and I will most likely convert to pure Nitrogen just for this reason.  However, I still believe that the extra tire pressure does more to prevent the bead from coming off of the rim than to cause it.  And to be clear, I say, "believe" because I have not tested, but I have heard the same story from a number of olde salts.  (Doesn't mean it's true     )

Incidentally I've been over 230mph with a flat front tire (21"... 3600rpm) and it didn't pull off the rim.  Perhaps because it was so "short" and so stiff.  My co-driver reported the car handled "kinda funny" so I took a pass to check it out and, son of a gun.  What do you know?  Thought those things were supposed to hold air for more than a day (there was a poor bead seal as it turned out).

Anyway, I'd be VERY interested in hearing from the Goodyear guy if they did anything new to the Land Speed tires since 2004.

Jim

[racergeo]

    Hey Jim, you are correct, he did mention in passing that the 21" tire was the one that did'nt use a front runner mold and was a autocross slick mold. Is that correct, it's a slick? Sorry about that, I was specifically referring to #2284.  I have a pair of the old 25's that were made in Chile and they are just a front runner with extra ply's.  The rest of the tires 2283, 2284, 2030,and 2286 are changed and I think USA made. I never discussed the 2222 with him.

[fastesthonda_jim]

Yeah, racergo, it is a slick, 'cept for leetle holes here and there so you can see how worn out it is.  And I guess the D2111 on the side of my tire refers sorta like all those other numbers you mention.  I guess it means 21" and then 11 of something else.  And I don't know if it was Chile made or North Tijuana made (U.S. for you, Kent).

I'd kinda like to get ahold of some of those 2030's if the 20 means 20" OD.

Keep the rubber side down (now if we can just figure out what that means)

Jim

[1212FBGS]

jim the 21-3.5x15 is the smallest lsr tire made... i think it's the best..
kent

[JackD]

"What we have here is a failure to communicate."

The PSI acting on the body of the tire at REST is of course air or some other gaseous mixture like Nitrogen.
As the tire is put to work, the power through it , the weight it carries , and the flexing as the contact patch compresses at the point of load and then goes oversize as it leaves the contact surface. Because it tries to find it's natural shape it repeats the cycle because the spring back nature of the tire is undampened.
The ripple around the outside is called a standing wave.
All contribute to the heat and subsequent failure that begins with tread separation at the casing bond, followed by "chunking" as the material leaves the tire.
If the force is great enough, the bead will pull away from the seal against the rim and the inside gases will go outside.
Ask Monte Wolfe about dirt clods inside the front tire after a run at EM with his back motored  car.
The extreme pressures seen by an LSR application can't be measured by the filler gas alone , but includes the centrifugal force of the tire material as it rotates.
That is where the huge increase in PSI against the structure of the tire can contribute to failure.
.

[fastesthonda_jim]

So, Jack,

Since we're dealing with my life here, not to mention a few others, what is your final point?  You do possess a wealth of information, well okay... experience, and I am interested in your point of view(s) on this whole matter of tire pressure.

Yes the standing wave scenario seems valid.  Yes, rubber can and does chunk off the tire if things go awry.  And yes inside gases do have a demonic way of finding their way outside. 

In a word, how about a conclusion, i.e., what have other racers found?  What works?  What will help you into the records books v.s what will send you cartwheeling into history?

Enquiring "minds" from a fellow club member and all that.

Jim