Sidewall strength, tire pressure, and tire quality

[IdaSHO]

You're talking about walking a fine line, pressure and puncture resistance are not inversely proportional, run too low of a pressure and you'll get sidewall issues too.

k

Not walking a fine line at all if you know how to read a tire load table.

Simply running the correct pressure for the conditions, speed, and load, instead of max pressure will make the tires less prone to punctures.


Its common practice, or should be :coffeedrink:, for guys running heavy with large campers, to go to an oversized tire with a higher load rating than stock.

Doing so allows you to run at a lower PSI, while supporting the same amount of weight, all the while softening the ride a bit, and having a larger footprint for trips onto the soft stuff.


Again, all fine if you consult the load table for the tire you are running.

 

[lqdchkn]

What people still don't understand about the old outdated letter ply ratings:
.
"Before load ranges were adopted, ply ratings and/or the actual number of casing plies were used to identify the relative strength with higher numeric ratings or plies identifying tires featuring stronger, heavier duty constructions.
.
Today's load range/ply ratings do not count the actual number of body ply layers used to make up the tire's internal structure, but indicate an equivalent strength compared to early bias ply tires. Most radial passenger tires have one or two body plies, and light truck tires, even those with heavy-duty ratings (10-, 12- or 14-ply rated), actually have only two or three fabric plies, or one steel body ply.
.
.
http://www.tirerack.com/tires/tiretech/techpage.jsp?techid=55

 

[Stumpalump]

What people still don't understand about the old outdated letter ply ratings:
.
"Before load ranges were adopted, ply ratings and/or the actual number of casing plies were used to identify the relative strength with higher numeric ratings or plies identifying tires featuring stronger, heavier duty constructions.
.
Today's load range/ply ratings do not count the actual number of body ply layers used to make up the tire's internal structure, but indicate an equivalent strength compared to early bias ply tires. Most radial passenger tires have one or two body plies, and light truck tires, even those with heavy-duty ratings (10-, 12- or 14-ply rated), actually have only two or three fabric plies, or one steel body ply.
.
.
http://www.tirerack.com/tires/tiretech/techpage.jsp?techid=55

Yes. 100 years ago the ply rating was perfect. Number of ply was directly related to load. As tires evolved people still remember an 8 ply was for a 1 ton truck so we generically call truck tires 8 ply. Today we use load rating. C is for a car or Jeep and D would be 1/2 ton pickup. E is for a one ton. Put a C on a one ton and it's loose and weak. Put an E on a taco and the tire will not conform to the road and ride stiff. On my overbuilt heavy XJ I'm still a C and if you followed the hardcore Jeep tire thread you may have noticed that every tire on my short list was a C range.
http://www.expeditionportal.com/forum/threads/160352-I-need-a-hardcore-Jeep-tire/page3
I never mentioned a Treapadors Bias with the super gnarly sidewalls that I really wanted because it only comes in a D rating. Those tires would suck in performance and ride on a Jeep. I would never recomend anybody buy a load rating higher than they need. If you think your ride is harsh then go look at your rating and I bet it's a D or E. Now if you think a D or E will survive a sidewall injury better then you are kidding yourself. A C has to be aired down less to perform. You won't slide into stuff you do not want to hit as often and when you do the side will flex instead of puncturing. You want that flex but don't air down so much that the tire will bottom out on the rim. That's what cuts the sidewall more than a slice. Some think that's why a D or E is better but it's not worth it. Those tires do not conform or perform as well as a C that is aired down correctly.

 

[OSV]

What people still don't understand about the old outdated letter ply ratings:
.
"Before load ranges were adopted, ply ratings and/or the actual number of casing plies were used to identify the relative strength with higher numeric ratings or plies identifying tires featuring stronger, heavier duty constructions.
.
Today's load range/ply ratings do not count the actual number of body ply layers used to make up the tire's internal structure, but indicate an equivalent strength compared to early bias ply tires. Most radial passenger tires have one or two body plies, and light truck tires, even those with heavy-duty ratings (10-, 12- or 14-ply rated), actually have only two or three fabric plies, or one steel body ply.
.
.
http://www.tirerack.com/tires/tiretech/techpage.jsp?techid=55

that looks a bit misleading, because there is no dual "load range/ply rating" combo listed on the side of lt tires; if it lists ply numbers then it's the number of actual plys, not the ply rating, because the ply rating is now called the load rating.

they try to clarify further on: "LT-metric, LT-flotation and LT-numeric tires are branded with their load range (load range E or LRE) or their ply rating (10 ply rated) on their sidewalls and list their appropriate load range letter in their descriptions as LT245/75R-16 E, 7.50R-15 D or 31x10.50R-15 C."

notice how it says "or", not "and", you get one or the other, and these days it'll probably be the load rating.

all of the lt tire specs that i looked at on that site listed load rating and ply count, not "ply rating"; listing both ply count and ply rating would be confusing as heck, lol

 

[IdaSHO]

yeah, it certainly seems to be a part of the industry that is stuck between nomenclature.

So you will see three terms used, in reference to basically the same index

Load rating
Load index
Ply rating



All that said, I run by what tires are rated for for max weight @ PSI per tire.

Afterall, regardless of tire, the tire should be inflated per MFG load charts, based upon your vehicles weight and speed of travel.

 

[Regcabguy]

A 50psi max D rated 285 nearly cost me my life with a complete tread separation. The truck veered towards the guardrail and a drop off but I was able to steer it away. $3300 damage in seconds. That followed flats and cuts on the same Bridgestone AT's.
I've ran E rated Toyos ever since on two trucks with no issues.

 

[eggman918]

I've been running the Cooper ST MAXX in 295-70-17 E and after a year and 12,000 miles of use I decided that I was running them with a bit too much air so I emailed them with my axle weights as it sits and they sent me inflation #'s and for the MAXX's I was running ~6psi higher than ideal......these were the first E range tire I've run that are happier at a lower psi.
I sent them this "I have a inflation pressure question,I have a set of ST MAXX in 295-70-17 load range E tires on 17X8 rims one axle is at 1,900# per tire and the other is 2,300# per tire both are single wheel axles can you give me a ballpark pressure for these loads? Thanks for your time"
I got this in less than 24 hours
"Thanks for your email and for your interest in the Cooper Discoverer ST Maxx. The proper tire pressure for your tires is 40 pounds on the 1900 pound per tire axle and 45-50 pounds on the 2300 pounds per tire axle."
Great customer support from Cooper, and the truck drives/rides much better.

 

[proper4wd]

Saying that a D or E rated tire "will not perform and will ride like crap" on a lighter weight vehicle like a Jeep is hardly true. At comparable air pressures, they are fairly similar. Run the E tire at ~10% less pressure and it will behave very similarly to a C (E at 15 and C at 17 for example). I run E-rated 295/75R16 BFG KO2s at 35psi street pressure on a ~5000lb Xterra and it is comfy - aired down to 15 off road they spread right out.

 

[Stumpalump]

Saying that a D or E rated tire "will not perform and will ride like crap" on a lighter weight vehicle like a Jeep is hardly true. At comparable air pressures, they are fairly similar. Run the E tire at ~10% less pressure and it will behave very similarly to a C (E at 15 and C at 17 for example). I run E-rated 295/75R16 BFG KO2s at 35psi street pressure on a ~5000lb Xterra and it is comfy - aired down to 15 off road they spread right out.

BS

 

[Robert Bills]

Saying that a D or E rated tire "will not perform and will ride like crap" on a lighter weight vehicle like a Jeep is hardly true. At comparable air pressures, they are fairly similar. Run the E tire at ~10% less pressure and it will behave very similarly to a C (E at 15 and C at 17 for example). I run E-rated 295/75R16 BFG KO2s at 35psi street pressure on a ~5000lb Xterra and it is comfy - aired down to 15 off road they spread right out.

I respectfully disagree. [I'm not a concise as Stumpalump.]

Although one can use the Tire and Rim Association load and inflation tables to find the appropriate street pressures for C, D and E load rated tires on a vehicle with a particular weight, when aired down to typical trail pressures an E rated tire will not conform as well to rocks and other obstacles as a C rated tire.

 

[Hilldweller]

I've run mostly E rated tires on my Jeeps for years with no complaints. The seem to ride the same as the D rated Cooper S/T that I have now.

 

[proper4wd]

Disagree all you want, I have thousands and thousands of off road miles on D and E rated tires under ~5000lb trucks with zero complaints. Yes - a C rated tire will ride MORE softly and conform MORE than a D or E (because it's a ligther weight tire) - but you cant say that a D or E wont work at all. Its simply not true.

 

[proper4wd]

That being said, there are tires that dont quite conform to load range standards. For example, a D rated Hankook RT03 in 315/75R16 will carry as much weight at 50psi as an E-rated 265/75R16 BFG Long Trail will at 80psi. Obviously the bigger tire at 50psi is going to ride far better than the small tire at 80psi (at the same weight rating).

 

[Robert Bills]

The questionable statement is "aired down to 15 off road [E load rated tires] spread right out".It doesn't matter how many "thousands and thousands of off road miles on D and E rated tires under ~5000lb trucks with zero complaints" one has driven, or how one tries to qualify the original erroneous statement after it has been criticized, the fact remains that at typical trail pressures an E load rated tire is less compliant over obstacles than a C load rated tire.


I have to laugh when someone tries to justify a position by claiming "thousands and thousands of off road miles" or "years and years" of experience. Time and mileage doesn't turn BS into gold.

 

[proper4wd]

You guys aren't understanding. The original statement was that "D and E rated tires dont work off road on Jeep type vehicles", which is an absolutely false statement. I agree with you - "at typical trail pressures an E load rated tire is less compliant over obstacles than a C load rated tire" - but my "time and mileage BS" (aka real world experience) tells me that in nearly all situations, a D or E tire is MORE THAN COMPLIANT ENOUGH and any lack of compliance compared to a C rated tire can be made up for by dropping pressure a few extra psi.

DO you guys *ever* get out from behind the computer screen?