Sidewall strength, tire pressure, and tire quality

[madmax718]

1. An air pump is cheap.
2. Ryobi makes a cordless air pump. Loud, but very useful.
3. Load range E is stiffer in the tread- To keep it uniform contact patch even under pressure and load. Anyone who has mounted tires knows there's a significant difference in flexibility.

Yes, a f350 with a camper aired down to 15 will spread some- but E range tires are generally designed purposely to not spread. E ranges are used heavily on dual wheels, where spread would allow tire to tire rubbing.

Likewise, using E range tires on a f150 will not spread nearly as much.

Im a huge fan of E range tires though. The ride is not as comfortable, though the safety from sidewall cuts, blow outs, potholes, etc are usually better.

When I used to offroad (not expo style- just offroad for offroading) we used to spray down the side walls with tire shine. Mud/sun dries out the tires- tireshine not only protects the tire from UV and drying out, it acts as a lubricant so that the tire can more likely take a glancing blow from a sharp edge.

 

[madmax718]

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?

I don't know about E on a 16" rim, because thats what I have experience with- it does not hold a bead as well as my 15" did. Airing down on my E 16" rims did loosen up the bead. It didn't pop off, but it did leak air.


Thats the only issue I have with airing down E range tires- too low and you risk popping a bead or leaking air.

Given the two though, 99% of my driving is on road- 1% off road.

 

[Hilldweller]

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.

Depends on the tire too.
Not all E tires are created equal...

My E experience is mostly with Cooper. S/T-Maxx, STT. Aired-down fine, handled rocks, handled mud, handled my bodacious tongue weight.
I just won a set of STT-Pros ---- that will be Es.

 

[proper4wd]

I don't know about E on a 16" rim, because thats what I have experience with- it does not hold a bead as well as my 15" did. Airing down on my E 16" rims did loosen up the bead. It didn't pop off, but it did leak air.

That can be a factor of wheel as well as tire - not all safety beads are the same. I've only pushed one tire off the rim in recent history - a 255/85 (D) KM2 which was aired down to about 15psi on a 7" rim. It peeled off when winching sideways out of a very deep, muddy rut/gulley due to the side force exerted by the winch.

Today I'm running 295/75 KO2s on the same 7" rim and I don't expect to have any problems due to the narrow rim width (compared to tire width).

 

[madmax718]

That can be a factor of wheel as well as tire - not all safety beads are the same. I've only pushed one tire off the rim in recent history - a 255/85 (D) KM2 which was aired down to about 15psi on a 7" rim. It peeled off when winching sideways out of a very deep, muddy rut/gulley due to the side force exerted by the winch.

Today I'm running 295/75 KO2s on the same 7" rim and I don't expect to have any problems due to the narrow rim width (compared to tire width).

Your absolutely correct on that. Some tires mount with very little effort. Others are like fighting smurfs over smurfberries.

 

[Stumpalump]

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?

A stiffy, I'm mean a stiff E can claw thru a lot of stuff just fine. Out west in the endless rocks you need the softer tire to soak them up. We may go 50 miles in a day on nothing but hard pack and rocks. You feel every golf ball sized rock. Just last weekend I hit a 30' stretch of trail that was smooth. We cheered, I gunned the engine and it was a celebration! The rest of the trails are lumpy bedrock. It's not just the sidewall flex but the tread has to give a little as well. E tread over the thick steel belts is solid even at low pressure. The C gives more on the side and tread making a huge difference after an hour of rattling bolts and your teeth loose. Clawing thru some mud, roots and a few rocks then 30 miles of rock free dirt is just not the West. We drive miles of rocky washboard roads just to get to a trail or road that's almost solid bedrock. In Colorado you can spend all day to do 20 miles of rocks the size of cantaloupe to the size of a dishwasher. They never ever end. Zero feet of smooth rock free trails. This is maintained Crow Road near Phoenix. See how wide it is? It's the good dirt road to the trails. Adverage 8 mpg on a C.

 

[OSV]

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.

look at this e-rated tire pic, and then tell us again how that tire is "less compliant over obstacles"... the upper sidewall tread is literally folding over itself.

here is the tire, fill in your own dot: wayalife DOT com/showthread.php?35046-NEW-Shoes-for-RUBICAT-37x13-50R17-Cooper-Discoverer-STT-Pro-M-T-Tires

 

[proper4wd]

A stiffy, I'm mean a stiff E can claw thru a lot of stuff just fine. Out west in the endless rocks you need the softer tire to soak them up. We may go 50 miles in a day on nothing but hard pack and rocks. You feel every golf ball sized rock. Just last weekend I hit a 30' stretch of trail that was smooth. We cheered, I gunned the engine and it was a celebration! The rest of the trails are lumpy bedrock. It's not just the sidewall flex but the tread has to give a little as well. E tread over the thick steel belts is solid even at low pressure. The C gives more on the side and tread making a huge difference after an hour of rattling bolts and your teeth loose. Clawing thru some mud, roots and a few rocks then 30 miles of rock free dirt is just not the West. We drive miles of rocky washboard roads just to get to a trail or road that's almost solid bedrock. In Colorado you can spend all day to do 20 miles of rocks the size of cantaloupe to the size of a dishwasher. They never ever end. Zero feet of smooth rock free trails. This is maintained Crow Road near Phoenix. See how wide it is? It's the good dirt road to the trails. Adverage 8 mpg on a C.

View attachment 355258

What psi do you typically run?

I've been out there - have done a lot of similar trails - and was never uncomfortable on D's or E's in the 15psi range. The massive contingent of people who run D rated 255/85's in the southwest would also indicate that they work just fine.

I'm glad you're getting out there and found something that works for you but I really think you'd go all the same places regardless of the letter stamped on the sidewall, assuming you adjusted the psi to suit....

 

[Robert Bills]

look at this e-rated tire pic, and then tell us again how that tire is "less compliant over obstacles"... the upper sidewall tread is literally folding over itself.

here is the tire, fill in your own dot: wayalife DOT com/showthread.php?35046-NEW-Shoes-for-RUBICAT-37x13-50R17-Cooper-Discoverer-STT-Pro-M-T-Tires

View attachment 355259

That screen shot is deceptive and not representative of the typical deflection of E load rated tires on the trail. What is depicted is the deflection against a vertical obstacle that the driver hit with speed. Watch the entire clip here for a more accurate representation: https://www.youtube.com/watch?v=lkqeb3Vrzs8 Based on statements in the owner's other posts he is aired down to somewhere between 8 psi and 12 psi.

To put things in perspective, here is a shot of a "C" rated tire aired down to 16 psi:

Ironically, in the thread that is linked the owner makes the following statement about his new E-rated Cooper 37" STT Pro tires: "

"Right off the bat, we aired these tires up to 30 psi and being that they are Load Range E tires, we can definitely feel it. At least, we can feel every stone and crack in the pavement but, that's nothing new to us. We'll be bringing them back down to about 26 psi and I suspect that will help out."

 

[andrew61987]

OP Here - A big reason I am looking at E now to replace my current Dakotas is because I want to run a 235/86/16 tire and they only come in E. 265/75/16 is an alternative that I can get in C or D but I want to run a tall narrow tire. my second choice was 255/85 but I'm worried about rubbing - still running stock suspension.

So, for those contending that E is not the best choice, is it worth deviating from my ideal tire size to get a C or D? Note that I've been running E for the past 20k miles and have no complaints about the ride quality on pavement. To put it another way, does the fact that my 235/85s will be E significantly negate any trail advantages of the narrower 235 over the 265 in C or D?

 

[Robert Bills]

To the OP:

I think if truth be told, many offroaders running E-rated tires are running them because the size they wanted is only available in an E load rating and size was more important to them than other features.

Only you can determine whether the advantage of having a tire better matched to the weight of your Tacoma, i.e. a C or D load rated tire, is more important than tire size. In my particular situation, I wanted a tough tire carcass and 3-ply sidewalls for better damage resistance against the sharp volcanic rock and logging debris prevalent in my area. The only tires available with 3-ply sidewalls in any size appropriate for my truck were E rated. There were C and D rated tires in appropriate sizes, but with 2-ply sidewalls. I chose the E rated tire, placing puncture resistance over other factors, which I run at 35 psi on the street to maintain ride quality. They are not as compliant over obstacles at trail pressures as prior LT tires I have owned with C and D load ratings, but I am not as much into rock crawling as I once was so the compromise works for me. The downside to E rated tires in my case is that I have to air down even for relatively short runs on dirt or gravel roads to avoid a tooth loosening ride. With C rated tires I could stay aired up with my speed down and not loose a filling.

As far as "tall and skinny" tires go, you might want to look at the LT255/85R16 Cooper Discoverer ST/Maxx again. They are not as tall as other brands, being 32.8" in diameter rather than the 33.5" diameter typical for that size. I know several guys running them on non-lifted Tacomas and Frontiers without clearance issues.

I have run LT265/75R16 ST/Maxx's on my Xterra for the past 12,000 miles and really like them as an aggressive AT tire (technically a "commercial traction tire"), and will probably replace them with another set in LT255/85R16 when the time comes, although I would still prefer that they were load range D with 3-ply sidewalls rather than load range E.

 

[Stumpalump]

OP Here - A big reason I am looking at E now to replace my current Dakotas is because I want to run a 235/86/16 tire and they only come in E. 265/75/16 is an alternative that I can get in C or D but I want to run a tall narrow tire. my second choice was 255/85 but I'm worried about rubbing - still running stock suspension.

So, for those contending that E is not the best choice, is it worth deviating from my ideal tire size to get a C or D? Note that I've been running E for the past 20k miles and have no complaints about the ride quality on pavement. To put it another way, does the fact that my 235/85s will be E significantly negate any trail advantages of the narrower 235 over the 265 in C or D?

Look at that you tube vid. If you don't mind bumping obstacles and spinning on a 1000' cliff then go with the E. I've never had a tire spin or had to back up and bump on Cliffhanger trail with a C. The only reason that's considered a hard trail is because the cliff edge is a few feet away. If your OK with typical expo campsites with easy trails and E is all you can get in your size then you will be fine. If you think you may want more out of your rig later then fix it to run the best tires you can get first. The entire vehicle and what you can do with it is all based around rolling, turning and flexing the suspension so the tire can do the best job. Only makes sense to have the most perfect tire to max out the capabilities of the rig. If your OK to compromise and your question is basically a small tire in C vs larger tire in E then bigger is better and you need to get the E.

 

[OSV]

That screen shot is deceptive and not representative of the typical deflection of E load rated tires on the trail. What is depicted is the deflection against a vertical obstacle that the driver hit with speed.

he didn't hit anything with speed, as the video proves, the tire is wrinkling back on itself because of the torque of the wheel pulling it up and over the obstacle, combined with the low air pressure... there is plenty of flexibility in that tire.

Based on statements in the owner's other posts he is aired down to somewhere between 8 psi and 12 psi.

guess what, airing down is what people do when they need traction in an off-road environment :sombrero: your 16psi in rocks like that is not enough, regardless of the load rating of the tire.

my d-rated 37" mtrs for example don't have squat for traction in deep sand at 16psi, because the contact patch is still too small, it doesn't start getting big enough to support a 4600lb truck until it's approaching 10psi.

read his 2500 mile update on the tires: "As far as airing down goes, I have to say that unlike our old 37" Toyo's which you'd have to take down to about 8 psi to get them to look and feel aired down, simply dropping the STT Pros to about 15 psi will give them the same look and feel and this in spite of them being load range E."

 

[Robert Bills]

. . . your 16 psi in rocks like that is not enough, regardless of the load rating of the tire. . . .

1. I still maintain that the screenshot from the You Tube video is deceptive because it is but one frame from the entire video which fails to reveal that the driver previously lost traction, rolled backward, and is now using horsepower and momentum to bump over the obstacle.

2. One doesn't always need to air down to extremely low pressures for tough trails, but I never said that I would run Cliffhanger with tires at 16 psi. For that trail, which is purely a rockcrawling trail, and depending upon the particular wheel and tire, flexibility of the suspension and weight of the rig, I would probably air down to 12-14 psi and adjust from there until I found the sweet spot.

As for 16 psi not being aired down enough, the previous photo of the C-rated tires at 16 psi was taken at "the Gatekeeper" after 3 days on the Dusy Ershim trail. By using finesse rather than horsepower there was no need to air down further. 16 psi was enough.

Here are the same C-rated tires at Pritchett Canyon in Moab, again aired down to 16 psi. It was enough.

Finally, another set of C rated tires (35" BFG MT) on the Rubicon. I typically ran them at 14 psi as a good compromise between compliance over obstacles and maintaining sidewall height (I've run the Rubicon 5 times - first on 32" tires, twice on 33's and twice on 35's - all were C-rated tires). This photo is from the 4th trip. 16 psi wasn't quite enough; 14 psi was.

The only reason I am running E load rated tires now is because I can't get the size and tire construction I want in any other load rating. I would much prefer a more compliant tire, which are still available with the tire diameter and width I want but only for 15" rims. It seems that for 16" and 17" rims E load rated tires are the only game in town. That doesn't make them better. For my purposes my current E rated tires were merely the best compromise.

 

[Stumpalump]

he didn't hit anything with speed, as the video proves, the tire is wrinkling back on itself because of the torque of the wheel pulling it up and over the obstacle, combined with the low air pressure... there is plenty of flexibility in that tire.


simply dropping the STT Pros to about 15 psi will give them the same look and feel and this in spite of them being load range E."

"Plenty of flexibility" but not as much and not near as much flex on the tread blocks where it counts. You can let more air out of an E to get it to look as low as a C but now your riding on more rubber and less air. Air rides better than rubber and holds the bead. You don't need to go near as low as a C. The other issue is higher tire weight and more rolling resistance. You will lug around more unsprung rotating weight. That wears components and eats gas. It may not be the end of the world to run an E and plenty do but there are really no benifits to it on a light vehicle. More expensive, eats gas, harder on your drivetrain, ruffer ride, more time and work to air them up, lost beads that are harder to reseat, more weight that the vehicle is not sprung or has shock valving for. There is not one thing an E does better on a light vehicle.