37s Load D or E?

[mk216v]

Tires are the topic where I find most people think whatever they have is the "best". But many have a limited experience base of tire brands, types to even know. So most reviews are not helpful.

Key item is load capacity rating. It doesn't hurt to run a E or F rated tire. But keep in mind, you'll need to run the specified pressure to achieve the load capacity.
So far, I've appreciated the lower 50psi rating for the ~3,500lb capacity. Much easier to live with off road to on road transitions.

In my experience, this rings true for most reviews that are auto-related; most people haven't experienced enough options to be able to compare clearly. Take their mileage life with a grain of salt too; one guy gets 10k on the tires and 3 others are getting 50k. Who knows if they're all checking/adjusting tire pressures weekly or not (time consuming, yes!).

Agreed on load capacity. Again, I found it very interesting comparing 37s and 35s for my '19 F350 4x4;
These 37"/D-load are 3525lbs Max/ea at Max 50psi;
https://www.tirerack.com/tires/tire...dewall=Blackwall&partnum=725QR7GRX3&tab=Specs

These 35"/E-load are 3195lbs Max/ea at Max 65psi;
https://www.tirerack.com/tires/tire...id Red Letters&partnum=525QR7GRX3RL&tab=Specs

Most feedback here on ExPo has been get the E vs D load due to stiffer sidewalls, thus better puncture resistance offroad.
Personally I've never run 35s (E350 4x4) at anywhere near 55psi+, especially an M/T tire--just too hard, worse handling and ride comfort.
So I'm leaning towards 37s for your reason (appreciated the lower 50psi rating for the ~3,500lb capacity. Much easier to live with off road to on road transitions.).

YMMV of course.

 

[mk216v]

Reviving this thread...
I'm still perplexed as to why tire mfr's aren't making E loads in 37", D or E load in 40". I asked that of Scott Brady here, but no answer;
https://expeditionportal.com/forum/...nd-journal-podcast.212065/page-3#post-2843853

I'd like to learn more and/or see a white paper. Can anyone else shed light on this?

 

[Regcabguy]

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.

 

[BretEdge]

I can't answer from a technical perspective but I can tell you that I'm running 37" D rated Toyo Open Country R/T's on 17" Method's on my 2021 F250 with a flatbed and FWC Hawk UTE. I've got around 17,000 miles on this setup and have had zero issues. Our total loaded weight is around 11,000 lbs. I run the tires at around 45 PSI year-round.

 

[Darwin]

They do make load E 37's. Toyo MT and also switching to an 18" wheel .

 

[pappawheely]

Does anyone with a serious load in the back actually air down their tires? The last thing I want when off road and with a heavy camper in the back is to have squishy tires, and my sidewalls more exposed to rock damage. If you want more traction, go with a wider tire. I run 37's on a 17 inch wheel without airing down. The only time I do air down is if I'm stuck, and I never get stuck (until I said that of course). More tire sidewall usually means a softer ride. A shorter sidewall is stiffer, so usually it increases your stability. Airing down is for jeepers, not for trucks with slide in campers.

 

[wild1]

Does anyone with a serious load in the back actually air down their tires? The last thing I want when off road and with a heavy camper in the back is to have squishy tires, and my sidewalls more exposed to rock damage. If you want more traction, go with a wider tire. I run 37's on a 17 inch wheel without airing down. The only time I do air down is if I'm stuck, and I never get stuck (until I said that of course). More tire sidewall usually means a softer ride. A shorter sidewall is stiffer, so usually it increases your stability. Airing down is for jeepers, not for trucks with slide in campers.

I tend to agree with you, I think a lot of folks think that they are going to drive their truck and camper like a big Jeep and discover the limits of a 11 to 12 thousand pound pretty quickly. My old 2001 superduty with a service body and 8 foot Alaskan camper was on 285/75-16’s for over 120,000 miles and 15 years from Alaska to Baja and never saw a day under 80 psi front and back. It tipped in at close to 11,000 pounds fully loaded. My new Ram 3500 has what I think is a perfect match for a heavy truck camper , Cooper 295/70-18’s. Over 4000 load capacity per tire, fits in the stock spare location, stock gearing is adequate and no rubbing with plenty of room for chains. Talking to the Toyo engineers at expo they designed these tire for exactly this purpose. I run mine at 80 psi with 7000 pounds of rear axle weight and it is stable on the highway and tolerable for long gravel slogs.

 

[montypower]

Does anyone with a serious load in the back actually air down their tires? The last thing I want when off road and with a heavy camper in the back is to have squishy tires, and my sidewalls more exposed to rock damage. If you want more traction, go with a wider tire. I run 37's on a 17 inch wheel without airing down. The only time I do air down is if I'm stuck, and I never get stuck (until I said that of course). More tire sidewall usually means a softer ride. A shorter sidewall is stiffer, so usually it increases your stability. Airing down is for jeepers, not for trucks with slide in campers.

Yep! We drove the entire state of Idaho off road (videos coming) with the tires aired down the entire time front 20-25psi and rear 30-35psi. 1,500 miles for 6 weeks. Fully loaded with camper (10-11k lbs). 23k miles on the 37x12.5R17 Load D

Tire letter is "old school" same as the "ply rating" (8 ply or 10 ply). Tires are not built that way! Todays tire construction is "ply equivalent". You're much better off looking at "load rating number" and proper PSI for the weight. When you are driving off road at lower speed (sub 40mph) you can run lower tire pressures.

I'd carefully review the actual tire carcass construction more than the "letter rating" or the "tread pattern". Tires designed for off road use with be constructed with a true "3 ply sidewall". There are not that many "less aggressive" tread design tires with a true "off road" tire carcass.

Hybrid tires I'd consider:
Yoko Geolandar X-AT
Maxxis Razr AT (3 peak)
MT Baja Boss AT (3 peak)
Milestar Pategonia X/T (3 peak) new tire and not as reputable
BFG Ko2 (3 peak) - note the 37" size wears quickly

Also note... it is much quicker inflating/deflating a load D tire. 30psi to 50psi. Compared to inflating to 80psi.

Or you can follow the internet advice... LOAD E on EVERYTHING! Including your Tacoma. HAHA

 

[eyemgh]

Every company publishes a weight capacity per wheel for all the sizes they produce at a whole host of pressures. I happen to run Toyo Es (A/T III, 35/12.5x17), but I NEVER run them at full inflation (65 psi). They are too hard and bouncy. I'm still WAY under their capacity at 50 psi, which is where I run them on the road. Technically though, they probably aren't E rated any more at 50. I don't care. They chalk test at that pressure. Roughly 1" of tread doesn't touch at 65 psi. How is that safer? I only approach their limit at 35 psi, which I would only do off road, at lower speeds. I think the whole discussion is a little more nuanced that always running E at full inflation.

 

[mk216v]

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.

They do make load E 37's. Toyo MT and also switching to an 18" wheel .

Thanks for the feedback. I'm personally searching for an A/T, or hybrid A/T, vs M/T.
Not all 18's, or even E load, have a higher rating. There are some goofy ones.
(I'm not a slide-in, but instead a composite flatbed camper, but I hear what you're saying)
For you moving to 18s, have you looked at the tires available in your desired size? For me, there are only two A/T options in 37x12.5.x18 for an E load, so I'd have to go to the wider 37x13.5x18 for more E-load A/T options. Seems the tire mfr's skipped over offering a myriad of options for 18" wheels.
https://tiresize.com/tiresizes/37X12.50R18.htm
https://tiresize.com/tiresizes/37X13.50R18.htm

I can't answer from a technical perspective but I can tell you that I'm running 37" D rated Toyo Open Country R/T's on 17" Method's on my 2021 F250 with a flatbed and FWC Hawk UTE. I've got around 17,000 miles on this setup and have had zero issues. Our total loaded weight is around 11,000 lbs. I run the tires at around 45 PSI year-round.

Yep! We drove the entire state of Idaho off road (videos coming) with the tires aired down the entire time front 20-25psi and rear 30-35psi. 1,500 miles for 6 weeks. Fully loaded with camper (10-11k lbs). 23k miles on the 37x12.5R17 Load D

Tire letter is "old school" same as the "ply rating" (8 ply or 10 ply). Tires are not built that way! Todays tire construction is "ply equivalent". You're much better off looking at "load rating number" and proper PSI for the weight. When you are driving off road at lower speed (sub 40mph) you can run lower tire pressures.

I'd carefully review the actual tire carcass construction more than the "letter rating" or the "tread pattern". Tires designed for off road use with be constructed with a true "3 ply sidewall". There are not that many "less aggressive" tread design tires with a true "off road" tire carcass.

Hybrid tires I'd consider:
Yoko Geolandar X-AT
Maxxis Razr AT (3 peak)
MT Baja Boss AT (3 peak)
Milestar Pategonia X/T (3 peak) new tire and not as reputable
BFG Ko2 (3 peak) - note the 37" size wears quickly

Also note... it is much quicker inflating/deflating a load D tire. 30psi to 50psi. Compared to inflating to 80psi.

Or you can follow the internet advice... LOAD E on EVERYTHING! Including your Tacoma. HAHA

Thanks to both of you for the firsthand user feedback! I've followed both of your travels, and you're doing much of the same driving as us.
Peter, your rig is only 10-11k with the Northstar slide-in-camper when wet?
And a caveat to your "When you are driving off road at lower speed (sub 40mph) you can run lower tire pressures." comment; Yes, you can run lower tire pressures, IF you're not exceeding the mfr weight rating at that pressure. As well, if you drove 39mph for 1000miles, on lower pressure, with a LOT of weight on each corner, couldn't you still possibly overheat the tire(friction), and possibly damage the sidewalls?

Does anyone with a serious load in the back actually air down their tires? The last thing I want when off road and with a heavy camper in the back is to have squishy tires, and my sidewalls more exposed to rock damage. If you want more traction, go with a wider tire. I run 37's on a 17 inch wheel without airing down. The only time I do air down is if I'm stuck, and I never get stuck (until I said that of course). More tire sidewall usually means a softer ride. A shorter sidewall is stiffer, so usually it increases your stability. Airing down is for jeepers, not for trucks with slide in campers.

2 rigs above that do. I will with my flatbed/composite camper.
As Peter (montypower) said and has done, we focus the tire search on a high quality 3ply sidewall tire (many tires have 2ply sidewall), then this is a benefit.
And you can only go so wide on a tire before it rubs...and even then when off-pavement, a wide tire at 80psi is NOT always going to give you more traction than a slightly narrower tire which is aired down (as tire airs down, yes the contact patch gets wider, but more importantly it gets loooonger.
Try airing down 5-20psi the next time you're off-pavement; HUGE difference in ride quality, puncture-resistance, grip vs slip, etc....as airing down is for lots more than just Jeepers.

I tend to agree with you, I think a lot of folks think that they are going to drive their truck and camper like a big Jeep and discover the limits of a 11 to 12 thousand pound pretty quickly. My old 2001 superduty with a service body and 8 foot Alaskan camper was on 285/75-16’s for over 120,000 miles and 15 years from Alaska to Baja and never saw a day under 80 psi front and back. It tipped in at close to 11,000 pounds fully loaded. My new Ram 3500 has what I think is a perfect match for a heavy truck camper , Cooper 295/70-18’s. Over 4000 load capacity per tire, fits in the stock spare location, stock gearing is adequate and no rubbing with plenty of room for chains. Talking to the Toyo engineers at expo they designed these tire for exactly this purpose. I run mine at 80 psi with 7000 pounds of rear axle weight and it is stable on the highway and tolerable for long gravel slogs.

How's your tire wear pattern at 80psi (ie max psi)?

Every company publishes a weight capacity per wheel for all the sizes they produce at a whole host of pressures. I happen to run Toyo Es (A/T III, 35/12.5x17), but I NEVER run them at full inflation (65 psi). They are too hard and bouncy. I'm still WAY under their capacity at 50 psi, which is where I run them on the road. Technically though, they probably aren't E rated any more at 50. I don't care. They chalk test at that pressure. Roughly 1" of tread doesn't touch at 65 psi. How is that safer? I only approach their limit at 35 psi, which I would only do off road, at lower speeds. I think the whole discussion is a little more nuanced that always running E at full inflation.

EXCELLENT point. While I haven't been able to easily find any published/online "matrixes" of weight capacity per tire at X psi, this is something I definitely need to ask for/look at for my own setup, to make sure a Xpsi offroad, I'm not weighing more per corner than they say is safe.

 

[eyemgh]

Does anyone with a serious load in the back actually air down their tires? The last thing I want when off road and with a heavy camper in the back is to have squishy tires, and my sidewalls more exposed to rock damage. If you want more traction, go with a wider tire. I run 37's on a 17 inch wheel without airing down. The only time I do air down is if I'm stuck, and I never get stuck (until I said that of course). More tire sidewall usually means a softer ride. A shorter sidewall is stiffer, so usually it increases your stability. Airing down is for jeepers, not for trucks with slide in campers.

I routinely do on the rig in the avatar (LT 275/70 R18 Wildpeaks) and I will on the new one we‘re building (Hallmark on a Bowen with LT 35 12.5 R17). I‘m still below the capacity per wheel, even aired down. They don’t feel “squishy.” I fact, on washboard, they are too bouncy if I don’t air down. I don’t do a lot of technical stiff through sharp rocks, but I have, multiple times. The Wildpeak sidewalls held up fine, and I expect the Toyos to do the same (knock on wood).

 

[wild1]

Thanks for the feedback. I'm personally searching for an A/T, or hybrid A/T, vs M/T.
Not all 18's, or even E load, have a higher rating. There are some goofy ones.
(I'm not a slide-in, but instead a composite flatbed camper, but I hear what you're saying)
For you moving to 18s, have you looked at the tires available in your desired size? For me, there are only two A/T options in 37x12.5.x18 for an E load, so I'd have to go to the wider 37x13.5x18 for more E-load A/T options. Seems the tire mfr's skipped over offering a myriad of options for 18" wheels.
https://tiresize.com/tiresizes/37X12.50R18.htm
https://tiresize.com/tiresizes/37X13.50R18.htm




Thanks to both of you for the firsthand user feedback! I've followed both of your travels, and you're doing much of the same driving as us.
Peter, your rig is only 10-11k with the Northstar slide-in-camper when wet?
And a caveat to your "When you are driving off road at lower speed (sub 40mph) you can run lower tire pressures." comment; Yes, you can run lower tire pressures, IF you're not exceeding the mfr weight rating at that pressure. As well, if you drove 39mph for 1000miles, on lower pressure, with a LOT of weight on each corner, couldn't you still possibly overheat the tire(friction), and possibly damage the sidewalls?


2 rigs above that do. I will with my flatbed/composite camper.
As Peter (montypower) said and has done, we focus the tire search on a high quality 3ply sidewall tire (many tires have 2ply sidewall), then this is a benefit.
And you can only go so wide on a tire before it rubs...and even then when off-pavement, a wide tire at 80psi is NOT always going to give you more traction than a slightly narrower tire which is aired down (as tire airs down, yes the contact patch gets wider, but more importantly it gets loooonger.
Try airing down 5-20psi the next time you're off-pavement; HUGE difference in ride quality, puncture-resistance, grip vs slip, etc....as airing down is for lots more than just Jeepers.


How's your tire wear pattern at 80psi (ie max psi)?


EXCELLENT point. While I haven't been able to easily find any published/online "matrixes" of weight capacity per tire at X psi, this is something I definitely need to ask for/look at for my own setup, to make sure a Xpsi offroad, I'm not weighing more per corner than they say is safe.

I ran various iterations of BFGoodrich all terrains on the superduty front and rear at 80 psi with 3000 mile rotations. The tears wore noticeable faster then the fronts but with steady rotation I would get around 35,000 miles out of a set. The Cooper ST max I have been running 80 rear and 65 front, over 15,000 miles they are wearing well. This is a stout tire, it is built on the armor ten tri wall carcass that they also use on there mud terrains but with a more highway and mileage friendly tread pattern that still performs well off-road.

 

[GeorgeHayduke]

View attachment 709330

That looks like a pretty big cantilever over the rear, any issues with rear axle weight or driving dynamics?

 

[pappawheely]

To make it clear, I don't air down, but I also don't run at 80 psi. I run at 45lbs. and leave it alone; on and off the road.

 

[pappawheely]

I routinely do on the rig in the avatar (LT 275/70 R18 Wildpeaks) and I will on the new one we‘re building (Hallmark on a Bowen with LT 35 12.5 R17). I‘m still below the capacity per wheel, even aired down. They don’t feel “squishy.” I fact, on washboard, they are too bouncy if I don’t air down. I don’t do a lot of technical stiff through sharp rocks, but I have, multiple times. The Wildpeak sidewalls held up fine, and I expect the Toyos to do the same (knock on wood).

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.