37s Load D or E?

[mk216v]

Thanks for the info above, all.

Also, MANY thanks to @klahanie for reminding me where the tire inflation "matrix" tables were located on the web. They can be found here;

Find the Correct Tire Inflation Pressure

These Load and Inflation Tables are intended to provide assistance when replacing tires with optional tire sizes including “plus sizes.”

www.toyotires.com

TOYO TIRES - Europe

Toyo Tires Official Web site

www.toyotires.com

Interesting to see, starting on pg23, what the load ratings are as tire pressure reduces.

Let's use @montypower (Peter's) setup as an example. He runs;
37x12.5x17 Yokohama Geolandar X-AT, D load.
Front 20-25psi and rear 30-35psi.
Front: 4,650lbs(~2325lbs/ea corner) and Rear: 6,150lbs(~3075lbs/ea corner)

Looking at the table at the very end of pg31 of the Toyo pdf, under 37x12.5x17 D load;
For front; weight spec at 20psi has no weight data, weight spec at 25psi is 2150lbs/ea corner.
For rear; weight spec at 30psi is 2470lbs/ea corner, weight spec at 35psi is 2755lbs/corner.

So, at Xpsi front or rear, Peter has been loading about 10% add'l weight onto each corner of his tires, beyond what Toyo suggests for Xpsi. And his tires have held up. Not saying that's always going to be the case, but it is here on this truck with the Yoko tires.

What is interesting, is if we look at the table for 37x13.5x17 E load, on pg32, here's the data from it;
For front; weight spec at 20psi has no weight data, weight spec at 25psi is 2205lbs/ea corner (55lbs MORE than 37x12.5x17 D load).
For rear; weight spec at 30psi is 2550lbs/ea corner (80lbs MORE than 37x12.5x17 D load), weight spec at 35psi is 2835lbs/corner (80lbs MORE than 37x12.5x17 D load).
My takeaway is that at lower pressures(40psi or less), there's not a whole lot of difference between 37x12.5x17 D load and 37x13.5x17 E load. And more importantly, a 17" E load tire wouldn't even support Peter's front or rear corner weights.

Now, if we look at 37x13.5x18, while there are many A/T tires available in E load in this size, the table doesn't list E load info, only typical D load (3525lbs max at 50psi max). I'm waiting to hear from a tire industry member to see if there's updated data for 37x13.5x18 E load (No info yet, but @klahanie sent this other load table; https://tirepressure.org/flotation-tire-load-inflation-chart which has 37x13.5x18 data).

But for now, there's data for 37x12.5x18 E load;
For front; weight spec at 20psi has no weight data, weight spec at 25psi is 2095lbs/ea corner (55lbs LESS than the 37x12.5x17 D load, and 110lbs LESS than 37x13.5x17 E load).
For rear; weight spec at 30psi is 2395lbs/ea corner (75lbs LESS than 37x12.5x17 D load, and 155lbs LESS than 37x13.5x17 E load), weight spec at 35psi is 2680lbs/corner (75lbs LESS than 37x12.5x17 D load, and 155lbs LESS than 37x13.5x17 E load).

So, what's the advantage to the 18" wheel? NOTHING I see in regards to Peter's weights, as the 37x12.5x17 D load and 37x12.5x18 E load are pretty even overall up to 40psi (with the 37x12.5x17 D load actually supporting more weight), then the 37x12.5x18 E load takes off at 55psi and begins to hold more weight (3590lbs at 55psi, then 3795lbs at 60psi, then 3970lbs at 65psi). Again, the issue I have with the 37x12.5x18 tire size is that there are only a few A/T tread patterns.

Interesting that the 371x12.5x17 D load has the same data as the 37x13.5x18 D load.

Of course if you have over 3500lbs/ea corner (55+psi), then the 37x12.5x18 E load is suggested. But if you have less weight than that, then there's no advantage I see to the 37x12.5x18 E load over the 37x12.5x17 D load. In fact, one could argue that if you do a lot of offroad low-psi driving, the 37x12.5x17 D load supports more weight than the 37x12.5x18 E load at 40psi or lower. And then the 37x13.5x17 D/E load supports even more weight than either of them at 35psi or lower.

Here's an easier view;

37x12.5x17 D/124 (there is a 37x12.5x17 F load in the table too, but it's data looks to be the same as the E load; 3195lbs/F/121 from 50-80psi);
25____30___35___________40____45___50psi
2150_2470_2755(C/116)_3005_3250_3525(D/124)lbs

37x13.5x17 (D/121 or E/121);
25____30___35____40___45____50___________55____60___65psi
2205_2550_2835_2955_3075_3195(D/121)_3195_3195_3195(E/121)lbs

37x12.5x18 E/128;
25____30___35___________40___45____50____________55___60____65psi
2095_2395_2680(C/115)_2915_3150_3415(D/123)_3590_3795_3970(E/128)lbs

37x13.5x18 D/124;
25____30___35____40____45___50psi
2150_2470_2755_3005_3250_3525(D/124)lbs

37x13.5x18 E/128?;
25____30___35____________40___45____50_____________55___60____65psi
2150_2470_2755(C/116?)_3005_3250_3525(D/124?)_3675_3820_3970(E/128)lbs


Since I want to focus on 12.5"W for myself, and the 37x13.5x18 is worst case for me, let's compare these 3 only;

37x12.5x17 D/124;
25____30___35___________40____45___50psi
2150_2470_2755(C/116)_3005_3250_3525(D/124)lbs

37x12.5x18 E/128;
25____30___35___________40___45____50____________55___60____65psi
2095_2395_2680(C/115)_2915_3150_3415(D/123)_3590_3795_3970(E/128)lbs

37x13.5x18 E/128?;
25____30___35____________40___45____50_____________55___60____65psi
2150_2470_2755(C/116?)_3005_3250_3525(D/124?)_3675_3820_3970(E/128?)lbs

IF the 37x13.5x18 data in the 2nd URL is true, then both the 37x12.5x17 D/124 and 37x13.5x18 E/128 allow more load than the 37x12.5x18 E/128.
As well, the 37x12.5x17 D/124 and 37x13.5x18 E/128 offer the same load capacity up to 50psi.
ONLY after 50psi does the 37x13.5x18 E/128 offer more than 3525/lbs per tire capacity; 3675lbs at 55psi, 3820lbs at 60psi, and 3970lbs at 65psi.
So if my actual corner weight is less than ~3000lbs (so I have ~15% buffer room), then either the 37x12.5x17 D/124 and 37x13.5x18 E/128 should work well for my use case.

 

[eyemgh]

I'm on Wildpeaks too, but a 37 on a 17 inch wheel. I've got 10 inches of sidewall, you have 7. Your sidewall is much stiffer. I have heard nothing but good things about Toyo's. They are really tough.

Good point.

My main argument is that we can intuit a lot from the pressure/load charts, and don’t have to only run E at max inflation to be safe. Like me, that’s what you elect to do. You don’t change pressures, but you are air’d down all the time.

 

[eyemgh]

Thanks for the info above, all.

Also, MANY thanks to @klahanie for reminding me where the tire inflation "matrix" tables were located on the web. They can be found here;

Find the Correct Tire Inflation Pressure

These Load and Inflation Tables are intended to provide assistance when replacing tires with optional tire sizes including “plus sizes.”

www.toyotires.com

TOYO TIRES - Europe

Toyo Tires Official Web site

www.toyotires.com

Interesting to see, starting on pg23, what the load ratings are as tire pressure reduces.

Let's use @montypower (Peter's) setup as an example. He runs;
37x12.5x17 Yokohama Geolandar X-AT, D load.
Front 20-25psi and rear 30-35psi.
Front: 4,650lbs(~2325lbs/ea corner) and Rear: 6,150lbs(~3075lbs/ea corner)

Looking at the table at the very end of pg31 of the Toyo pdf, under 37x12.5x17 D load;
For front; weight spec at 20psi has no weight data, weight spec at 25psi is 2150lbs/ea corner.
For rear; weight spec at 30psi is 2470lbs/ea corner, weight spec at 35psi is 2755lbs/corner.

So, at Xpsi front or rear, Peter has been loading about 10% add'l weight onto each corner of his tires, beyond what Toyo suggests for Xpsi. And his tires have held up. Not saying that's always going to be the case, but it is here on this truck with the Yoko tires.

What is interesting, is if we look at the table 37x13.5x17 E load, on pg32, here's the data from it;
For front; weight spec at 20psi has no weight data, weight spec at 25psi is 2205lbs/ea corner (55lbs MORE than 37x12.5x17 D load).
For rear; weight spec at 30psi is 2550lbs/ea corner (80lbs MORE than 37x12.5x17 D load), weight spec at 35psi is 2835lbs/corner (80lbs MORE than 37x12.5x17 D load).
My takeaway is that at lower pressures, there's not a whole lot of difference between 37x12.5x17 D load and 37x13.5x17 E load. And more importantly, a 17" E load tire wouldn't even support Peter's front or rear corner weights.

Now, if we look at 37x13.5x18, where there are many A/T tires available in E load in this size, Toyo's R/T or M/T however are both D load, so this size from Toyo doesn't offer any improvement in load characteristics (where it might with another tire mfr who offers this size in E load).

But, Toyo also has E load in 37x12.5x18, and here's the data from it;
For front; weight spec at 20psi has no weight data, weight spec at 25psi is 2095lbs/ea corner (55lbs LESS than the 37x12.5x17 D load, and 110lbs LESS than 37x13.5x17 E load).
For rear; weight spec at 30psi is 2395lbs/ea corner (75lbs LESS than 37x12.5x17 D load, and 155lbs LESS than 37x13.5x17 E load), weight spec at 35psi is 2680lbs/corner (75lbs LESS than 37x12.5x17 D load, and 155lbs LESS than 37x13.5x17 E load).

So, what's the advantage to the 18" E load? NOTHING I see in regards to Peter's weights, as the 37x12.5x17 D load and 37x13.5x18 E load are pretty even overall up to 40psi (with the 37x12.5x17 D load actually supporting more weight), then the 37x13.5x18 E load takes off at 55psi and begins to hold more weight (3590lbs at 55psi).
Of course if you have over 3500lbs/ea corner, then the 37x13.5x18 E load is suggested. But if you have less weight than that, then there's no advantage I see to the 37x13.5x18 E load over the 37x12.5x17 D or 37x13.5x17 E load.

Something to consider too is that there are many advantages of staying with 35s. That’s why I didn’t go to 37s. Peter does a lot of crawling where the clearance helps. For the rest of us, 37s might not be worth it.

The attached pic is my SD with a Carli Pintop and Carli designed Deaver leaf pack. There’s obviously no camper, hence the high rear. The 35s look fine and in reality, they measure a little less than that.

 

[mk216v]

Something to consider too is that there are many advantages of staying with 35s. That’s why I didn’t go to 37s. Peter does a lot of crawling where the clearance helps. For the rest of us, 37s might not be worth it.

The attached pic is my SD with a Carli Pintop and Carli designed Deaver leaf pack. There’s obviously no camper, hence the high rear. The 35s look fine and in reality, they measure a little less than that.
View attachment 709877

Looks good on 35s. Personally I like the look/offroadiness of 37s so I'm pushing forward for them.

Update on my end....talking to our TireRack guy (10yr industry veteran), I ask for load/psi tables from Yoko for the Geolandar X-AT tire. He says that the load/psi tables Toyo has on their site are industry standard, it's not Toyo specific info, so the same data applies to the Yoko. Ok, but why Yokohama and others don't have the same info on their sites, it's a mystery, but whatevs.

So I go along with notion that until I'm looking in the Toyo table for what the data looks like for a 37x13.5x18 E load tire (https://tiresize.com/tires/Yokohama/Geolandar-X-AT-37X13.50R18.htm), but there is NO data whatsoever for a 37x13.5x18 E load tire. Only D load.
So perhaps this size is new and the industry hasn't updated the load/psi table yet? That's probably the case.

So I flip it back to him again...waiting to see if Yoko can provide the data on this size.
He said that based on my truck, and desire to tow an aluminum 2horse trailer, in big bold yellow highlight he does NOT recommend a D load 37x12.5x17 based on the load data in the Toyo table, even though he/I don't even know my final load yet.

More to come in my tire search...

PS--big thanks to @klahanie for some things to think about, like (in regards to trailer tongue weight);
One possible gotcha is the weight placed behind the rear axle is effectively greater than the stand alone weight of the item.
Easy to calculate if you use the wheelbase/100 = 1% weight transfer. So 160"WB means every 1.6" aft of axle adds 1% more effective weight to the rear axle and 1% reduction to the front axle. That 200# rear winch mounted 48" back from the axle adds 30%, 200 becomes 260#.

 

[ramblinChet]

My AEV Prospector came with 17x8.5" Salta HD rims with the correct backspacing for their 3" DualSport RT suspension system. That package also included 37x12.5R17LT BF Goodrich All-Terrain KO2 tires with a load range of D. My GVWR is 11,000 lbs and each tire has a maximum load of 3,525 lbs so I have no worries. AEV crunched the number and performed the testing.

 

[wild1]

My AEV Prospector came with 17x8.5" Salta HD rims with the correct backspacing for their 3" DualSport RT suspension system. That package also included 37x12.5R17LT BF Goodrich All-Terrain KO2 tires with a load range of D. My GVWR is 11,000 lbs and each tire has a maximum load of 3,525 lbs so I have no worries. AEV crunched the number and performed the testing.

Maybe, what is really the important number is how much actual loaded weight you are carrying on your rear axle and how much of a safety margin do you want. In your case with a figure of 10% below max you would have around 6300 pounds of rear axle weight to work with. That’s a number that is very easy to exceed with most slide in campers and built trucks.

 

[montypower]

Why is there so much concern over the Letter Rating? Load rating is the important number. There are many (possibly even the majority) Load E tires that are rated at 3,195lbs. This is significantly less than the Load D 37s.

Also.... Giving additional "buffer room" isn't necessary. Tire manufacturers build in "margin" to their ratings already. Just staying within the rated load is fine. For instance, while driving off camber off road or steep hills the majority of the load is shifted to 2 tires and will exceed the "rated load" yet they don't blow up. This is because the "break strength" is significantly above the load rating. In addition, there's a massive difference at slow speed vs high speed. Same with airing down the tires... those charts don't really apply to "off roading" but on road driving. Which makes sense for the PSI and load numbers.

But if you are really concerned and want overkill....

Toyo MT 37x13.5R17 E - This is your answer! 4,300lb load per tire! And only 94lbs... This is the tire used on the Earth Cruisers and is a seriously beefy tire. Just make sure you buy wheels that match or exceed 4,300lb rating. But you will be giving up a few things: braking, acceleration, mpg, noise... but lots of "load margin". HEHE

 

[wild1]

Why is there so much concern over the Letter Rating? Load rating is the important number. There are many (possibly even the majority) Load E tires that are rated at 3,195lbs. This is significantly less than the Load D 37s.

Also.... Giving additional "buffer room" isn't necessary. Tire manufacturers build in "margin" to their ratings already. Just staying within the rated load is fine. For instance, while driving off camber off road or steep hills the majority of the load is shifted to 2 tires and will exceed the "rated load" yet they don't blow up. This is because the "break strength" is significantly above the load rating. In addition, there's a massive difference at slow speed vs high speed. Same with airing down the tires... those charts don't really apply to "off roading" but on road driving. Which makes sense for the PSI and load numbers.

But if you are really concerned and want overkill....

Toyo MT 37x13.5R17 E - This is your answer! 4,300lb load per tire! And only 94lbs... This is the tire used on the Earth Cruisers and is a seriously beefy tire. Just make sure you buy wheels that match or exceed 4,300lb rating. But you will be giving up a few things: braking, acceleration, mpg, noise... but lots of "load margin". HEHE

My conservative approach comes from having a couple of highly rated mud terrains tire that I was running near max capacity come apart at highway speed on a trip to Moab. These were catastrophic blowouts at 65 mph. Both occurred within 500 miles of each other and did substantial damage to the rear fenders of the truck besides almost causing a wreck. If you follow the more road oriented truck camper forums rear tire issues are a major concern because of the number of folks that have had real experience with tire failure. I agree that off pavement there is little safety concern from running your tires at the lower pressure it is the potential for damaging the tire structure and then having them come apart at highway speeds that concerns me.

 

[montypower]

What were the factors with the tire failures? Age of tires? Stored outside? Tire pressure? Wear? Load? Tire brand? Load rating?

I agree. It's good to be mindful of all the factors. Maintained quality tires within load spec should be fine. Of course, failures can and will happen regardless.

The Ford dealer "overinflated" our tires to 80psi (50psi max rating). I didn't figure it out for 2 weeks and was concerned the tires might have been compromised. Especially since we were hauling the camper and trailers during that time. However, Yokohama customer service, Discount Tire and the Ford dealer were not worried. Just recommended rebalancing them. That was a year ago. They were cupping a bit. So I've been running them on the road at 32psi with the camper removed and hauling trailers. They seem to like the lower pressure and tread is flat again.

Will be heading to Moab in April with the camper and enclosed trailer (with SxS). Will probably run 40psi front / 45psi rear due to the heavy load. Will keep the trailer tongue weight under 500lbs (have a scale to verify). Should still be under the load limit by a bit.

Planning to replace the tires at then end of the year. We should be over 30k miles and I like to keep fresh rubber.

 

[wild1]

What were the factors with the tire failures? Age of tires? Stored outside? Tire pressure? Wear? Load? Tire brand? Load rating?

I agree. It's good to be mindful of all the factors. Maintained quality tires within load spec should be fine. Of course, failures can and will happen regardless.

The Ford dealer "overinflated" our tires to 80psi (50psi max rating). I didn't figure it out for 2 weeks and was concerned the tires might have been compromised. Especially since we were hauling the camper and trailers during that time. However, Yokohama customer service, Discount Tire and the Ford dealer were not worried. Just recommended rebalancing them. That was a year ago. They were cupping a bit. So I've been running them on the road at 32psi with the camper removed and hauling trailers. They seem to like the lower pressure and tread is flat again.

Will be heading to Moab in April with the camper and enclosed trailer (with SxS). Will probably run 40psi front / 45psi rear due to the heavy load. Will keep the trailer tongue weight under 500lbs (have a scale to verify). Should still be under the load limit by a bit.

Planning to replace the tires at then end of the year. We should be over 30k miles and I like to keep fresh rubber.

I had those blowouts back in 1998 on a set of the new Interco radial mud tires that had a 126 load rating 3750 at 80 psi. They were almost new, the rear axle was below their rated weight and they were at 80 psi. I still have the two from the front on my yard trailer that makes an occasional trip to the dump. They still look great, they were certainly a stout tire. They did comp me the full price of the two that let go. I enjoy seeing your adventures safe travels. Here’s a shoot of us heading down to sag the White Rim Trail for my son on his Mt bike.

 

[vintageracer]

The 4th Load Range E Toyo out of a set of 6 just broke a cord the other day on the diesel dually Ford used almost exclusively for on road travel.

Toyo has been a PITA as far as warranty on these tires for broken cords.

Since the first broken cord issue with the first tire TOYO claims it's a problem with the truck not their tire. Then WHY in the first 170K miles I put on the truck did the first two tire brands not have any tire problems at all and your TOYO tires all have less than 20K miles on them break tire cords TOYO Customer Service does not want to answer or even talk about this question.

All 4 TOYO tires with broken cords were mounted on the rear. First set of tires on the truck Michelin's. 85K miles No issues. Second set of tires on the truck Firestone's. Another 85K miles No issues. 3rd set of tires on the same truck Toyo's. 4 of the Toyo 6 tires have broken a cord in less than 20K miles. This will be the last time I take a tire recommendation from a tire salesman!

Don't think it's a truck issue!

It's a TIRE ISSUE!

 

[mk216v]

Why is there so much concern over the Letter Rating? Load rating is the important number. There are many (possibly even the majority) Load E tires that are rated at 3,195lbs. This is significantly less than the Load D 37s.

Also.... Giving additional "buffer room" isn't necessary. Tire manufacturers build in "margin" to their ratings already. Just staying within the rated load is fine. For instance, while driving off camber off road or steep hills the majority of the load is shifted to 2 tires and will exceed the "rated load" yet they don't blow up. This is because the "break strength" is significantly above the load rating. In addition, there's a massive difference at slow speed vs high speed. Same with airing down the tires... those charts don't really apply to "off roading" but on road driving. Which makes sense for the PSI and load numbers.

But if you are really concerned and want overkill....

Toyo MT 37x13.5R17 E - This is your answer! 4,300lb load per tire! And only 94lbs... This is the tire used on the Earth Cruisers and is a seriously beefy tire. Just make sure you buy wheels that match or exceed 4,300lb rating. But you will be giving up a few things: braking, acceleration, mpg, noise... but lots of "load margin". HEHE

Peter makes an excellent point, and I just amended my post #46 with further load(lbs) data, as well as load range info.

It's more than just D load or E load that is important. What is key is the specific load index of the tire/tire size;
https://www.tirerack.com/tires/tiretech/techpage.jsp?techid=35 (note 127 and 128 not shown there, but those seem to be ~3860lbs and 3970lbs respectively; YMMV).

For now, it's a moot point to guess my corner weights and look at tires. I'll wait until my camper is on, everything loaded in/on, weigh it at 2 scales for accuracy, then decide on 17"tires or 18" tires/wheels.

 

[ramblinChet]

Maybe, what is really the important number is how much actual loaded weight you are carrying on your rear axle and how much of a safety margin do you want. In your case with a figure of 10% below max you would have around 6300 pounds of rear axle weight to work with. That’s a number that is very easy to exceed with most slide in campers and built trucks.

I appreciate your concern although I am paid to play with numbers so this was pretty elementary. My base weight is 6,407 and my FWC adds 1k. Add another 500 for my AEV Prospector package along with another 500 for clothes, food, etc. Top off the tank and add me for another 500 and we are still under 9,000 total. My front axle is good for 5,500 while my rear is at 7,000. I have the correct tires and I have no worries.

Regarding the safety factor for tires I am sure it is up around four times the published load. The only times I have witnessed lower factors such as 1.5 or 2.0 it has been associated with aircraft or spacecraft.

 

[KiwiMtnClmbr]

I'd go with 18's actually. They have a way higher load rating along with the 18" x 9" wheels with the wider bead. Much more stable. Regardless of the wight rating a 50 psi tire doesn't inspire confidence for me with a slide in on the highway. I have 17 x 8.5 Methods and 285-75-17 Toyo AT3's. I wish I'd gone with the 18" combo. I have the suspension upgrades but still feel some tire squirm at highway speed in windy conditions.

Do you happen to have the C load rated version of the AT3… I ask b/c I’m currently in the 17 vs 18 rabbit hole and noticed that there is an 80psi and a 50psi 285/75/17.

Technically your psi setting should be the same for either as it’s based on the actual front/rear weights you’re running, but the carcass must be quite different between those two versions (62 vs 59# per tire difference too).

 

[mk216v]

Look at the Toyo tire table data (it's not specific to Toyo but is tire industry data).
I'm unsure if the carcass is different C vs D vs E load, since they're no longer 6 vs 8 vs 10ply.
I've chosen to run a 37x12.5x17 D load vs E load, as looking at the table data vs my actual axle weights, there was no advantage to run an E load as I'd never be weighing heavy enough to hit the higher psi/load rating of the E (meaning, D and E data were the same load rating at 50psi up to something like 3200lbs or so).