All things being equal, INCLUDING BRAND AND TYPE OF TIRE, an E rated tire will run cooler than a D rated tire AT THE SAME LOAD and SPEED.

 

I think this way over simplifies a tires function and construction. Air pressure would seem to me to be a factor in a tires load capacity, not the determination of it. This example implies the tires construction based on the needed air pressure for a load.

AGREED!

Excellent well thought out post btw!

However, I would normally say, it's your truck do what you want except in this case YOUR tire failure could cause YOUR truck to run into ME!

Personally, I don't trust most of the employees at the tire center very far. Most have a basic understanding but seem to be better order takers than tire experts. No one I would hope would intentionally steer anyone wrong, but if they are not properly informed could inadvertently do so.

I feel there are more factors at play here that specify a particular tire for a particular application than we as "novice" tire people are aware of. By novice, i mean someone who is not educated in the specific engineering, chemical and physical construction properties of tires. We can make a very informed an educated interpretation of ratings and make some assumptions but at the very best they seem to be assumptions.

 

After reading your posts in the trans fluid threads I know how much you like actual facts. So, could you please post the information that shows this to be true??? The only place I know of to get information on a tires ability to dissipate heat (therefore run cooler) is a UTQG (Uniform Tire Quality Grade) rating and I've searched and searched and all I can come up with is that tires in these sizes and load ratings are not required by the DOT to be tested and given a UTQG rating. Now a days, you can't even use # of plys to distinguish between load ranges. My E tire has the same configuration of plys listed on the sidewall as my D tires do.

 

We're over 1000 miles apart I don't make it to the east coast often enough, you're safe!!

There are enTIREly (sorry) to many places that will hire any Joe Schmoe off the street and let him wrangle tires. Personally, I had 5 years experience as well as numerous training courses through BFG and I still wouldn't feel comfortable telling someone else to use anything less than what was recommended. That being said, the person I trust has worked around tires most of his life, bought his tire shop from his dad, and has run/owned it ever since (I don't know how long exactly but easily 20+ years), for the most part is my father in law (6 years still not married), knows that I regularly drive with his grand kids in the truck, and meets with BFGoodrich almost on a monthly basis to discuss tires and everything related to that subject. So, with what little I know coupled with everything he knows, I have no doubt in my mind that my truck is as safe if not safer (I don't trust Firestone AT ALL) than it was the day it rolled off the factory floor. But this is just me, the rest of you need to do what you feel safe/comfortable with.

 

I believe you are making a misapplication of centrifugal force. For our purposes, automotive tires, without damage and properly balanced, we can treat the entire tire as a single point of mass. The entire mass of the tire is being acted on by the centrifugal force from rotation, similarly.

I believe higher speed rated tires need a stonger construction to cancel the forces created by turning, cornering, etc. at high speed .... not the centrifugal force.

In science, be extremely careful of making assumptions without doing any math. Differences in Contact Patch can be a good indicator of some handling characteristics between tires.

Its only that simple if ... the items being compared are completely identical, with only to-scale differences in size. The two tires you are comparing are far from identical in construction. Your analogy of snowshoes vs. regular shoes isn't valid here because they are two significantly different items, not very similar items that only differ in construction methods and materials --- like our tire discussion. Your analogy does work with different snowshoes .... the same model snowshoe in a larger size will distribute your weight over a greater area than a smaller snowshoe.

Freshly produced tires, in pristine condition, tested under ideal conditions in a lab.

From my reading .... the tire manufacturors don't know what to make of all their testing ... if it is really useful at all? They try their best to come up with data, but real world conditions and usage vary widely, with extremes in many different forces. It makes it impossible to make most predictions.

Starting with the time of purchase ..... the workmanship of the installation and balancing. What rim width is being used? Tires are tested at one rim width. Different results come from different widths --- even within the recommended rim width range. Then, you have people mounting the tires on rims that do not fall into that range.

Tire integrity starts to degrade from heat at the start of use -- under ideal conditions. Add to that periods of underflation, overinflation, and overload ---- mild (so mild that you don't realize it) to severe, short duration to long duration.

The wearing-out over time of stock suspension/steering components, and the change of those componets from lifting, etc both produce new forces on the tires.

Hot brakes. Aggressive driving. Tires slowly coming out of balance. Unknown damage to the tire. Etc Etc

All doing damage to the tires. Mostly very small damage, but it is cumulative ..... any damage done to tires via heat is forever.

I am confident in that the manufacturers and I agree ..... take their ratings with a big, fat grain of salt. I'll go further and say that there is no such thing as overkill when it comes to tires. And, since the tires are our connection to the earth as we fly down the interstate ... if there such thing as overkill ---- I want some!

I'm not trying to pick a fight with anyone, just some friendly disagreements. Plus, I'm procrastinating in my office ---- not being so thrilled that I am here on a Saturday. Lol

Just my 2 cents to the discussion.
Over. Out.

 

The load rating is a relative measure of how "strong" a tire is. The "stronger" the tire, the less it flexes. The less flex, the less heat generated.

Of course, I can get a D-rated tire of one brand that will flex less and generate less overall heat than another manufacturer's E-rated tire, but like I said, SAME BRAND, SAME SIZE, different load ratings, the higher the load range, the cooler the tire will run.

I ran D-rated BFG AT's on my '74 highboy - I hated them. I switched to E's, and it had a lot less flex in the sidewall than the D's. Less flex, less heat. I could even feel it when I traveled with them on the NYS thruway, over a few years time, about the same ambient temp (and driving style) each year, and the D's were noticeably hotter to the touch when I'd stop at the same rest stops each time. I was very happy with the E's.

 

Wherever the snow shoe analogy came from...

The snow shoes don't carry more weight, it allows the snow to support more weight on top.

Tires at the same pressure deflect the same amount. A wider tire just means the contact patch is a different shape (wider) but not overall larger. To get a larger contact patch you would have to lower the air pressure. I wish I could find the original article I read about this because it was quite enlightening. The discussion centered around the fact that contact patch was mis perceived as the reason for the better handling, when in fact it was attributable to different tire construction, typically a stiffer shorter sidewall to maintain the same overall height. They had examples that showed the tire deflection underneath and how it just changed shape. It was a tradeoff of width vs length of the contact patch.

 

Well just my 2 cents on this. mine came with e-rated (3195 lbs) new. I ungraded to 33" tires with a D rating but they weight (3195) was the same. So I ran with it. put 3700 lbs of concrete on em several times with no problem.

 

Aldridgec .... not sure if you are addressing me ......

Fivonut juggled the analogy a bit, but I think we all know he was trying to illustrate the concept of surface area. I stated that I thought it is too simple to be used in our discussion of similar tires. I saw no reason to say anymore ... I'm wasn't trying to bust *****.

Contact Patch ..... I believe people here are changing tires and reducing their air pressures (without reducing their load) at the same time, therefore increasing their contact patch area. So, I didn't go anywhere with that. I just suggested to Fivonut that he not make assumptions before looking at the math.

I stand by my comment that "Differences in Contact Patch can be a good indicator of some handling characteristics between tires." As I said, its all about tire construction, not just size. And, as I said, a tire with a higher speed rating is due to its stronger construction against lateral forces, which helps to keep its contact patch wide during turning, concerning, etc. (unlike Fivonut's contention that the designers where concentrating on centrifugal forces). A wider performance tire can provide better handling.

Concerning the article you read ... I can't search now, but there are many places on the web that deal with tire motion, contact patch, etc ..... and I'm not talking about TireRack, etc .... but the actual engineering. Like you said, interesting stuff. With some actual videos, made with different cameras (infared, etc). Showing deflection, etc. As load and speed increase, such as with aircraft tires, the rebound from deflection starts to get wild.

What publication was your article from?

My 2 cents

 

I had just gleaned some highlights from your post. I agree that contact patch is a good idicator of handling characteristics, you just can't imply that a wider tire always has a bigger contact patch and therefore will handle better.

Half the problem of finding it is remembering where it came from and I can't do that so...