[vex]

Originally Posted by sofaking

The part I don't think you guys are understanding is the difference between theory and fact. You're talking in theory, not fact. I'm talking in experience, not fact. I understand that all I can tell you is my experience, and that the only testing is seat of the pants and lack of problems. I agree this doesn't prove anything other than that I haven't experienced problems from the setup.

Let me help you better understand:
Fact
Theory
Material Science

Material Science is not theory (in fact do a word search for 'theory' within that article).

What I want from either of you is PROOF not theory. Which I don't think you can provide. I.E. even if I test with your technique of stretching the tire and driving around, then doing the same with a non-stretched tire (which isn't a bad idea). I don't have a way to test that the sidewall is:
1) weaker than it was previously
2) weaker than the non-stretched tire after the same miles
3) the strength of the tire is negatively effected enough that it's not strong enough to hold (or degrades at X rate and will not be strong enough to hold after X miles).

Measuring the plastic deformation automatically ensures weakness is present in the polymer. That's the nature of the beast. That's fact. If you wish to argue it I can freely back up that claim.

I'm not arguing for the sake of arguing, I'm offering you the opportunity to prove me wrong. I admitted I was wrong when you showed that the wheels were 10" wide in my video. I'm not sure if you want me to jump on one foot in circles or something to make sure it's sincere, but I am willing to admit I'm wrong if proven.

You're arguing from a false presumption. Feel free to question what I provide, but you better be able to support your question with sound understanding of the mechanics of the materials in question.

YOU ARE TALKING IN THEORY.

See above. It's not theory. In fact I can get you values of various materials for you. Point in fact check out this website for more information on what material science provides:
Matweb

I'm not saying that you can't be right. I'm saying if you want me to admit it, you have to prove it. Otherwise admit you're talking in theory, and you believe your theory is sound. Because that's what's currently happening. Science is theory until proven.

I guess I can hang up all understanding of how materials works. I mean, how materials deform and work under load just is theory and not knowledge or application of the theory in question. I mean surely I couldn't get the yield and ultimate stress for the materials with a science... oh wait.

If you want me to take you seriously you might want to back away from what you're attempting to do as you will fail miserably.

An acceptable answer could be as simple as an equation taking into account a given car weight (take an FC), a given tire (pick one that you can find data on), all the forces in question acting on the tire (stretch 215/40-17 on 9.5" wheel, load, pressure, etc.) and tell me how long a given tire will take to explode, deform to failure, break bead, whatever your premise that's supposed to happen.

Would you also like me to use a Monte Carlo simulation to ensure I capture 99% of all possible mileage outcomes across all proprietary tire compounds--Give me a break, I'm not going to waste my time doing that. I know how the rubber is going to react and have asked people who have worked for tire companies and I have yet to find a single individual who would endorse or recommend doing such.

Then do the same math on a non-stretched tire and see if it should fail farther out, and if so how much farther. This would still be theory because it hasn't been tested but if you want to do this without making up numbers that would be a reasonable argument. I personally know I'm not good enough at math to be able to be accurate (mainly the math about the plastic and elastic sections and force exerted on them). I would venture to guess that the rate of the non-stretched tire is WAY beyond the warrantee of the tread life, and the stretched tire would probably be less, but I'd guess still tens of thousands of miles (guess based on experience).

So what you're saying is that you're willing to sacrifice factors of safety for deforming a tire and putting strain on the shoulder that is not normally there. Thereby negating entirely the built in factors of safety which the company determined prior to construction. (Just so you know, this is fact. It is standard operating procedure for any engineering done within any field).

Short version: Admit you're talking in theory or post data. Actual numbers of when the tire will fail.

Admit you have no idea what you're talking about at all and read what material science is and does. It's not theory.

Originally Posted by sofaking

Yes, the tire will fail, all tires fail. Tires are designed to fail. But if the estimated point of failure is 60,000 miles... then it's not really a problem. If the estimated point of failure is 10,000 miles... then obviously it is a problem. Meanwhile arguing with no facts about the science of it besides making it "weaker" doesn't prove anything.

Weakening a tire in any respect is not a good thing. Would you be willing to drive on a tire that has a weakness in the binding agent between the tread and sidewall?

I mean, sure what could 1% hurt

1% weaker is nothing, 500% weaker is huge. No numbers are being discussed. If you break a leg after it heals it may be "weaker" but it's still going to last you your whole life.

Broken legs, once healed, are actually stronger than they were before they broke. Tires are another matter, so why discuss it?

Additionally how are you going to determine 'weaker'? Are you talking yield (which is the limit before plastic deformation occurs) or ultimate (catastrophic failure)? From matweb posted above Butyl Rubber has an Ultimate Tensile stress of 17.0 MPa. Preloading the sidewalls to an unknown state of stress reduces the amount of elastic region available, loading until the ultimate stress in a corner could be possible depending on the amount of preload and the lateral force applied.

If you hit a home run with a wood baseball bat it will be "weaker" but it doesn't mean it doesn't have 500 more home runs in it.

Neither here nor there in this discussion.

More and less are simple concepts to define larger or smaller amounts. To not define the degree of more and less is useless to argue. Can I have more coffee please? 3 drops is more, an overflowing cup is more. Obviously in that case you just want the cup topped off, but its a pre-determined amount that the person pouring assumes based on experience. If you only want a half a cup you have to specify that amount. We're not talking about amounts, we're talking about more or less.

Unfortunately we're dealing with engineering and tires, not coffee. Keep it on point or stop talking. Your choice.

If that's the case, with my understanding of physics I can say... Yes, I believe you're right. The tire will last less time than would be possible without stretching. But do I agree it's unsafe, or won't last the life of the tread? No.

To what are you referring in physics? More to the point; how much stress are you putting the sidewalls under and what cornering loads are nominal for the tire? When you stretch you remove the ability for the 100's of hours put into development to be applied correctly. You could have 50,000 miles on a stretched tire, or you could have 0.001 miles on a stretched tire. The issue is you alter the geometry of the wheel to the point where weight, friction, heat, cornering loads, and manufacturing defect are all applied differently than what was tested.

I'm not trying to be a dick at this point. I'm not attacking either of you, I'm merely clarifying in different ways to see if you can understand what I'm saying. Sometimes when talking to people it requires explaining in different ways what you're trying to convey. I'm not belittling, I'm merely trying to get you to look at the argument from the other side using real world examples.

And I'm using proven and applied science to show you why it's not a good idea.