New Rear Bridgestone Tires
#41
Registered User
Join Date: Oct 2000
Location: The wilds of
Posts: 616
Likes: 0
Received 0 Likes
on
0 Posts
[QUOTE]Originally posted by Nick T:
[B]...22.7 square inche contact patch?!?!? How did you get that? 725lbs divided by 32 psi? Does that mean if I only put in 10psi I have a 72.5 square inch contact patch? A contact patch that is 3 times as large as running 32 psi? You can not measure contact patch with algerbra... If the contact patch stays the same
[B]...22.7 square inche contact patch?!?!? How did you get that? 725lbs divided by 32 psi? Does that mean if I only put in 10psi I have a 72.5 square inch contact patch? A contact patch that is 3 times as large as running 32 psi? You can not measure contact patch with algerbra... If the contact patch stays the same
#42
Originally posted by Nick T:
Let's further assume that any tire you put in 185/60 205/55 225/50 255/45 has the EXACT same sidewall height. Therefore deformation of the sidewall is the same under the same amount of weight.
Let's further assume that any tire you put in 185/60 205/55 225/50 255/45 has the EXACT same sidewall height. Therefore deformation of the sidewall is the same under the same amount of weight.
Let's not get hung up on the tyre stifness issue. We all agree that the tyres are not balloons but they are not made of steel, either.
#43
Registered User
Join Date: Oct 2000
Location: The wilds of
Posts: 616
Likes: 0
Received 0 Likes
on
0 Posts
Originally posted by Luis:
...Let's not get hung up on the tyre stifness issue. We all agree that the tyres are not balloons but they are not made of steel, either.
...Let's not get hung up on the tyre stifness issue. We all agree that the tyres are not balloons but they are not made of steel, either.
So interpolating from a perfectly rigid tire to a perfectly deformable one, it appears that whichever tire is more deformable will have the greater contact patch, regardless of shape.
#45
Registered User
Join Date: Oct 2000
Location: The wilds of
Posts: 616
Likes: 0
Received 0 Likes
on
0 Posts
Originally posted by Luis:
...But they can do so at different rates, can't they? (you know, like 1/x and 1/x**2 when x->oo)
...But they can do so at different rates, can't they? (you know, like 1/x and 1/x**2 when x->oo)
Originally posted by Luis:
...A bit of experimentation. Would you like to try your spare tire on, paint it black, lower it into a sheet of white paper and measure? Do the same with stock tyres. Make sure that they are both at the same pressure.
Then deflate to 1 bar and repeat.
...A bit of experimentation. Would you like to try your spare tire on, paint it black, lower it into a sheet of white paper and measure? Do the same with stock tyres. Make sure that they are both at the same pressure.
Then deflate to 1 bar and repeat.
[QUOTE]Originally posted by Luis:
[B]...I could do it, but you owe me one...
#46
This will be my last post on this thread, I do not want to beat this subject to the ground. But listen to yourselves."The problem with simplistic calculations is that it's possible to simplify much of the truth out of them -- the modeler's nightmare." Simplistic = algerbra. "area tends to zero as stiffness tends to infinite, " That's a CALCULUS problem not ALGERBRA. From how you guys are talking, it does not seem you have taken any courses in Deformable Bodies and Strength of Materials. Two very important courses for any Mechanical Engineer major. While you are experimenting with your different size tires etc etc. Try this experiment. Get two carboard pieces of exactly the same size and material. This will represent the sidewall of your tire. Hold them straight up from the ground 2 inches apart in parallel and put weight X onto each them. Note how much they bend. Now do the same thing only this time have them 20 inches apart. They WILL BEND the same amount. Extrapolating that data you will see it does not matter how WIDE a tire is, with the same amount of force acting against the same size sidewall ( my previous post already postulated we have identical height and material sidewall ) the "bend" or deformation is the same. This is a very simple experiment that does not take in consideration other varibles a real mechanical engineer must include in designing any deformable body construction but the other varibles have little to do with how it will deform but more in things such as how much total force it can withstand, it's heat index and thermal transfer etc etc etc
I have only been on this board a short time and I am sure Luis and Tox have given alot of good advice on other things. Might I suggest you ask around, ask some mechanical engineers and/or college professors. I love to learn new things, but I'd rather not learn anything at all then to learn something that is wrong
Regards
P.S. This was not intended in anyway to be a flame
[This message has been edited by Nick T (edited December 21, 2000).]
I have only been on this board a short time and I am sure Luis and Tox have given alot of good advice on other things. Might I suggest you ask around, ask some mechanical engineers and/or college professors. I love to learn new things, but I'd rather not learn anything at all then to learn something that is wrong
Regards
P.S. This was not intended in anyway to be a flame
[This message has been edited by Nick T (edited December 21, 2000).]
#47
[QUOTE]Originally posted by Nick T:
[B]Get two carboard pieces of exactly the same size and material. This will represent the sidewall of your tire. Hold them straight up from the ground 2 inches apart in parallel and put weight X onto
[B]Get two carboard pieces of exactly the same size and material. This will represent the sidewall of your tire. Hold them straight up from the ground 2 inches apart in parallel and put weight X onto
#48
Registered User
Join Date: Oct 2000
Location: The wilds of
Posts: 616
Likes: 0
Received 0 Likes
on
0 Posts
[QUOTE]Originally posted by Nick T:
[B]...I have only been on this board a short time and I am sure Luis and Tox have given alot of good advice on other things. Might I suggest you ask around, ask some mechanical engineers
[B]...I have only been on this board a short time and I am sure Luis and Tox have given alot of good advice on other things. Might I suggest you ask around, ask some mechanical engineers
#49
Originally posted by Luis:
I'm sorry but your model is not useful. A tyre is not two pieces of cardboard. It's a deformable enclosed space. Get a model that sticks to these rules and we can discuss its merits.
And, I am sorry again, you have just shown that you know as much about "Deformable Bodies and Strength of Materials" (sic) as I know about the application of dried ant foreskin in oriental cooking. That is, not much.
P.S. This was not intended to be a flame either.
I'm sorry but your model is not useful. A tyre is not two pieces of cardboard. It's a deformable enclosed space. Get a model that sticks to these rules and we can discuss its merits.
And, I am sorry again, you have just shown that you know as much about "Deformable Bodies and Strength of Materials" (sic) as I know about the application of dried ant foreskin in oriental cooking. That is, not much.
P.S. This was not intended to be a flame either.
This will be the last post on this thread, I do not have the time nor the inclination to explain every little detail and as it seems my model was too simple, please again I ask... print this page and go ask some mechanical engineers.
#50
Registered User
Join Date: Oct 2000
Location: The wilds of
Posts: 616
Likes: 0
Received 0 Likes
on
0 Posts
Since we're making things "relatively simple so that you could UNDERSTAND," understand this:
The sidewalls don't hold the car up. Air pressure holds the car up. If this is not clear to you, go let the air out of your tires and watch what happens. (Many people who lack engineering degrees already seem to know this.)
Now get a large airtight plastic bag. Blow it up and seal it. Put it on the floor and lie on it. What's keeping you off the floor? Sidewall stiffness?
Air pressure is not an "extra variable." It is the main variable. Sidewall stiffness is an extra variable.
PS: Taking your illustration of, say, a tire 1 foot wide with a 2-inch sidewall and a tire 6 inches wide with the same sidewall, both holding up the same weight and at the same air pressure -- the narrow tire will deform more than the wide one. I invite you to see for yourself with your car, using your space-saver spare. I'd do it myself, but I already know what will happen.
The sidewalls don't hold the car up. Air pressure holds the car up. If this is not clear to you, go let the air out of your tires and watch what happens. (Many people who lack engineering degrees already seem to know this.)
Now get a large airtight plastic bag. Blow it up and seal it. Put it on the floor and lie on it. What's keeping you off the floor? Sidewall stiffness?
Air pressure is not an "extra variable." It is the main variable. Sidewall stiffness is an extra variable.
PS: Taking your illustration of, say, a tire 1 foot wide with a 2-inch sidewall and a tire 6 inches wide with the same sidewall, both holding up the same weight and at the same air pressure -- the narrow tire will deform more than the wide one. I invite you to see for yourself with your car, using your space-saver spare. I'd do it myself, but I already know what will happen.