Tires...E or D?

[Bronco bobby]

I recently purchased a 15 passenger 09 E350 which already has the Camburg Long Travel suspension as well as 285-75-16 tires and wheels. I noticed while washing it that the tires are load range D. I know that the tag in the door opening calls for a load E tire. This concerned me, so I looked up the load carrying capacity of several tires in my size. Both the load D and E tires have a max capacity or weight of 3195 lbs. D range tires have a max air pressure of 65, while the E tires have a 80 pound max pressure. Does anybody run the D tires since they have the same carrying capacity, or was this a huge error made when the previous owner purchased the tires? Any input would be helpful.

 

[naterry]

D is fine as long as you keep the load rating in mind (i.e. stay under ~12k#'s). Also, not all D rated tires have the same load capacity, worth a double check.

 

[Bronco bobby]

Thanks. Yea I compared the rating of BFG all terrain both D and E, BFG Trail Terrian E, and General All terrain E. Mine are General D rating. I will check it when I get home.

 

[JHa6av8r]

The D were probably put on to soften the ride. The side wall of the E should be stronger.

 

[Bronco bobby]

Yea that is what I was wondering. I had heard that people don't usually run the 80 psi in the rear as recommended due to harsh ride.

 

[JHa6av8r]

Yea that is what I was wondering. I had heard that people don't usually run the 80 psi in the rear as recommended due to harsh ride.

I run mine at 80 but I almost always have 2,000 lbs in the back.

 

[Mwilliamshs]

80 psi max on a sidewall doesn't mean inflate the tires to 80 psi all the time. The tire manufacturer should be able to provide a load chart with varying inflation pressures in correlation to various loads. There will be an absolute minimum and 80 is the absolute maximum and if you'll notice it should say cold too, not just max. If you inflate your tires to their max all the time you'll experience accellerated tread wear in the tire's center unless you're carrying near the tire's maximum load (evenly distributed side-to-side) all the time, not to mention the harsh ride which is in fact less safe from a traction/braking/handling stand point. You can mark a line across the tread in chalk and drive in a straight line across smooth pavement for say 100 yards or so and run the maximum tire pressure that results in the chalk being worn off evenly across the tread face. You can go further by reducing the distance traveled and applying less chalk while continuing to adjust tire pressure until the chalk wears off evenly in 50 or even 25 yards. An even contact patch is your goal for longevity, safety, traction, etc and by running as much air pressure as possible to do so you'll prevent excessive tread wear or tire sidewall flexing, which causes excess heat and eventual tire death. This is all related to on-road tire pressures. Off-road use is a whole 'nother thang.

With regard to load range D vs E, all E's are 80 psi rated, all D's are 65. E's have stronger construction to withstand prolonged exposure to elevated inflation pressures and thus flex less at all inflation pressures to comparable D's at equal pressures. D's are likewise stronger and stiffer than C's, etc. My suggestion is to use D's if they are available in your desired size and required load capacity if you intend to drive off-road. D's improved flexibility is an asset in traction-limited terrain more often than E's improved durability is for most people. The durability of an E-rated tire is often misunderstood because it's intuitive to think a stronger tire is a better tire. That strength comes at the expense of flexibility and is only an improvement over a D rated tire at street pressures. Below that the E's NEED more air pressure to carry a load and will die without it. They also are more prone to absolute bursting when punctured rendering them unrepairable whereas a D can more often than not be plugged or patched. This is a result of the stress on the tire from holding in more or less inflation pressure. Think of how easily a very highly inflated ballon can be popped versus one lying limp and uninflated. If you did poke a hole in an uninflated balloon it would likely be round and easily patched but if that highly inflated balloon is punctured, the rubber tears as its inflation pressure escapes violently. That's an exaggeration of course but still a valid illustration of how a highly inflated tire can be more seriously damaged off road and again, an E rated tire NEEDS to be more highly inflated at all times than does a D rated tire.

 

[Bronco bobby]

Thanks for the information everyone. I'm just trying to make the right choice.

 

[86scotty]

I would recommend E's for sure. I don't run them nearly full PSI though. I've had Toyos, Generals, and now Coopers and they ride really great at about 60-65.

 

[stormlover]

not all E-rated tires have a max PSI of 80

Goodyear Wranger Duratracs are E-rated with a 3650 load rating at max 65 psi. I run them at 45 to 50 psi on my 10,000 lb van.

If you do a search on the SMB forum there were quite a few issues re[ported of D rated BFGs falling apart on 4x4 vans. If it were me I'd stick with an e-rated tire just from the safety standpoint.

 

[Mwilliamshs]

I recently purchased a 15 passenger 09 E350 which already has the Camburg Long Travel suspension as well as 285-75-16 tires and wheels....

80 psi max on a sidewall doesn't mean inflate the tires to 80 psi all the time. The tire manufacturer should be able to provide a load chart with varying inflation pressures in correlation to various loads. There will be an absolute minimum and 80 is the absolute maximum and if you'll notice it should say cold too, not just max...With regard to load range D vs E, all E's are 80 psi rated, all D's are 65. E's have stronger construction to withstand prolonged exposure to elevated inflation pressures and thus flex less at all inflation pressures to comparable D's at equal pressures....an E rated tire NEEDS to be more highly inflated at all times than does a D rated tire.

"not all E-rated tires have a max PSI of 80" Goodyear Wranger Duratracs are E-rated with a 3650 load rating at max 65 psi. I run them at 45 to 50 psi on my 10,000 lb van...

Stormlover, Your claim that not all load E's are rated at 80 psi is absolutely correct. I was speaking specifically to the OP's needs as they were stated (285/75-16) but I can certainly see how I could be misunderstood and thought to be speaking in generalities for all tire sizes. I wasn't. Neither are all (or any...) Goodyear Duratracs rated as you claim and since you didn't post a specific size AND since NO Duratracs exhibit the Max Load Rating you claim (3650): I give you Duratrac Specs for all sizes (might have to click the "Specs" tab to see the list) and to clarify the larger issue: see Load Ratings explained which states, "LT-sized tires featuring section widths of 305mm/12.50 inches or wider have their maximum loads and cold tire pressures rated at reduced maximum load pressures" which for E-range tires is, as you state, 65 psi, not 80.

I've said it before somewhere but I'll say it again, running excessively stiff tires (higher than needed load rating) and airing them down for a smoother ride is what caused the Ford Explorer/Firestone fiasco. That's why vehicles have TPMS now. (Tire Pressure Monitoring Systems)

 

[stormlover]

Stormlover, Your claim that not all load E's are rated at 80 psi is absolutely correct. I was speaking specifically to the OP's needs as they were stated (285/75-16) but I can certainly see how I could be misunderstood and thought to be speaking in generalities for all tire sizes. I wasn't. Neither are all (or any...) Goodyear Duratracs are rated as you claim and since you didn't post a specific size AND since NO Duratracs exhibit the Max Load Rating you claim (3650): I give you Duratrac Specs for all sizes (might have to click the "Specs" tab to see the list) and to clarify the larger issue: see Load Ratings explained which states, "LT-sized tires featuring section widths of 305mm/12.50 inches or wider have their maximum loads and cold tire pressures rated at reduced maximum load pressures" which for E-range tires is, as you state, 65 psi, not 80.

I've said it before somewhere but I'll say it again, running excessively stiff tires (higher than needed load rating) and airing them down for a smoother ride is what caused the Ford Explorer/Firestone fiasco. That's why vehicles have TPMS now. (Tire Pressure Monitoring Systems)

Your right, my bad it's 3860 at 65 psi. http://www.tirerack.com/tires/tires...idewall=Blackwall&partnum=175QR6WDT&tab=Specs

So, by referencing the Explorer/Firestone tire fiasco/fiery deaths/lawsuits to my post you are implying that by running the e-rated Duratracs at less than their load rating (in my case 45 or 50 psi instead of the max 65 psi) that I am being irresponsible?

I don't believe you. And I don't believe people were dying because they were airing down their firestone tires. There was a design/manufacturing flaw. Joe Schmoe in his Ford Explorer wasn't running 20 psi at 80 mph because the ride was too stiff? On the other hand, there seemed to be a high percentage of repeated tread separations on D rated BFGs from folks with sportsmobile vans. Was it because they were airing them down? Maybe, but if I was the OP I would just run E-rated and adjust the pressure accordingly. And the point I make was that you get roughly equal load rating at lower pressure.

 

[Mwilliamshs]

The "design flaw" was Ford's design of the recommended tire pressure sticker. The number they "designed" into the sucker was lower than Firestone recommended. It wasn't that drivers wanted to improve the ride of the car they bought but that Ford wanted to sell a better riding car with big truck tires on it for looks. Joe Schmo, his oil change guy, his wife, etc thought they were doing things right by inflating the tires to the sticker's pressure but they weren't. This is why the case's result was the addition of systems to vehicles to monitor tire pressure. If it were a design flaw the designs would change, not the tire pressure and the need to alert drivers to low pressure conditions (which obviously were the cause of the problems, else the result of all the investigations would have been some other changes). I referred to that as an extreme example not as a comparison to you. I am curious how you arrived at 45-50 as the correct pressure for your application (a 25-30% reduction from max). If you read my post about load charts and tire wear you'll see I'm not for airing up tires too high or too low. Download this small pdf from Toyo Go to page A1. Read the charts. Contemplate their meaning. Understand there's a correct inflation pressure for every load within a tire's load range. Notice it's load "range" not maximum load "limit"? My point was that D range tires are a better fit for a van that's not loaded beyond them and sees off road use requiring tire flexibility. Lots of things affect the life of a tire and how it dies. Strange you see the firestone thing as a "design flaw" but the bfg thing as a load-range-D-sucks-on-sportsmobiles failure when they both end in tread-separation.

 

[stormlover]

Interesting info. And what was Ford's recommended psi for the tires versus Firestone? Anyhow, I can't explain the D range BFG thing. I had to assumed too much weight for the load index but even then on a 10,000lb it should have been adequate. Perhaps not enough sidewall?


Here's how I arrived at 45-50 as the correct pressure for my 4x4 SMB van. Weight 10,000 lb fully loaded. (max psi/max load) x actual load=min load capacity + 15% safety factor
(65/3860) x (50000lb per axel/2) = 42 psi + 15% = 48 psi


The Duratrac has a load index of 127. If you believe the charts max pressure of 65 psi at 3860 would have a load capacity of 15440 lb. Since I don't have an Earthroamer I believe 45 to 50 psi is more than adequate from my application. Read the charts. http://overlandexpo.squarespace.com/storage/downloads/Discount Tire inflation.pdf
If I am contemplating their meaning correctly (thanks for the help on reading comprehension by the way) then Discount actually recommends 35 psi for my application.
Thanks for the lively discussion.

 

[Mwilliamshs]

we were typing simultaneously. I'll post now what I had ready and edit it after reading yours...

All the following information comes from here: Duratrac Specs @ TireRack or here: Goodyear Tire Load pamphlet


ok stormlover since you still haven't shared what size tire you have I looked up the maximum rated load you posted, 3,860 lbs and think you must have LT325/65-18's. That tire has a service description of 127/124Q E. The first number (127) is for single wheel applications and you haven't stated your van is a drw so I'll assume it isn't. A service description of 127 means that tire is rated to carry 3,860 lbs in a single wheel application and 124 means 3525 in dual applications. The reason I included the dual information will be clear soon and the upcoming asterisk (*) is gonna become important too. The Q means it's rated to carry that weight or less at speeds of 99 mph*. Now, because your tires have a service description this does not apply directly to them, but you should know and I want to make it clear so I'm not misunderstood again to be speaking more generally than I am, that *Goodyear requires a 10% PSI increase in cold inflation pressure for speeds of 65 mph-75 or below 15 mph for LT tire sizes without relevant service descriptions* at reduced speeds (less than speed rating) on improved surfaces. This does apply to your tires as well, just not directly. If that seems unclear, question Goodyear about what they mean in their pamphlet, because that's exactly how it's written. A further caveat, is that all inflation pressures and loads must not exceed the lesser of axle ratings, wheel ratings and/or tire ratings and overall vehicle ratings. Goodyear also specifies an increase of maximum load based on maximum travel speed but this increase is expressed as a percentage and that percentage is calculated with the appropriate single or dual application max load then added to the dual-tire load ratings, even if the tire is used in a single-tire application. Simple, huh? Goodyear doesn't provide a useful chart like the one I linked to from Toyo, but instead uses a worksheet on page 43 of that pamphlet which you may complete. You could perform the calculations multiple times with varying loads and record them in chart form if you wanted I guess, but Goodyear is too busy.

My point is this: I'll work through how you got to 45-50 as the correct pressure for your application but still, spouting off things like "Duratracs are rated at xx psi and xxxx pounds" without application or sizing data is not only unhelpful but could be dangerous should someone take your "information" and use it in the real world.

Interesting info. And what was Ford's recommended psi for the tires versus Firestone? Anyhow, I can't explain the D range BFG thing. I had to assumed too much weight for the load index but even then on a 10,000lb it should have been adequate. Perhaps not enough sidewall?

I think, it's been a decade+ since I last really closely examined the Ford/Firestone case in school, that Ford was suggesting 22 psi where Firestone wanted them to say 30 psi. That's at least close to the spread if not the range. The BFG tires that were delaminating were probably underinflated was my whole point. I've seen multiple folks first-hand airing their F250 tires down to 10 psi off-road because that's what they do on their Jeeps. Apples and watermelons. As for not enough sidewall...that doesn't make any sense to me. Are you saying it takes x amount of sidewall height to support a given load? How then do tires of differing heights have comparable load ratings and why would tires of equal heights but larger wheel sizes (16" vs 15" for example) have higher load ratings and shorter sidewalls instead of the other way round?

Here's how I arrived at 45-50 as the correct pressure for my 4x4 SMB van. Weight 10,000 lb fully loaded. (max psi/max load) x actual load=min load capacity + 15% safety factor (65/3860) x (50000lb per axel/2) = 42 psi + 15% = 48 psi

You calculated what each pound of pressure is capable of supporting in your tire, which is erroneous because there is an absolute minimum, then assumed a 50/50 weight distribution, which is erroneous unless you've measure your van to have such which is very unlikely for the former and unproven for the latter, and used the same pressure front and rear which matches that last mistake but in reality creates one of its own, then used a safety factor smaller than your overall change, which is a false equivocation. The answer might be right (too many assumptions to know) but the formula sure isn't.

The Duratrac has a load index of 127.

"The Duratrac"? There's only one? Still no real idea what size tire your talking about but since your information here agrees with mine above I guess I guessed right.

If you believe the charts max pressure of 65 psi at 3860 would have a load capacity of 15440 lb. Since I don't have an Earthroamer I believe 45 to 50 psi is more than adequate from my application.

What about your safety factor? 15,440 -15% = 13,124

Read the charts. http://overlandexpo.squarespace.com/storage/downloads/Discount Tire inflation.pdf
If I am contemplating their meaning correctly (thanks for the help on reading comprehension by the way) then Discount actually recommends 35 psi for my application.
Thanks for the lively discussion.

Who is Discount? Where did these charts originate? Who wrote them? These are for determining what pressure to run in new tires based on the ratings of the original ones and their recommended inflation pressures. What were your original tires? What was their load range? What was their service description? What was their original recommended inflation pressure? Have the charts you posted been verified by your tire manufacturer? or by uhm, anyone?

As for original tires: the last new van I was in was 2010 E-350 with 225/75-16 load range E all-season Bridgestones on it. The closest match I can find by memory is the Duravis R500 HD with a service description of 115/112R, giving them a max load rating of 2680 @ 80 psi. Ford's recommended inflation pressures (it was a fleet van @ work, I did its pre-trip checklist almost daily, and that included inflating them to a pressure matching the door-jamb sticker) were I think 60 psi front and 75 rear. The van was always loaded (it had an installed piece of equipment) so 75 wasn't uncomfortable but had I used it empty I would've dropped that pressure some. Taking that information and using the charts you shared, I find that 115 E @ 60 psi is good for 2190 lbs front and 75 psi is good for 2560 rear. Moving that info to E2 127 (wide base, like your replacement tires) supports 2535 lbs at only 35 psi which is the lowest the chart goes. Did you consult these charts before deciding on replacement tires? They seem a poor match based on the information you've shared. So the front tires should be below 35 psi according to your charts and the rears should be between 35 and 40 psi. That all seems too low and like you've got too much tire for your load. Not saying you'll have problems but wow that seems like a serious component mis-match and proves my case than an E rated tire isn't necessarily necessary and I bet you're WAY below the load ratings for your tires if you're within Ford's gvwr and gawr's. Who knows you might onto something for floatation and tread life if you can keep them level across the face on road.