Towing often? Make sure you have proper truck tires equipped

J.G.
By J.G. Pasterjak
Sep 22, 2021 | Towing, tires | Posted in Tires & Wheels | From the Nov. 2021 issue | Never miss an article

Photography by J.G. Pasterjak

Most half-ton pickups sold in the U.S. don’t actually come with truck tires,” says John Wu of Maxxis Tire. Bafflingly, he’s not wrong: Most 1500-series pickups sold in this country come standard with P-metric passenger-series tires.

To get a true LT-grade tire on your new truck, you have to either go deep into the options sheet, swap out to upgraded rubber, or make the leap to at least a 2500- series pickup.

It’s just the way most people use trucks,” Wu continues. “Most pickups are basically passenger cars or SUVs with beds. Owners might throw a couple bags of mulch or a few 2x4s in at Lowe’s or Home Depot, but mostly they’re not being used as high-load vehicles.”

And that’s the key term right there: load. Because that’s what separates a true LT truck tire from a passenger tire that just happens to fit a truck.

When we bought our 2010 Toyota Tundra, it had a lot of comfortable and pleasant bells and whistles, but we knew that 90% of its use would involve hauling a loaded trailer to a race track or autocross site. The tires that the previous owner had installed looked nice enough, but they were far more suited to a large luxury SUV than a truck that would see some hauling use.

And these tires were utterly incapable of dealing with any sort of soft ground. This point was driven home at, well, our home, when the truck almost got stuck in our yard–on level ground–just because the tires could get zero purchase on the wet, muddy grass.

While we never plan to go off-roading in our two-wheel-drive Tundra, race track paddocks don’t always offer the most well-groomed surfaces for trailer parking. If we couldn’t even comfortably negotiate our own yard, we had to look for some more capable rubber.

But did we need a “truck” tire? And what even is a truck tire? Is it notably different from a passenger car tire that just happens to fit your truck? That’s where our conversation with John Wu started.

When our Tundra’s passenger car tires nearly left us stuck in our own yard, we upgraded to real truck tires from Maxxis. The result: better grip and increased load capacity.

When our engineers are designing a tire–any tire, really–they have a list of priorities of things they want that tire to do,” he explains. “Ride, handling, steering response, load capacity, longevity, off-road traction, road noise: All of these factors and more are involved in every tire.”

But designing those factors into a particular tire is a lot like building a character for a video game where you have finite resources to assign across several talents. Adding extra hit points may mean you need to take away some damage ability and vice versa.

Well, the same is true with tires. “Our engineers will just reprioritize those design parameters for each tire,” he continues, “whether it’s a tire designed for track days, where grip and feedback are more important than ride and wear, or a truck tire, where load capacity is usually the prime consideration.”

When it came to our Tundra, Wu suggested a set of Maxxis Razr AT tires in 33X12.50R20LT to replace our P305/50R20 P-passenger rubber. The outside diameter would barely change, but the load capacity and design philosophy would be far more industrial-grade.

Those Maxxis Razrs are designated with an F load range. That means they have the equivalent strength of a 12-ply tire from back in the day–when the load range of tires was defined by their carcass thickness, not their absolute strength.

Our old passenger-based tires carried a C load range– just a six-ply rating–and their accelerated wear and poor ride when towing told us a lot about why car tires aren’t truck tires. Our new truck tires are rated for a load of 3000 pounds per tire and can hold as much as 80 psi of air, making them far more suitable for doing actual truck stuff.

True LT tires have a few other differences from P tires. “Usually, you’re also going to see a more square edge on the tread and deeper tread blocks on an LT tire,” Wu explains. “This is for a couple reasons. First, we’re tryingto design the tire to have an optimum contact patch under higher loads, which is when it matters the most. And also, we can build a little more depth into the tread just to give a little more longevity before the tire needs to be replaced.”

We expected the move from passenger to truck tires to come with sacrifices to ride quality, road noise and steering feel. (Remember the idea of having a finite pool of ability to draw from?)

But what we experienced was precisely the opposite. All the “luxury” qualities of the truck were instantly improved after we switched to the LT tires. Part of this could be because we were replacing older tires with newer ones– or maybe the Razr ATs just hit a sweet spot in balancing capability with comfort.

Our 33X12.50R20LT Maxxis Razr ATs are available from various outlets for around $325 each. LT tires are frequently priced a bit higher than similar-sized P tires, but the extra money means extra capacity for doing the things that trucks do. And that was Wu’s standard when we asked him how to decide between true truck tires and tires that simply fit a truck.

How much of your truck’s capability are you using?” was Wu’s rhetorical answer. “If you’re never putting any stress on it–just driving it like it’s a car with a big bed in the back–then passenger tires are probably a fine choice.

But if you’re using more than half the max bed capacity a couple times a month, or towing something like a car even once or twice a month, that’s kind of when I start suggesting having a tire that’s rated for the job,” he says. “You need to pick your tire to handle your most difficult usage scenario, because that’s when you rely on your tires the most.”

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Comments
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KyAllroad
KyAllroad UltimaDork
9/21/21 8:45 a.m.

That's a penalty of the 2wd truck: noisy tires.  Also (generally speaking) aggressive tread blocks like that get worse mileage than quieter HT tires.

But totally agree about the load rating, if you tow, get AT LEAST a 'D' rated tire.

Opti
Opti Dork
9/21/21 8:49 a.m.

If you are towing all the time within the manufactures tow rating, the tires that come on it from the factory will work at that tow rating, even P rated tires.

LT tires hold less weight at the same pressure as the same size P tire. So to actually increase their load capacity you have to run considerably more pressure. That does nothing to address suspension and drivetrain limitations.

With an LT you will sacrifice ride quality, cost and normally wear, and in many cases without actually increasing towing capacity.

If traction or quality is a problem most times you can correct that without actually moving to an LT

chaparral
chaparral Dork
9/21/21 11:35 a.m.

The other disadvantage of an LT is typically higher rolling resistance - so gasoline mileage will drop. 

Your truck is rated to tow with the tires that came from the factory on it, so a new set with the same load range will allow you to tow.

If you're right at the limit of the truck, it will work better than trucks used to at their GCW, as the SAE standard now requires you to get up Davis Dam and all OEMs that I know of require that the truck also descend from Davis Dam at that weight. 

 

 

mhisstc
mhisstc New Reader
9/21/21 7:07 p.m.

“You need to pick your tire to handle your most difficult usage scenario, because that’s when you rely on your tires the most.”

That sums it up right there.

 

Over the last few decades I've used my trucks exclusively as trucks to haul and tow things, while I use my passenger cars to haul people more efficiently than a truck could ever do.  I learned this the hard way a couple of times when I was in my 20s pulling U-HAUL trailers during a couple of moves.  On the first occasion I got stuck in about 3 inches of snow on top of a light glaze of ice following an unexpected snow squall going up a slight grade on a very rural U.S. Highway.  The second time I had a blowout on the Interstate.  Both instances were late at night while using the tires still within, but near the top of their load range at the appropriate inflation pressures.  Not cool.  Those were the last set of passenger car tires I ever put on my trucks.  I've managed to avoid any similar issue since.

 

Pay attention to inflation pressures!  Those load ratings only apply at maximum inflation pressures.  Anything less than max pressure means a lower load capacity.  Any significant change in load will likely require a corresponding change in air pressure from what's printed on the sticker in your door jamb.  The varying of tire pressures to accommodate different loads should be common practice for anyone towing the same trailer at different weights, and can be carried over to varying loads in regular passenger vehicles, although the differences are usually not as dramatic as with a trailer, or a pickup.  There are tables you can Google that show the relationship between %max load vs. %max inflation pressure.

 

Another benefit of light truck tires over passenger vehicle tires is their overall toughness.  This becomes evident if you make a lot of trips down dirt roads with larger and sharper aggregate, or if you do things like make a lot of trips to the dump.  You will have a lot fewer punctures and tread damage with light truck tires than passenger vehicle tires due to the thicker tread blocks and thicker carcass.

 

If, however, all you do is drive your Pickup/SUV/Crossover on dry paved roads carrying 4 passengers and the occasional bed frames, bicycles, and big screen TVs, all you'll ever need is passenger vehicle tires.  Just don't blast into the first snow storm of the season in October in your shiny 4x4 with those passenger vehicle tires thinking you're still going to be able to execute that 75+ mph morning commute like you did in early September.  Wait.  How did I get up on this soap box?

rustomatic
rustomatic Reader
9/26/21 2:10 p.m.

This sounds like manufacturers knowing their audience (mall transport with the occasional trip to Home Depot to buy the extra-large bleach and a can of Raid) and faking ride quality.  They don't do this with 2500s.

For a dose of reality, test drive a new 2500 of any brand with the ridiculous Firestones they all come with inflated to 80 lbs.  That's truck ride quality.

Opti
Opti Dork
9/26/21 2:35 p.m.

In reply to rustomatic :

Yah for a long time Dodge was the only one that did it right. All the manufacturers specified one air pressure on their big trucks. Normally like 65F and 80R. This was great when towing. When you weren't towing it rode and wore like hell.

Dodge had a loaded and unloaded pressure and their TPMS even worked at both pressures. The people that followed it got way more life out of their tires and their truck didn't ride like crap all the time

Curtis73 (Forum Supporter)
Curtis73 (Forum Supporter) GRM+ Memberand MegaDork
9/26/21 6:30 p.m.
Opti said:

If you are towing all the time within the manufactures tow rating, the tires that come on it from the factory will work at that tow rating, even P rated tires.

LT tires hold less weight at the same pressure as the same size P tire. So to actually increase their load capacity you have to run considerably more pressure. That does nothing to address suspension and drivetrain limitations.

With an LT you will sacrifice ride quality, cost and normally wear, and in many cases without actually increasing towing capacity.

If traction or quality is a problem most times you can correct that without actually moving to an LT

Way more to unpack here.  When you're towing, you throw the weight part out the window.  I mean, yes, you have to make sure the tires can take the weight, but that has nothing to do with how it will handle a trailer.

LT tires are constructed completely differently than P tires.  P tires are designed to be compliant and cushy.  LT tires are designed to hold more pressure and not puncture every time they roll over a rock.  The net result is that LT tires have stiffer sidewalls which pays HUGE dividends on sway control.

Put it this way... I had an F250 that the idiot former owner skimped out and got P tires put on it.  My Branger has proper LTs.  I had completely white knuckles towing my 3500 lb boat behind the F250, but the Branger handled it like a boss.

You also have to keep in mind that stiff sidewalls have nothing to do with weight capacity.  The sidewall's only job is to not explode with the pressure inside the tire, but it is 100% the air pressure that suspends weight, not the stiffness of the sidewall.  E range tires have stiffer sidewalls which helps greatly with towing ability, but it has nothing to do with their weight capacity.  Their weight capacity comes from the fact that they can hold 80 psi without going boom.

The other big factor that many overlook is tread deformation.  With a P-tire, you give it (let's say for example) 32 psi.  Period.  That is a pressure that suspends the weight of the car and makes a flat contact patch.  If you inflate it to 36, you'll wear the center of the tread faster.  Deflate to 28 and you'll wear the outsides faster.  This is partly because a passenger car might have a 500 lb payload capacity so the difference between empty and full is much less than the typical truck.  LT tires are designed to operate over a far broader range because they might have a 3000 lb payload capacity.  You can run E-range tires at 40 psi or 80 psi and not really notice much difference in tread wear across the patch because LT tires (especially the heavier you go, like D and E range) are designed to not deform the tread as much as a P tire as pressures change.

The actual weight capacity of a tire is one of the least concerns.

Opti
Opti Dork
9/26/21 7:57 p.m.

In reply to Curtis73 (Forum Supporter) :

I was a tire guy in truck country for many years and I couldn't disagree with you more.

Most of the cowboy Cadillacs out here that are never hooked to a trailer and are ran at the manufacturer's recommended spec (which is generally geared towards the towing side) wear out the centers long before the edges, especially on the rear axle. A truck made and pressures designed to tow 13k pounds are not happy riding around with only 6 or 7k pounds on them. Contact patch is dependant on weight (which can vary greatly with and without a load) and pressure (which 99 percent of the population just run what is on the door, which is what it takes for max towing capacity, especially on newer trucks that will normally throw a TPMS light unless you've got them cranked to the door spec of probably 70f and 80r)

An LT tire in the same size and pressure as a P tire has a lower weight capacity than said P tire (until you go beyond the P tires max capacity pressure, and in most cases about 10 psi later the LT has a higher weight capacity)

So most people that put an LT tire on a half ton and then just run them at the stock pressure have greatly decreased the vehicles capability, and have no idea what they've done. This is not correct but it is what the majority of the population around here do when they make the switch. I can tell you that the vast majority of LT tires on a half ton are not happy at 40 or lower and drive like they are made out of jello

I used to tow extensively with half tons including a 30 foot camper and full size pick ups that barely fit on my flatbed. I've ran P and LTs. I have seen no difference in sway control from a good properly inflated factory spec p tire to an LT tire inflated to offer the same weight capacity as factory. If the argument is I should have ran them at an even higher pressure to stabilize the carcass then I just shrink my contact patch, which is the last thing I want while towing a 30 foot camper. The only major difference I've seen in sway control in similarly equipped trucks is DRW vs SRW which makes a massive difference.

My position is, when towing within the manufacturer's capacity, which was designed for the stock (normally P) tires and pressures, you gain nothing (maybe sidewall puncture protection, but I've pulled plenty of nails and screws out of the sides of LT tires), but sacrifice everything (cost, fuel economy, wear life, ride comfort, weight)

I do not believe that running an LT tire on a half ton that came with P raises the towing capacity at all, it does not address suspension, or drive train and if it was as easy as throwinh some LTs on and spec a higher pressure every manufacturer would do it because then they could claim the title of most in class blah blah blah.

maj75 (Forum Supporter)
maj75 (Forum Supporter) Dork
9/26/21 8:22 p.m.

I'm with Curtis.  His experience mirrors mine.  I always ditch the P rated tires on my Pickups.  Towing or hauling, I want the safety margin in handling and sway control that 80 psi gives.  Drop it down when not hauling to 50-60 and it doesn't ride any different than with the P tires.

frenchyd
frenchyd UltimaDork
9/27/21 2:06 p.m.
Curtis73 (Forum Supporter) said:
Opti said:

If you are towing all the time within the manufactures tow rating, the tires that come on it from the factory will work at that tow rating, even P rated tires.

LT tires hold less weight at the same pressure as the same size P tire. So to actually increase their load capacity you have to run considerably more pressure. That does nothing to address suspension and drivetrain limitations.

With an LT you will sacrifice ride quality, cost and normally wear, and in many cases without actually increasing towing capacity.

If traction or quality is a problem most times you can correct that without actually moving to an LT

Way more to unpack here.  When you're towing, you throw the weight part out the window.  I mean, yes, you have to make sure the tires can take the weight, but that has nothing to do with how it will handle a trailer.

LT tires are constructed completely differently than P tires.  P tires are designed to be compliant and cushy.  LT tires are designed to hold more pressure and not puncture every time they roll over a rock.  The net result is that LT tires have stiffer sidewalls which pays HUGE dividends on sway control.

Put it this way... I had an F250 that the idiot former owner skimped out and got P tires put on it.  My Branger has proper LTs.  I had completely white knuckles towing my 3500 lb boat behind the F250, but the Branger handled it like a boss.

You also have to keep in mind that stiff sidewalls have nothing to do with weight capacity.  The sidewall's only job is to not explode with the pressure inside the tire, but it is 100% the air pressure that suspends weight, not the stiffness of the sidewall.  E range tires have stiffer sidewalls which helps greatly with towing ability, but it has nothing to do with their weight capacity.  Their weight capacity comes from the fact that they can hold 80 psi without going boom.

The other big factor that many overlook is tread deformation.  With a P-tire, you give it (let's say for example) 32 psi.  Period.  That is a pressure that suspends the weight of the car and makes a flat contact patch.  If you inflate it to 36, you'll wear the center of the tread faster.  Deflate to 28 and you'll wear the outsides faster.  This is partly because a passenger car might have a 500 lb payload capacity so the difference between empty and full is much less than the typical truck.  LT tires are designed to operate over a far broader range because they might have a 3000 lb payload capacity.  You can run E-range tires at 40 psi or 80 psi and not really notice much difference in tread wear across the patch because LT tires (especially the heavier you go, like D and E range) are designed to not deform the tread as much as a P tire as pressures change.

The actual weight capacity of a tire is one of the least concerns.

Sway control?   Honestly?   Towing is about balance. Sway is caused by too much reward balance on the trailer. Not by the tires.  Well,  it can also be caused by improper trailer wheel alignment.  But again not by  tires. 
   Next time you have a sway situation  weigh  the trailer hitch. And string the tires. 
 OK grossly overloaded maybe a LT tire might give you a tiny bit more load capacity.   

Curtis73 (Forum Supporter)
Curtis73 (Forum Supporter) GRM+ Memberand MegaDork
9/27/21 2:51 p.m.
frenchyd said:
Curtis73 (Forum Supporter) said:
Opti said:

If you are towing all the time within the manufactures tow rating, the tires that come on it from the factory will work at that tow rating, even P rated tires.

LT tires hold less weight at the same pressure as the same size P tire. So to actually increase their load capacity you have to run considerably more pressure. That does nothing to address suspension and drivetrain limitations.

With an LT you will sacrifice ride quality, cost and normally wear, and in many cases without actually increasing towing capacity.

If traction or quality is a problem most times you can correct that without actually moving to an LT

Way more to unpack here.  When you're towing, you throw the weight part out the window.  I mean, yes, you have to make sure the tires can take the weight, but that has nothing to do with how it will handle a trailer.

LT tires are constructed completely differently than P tires.  P tires are designed to be compliant and cushy.  LT tires are designed to hold more pressure and not puncture every time they roll over a rock.  The net result is that LT tires have stiffer sidewalls which pays HUGE dividends on sway control.

Put it this way... I had an F250 that the idiot former owner skimped out and got P tires put on it.  My Branger has proper LTs.  I had completely white knuckles towing my 3500 lb boat behind the F250, but the Branger handled it like a boss.

You also have to keep in mind that stiff sidewalls have nothing to do with weight capacity.  The sidewall's only job is to not explode with the pressure inside the tire, but it is 100% the air pressure that suspends weight, not the stiffness of the sidewall.  E range tires have stiffer sidewalls which helps greatly with towing ability, but it has nothing to do with their weight capacity.  Their weight capacity comes from the fact that they can hold 80 psi without going boom.

The other big factor that many overlook is tread deformation.  With a P-tire, you give it (let's say for example) 32 psi.  Period.  That is a pressure that suspends the weight of the car and makes a flat contact patch.  If you inflate it to 36, you'll wear the center of the tread faster.  Deflate to 28 and you'll wear the outsides faster.  This is partly because a passenger car might have a 500 lb payload capacity so the difference between empty and full is much less than the typical truck.  LT tires are designed to operate over a far broader range because they might have a 3000 lb payload capacity.  You can run E-range tires at 40 psi or 80 psi and not really notice much difference in tread wear across the patch because LT tires (especially the heavier you go, like D and E range) are designed to not deform the tread as much as a P tire as pressures change.

The actual weight capacity of a tire is one of the least concerns.

Sway control?   Honestly?   Towing is about balance. Sway is caused by too much reward balance on the trailer. Not by the tires.  Well,  it can also be caused by improper trailer wheel alignment.  But again not by  tires. 
   Next time you have a sway situation  weigh  the trailer hitch. And string the tires. 
 OK grossly overloaded maybe a LT tire might give you a tiny bit more load capacity.   

Hardcore disagree.  Side forces are caused constantly by ruts in the road, crosswinds, passing traffic, steering wheel corrections.  The trailer places intense side-to-side forces on the sidewalls of tires constantly.  I'm not talking about when the trailer is out of control in an oscilation event, I'm talking about the constant side forces caused by everyday normal driving.

Grab the fender of a leaf spring car and shake it back and forth while watching what the tire sidewall does.  Now do the same thing with a 3/4 ton truck with E-range tires. Massive difference.  The amount that the trailer's side forces are able to deflect the tire's sidewall has an immense affect on how the vehicle is able to control the trailer safely.

I'm talking about when a truck passes you and you have to correct the steering wheel.  With P-tires, you are multiple times closer to an oscilation event than you are with E-range.

How is this not common sense?  It's physics 101.  Squishy tires can't control side loads the same as non-squishy tires.  It's the same reason we rip out rubber bushings and put in Delrin, or that we ditch the 15" wheels in favor of 17", or replace rubber body mount bushings with solid, or motor mounts... or steering isolators... or .... you get the idea.

P= squishy.  LT = less squishy.

frenchyd
frenchyd UltimaDork
9/27/21 3:38 p.m.

In reply to Curtis73 (Forum Supporter) :

Curtis I really respect you and the advice you give but I must disagree

     There is a video someplace where they put a unbalanced load on a trailer and show how things like ruts, wind gusts,  etc cause the trailer to sway wildly. 
    As I've said I built enclosed trailers for a while and was careful to align the wheels, yet even I knowing the rule about load balance got caught in Atlanta.  My tandem car trailer (2 cars 1 trailer) pulled by a Suburban was easy towing. All the way to just outside of Atlanta. When the generator in the trailer broke loose and slid back about 4-5 feet. It only weighed a little over 200 pounds but that was enough to shift the load balance.  Suddenly in rush hour Atlanta traffic I was completely sideways with a Suburban and a 28 foot trailer.  Back and forth it went with me dancing on the pedals trying to thread that train into open spots. 
 When I finally got it over to the side of the road and saw the generator wedged under the car in back I got new straps out and pulled it as far forward as possible. 
All the rest of the way to the Bahama's it was baby buggy smooth.  A decade later that trailer was totaled when the owner loaded his Tractor on in the back couldn't get it all the way into the trailer because of the roll over hoop and since it was so close to the dealer  left it hanging there.  Whip sway into the ditch it went ruining the trailer, his tractor, and the suburban. 
     I've towed tandem enclosed trailers all over the country including all the mountain ranges with little S10 Blazers. Without so much as a oops.  Yes Semi's blowing by me, wind gusts, ruts, pot holes etc. for decades. Never a problem. Nor any sway.

I've blown out a left side single axle trailer tire doing 100 mph pulled with my Buick next to the salt flats when the $15 recapped tire had enough, and gradual lifting of the throttle had me smoothly pull to a stop.  Throw my spare on and continue on.  They fixed the dented wheel for $10 and threw on a good used recap and I was off to Wisconsin.    
  that trailer was a welded together piece of Junk with a unsprung single axle midway between the load front and load rear. It had a 2800 pound Jaguar XK150 on it that was slightly tail heavy but I loaded all my heavy spares in the 3 ammo boxes welded to the tongue. About 300 pounds tongue weight if I remember correctly.   
     Balance and alignment. 

Curtis73 (Forum Supporter)
Curtis73 (Forum Supporter) GRM+ Memberand MegaDork
9/27/21 3:51 p.m.

When did I say anything about balance?  I can answer that.  I didn't say anything about balance.  And if you think that balance and alignment are the only things that can cause an oscilation, you're mistaken.  I respect you too, but you're not reading what I'm typing.  You're talking about near-death experiences because of a tail-heavy load.  I'm talking about side forces caused by towing seen by the sidewalls.

Take a perfectly-loaded trailer.  Put it behind the same vehicle and only change the tires between E-range and P-metric.  Sidewall deflection has a TON to do with controlling side loads caused by towing.  How can you not agree with that?

Why are you talking about balance?  No one has said anyting about balance.  In fact, I just ctrl+F'ed and you're the first person to use the word balance.  Stop saying balance.  We're talking about tires, not how to load a trailer.

All I'm saying is that a squishy tire is less able to prevent deflection under side loads than a not-as-squishy tire and you're spouting stories about a generator wedged under a car.

Opti
Opti Dork
9/27/21 4:37 p.m.

In reply to Curtis73 (Forum Supporter) :

The sidewall on a conventional LT or P tire isnt what supports the weight, air is. An LT tires sidewall can be moved back and forth like a p tire, because it isnt the support structure. If you take a Michelin LT tire you can turn the bead  inside out just like you can a Michelin P tire. 

If your illustration of shaking a truck is comparing a P tire at 40 psi vs an LT at  80 psi, well one tire has considerably more pressure stabilizing the carcass of the tire. If your talking about them being at the same pressures and the LT being more stable, I reject that completely because an LT tire aired down to 40 is about as stable as jello and drives like it also. If the point is to put an LT on a half ton and then crank the pressure up that may stabilize the carcass some but at the expense of shrinking the contact patch.

And in the article they didnt even move to a conventional LT tire, they went to a flotation size which is worse than a conventional LT tire.

frenchyd
frenchyd UltimaDork
9/27/21 5:29 p.m.
Curtis73 (Forum Supporter) said:

When did I say anything about balance?  I can answer that.  I didn't say anything about balance.  And if you think that balance and alignment are the only things that can cause an oscilation, you're mistaken.  I respect you too, but you're not reading what I'm typing.  You're talking about near-death experiences because of a tail-heavy load.  I'm talking about side forces caused by towing seen by the sidewalls.

Take a perfectly-loaded trailer.  Put it behind the same vehicle and only change the tires between E-range and P-metric.  Sidewall deflection has a TON to do with controlling side loads caused by towing.  How can you not agree with that?

Why are you talking about balance?  No one has said anyting about balance.  In fact, I just ctrl+F'ed and you're the first person to use the word balance.  Stop saying balance.  We're talking about tires, not how to load a trailer.

All I'm saying is that a squishy tire is less able to prevent deflection under side loads than a not-as-squishy tire and you're spouting stories about a generator wedged under a car.

Fair enough. I'm sorry I didn't make the connection clearer.  I will agree that if a trailer is properly balanced and wheels properly aligned so it's not pulling the trailer one way while the tow vehicle is going another  an LT properly inflated has a stiffer sidewall than a P series tire properly inflated. 
       My contention is  that those two items. Alignment and balance have much more to do with sway than sidewall strength.  
  Let me see if I can use your argument to explain it better.   
  Let's take a mushy soft car, a big Lincoln or Cadillac  and drive it as hard as possible around a race track. Nope, it's not going to go as fast as a stiffly sprung car, but while the under steer will be horrible. It will go into those corners taking a set and heeled over but unless the driver is wildly over steering  it'll just be slow.   
     A trailer out of balance or out of alignment will go around those race track corners constantly changing directions, pulling the tow vehicle one way and then the other. Making  the steering impossible to catch up or predict. Changing to still sidewall tires won't change that. 
Whereas the balanced trailer, aligned trailer will simply follow the tow vehicle.   

Curtis73 (Forum Supporter)
Curtis73 (Forum Supporter) GRM+ Memberand MegaDork
9/28/21 8:51 a.m.
Opti said:

In reply to Curtis73 (Forum Supporter) :

The sidewall on a conventional LT or P tire isnt what supports the weight, air is. 

Which is exactly what I said above

If your illustration of shaking a truck is comparing a P tire at 40 psi vs an LT at  80 psi, well one tire has considerably more pressure stabilizing the carcass of the tire. If your talking about them being at the same pressures and the LT being more stable, I reject that completely because an LT tire aired down to 40 is about as stable as jello and drives like it also. If the point is to put an LT on a half ton and then crank the pressure up that may stabilize the carcass some but at the expense of shrinking the contact patch.

You're still missing what I'm saying.

A P tire at 40 will not stabilize side forces as well as an E-range LT at the same 40 psi.  And the other whole point is that it will deflect the contact patch across a wider range of pressures LESS because of it's construction

Curtis73 (Forum Supporter)
Curtis73 (Forum Supporter) GRM+ Memberand MegaDork
9/28/21 8:54 a.m.

In reply to frenchyd :

All good, brother.

frenchyd
frenchyd UltimaDork
9/28/21 9:50 a.m.

In reply to Curtis73 (Forum Supporter) :

I think this is a good subject for GRM to test. Look,  my opinion differs from yours. We are both good smart people with experience  on the subject. 

Opti
Opti Dork
9/28/21 10:35 a.m.

In reply to Curtis73 (Forum Supporter) :

No Im not, I just disagree with you. If they are at the same pressure the LT actually holds less weight. LT tires are just as susceptible to inflation wear as P tires, In the real world I would say more so because the vehicle manufacturers do such a poor job or specifying pressures. It is common place around here for everybody to move to an LT tire on a half ton "Because they tow" and when they switch and run them at the same pressure as the OE P tires, the trucks drive terribly, they are wallowing and steering response is terrible, when you add about 10 psi they drive similarly to P tires.

Curtis73 (Forum Supporter)
Curtis73 (Forum Supporter) GRM+ Memberand MegaDork
9/28/21 3:07 p.m.
Opti said:

In reply to Curtis73 (Forum Supporter) :

No Im not, I just disagree with you. If they are at the same pressure the LT actually holds less weight.

I'm sorry, but your replies indicate that we still aren't on the same page.  I agree with you on this.  Stop talking about weight.  I'm not talking about weight.  AT ALL.

I'm saying this:  Eject ALL other factors.  Assume that you have adequate weight capacity in the tires.  Assume you have a properly loaded trailer.  Assume you have 40 psi always and that you still have the weight capacity AT 40psi.  There is a huge difference in lateral (that is side-to-side) stiffness between the P and the E.  When the trailer exerts side loads on the vehicle, they are transmitted through the frame, suspension, and to the tires.  If you're riding on P tires with less lateral stability, the trailer's side loads are able to generate greater movement in the actual angle of the vehicle due to tire deflection.

I feel like a broken record.

Please, I'm not talking about weight.  I'm not talking about trailer alignment.  I'm not talking about proper tongue weight.  Ever.  I never talked about those.  I'm talking about the difference between the ability of the tires to not deflect under side loading.  Period.

Curtis73 (Forum Supporter)
Curtis73 (Forum Supporter) GRM+ Memberand MegaDork
9/28/21 3:15 p.m.
frenchyd said:

In reply to Curtis73 (Forum Supporter) :

I think this is a good subject for GRM to test. Look,  my opinion differs from yours. We are both good smart people with experience  on the subject. 

Let's get the GoPros ready along with a few dozen test drivers and two vehicles as identical as possible.

Tire Rack... you in?

Opti
Opti Dork
9/28/21 3:41 p.m.

In reply to Curtis73 (Forum Supporter) :

I understand what you are saying (an LT tire has more carcass (specifically sidewall) stability at a given pressure compared to an equivalent P tire, which leads to increased sway control, due to the differences in construction) but I disagree with your premise.

It hard to find actual hard data on this stuff, but personal experience over about a decade in the auto industry in truck country, has been that an LT tire drives like a squishy mess at the same pressure a P tire drives perfectly fine, on the same truck. Ive asked multiple manufacturers why this is, and if i got an answer it was you dont run an LT tire at the same pressure as a P.

I cant count the number of times a customer would come in asking for an alignment or suspension check because their truck was all over the road and steering was unresponsive, and upon inspection I found an LT tire on a truck that came equipped with a P and they were inflated to the spec on the door placard of about 35 psi. I could air them up to about 10 psi over OE spec in most cases and they would drive completely different. This experience seems to run counter to your position that at the same pressure an LT would have more sidewall stability.

Ive have heard people say an LTs construction means it requires more pressure to stabilize it, but I dont know how that would work. I can only speak to what ive seen in practical application.

AnthonyGS (Forum Supporter)
AnthonyGS (Forum Supporter) SuperDork
9/28/21 8:00 p.m.

This is an interesting article.  My Colorado Z71 needs new tires soon, and I do tow a few times a year or go camping fully loaded also a few times a year.  It'd be nice to have something XL rated or better.  I went and searched tirerack for my truck, and most of the tires are SL rated indeed.  I also like driving on terrain that isn't very good either sometimes, and finding load rated all terrain tires is more of a challenge too. 

My tires have legal tread but today in TX rain they had noticeably less traction than when new.  They have 31k miles on them and are 2 to 2.5 years old.  It's a 60k mile rated tire too, but I know they aren't going to get me to 60k and still be viable for how I drive.  I don't even think they'd make it that long in Arizona on highways. 

 

Curtis73 (Forum Supporter)
Curtis73 (Forum Supporter) GRM+ Memberand MegaDork
9/30/21 8:53 a.m.

In reply to Opti :

I can dig it.  We're not too far off, just disagree a bit.

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