Drifting, hellaflush, slammed, tire stretch blog/bash thread.

[sofaking]

Originally Posted by vex

I haven't seen 'em answered but if you have a post number to refer me to I'll gladly re-read them.

I don't feel like going back and quoting, but everytime you asked for information about what I would like it was completely sarcastic and ended with you telling me that you didn't want to do the math. I got as specific as I was looking for and told you that you could use constants for variables if it made it easier. Your response was that you didn't want to waste your time. So quoting myself getting told that you aren't going to do it doesn't help. Move on to the physics lesson if you'd like to make a point, it's the closest thing to figuring anything out we've gotten to.

Originally Posted by vex

Unfortunately what you describe isn't scientific. Tensile side wall strength is compromised with stretch.

I already said that was your point... so if you're not adding anything what is the point in saying it again?

Originally Posted by vex

Thereby removing factors of safety.

So you're saying that there is no possibility that the tire can sustain this, or you're just saying that you know a lot of factors determine the safety of a tire and without the math you can't do anything but speculate what may or may not happen?

Lets define for the sake of discussion that safety is the tire not failing (in any way) before the tread is used up during normal driving conditions. I understand it doesn't meet the original specifications, but the only information we know as of yet is that it will fail to the left side of my graph. Whether it gets even close to the green area is complete speculation.

Originally Posted by vex

Additionally what tire would are you desiring?

I'm using a Falken Azenis RT615k 215/40-17 on a 17x9.5 wheel.

Originally Posted by vex

Your forces are off. Displaced air is not needed and can be removed (unless we have lighter molecules than air). You're also missing a normal force (acts perpendicular to the tire) that keeps the tire from pushing through the ground.

This was the point I was making about drawing the diagram and getting to the point. Going back and forth to prove you know where you're going with your point is a waste of both of our time.

[vex]

Sorry didn't see this until just now.

Originally Posted by sofaking

I don't feel like going back and quoting, but everytime you asked for information about what I would like it was completely sarcastic and ended with you telling me that you didn't want to do the math. I got as specific as I was looking for and told you that you could use constants for variables if it made it easier.

Using variables in this sort of math will cause you to get a bunch of variables in equations that do not make much sense. We'll use constants sure enough, but leaving variables into the equations of question is going to be worse than just using real values.

Your response was that you didn't want to waste your time. So quoting myself getting told that you aren't going to do it doesn't help. Move on to the physics lesson if you'd like to make a point, it's the closest thing to figuring anything out we've gotten to.

This isn't physics in the true sense of the word (at least not from when I took those classes). This is basic material science.

I already said that was your point... so if you're not adding anything what is the point in saying it again?

It seemed to me that you were attempting to sustain this as scientific procedure. If you're no longer sustaining that or if I misinterpreted that from your post then by all means the point is moot now.

So you're saying that there is no possibility that the tire can sustain this, or you're just saying that you know a lot of factors determine the safety of a tire and without the math you can't do anything but speculate what may or may not happen?

This may better help you understand: Factor of Safety. A reduction in the FOS reduces the ability for the tire to handle the same stresses as a properly mounted tire would otherwise be able to endure.

Lets define for the sake of discussion that safety is the tire not failing (in any way) before the tread is used up during normal driving conditions. I understand it doesn't meet the original specifications, but the only information we know as of yet is that it will fail to the left side of my graph. Whether it gets even close to the green area is complete speculation.

I think this is a failure to communicate what FOS is.

I'm using a Falken Azenis RT615k 215/40-17 on a 17x9.5 wheel.
This was the point I was making about drawing the diagram and getting to the point. Going back and forth to prove you know where you're going with your point is a waste of both of our time.

Again, I think you miss the point. Discussing the science isn't for my benefit but yours. If you do not understand where the number comes from at the end of the day all it's going to be to you is a number--But if you understand where that number came from at the end of the day you will know and understand what the material is doing when you stretch the tire and place it under load.

[sofaking]

Since I clearly don't understand how to apply a torque to offer a direction because I thought it could be used as a force I wouldn't know how to add it. For the sake of this analysis lets say the tire is static.

I read the FoS link, interesting stuff. To my knowledge (making an assumption without taking hours of classes on the subject)... Passenger tires would have an MoS of +3 or +4 if the sidewall lasts 3-4 times longer than the predicted load, correct? Not to mention that any given tire usually isn't at its maximum load when installed on a passenger vehicle anyway (Which is what the FoS is engineered to. I.E. max inflation pressure/weight), correct?

Also the article covered a sentence on my point as well...

Many systems are purposefully built much stronger than needed for normal usage to allow for emergency situations, unexpected loads, misuse, or degradation.

This would lead me to believe that it is possible I am right. I'm not saying that it is or isn't "safe". I'm saying that it's possible that it is safe, correct? If it is possible that it is safe, then the obvious conclusion would be that it would not be a fact to call it "unsafe", correct?

[vex]

Originally Posted by sofaking

Since I clearly don't understand how to apply a torque to offer a direction because I thought it could be used as a force I wouldn't know how to add it. For the sake of this analysis lets say the tire is static.

Roger. Now lets look up the material properties for the Rubber of the tire (we'll assume some generic vulcanized rubber). We'll also assume (for simplicity) the rim is solid (IE it is going to deform orders of magnitude less than the tire).

I read the FoS link, interesting stuff. To my knowledge (making an assumption without taking hours of classes on the subject)... Passenger tires would have an MoS of +3 or +4 if the sidewall lasts 3-4 times longer than the predicted load, correct?

No. The factor of safety is calculated using yield and/or ultimate stress criteria. Sidewalls may or may not have 3 or 4, but it is completely determined via structural criteria (not life expectancy).

Not to mention that any given tire usually isn't at its maximum load when installed on a passenger vehicle anyway (Which is what the FoS is engineered to. I.E. max inflation pressure/weight), correct?

No. They're engineered to load criteria IE; cornering loads, static loads, etc. Although max inflation pressure and weight due play a roll into deciding the static loads they do not fulfill the entire criteria for the loads themselves (thermal, adhesive stress, etc factor in as well).

Also the article covered a sentence on my point as well...


This would lead me to believe that it is possible I am right. I'm not saying that it is or isn't "safe". I'm saying that it's possible that it is safe, correct?

Not really. It would be similar to say that a non-firing round from a gun will never fire, which isn't necessarily true. There is a possibility that the round may never fire, but would you risk it (if you're a gun enthusiast)?

If it is possible that it is safe, then the obvious conclusion would be that it would not be a fact to call it "unsafe", correct?

It's arguing a logical fallacy. A car with a slow leaking break master cylinder is safe until you're sucking in air on the freeway--that is to say, no. Using a product outside of engineering criteria is going to be unsafe especially with the current trends of lean manufacturing.