Daveinet wrote: I think there is some practical reality that one needs to consider. First of all, the statements that over inflated tires are more prone to blow outs is just plain false. As long as the tire is within the maximum rated pressure, the tire is fully designed to handle that pressure. Consider that if the tire is running at maximum load and maximum air, reducing the load, without reducing the air will reduce stress on the tire compared to maximum load. Less load = less stress period. Its pretty simple physics. You can not invent more stress with less weight. DO not get confused with stress that is transferred into the coach. Yes, it will transfer more stress to the coach, but that is the transfer of existing stress. A tire that is matched to the load, actually absorbs the stress, rather than transferring it to the coach. YOU CAN NOT INCREASE STRESS, you can only choose where the stress is absorbed.
As far as wear, I think we imagine things incorrectly. Tires have belts wrapped around that tire that prevent the tire from expanding by any large amount, the belts tend to keep the tread area fairly flat. The reduction in contact patch from excessive air is mostly for to aft, not so much side to side. This can be very easily seen if you look at contact patches of tires going around corners. The contact patch changes to V-shaped, rather than lifting the whole side of the tire. As it turns out, I run my tires over inflated do to the improved handling characteristics. Since I drive my coach rather than letting it sit, I wear out my tires. Tires are overinflated by about ~20%. My rear set is down to the tread indicators. You have to study the tire carefully to see that the inside has ever so slightly less tread than the outside. In otherwords, the tire wear difference is negligible over the full life of the tire. If you have really wide car tires, you will see it, but for narrower high pressure RV tires, not so much. AS far as traction, I defy any logical explanation that can prove it is significant. Under inflated tire will absolutely give less traction, but not so much for overinflated tires. The reason is that anytime you are in a situation where traction is critical, there is significant weight transfer to the tires most critical to the traction component. (braking results in weight transfer to the front wheels, swerving side to side will transfer weight to the outside tire) Since the weight on the critical tire is increased, that will make a matched inflated tire become effectively under inflated for the load at that time. In some extreme cases you maybe able to measure some minor difference for an over inflated tire, but the practical reality is its pretty insignificant, particularly because of the weight transfer.
You really need to conduct a thorough investigation into tire technology and design before you make any more replies regarding tires. I worked for one of the big 3 tire companies for many years and not one thing you said is accurate. However, you are free to inflate your tires at whatever pressure you chose. I just hope no one reading your post follows your advice.
Ray
I disagree with YOU and agree with Daveinet!
2000 Country Coach Allure; Cummins ISC 330 HP; 71/2 - 8 MPG regardless
2002 Jeep Liberty
Raymon wrote: You really need to conduct a thorough investigation into tire technology and design before you make any more replies regarding tires. I worked for one of the big 3 tire companies for many years and not one thing you said is accurate. However, you are free to inflate your tires at whatever pressure you chose. I just hope no one reading your post follows your advice.
Ray
Without a specific analysis, your post does not benefit anyone.
Dave
The Flying Fortress
FMCA F298817
'83 Revcon Prince 31' FWD
502 w/Howell/GM 16197427 ECM/Edelbrock MPFI,Thorley's & Magnaflows,
4L85E 4 speed, KoniFSD,
6% grade = wanna drag? MISC photos Revconeers Forum
Raymon wrote: You really need to conduct a thorough investigation into tire technology and design before you make any more replies regarding tires. I worked for one of the big 3 tire companies for many years and not one thing you said is accurate. However, you are free to inflate your tires at whatever pressure you chose. I just hope no one reading your post follows your advice.
Ray
Without a specific analysis, your post does not benefit anyone.
My post was directed to you. A couple statements that were false are: (1)belt tend to to keep the tread area flat - truth: the mostly 2-ply sidewalls flex while keeping the tread in contact with the road surface; (2) The reduction in contact patch from excessive air is mostly for to aft, not so much side to side. This can be very easily seen if you look at contact patches of tires going around corners. - truth: over inflation lessens the tire's shoulder contact with the road surface and causes premature wear on the center of the tread.
I stand by my original post. You need to do a more thorough investigation on tire construction, design and technology.
DO you want to look at my "over" inflated tires. They are completely worn out, down to the markers. One would be hard pressed to measure the difference in wear from the inside of the tire to the outside.
Do you want to address the fact that under traction demand conditions, the weight transfers to the tire needing the most traction. How do you feel that weight transfer effects the contact patch?
I take this to mean that the overall footrpint changes a lot in length for both load and inflation pressure, but very little in width. I also notice that while the pressure distribution doesn't change much, there are some differences towards higher pressures and lower loads causing more pressure in the center. That might explain why some folks experience center wear on over inflated tires, but others don't. In other words, the effect is slight.
Yes, Truck tyres have a very square shoulder on the edge of the tread which itself sits right up off the actual tyre casing so it can't really change much in width until it is just about flat..
Something else that maybe should be said. If you compare an under inflated tire, the sidewall starts to carry some of the load rather than the air, so a larger part of the load is carried at the outside of the tire. When the tire pressure is matched to the load, the air is carrying the load, so it will find its own level and apply equal pressure in all directions. An over inflated tire, still has the air carrying the load, so still ends up fairly even pressure.
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