tugging / bucking when towing

[taylor.coyote]

This is my first post. I recently purchased hull #124, a gently used 2016 Legacy ll. We took a short 300-mile two day round trip as s shake down first outing. The advice i seek is to improve the towing ride.

 

I’m towing with a 2019 F250 diesel 4×4 short box, standard 18″ wheels/rubber with a tow package. The dry empty trailer hitched to the empty truck sits with the rear of the trailer about 1/4 – 1/2 inch lower than the hitch.  I attempted to set up the hitch to be slightly lower that the rear with a variety of different combinations of drop balls but this always resulted in the hitch being two or more inches below the rear. Thus, decided upon the before mentioned set up of the hitch 1/4 – 1/2 inch higher than the rear of a dry trailer/empty truck.

 

I’m towing with a standard hitch although tried to use an Anderson weight distribution hitch.  The truck’s anti-sway automatically “defaulted to on” every time the truck is turned off and re-started. Each time the “on” default needed to be manually turned off. This is a pain and a possible safety issue when the truck’s anti-sway corrections are fighting the hitch’s corrections.

 

Now that you know the background and set-up: The issue I’m experiencing with both the Anderson and the standard hitch is the trailer bucks more than I think it should with a truck this size. The bucking does not push the truck around but is a noticeable and annoying up and down “tugging” on a frequent basis when traveling over dips and rises in the road.

 

I don’t know the hitch weight but the hitch’s weight makes my truck squat an inch+ when dropping the trailer on t0 the ball. Additionally, I moved most everything heavy that was in the trailer into the closet midway through the trip thinking the hitch might be too light. Moving the weight forward did not improve the “tugging”.  The trailer wet and loaded for the trip weighed 5,200 lbs (trailer hitched to truck with just the trailer wheels on the scales).

 

After reading how well Olivers tow, I was under the impression that we would hardly know we were towing a trailer with truck the size of an F250. Clearly, we know the trailer is attached every time it makes an annoying “tug”. This feel a lot like too much weight behind the axle or exceeding the GCWR or payload. I’m sure the load is well within the truck’s capabilities and 95% certain the hitch weight is ok but have not actually weighed the hitch.

 

Is this normal or are my expectations too high? Have I missed something on the set up? Your input will be greatly appreciated

[Raspy]

taylor,

 

I see absolutely no reason to be using an Anderson Hitch with your F-250.  Why are you using it?

 

Turning off your truck's "anti Sway" seems like a bad idea too.  Why are you placing more faith in the Anderson Hitch than in your truck's safety systems?  Turning off a safety system to compensate for a hitch problem is not a good idea.

 

Towing with a WDH will probably always make the tow rougher because there is so much force and friction at the hitch area.

 

Ditch the Anderson and try it again.  What kind of brake controller are you using?  Set up the trailer so it sits level, or as close to level as possible, when hooked up and ready to go.  When you are on your next trip, with all gear loaded up, the trailer should be riding level.  You also don't need 80 PSI in the truck tires.  Try 60 or so to get some cushion from them.  Oliver tire pressure should be about 55.

 

Olivers are very stable when towing.  There is no special requirement to move weight around to avoid problems.  People put bikes on the rear, or generators on the tongue, or run with full or empty water tanks, or a large variation of gear, or full or empty propane tanks.  Normal weight distribution differences don't seem to have an affect on the stability.

 

Go on a test drive with these suggestions in place:  No Anderson hitch, sensible tire pressures of 60 in the truck and 55 in the Oliver, Oliver level or slightly down in front.    Report back your findings.  Careful, you may forget the trailer is back there.

 

 

[Landrover]

It sounds like you may have some worn suspension parts, being your Ollie  is a 2016. Do you know much of the history of the trailer?  First check your ball size.  It should be 2in but some owners changed the coupler to 2 5/16?  Check mounting bolts for bulldog hitch bolts tight? Mounting hole in alum frame enlarged? Then move to the rear of the Ollies suspension check shackles, bolts, and bearings etc. for wear,  if all that is good, next look at the truck. You have a 2019  is it new or lease turn in.?  Just because the truck is new  don’t discount defective parts in the drive line, rear end, drive shaft, transmission. I’d go back to the dealer doesn’t sound like the anti sway control should be coming on, unless  there may be a elec. connection problem when Ollie is plug into the truck. And as Raspy said you shouldn’t need the Anderson hitch with that size truck. If all that fails scratch your head. Good luck.

[Overland]

I think it’s clear that he tried using the Anderson but took it off. What may not be clear is that Ford says to turn off sway control when using a sway control hitch like the Anderson - so turning it off every time he got in the truck was a pain.

 

I agree with Landrover - check the ball, check that there’s no excessive play in the receiver, check that nothing is broken on the trailer suspension and that the shackles haven’t flipped (the trailer should ‘hang’ from the springs), and then check the truck.

[Mike and Carol]

Hull 124 would have been built without the Dexter suspension. Mine wasn’t. When we had the Dexter added Jason showed me some of the old suspension parts and they were totally worn out. That was after about 18 months. I’d check it. Mike

[Trainman]

That does sound odd for a 3/4 ton pickup to handle the Oliver like you say it is doing, I would expect almost no bucking from a truck of that size. I did pull our new Oliver just two weeks ago with no Anderson for some 100 miles and our new Ram 1500 handled the Oliver with very little bucking, in fact you had to be looking for it to notice any detectable feeling of it. I did have a 2" sag which was too much for my comfort and I did install the Anderson at the camping site the first night I was there, this was planned in advance to do this. Like others have said, I would look at the trailer first, check the shocks, springs, coupler, and go from there. Oliver's pull so well I hope someone here can give you a advice that will help with you situation. I guess it is possible that your new F250 is sprung so stiff that you could be getting the noticeable ride difference when the trailer is hooked to the truck, but were only talking 500 pounds tongue weight here so, this should not be a factor. I assume you do not have helper springs like the Sumo, or your air shocks aired too high up, this should not even be needed for a F250 with the Oliver.

 

trainman

[DavePhelps]

The first thing that came to my mind that can cause this symptom is that your brake controller is set too high.

Brake controllers are not a set and forget proposition, and need to be adjusted for the terrain and road conditions you are driving in. If the voltage is set too high the trailer will not brake in sync with your TV and cause some lurching.

 

That said, all the other ideas presented here are valid and worth looking into. The old suspension shackles had nylon bushings, were not greaseable, and generally not up to the job. New suspension kits use bronze bushings and much heavier duty components: https://www.etrailer.com/Trailer-Leaf-Spring-Suspension/Dexter-Axle/K71-359-00.html

 

One other possibility to check, even though your trailer is a 2016 would be to make sure your trailer is properly grounded to the TV as per this Oliver TSB: https://olivertraveltrailers.com/topic/7pin-ground/  Sub- optimal grounding would affect your braking also causing a rougher ride.

 

I feel your pain about trying to get the trailer and TV in plane with each other. There are ball mounts, however, that have drops in 1/2" increments out there. What is your current drop? Good Luck!!

 

Dave

[Landrover]

The first thing that came to my mind that can cause this symptom is that your brake controller is set too high.

 

Brake controllers are not a set and forget proposition, and need to be adjusted for the terrain and road conditions you are driving in. If the voltage is set too high the trailer will not brake in sync with your TV and cause some lurching.

 

That said, all the other ideas presented here are valid and worth looking into. The old suspension shackles had nylon bushings, were not greaseable, and generally not up to the job. New suspension kits use bronze bushings and much heavier duty components: https://www.etrailer.com/Trailer-Leaf-Spring-Suspension/Dexter-Axle/K71-359-00.html

 

One other possibility to check, even though your trailer is a 2016 would be to make sure your trailer is properly grounded to the TV as per this Oliver TSB: https://olivertraveltrailers.com/topic/7pin-ground/ Sub- optimal grounding would affect your braking also causing a rougher ride.

 

I feel your pain about trying to get the trailer and TV in plane with each other. There are ball mounts, however, that have drops in 1/2″ increments out there. What is your current drop? Good Luck!!

 

Dave

 

Good point on the brake control adj. too high output could cause jerking. Sorry to say you can have a host of things causing the problem.

[taylor.coyote]

Wow,

 

You guys are really good. lots of great ideas... after digesting your coaching, let me give you more information.

 

facts:

 

2" factory bulldog / all hitch bolts tight/solid

 

tires are inflated hard on the trailer (70 lbs) and truck (70 front / 65 rear).. i plan to make adjustment going forward per your coaching

 

trailer is very near level in all applications

 

all hitch parts of solid on the trailer

 

F250 has stock springs with towing package and no air bags or helper springs

 

the current drop is 2" and the f250 has stock 18" wheels

 

I will not toss out the issue is to do with the truck entirely but i think our focus needs to be on the trailer. I'm choose to focus here because I have now towed the trailer with two trucks. One is a Tundra and the other is the f250. The surging /tugging is much more evident with the Tundra (with Anderson hitch) than the F250 but is clearly present with both trucks. The Tundra had a tight fit with the 2" receiver  / ball insert. The f250 (no Anderson hitch) has a 2.5" receiver and using spacer to shim to fit a 2" ball tongue. the f250 does have some "play".

 

So let's talk about the trailer's history. The trailer has been towed across the country on a couple of long trips plus a few regional trips. The trailer sit on the original factory Michelins that have almost all of the the original tread depth. It was mostly towed from RV park to RV park with very little if any off-pavement action. The trailer has been in mothballs in a barn for the last two years (wife did not care for the trailer travel much). Evidence of this was antifreeze in the water systems and dry / dead battery cells. The trailer is incredibly clean (body glass and throughout the inside).

 

All of this said, when the owner prepped the trailer for a 600 mile trip for him to deliver the trailer to me, he discover the rubber bushings at the bottom of the shocks had been installed from the factory without washers between the bottom of the shocks and top of lower bushings. The shocks had wedged themselves almost the way through the lower bushings.

 

I promptly took the trailer to a suspension shop to have the bushing replaced/installed correctly and the shock checked for damage. The shocks were deemed to be good shape and all of the bushings were replaced plus the bearings were repacked.  At this time we did not know about surging/tugging and did not have concern about the suspension and did not call out for a full inspection. This said, the tech that did the work to replace the bushings had his hands all over the other suspension components when replacing the bushings. I would think he would have noticed if anything was damaged or not normal.

 

I don't know much about suspension but  I just went out and put my hand on all of the suspension parts.  All are solid and in apparent good condition. The springs are properly sprung and solid. The shackles have not flipped. One observation was both equalizes are tilted forward with then front of the triangle lower than the back making the shackle angels less than a 90 degree angle to one set of axle springs and more than 90 degrees on the other set of axle springs.   I'm assuming they move dynamically and this position is normal  based on the trailer sitting on a forward sloping slab with the front jack up high to level the trailer. The  springs and shackles do have some modest corrosion but nothing that would be of concern.  The suspension looks like it could use some grease but i don't see any grease zerks

 

My equalizers are just metal triangles w/three bolt holes without any bushings and no apparent place to grease or service them. They do not look like the image of the equalizers that have rubber bushings that on the Oliver website..

 

regarding the brake grounding. I had an auto electric shop review all the wiring including the ground as the next stop for after the shock work. this said i will double check the ground wire per the link that was shared.

 

Nothing appears to be damaged or loose and all seems to be in good shape and the wiring has been inspected. The trailer has been towed with by two trucks/ two brake controllers with basically the same poor towing experience.

 

I have yet to tow with lower the tire pressure and double check the ground wiring.  Aside from this,  do you have other ideas or do you think i have wrongly overlook any of your suggestions?  Montana is calling and I might get sea sick towing this tub.

 

 

[Townesw]

How much weight do you have in the back of your truck? The 250 is an HD truck and the Oliver is a light trailer with a fairly low tongue weight. It might ride better with more weight in the bed. Just a thought.

[Landrover]

I’m fairly confident that you still have some suspension issues. You ruled out the TV by testing with two trucks same results.  A more in-depth inspection made be needed. Trailer off the ground wheels off,  with large pry bar you need to move each suspension part to check for play. Not a easy job, you may want a trailer shop do this. Changing the shock bushings and repacking bearings is good. As Mike and Carol said the older models showed a lot of wear in the suspensions especially with no grease points. One last check long shot check the mounting bolts where the suspension frame mounts to the aluminum frame. Frustrating for sure.

[John E Davies]

Just fix the suspension, it is probably shot. Without disassembly you will never know. The base Dexter teeny bolts and thin plastic bushings should not even be sold for any trailer except possibly for a small utility trailer that rarely gets used..., it is unsafe and a disgrace.

 

Until you overhaul it, and install an upgrade kit that can be lubed, you are just spinning your wheels, chasing other phantom problems.

 

I guarantee that several cross country trips have worn the suspension out. The 70 psi in the tires just amplifies the problem. They should be 50 or less.

 

Here is a shackle bolt pic I found online.

 

 

John Davies

 

Spokane WA

[Raspy]

taylor,

 

It's possible you have the grounding problem, as it was not completely fixed until after hull 200.  It's unlikely, with your factory brake controller, that the ground is causing any handling problems.  But you should check this and make sure it's OK.  Here is how you do it:

 

1. Unplug the trailer from any shore tie and let the batteries stabilize at about 12.6 volts or less. Monitor this voltage at your panel inside that reads the battery voltage.

 

2. Back up to the trailer but don't connect the hitch or chains.  Just come up close and plug in the umbilical from your truck.

 

3. With the truck running, check the trailer voltage again and begin to watch it for a few minutes.  It should climb to at least 13.2 and probably 14.1 volts over some time.  It should match the truck voltage when running, so if you can check the truck voltage on your dash, that would be good.

 

4. If the trailer voltage comes up during this test, you have a good ground.  If not, you are probably grounding through the trailer ball which is a very poor connection.  A bad connection can throw codes in the truck, cause bad brake performance and cause the batteries to not charge while towing.

 

5. If you decide you have a bad ground, I can help you find the problem.

 

I hope you will just lower your tire pressures and do another test run.  This will make a difference.  With your factory towing package, you may have very stiff shocks on the back of the truck.  My Ram did and it was brutally stiff.  I fixed that problem by installing a set of Bilstein shocks on the back.  This made a significant difference in both handling and comfort.  I did the same thing on my older Ram, but on that one I installed a set of Rancho 9000 adjustable shocks.  These are even better!  If you decide the rear of the truck is too stiff, put on a set of the Rancho 9000 shocks.  These are adjustable, velocity sensitive, and they work wonders.  You just click the adjusters until you find the perfect balance between stiffness and comfort for your particular load.  And they keep the tires planted over rough surfaces.

 

I've played with the tire pressures on my Ollie and it seems 55 is near perfect for all-around use. It gives just a bit of cushion, while not being low enough to run hot.  This is a good highway pressure for covering a lot of miles.   If you get on gravel roads for a lot of miles you can go down to about 40.  For severe rocky and rutted roads, even less is OK if you slow way down.   But 70 or 80, as they come from Oliver, is not a good plan because they transfer a lot of shock loads and add more stress to the suspension system and the trailer.  Oliver has said that the tires and wheels they order come at the higher pressure and they just install them that way.  The tire manufacturer weight vs pressure charts show a minimum pressure for the load to be at about 35 PSI.  This is not the recommended pressure, but the minimum allowable.  The max on load range E tires is 80 PSI and way overkill for this load.

 

Getting your truck tires down to a sensible pressure is good too. When rock hard they will ride rougher and skip around on rough surfaces.  Oliver is not a big load for your truck at only about 560 lbs of tongue weight, and approximately 5,700 lbs total, geared up for camping. Hopefully, your TPMS will allow 60 PSI without giving you a warning.

 

A number of us have said that Oliver's tow so well "you'll forget it's back there".  This is fun to say, but it's not really the case, except on absolutely smooth highways.  But it is true that they have excellent towing manners and are very stable.   I don't know what you expected when you began to tow yours.  Once everything is set up approximately right, that will be the best you can do and it will be fine.  You'll always feel bumps as the trailer adds shock loads to the hitch.

 

Set up your brake controller such that you can just feel it working when you stop.  I like mine to be aggressive enough that the trailer is always trying to pull back just a bit on the truck while stopping, but not so much that it skids on pavement.  This gives a constant reminder that it is working and it does it's own stopping without pushing on the truck.  The 3500 lb axles and 10" brakes are very likely what you have.  These brakes seem to have some character to them.  As they wear, they will get weaker and need to be adjusted.  So if you find you are going gradually higher on your settings and don't seem to be getting a good aggressive brake action, it's time to adjust them.  If you re-pack your bearings, you might find the brakes are weak for a while as they break-in again.  If one wheel is more aggressive than the rest, it likely means that grease has gotten onto the shoes.  This makes them more aggressive, not less, and it tends to make the trailer steer toward the grabbing brake, which steers the truck in the opposite direction.  Initially, when my trailer was new, the brakes had to break-in too, and gradually I reduced the setting to keep them from getting too powerful.  Every time I hook up and pull away, I reach down and apply them manually on the controller.  This confirms they are working, and I'm good to go.  At every fuel stop, out on the highway, while the truck is filling, I walk back and touch each tire and each hub.  If I can hold my hand on them, they are fine.  The trouble would be if one was way different than the rest.  Tires are fine until they are much hotter than we can hold our hands on.  I'm looking to see if everything is nearly the same.   Warm is normal.

 

 

[Raspy]

taylor,

 

John is absolutely right about the suspension.  Get the Heavy Duty Dexter suspension kit with greaseable bushings and better shackles.  I don't recommend the EZ Flex, but I don't recommend against it either.  I'm not sure it has an advantage over the standard HD kit, and it costs about $100. more.    The EZ Flex is designed for trailers with very stiff springs, to absorb some shock loads, but Olivers have soft springs.  Either kit has the same greaseable bronze bushings and heavy duty parts.  This should have been installed from Oliver from the very beginning.  They began installing the EZ Flex, as standard equipment, in early 2018 IIRC.  The stock plastic bushings used on the earlier setup, like mine, was barely good enough for a utility trailer and definitely not up to what we expect from Oliver.

[taylor.coyote]

ok guys.. I'm bought into the following:

 

I will test the ground first

 

Lower the pressure on both rigs. hopefully the truck's nanny alarm will not be a pain

 

Upgrade the old Dexter with the HD Dexter kit even if the grounding turns out to be problematic

 

likely will replace the truck's rear shocks with something adjustable as the truck's rear is very light and stiff (3,120 lbs vs front at 4,880 lbs)

 

I have never done suspension work. I'm not a pro with tools but reasonably handy, have a shop and a good assortment of tools. Do the parts go together easily or will I have to wrestle them onto place? Is this work something I can do if I'm prepared to skin my knuckles and some grunt work or should I sign up to pay a shop?

 

Thanks so much for all the coaching.  Your collective experience is amazing. Hopefully this will make the trailer agile and my truck a better ride.

 

Best to all,

 

Chris Chadwick (All my friends call me Chad)

 

 

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[Raspy]

The HD suspension kit can be done at home with some jack stands and a floor jack.  The bushings can be done, one side at a time, by pushing the new bushings in with a C clamp.  This will push the old ones out and into a short piece of pipe or a deep socket on the other side of the spring eye.  It can also be done with a piece of threaded rod, some nuts and washers.  When ready, install the new pins with the grease holes facing fore or aft.

 

Run the stabilizer jacks down and adjust until the weight is being shared with some jack stands under the frame.  Lift the tire off the ground with the floor jack and remove it.  Lower the jack until there is no weight being carried by the suspension on that one side only.  Pull the shackle pins and the equalizer pins.  Push the new bushings into the spring eyes and into the new equalizer.  Reassemble the system on that one wheel with the grease holes placed as mentioned and with Locktite on the threads.  Then do the second wheel on that side.  Two floor jacks or some blocking might help.  Torque the nuts to spec with a torque wrench.  Make sure the zerk fittings are pointed to where you can get on them with the wheels on.  Grease that side.  Re-install the wheels and torque the lugnuts to spec.  The go to the other side and repeat.  Re-torque the lugnuts after a few miles.

[taylor.coyote]

Hello guys,

 

One last question. The link you have given me for the Dexter parts is https://www.etrailer.com/Trailer-Leaf-Spring-Suspension/Dexter-Axle/K71-359-00.html

 

this kit has brass bushing but not the kit that has the equalizers with the shock system.  What kit would do the best job. I want to fix this and put in the rear view mirror. If you think the kit with the shock is best can you please be so kind as to give me a link so I get the correct parts the first time.

 

best

[Raspy]

Chad,

 

The kit you listed in the post above is the kit I used and the one I recommend.  Re-read my earlier post as to why I chose this kit.

[taylor.coyote]

Hello all,

 

Thanks for sharing your expertise and the coaching. The ride is much better but seem more room for improvement.

 

Actions taken:

tire pressure now at 55/trailer  60/truck

repacked bearings

Ground tested good

Installed Heavy Duty Dexter suspension kit with grease-able bushings and better shackles

the old nylon bushings were toast but but the other parts such as the bolts had only modest wear

all other suspension parts such as shocks, springs and attachments to frame are in good shape

bulldog hitch solid on frame

trailer tongue about 1/2" down from level

standard 2" ball hitch

Trailer tows much better and tugs less but still more than I think it should when towing with an F250. Took a 30 mile test drive with the new Dexter Hd kit installed, about 500-600 lbs load in the truck bed and put weight in the trailer 's closet to insure good tongue weight.  All this and we still experience a more than subtle tugging up and down when traveling over dips and rises in the road on a normal country highway.   We do have an improved ride that we can live with as long as all is safe.  When towing I  feel like i'm having to "work a little to drive the load vs just towing a load".  On completely smooth sections of road we don't know we are pulling a trailer.  Towing still does not seem right based on towing a few other trailers and driving a truck that weighs 8,000 lbs.

 

Any thoughts?

[Overland]

I think your tire pressures are still too high, especially the truck.

 

I've been keeping mine at 40 front and 42 rear when towing (38 daily) and the tread wear seems to indicate that those pressures are high.  (My KO2's are ready to replace, with the center of the tread worn thin.)  35,000 miles, roughly half of which have been towing.  Trailer at 45.

[Raspy]

Taylor,

 

 

 

If you think you'll get it to where you can't detect that it is back there, forget it.  Putting an approximately 5,500 lb weight behind your truck and then going over bumps and through dips WILL cause some pulling and pushing.  Nothing wrong with that and no way around it.

 

It will always jar you a bit when hitting bumps, and it will always push or pull depending on the road.

 

A favorite way for so many guys to describe how well Olivers or others tow is to say  "I can't even tell it's back there"  It's a cute saying, but the reality is, yes you can tell it's back there.  And so can the truck as it pulls 2 1/2 -3 tons along over grades, bumps, driveways, pot holes, speed bumps, dips and corners.

 

When on a perfectly smooth and level highway, and cruising along at speed, yes, you might forget it's back there, or it's impact on the driving experience will become minimal and unimportant.  But in any other conditions, it will keep reminding you it's there by tugging, jarring the suspension, pushing and pulling a bit.  Not violently, but noticeably.  How could it not?  And again, that is not a problem.  The simple physics of the trailer weight, compared to the truck weight, the uneven surfaces, and corners, all mean, yes, you can detect it back there.

 

You've done all that you can do to fine tune the entire setup, short of maybe a final tire pressure adjustment.  Now go out and enjoy it.  After a while you won't be troubled by how your truck drives differently while towing.  It should and it will.

[Overland]

One additional note on tire pressures is see if you can get a load inflation chart for the specific tire you have.  That will tell you the maximum load for each 5lb increment in pressure and with that in hand, you can stop by a CAT scale on your next trip to get your axle weights and  figure out a reasonable pressure that will give you a safety margin but won't beat you up.

[Raspy]

One additional note on tire pressures is see if you can get a load inflation chart for the specific tire you have. That will tell you the maximum load for each 5lb increment in pressure and with that in hand, you can stop by a CAT scale on your next trip to get your axle weights and figure out a reasonable pressure that will give you a safety margin but won’t beat you up.

 

 

Good plan.  But be aware that the tire charts list the maximum weight that can be carried at a given pressure, not the recommended pressure for that weight.  Then, as a safety factor, consider the situation, such as towing at high speed in the hot summer.   Or remember, that at the lowest acceptable pressure there is no safety margin for a slow leak as you go along.

 

It seems Oliver installs their tires with 80 PSI because that is what the tires have when they com from the supplier.  I would never run that much pressure because the tires are rock hard.   I used to run 60 PSI on my Oliver and it worked fine.  Then I needed to run them at 45 for a few miles once after leaving a dirt road in the desert, and that worked fine too, but a little warmer.  I went to 55 PSI and it worked very well.  A bit softer than 60 and no heating up.  Then I went to 50 as an experiment, and found the tires were warmer than at 60, but not dangerously so.  And I like them to be a bit soft to absorb impacts.

 

As far as tire temp goes, if you can hold your fingers on them, they are fine.  They would have to be quite a bit hotter than that before they might get into trouble.

 

Bottom line:   A warm tire is OK.  A softer tire than one at full rated pressure is a good idea to reduce impacts.  Pressures can be lowered when off road, and should be.  30-35 is a reasonable place to start on rough surfaces. This helps to reduce cuts from sharp rocks, reduce the pounding from the rough surface, and the trailer, or the truck, will skate around less since the tire can conform to the surface and absorb the irregularities better.  60 PSI is a good default pressure on the highway in summer, and as high as you'll ever need to go.  50 PSI will run slightly warmer, but will ride smoother, and still will not heat up.  The minimum pressure that will carry the load, may be too low for practical use, in fact I think it is quite low.  On tandem axle suspension systems, it seems both axles would carry the same weight, when the trailer is near level.  But they don't.  Side to side will also vary according to the layout of the trailer and the gear on-board.  So, if you just weigh the trailer and divide by four to get each tire's load, you could easily be 100 lbs off.

 

Start out at 50-55 PSI and adjust from there as you see fit on the highway.  This gives you a safety margin if you get a slow leak, will ride well, and will run cool.  By "cool", I mean, you can probably hold your fingers on it without getting burned.

 

This pressure assumes you will set it when "cold".    Make adjustments as you see fit, but use the cold inflation pressure as your standard.

[taylor.coyote]

Raspy,

 

thank you for the detailed tire information. one question. what do you use to put air bak in the tires after airing down for rough off roads?

[Overland]

I think John Davies said that he was running his trailer tires at ~40 now.  I keep saying that I'm going to experiment with that but still haven't.