The accident in the thread posted above wasn't due to stretch. It was just a tire blow out. Shit happens all the time.

I'm not defending tire stretch, nor do I think it's MAD TYTE ILL

Just sayin'

who knows... might have been the rota wheel.... lol


J.

Vex, if you can't do the math just admit it. I don't care if you can't, I can admit I can't. But pretending you're more educated than you are doesn't help your argument. Prove something instead of attempting to pull apart my paragraphs line by line in an attempt to change my point. Everyone else can read what I'm saying. I'm not arguing emotion, I'm not trying to attack anyone. I'm merely saying that you can either 1) Prove your point, or 2) admit you're working in theory. Just because scientific concepts (valid and all) are backing your premise, it doesn't mean that it's not theory. You're dealing with concepts not application, that's theory. What I have a problem with isn't your opinion, it's the fact that you're stating your opinion is some sort of fact. Though you yourself aren't proving it in anything other than theory without application.

@RotorDad
Even the letter from the manufacturer uses the word "could". Because he doesn't have the math to prove. I've got no argument with the letter, even the letter doesn't state as a certainty what's going to happen.

@Mazdabater
That's really your argument? After everyone is arguing intelligently from thier perspective you thought you would add that someone else's opinion makes them an idiot? Classy. As for the pictures that sucks, you can see at a glance how the car hit he was probably drifting. Think the insurance company covers you drifting on the streets?

To see that some but not all the professionals do it leads me to believe that it could go either way. Well let's say okay it's good for drifting on the track, that's not where I have an issue. The use of Hipari style tires on a daily basis is where I have questions. When I go to the track I use a different wheel & tire combo then what I drive around on, as do most of my friends. So why do a lot of these so called drifter boys insult others for not slamming the car & stretching the tires on a vehicle not intended for drifting. I'm not trying to shit on anyone, just simply saying tire stretching is impractical for everyday street use. Just as I would not run my slicks on a regular basis even though they work & hold up at the track.

I had a blow-out over the summer from hitting a pothole on the GWB. My tire looked NOTHING like that when I was done. I've also seen a tire that was over-inflated blow out.... it looked identical to that one.... actually, identical.

I lol'd

The guy wasn't drifting when it happened, probably was over inflated though, 40-45psi.

I know the guy. lmao Just throwing that out there.

The truth of the matter is I'm not going to waste my time and vacation doing the math when you admit the followingDo you see the issue? What's the point in doing something when you don't understand it from the get go? I mean, I don't sit down and work with viscoelastic materials for a living, I don't work with aluminum impregnated 'tire rubber' and run simulation after simulation of stress and strain in FEA for both pressure and temperature variations. Perhaps you should look at some of my posts before pretending you know the first thing about what I can and can not do. I mean, solid rocket motors have no bearing on anything engineering related... oh wait.

Let me put it another way; why should I waste 1-4 hours of my life to prove something to you that you would not believe or understand in the first place.
Let alone do it pro bono?

You're right. Good thing I'm not pretending. Material Science, Computational Fluid Dynamics, Kinematics, Thin wall structures are just a small portion of my interests and occupation. Do you really want me to teach you the very basics so you can even hope to understand the math behind non-linear material deformation and stress levels? How about I just hand you a book for you to read so you understand the basics.

You change you're own points, and have yet to address the issues I've raised. I've already given you enough information to understand the science on a basic level. Which according to your previous posts show that you have yet to even attempt to understand but attempt to dismiss Material Science as theory (which you still have yet to concede).

Yeah, but not everyone is able to cut through your BS as effectively as me and waste my time in responding to you (remember you said I belittle you in one of your first posts, this is what belittling from me feels like and I have a large resivour to pull from if you want to keep going).
Unfortunately I have justified my point using material science (which contrary to your made up definition is not theory).
Then you have no idea what theory and science is and how they work together. Let me put it this way: Science is the application of laws and mathematics to model and derive real world outcomes from basic knowledge. Theory is used to test via the scientific method. For instance: Material science allows you to design, build, and test various materials and their behavior under duress. From the wiki article previously posted:
No. Sorry. It's not.
As has already been shown. The science I've stated is fact. Whether YOU choose to believe it is of little consequence to me. You have as of yet, failed to address any of the numerous points I've brought up. It also appears to me that you fail to understand the basics of this science on a fundamental level. Which leads me all the way back to this point: If you don't understand how the tire is deforming or being stressed, what are you doing stretching the tire in the first place.

In an effort to help YOU better understand the science behind the deformation of the tire. Let's start even more basic than material science. What forces are acting on a tire (entire wheel assembly rim-tire combo mounted on a running car--We'll keep it simple. 2D only for right now)?

I dunno if this was a joke...

40 - 45psi "overinflated"?
We've run 60psi+ in autocross without any ill effects during the runs.
I've seen guys run inflations up to 80psi at the autocross without blow-out's.

Of course, this is with PROPERLY sized tires to wheels.


-Ted

I've ran 60psi too. I'm just guesstimating. I don't know why you'd wanna run tire pressure that high though, especially during autox. Hell, I seldom go over 35psi while drifting now. I'm just saying, since people are bringing up factory recommendations. I don't really think I've ever seen any cars with a suggested tire pressure close to 50psi.

There are BMW's with recommended tire pressure above the normal level (at least that's the rumor I've heard).

I guess it would depend on the setup/track. On the smoother courses I find myself running higher pressures, on the lumpier tracks I find that tire deformation is my friend.... as is the case in the vid I posted were the tire was moving all over the rim but traction was maintained even when exiting a corner HARD on the gas...


Of course your experience may and probably will differ

Yeah, I can see what you mean. Can't really say a lot, just due to the fact that I've never really done the whole autox thing before. So I don't have any experience there.

Vex...

Note how the application of laws AND MATHEMATICS are used to model and derive real world outcomes? You're refusing to do the math under the premise that you're right? Prove it. As for thinking you're so intelligent that I wouldn't understand the math because I'm somehow beneath you for not going to the same classes as you in college? Jumping to conclusions again. I can't write programming for shit either, but it doesn't mean when a program isn't working I can't look at the code and see flaws in it. That doesn't mean I can program from scratch though.

The part I don't get is how you still can't understand that without the math you're speculating based on your understanding of the materials. YES, IT IS WEAKER. NO, THAT DOESN'T MEAN IT WILL BREAK. The math is what ties your your information about the materials to the theory that it is unsafe or will break. Without the math, you're talking theory.

If you want to argue dick size or IQ I've got enough of both. I'm not trying to argue that, I'm trying to argue that you can't stamp something as a fact without testing it or doing anything to prove it. I can cut through your BS and see that you aren't willing to do the math because of one of 2 options, 1) you don't know how (which based on your line of work I'd imagine you probably have the formulas) or 2) you're afraid that the math might give me more to argue with.

I understand the laziness factor; I wouldn't want to do 1-4 hours of math either to prove a point. But without it you're speculating. If you just admit that without the math you're speculating, then we can move on. As someone in the field of this type of mathematics I would venture to say that if you can't admit the math ties your premise to facts then I wouldn't imagine you're very good at your job. It's cool, some engineers get into the field because they heard there is money in it, not because they're naturally good at it.

Oh as for your question, I'm not sure what you're looking for here so I'll just list some stuff off the top of my head and let me know if I'm close to what you're looking for...
Tire pressure, weight on the particular wheel/tire, temperature of all materials and outside temperature, what the tires are filled with (nitrogen, air, helium), The stretch of the tire (still an inch and 1/2 of difference between the recommended wheel widths for a given tire without being outside of spec), the materials used for the wheel and tire, and camber.

Once in motion I would guess...
friction, shock/spring combination, lateral forces and additional compression from the various loads during cornering, braking, acceleration, bumps in the road, wheel/tire balance, toe, and caster.

I'm sure you'll find something I missed, but that's a basic list of shit off the top of my head.

I really can't understand why it's so hard to admit that mathematics is required to prove your point. Without it the only thing that you can say for a fact is that the tire is weaker, weaker =/= failure or unsafe.

@Rotordad
Your argument is valid. If it's not your preference don't do it. I agree and I'm not saying it's the coolest or that anyone should do it. I'm just arguing with Vex about concepts of calling something a fact without proving it. EVERYTHING in this thread is speculation. Lots of facts have been stated, but none prove much. I haven't argued at all (not thinking it was directed at me but just commenting) about people needing to slam their cars or stretch their tires. I have my drift car highly modified that is slammed and stretched, but I have stock cars too. I understand the desire for a comfortable street car. Stretched tires aren't horrible on the street, but if your suspension is stiff they remove even more absorption.

@RETed
The 80psi argument sounds remarkably similar to the stretched tire argument. Though you appear to be backing the inflation out of spec, but not stretching out of spec. Just pointing out the similarities of the arguments, not trying to debate another one. I can see that you're also arguing for track purposes and not street driving. I also wouldn't be able to perform math to prove the air pressure thing either way. But I definitely see similarities between the arguments.

Holy shit. Do you know how uneducated you sound when you typed that? Here's some sample FEA, tell me if it's going to fail:

http://www.designworldonline.com/upl.../mar-fea-1.jpg
http://www.schultz-creehan.com/Porta...-pic-FEA-2.jpg
http://www.ctd-materials.com/images/FEA%20Tank.JPG

Look up spring mass damper systems if you're a little hard pressed to understand. From there pick this book up:
http://www.amazon.com/Deformable-Bod...662630&sr=1-10

Once you understand those we'll have something to discuss.



There is not a face palm big enough for what you just typed.
Apparently not, but your foot size sure seems sufficient to keep putting in your mouth.
Do you need to do math to understand a weaker material is present based on geometry? Nope. Do you need to do the math to tell you a material is an insulator or a conductor? Nope. Your argument is a logical fallacy.
We'll work with what you posted.
YesAre not forces and are not needed for a preliminary analysisAgain not really needed, but good to know.This confuses me a little. Are you saying preload of the tires deflection? Yes Yes, but only dictates the location of the force acting on the tire.
Okay, how are you going to calculate that force? Static friction, dynamic friction, all are based of the weight of the wheel in question. Furthermore different compounds have different friction values. Only matters if you're doing an unsteady deformation analysis (which isn't even done for rocket engines)Then it's not exactly 2D is it, but for 3D analysis is spot on. Which are... what exactly? Again, dynamic, but not really needed for preliminary analysis. Is not a force. Is not a force. Only needed for 3D analysis.
Which has basics of it, but are not everything we need. I'm keeping it simple for your benefit.
Nor have I intimated it as such. I have stated that deforming a tire outside of manufactures spec prior to normal driving forces will weaken the tire. The difference is do you know how much weaker the tire has become? The obvious answer through your posts is of course, no; you do not.

Now that we have a rough idea of forces I'm going to ask you to draw a picture. Draw a circle. This circle is representative of a tire. Draw the forces on that tire. (I'm thinking of the view you'd get if you looked at a tire from the side) Draw the forces for friction, weight, pressure, etc.

In determining the stress levels we have to use statics (unless you want to do dynamic analysis which is a whole bunch of worms worse than what you think is possible). That means, application of the forces must result in 0 displacement of the body--or the body must undergo stress to maintain unity. But that's getting ahead of ourselves. Lets keep it simple.

Draw a circle and place those forces you've described.


(Just for future reference:
In mathematics, a proof is a convincing demonstration (within the accepted standards of the field) that some mathematical statement is necessarily true. Proofs are obtained from deductive reasoning, rather than from inductive or empirical arguments. That is, a proof must demonstrate that a statement is true in all cases, without a single exception. An unproven proposition that is believed to be true is known as a conjecture.)