HYPERMILING & TOWING: A Misconception
 

I found this under hypermiling tips. I believe it to be incorrect in several ways.

Safety is well-enough represented, but what of utility? What can my vehicle do, and how do I minimize costs without minimizing safety? Utility is a vital part of "economy".

106) Avoid towing
Trailer towing delivers the triple whammy of increased weight, higher aerodynamic drag, and a third (or fourth) set of tires for more rolling resistance.

Carry loads in the vehicle if possible.

If not, minimize towing speeds and adjust your technique to account for the extra momentum the trailer and its load will add.


To reverse the order, point two Carry loads in the vehicle if possible goes against all advice and experience I have seen in re long-term economy (longer drivetrain life due to decreased engine load).

1,000-lbs loaded onto a trailer is much easier for a vehicle to deal with than the same load placed in the tow vehicle. A pair of draft animals can transport a heckuva lot more with a wagon than some magickly balanced load distributed on their backs. Same with soldiers dividing up a load onto bicycles or a cart versus humping same.

Point one is a bit ridiculous. Of course one will use more fuel, but, following manufacturer guidelines, it is well within the practical use parameters of the vehicle. Rather like saying, never carry any passengers. I buy a vehicle to do work, this is obvious. Could be your fragile little eco cars aren't worth much (air conditioned go karts), but most of us need practicality in our single do-it-all vehicle. And that assumes a bit of robustness.

No, the real question is properly matching the cargo trailer (CT) and tow vehicle (TV) and being certain the hitch rigging is dead-certain.

A well-balanced rig -- TV & CT -- according to actual weight on the axles derived from a scale (CAT Scale Search)

where the load on the steering axle has not decreased; or, has increased according to formula is the basic rule. Trailer tongue weight (TW) needs to be 10-15% of the trailer weight (again, generally; depends on trailer type); and TW needs to show up on both TV axles AND CT axles when all is said and done.

There is more to it than this -- the devil is in the details -- but this is the basic way of perceiving this problem.

Let's assume an enclosed cargo trailer, tandem-axle. Dry weight of 2,500-lbs with a 2,500-lb load capacity for a CT gross weight rating (GVWR) of 5,100-lbs.

The TV is a larger car/minivan or pickup.

An ideal TW would be (13%) 650-lbs. Now, let's assume that our TV can deal with this load with proper hitch rigging and we have perfected same with trial & error attempts. In other words, the two vehicles weights & capacities are not an impediment to moving the load SAFELY.

What is the mpg problem?

According to a White Paper published by both Cummins and Kenworth -- for the big truck industry -- the single impediment to mpg is

Below 50 mph: rolling resistance

Above 50 mph: aerodynamic resistance

So, my enclosed CT should have, at a minimum, appropriate load-rated tires designed for least rolling resistance on the road; a "highway tread".

And here is what is missed by many:

The axles should be aligned, professionally.
The brakes should not drag or bind.
The suspension should have shock absorbers.
One wants a state-of-the-art brake controller in the TV.
One wants a hitch that prevents -- not just damps -- trailer sway. (All trailers sway, it is only a question of how much).

The trailer, empty, should roll straight. Loaded, same (load must be balanced side-to-side, not just front-rear.

Assuming that the TV has been checked in the same way (drivetrain reliability questions concerning heat management, brakes, etc) then

the only thing left is aerodynamics.

The White Paper[s] go on to explore aero aids. The biggest "problem" is airflow between the TV and CT. A gap wider than 30-inches is the airflow killer for the hitch rigging,

and,

I would state, the one least likely to be remedied in other than a purpose-built vehicle. (My truck and [bumper pull] travel trailer saw a gap of just over five feet, as an example).

What remains is CT height, and width.

A width the same or less than the TV is ideal. (And easier to deal with in traffic for sightlines and general maneuvers).

Height is the real mpg killer once we have adjusted for all other conditions as found.

So, if my 5,000-lb trailer is the same width or less as the TV, and is no taller

my fuel economy is not so adversely affected. Length, weight, etc, are not so nearly important. Give me a longer, but lower, trailer.

Second is an overall aerodynamic shape. RV'ers have a hard time understanding this one, but I know this crowd won't.

No square corners, and enclosed undercarriage are great.

But pale next to height.

I'd rather have the trailer above: optimized rolling resistance and best aero compromises present when I'm contemplating a load for a trailer.

We all have need, on occasion, where a trailer is the best choice. We can all imagine a scenario -- weather, earthquake, fire, war, etc -- where time and our choices are limited AND our vehicle is the only way to do it.

Economy is best with optimizing details in that situation. Mainly, a road speed around 45-50 mph. And spare fuel aboard.

In the steady-state world, 58-60 mph on the Interstate (roughly, 10 under).

For "peacetime" then some study, and some investment into the best tow vehicle and matching trailer -- cargo, construction, travel, etc -- pays dividends.

The third point, [above] is to adjust driving. Of course. One will need more power at many points: acceleration, braking, etc. It isn't hard with practice

when one understands that he is the slowest, worst-handling vehicle on the road.

The trailer I used as an example is the largest enclosed trailer offered by U_Haul at under 6' tall and 12' long. I loaded it and my truck, and, with an estimated gross weight of between 12 and 13,000-lbs I saw a solid 19 mpg to move over 3,000-lbs of goods on a 300 mile trip. I could have loaded both vehicles to a higher level had I another sort of goods and likely returned the same or similar miles.

My 300-mile fuel cost was (at $2.6/gl) $41. Or, 13.5 cpm (cents-per-mile).

The industry of moving things (trucking) looks at that: all expenses divided into miles to understand cost.

Previous to this I was averaging 15 mpg with a 7,500# 34' travel trailer at a higher road speed. I could likely have broken 16 mpg had I dropped some rpms/speed. This is consistent with some others I know of with similar trucks and trailers; or, simply: a diesel pickup and a lighter weight aero trailer; where the scale tickets showed a gross of nearly 16,000-lbs with a 9' high trailer.

Mpg, solo (7,360#; at the higher speed) is 22+ (versus 15 towing the TT; 16,000#).

Mpg, solo (at the lower speed) is 24+ (versus 19 towing the CT; 13,000#).

Diesel is the magic when it comes to towing. High compression just flattens out the hills. A manual transmission means all miles are within the "sweet spot" for the engine: accelerating, cruising, etc.

A gasoline powered 3/4T truck of the same make & vintage would average, (per others experience) around 7-9 mpg towing, and 15-17 mpg solo. Even if higher, you can see the "diesel benefit" (exclusive of initial cost [offset by greater capacity and longer life; i.e., buy a used truck]).

And so forth.

If you understand your cost-per-mile (all costs, including depreciation, finance [foregone investment], taxes, insurance, fuel, repairs, maintenance, tires, etc) then the "cost" of towing is one where vehicle life is maximized, safety is never compromised and driver condition is comfortably alert over a long day.

Why? If you have 1000 lbs in the vehicle, you have to move an extra 1000 pounds. If you have it in a trailer, you have to move 1000 pounds plus the weight of the trailer. Plus you have extra air resistance, tire & bearing friction, etc.

That may be 'cause you have problems finding draft animals that come with wheels :-)

...provided you can safely load the stuff internally in the first place. A thousand pounds is generally a pickup load, depending on bulk, and I would not recommend loading it *inside* the average economy car at all, though the same car can probably safely pull way more than that in a trailer.
While it's a great thing, trying to drive as efficiently as possible, I'll still keep safety higher on the list.

By the way, trailers don't handle badly at all when properly loaded. The person who believes otherwise could probably use some instruction in that regard.

This is a matter of forgetting acceleration, deceleration and any handling dynamics.

A static load is easy. Driving a vehicle where the load is nearly the capacity rated is not. A trailer removes that burden.

The loaded tow vehicle is straining more than you realize (and station wagons through the 1990's could carry up to 1,200-lbs; minivans are impressive, too); the trailer places that load onto a platform designed only to carry a load, not passengers, etc. Rolling resistance is lower than many realize. A child can push around a balanced trailer when a slimp wheel is mounted.

And, with a top speed of around 58-60 mph, wind resistance is minimal where trailer height and width are kept down.

Think of a Tahoe with Dad, Mom and the kids. The cargo area is maxed out. There's a pod on the roof. And a hitch receiver mount cargo carrier with a box. Every aspect of utility and economy would be better with a trailer (and, obviously, a smaller vehicle could have been used in the first place).

A well-sorted rig can also stop faster -- in a shorter distance -- than the solo vehicle can alone.

Trailers have their place, but don't assume you've ever

A) seen correct hitch rigging; and,
B) seen a well-matched TV and trailer.

You'd change this "obvious" opinion in a hurry.

The numbers work well in favor of a trailer in many circumstances.

Loading, hitching, etc, is a different thread topic.

I like trailers very much, but only because I rarely need to use them. It allows my vehicle to stay relatively tiny (and efficient) most of the time without the added expense/maintenance of a large vehicle that would be underutilized.

For the few times that I need to move a washer/dryer, or a couple motorcycles, or landscaping, it is awesome, and easy to load.

The handling/safety question is irrelevant IMHO, all vehicles are different and it is the drivers job to operate it safely in any configuration. We can't all drive Porsches.

I once bought a dryer, and it just fit into the hatch for transport. I was better off with it inside than in a trailer. I also had to move an empty 18 cube feet rooftop cargo box once. I was able to fit it in the back seat of my sedan instead of putting it up on a roof rack. I think that's the nature of the discussed fuel economy tip.

I moved a washer, dryer, and 2 stoves inside my van. I guess they'd have been better off on a trailer behind my van?

Inside my Caravan, I can move 7 people (which already maxes the weight limit, but not the cargo space, not nearly), and still have room for a couple bikes or camping equipment inside the van, if one were inclined to "roughing it".

If the van was able to do it well, and without any handling difficulties, not at all.
As far as my post was concerned, my concern was mostly the ability of the vehicle to safely carry the weight, and why a trailer is a safer bet if not. Any assumptions otherwise belong to the originator of that assumption.

I think that's the nature of the discussed fuel economy tip.

If read one way, yes, that could be seen. It might also lead one to think that having a shipper handle the goods is the better decision. In fact it may always be, but it is considerably more expensive, even prohibitive.

As to moving an appliance across town, yes, it fit the hatchback; by the above, would one want to move across state thusly? Because one can, does that mean one should?


The handling/safety question is irrelevant IMHO,

Safety is never irrelevant. One has -- always -- but a single chance to avoid disaster. Planning otherwise, as in, "I'm exempt from physical laws", or, "I've never had a problem taking shortcuts in hitch rigging, are ways of inviting $$$ problems as well as legal liability.

In trailer towing the tail wags the dog. A lightweight trailer, improperly loaded and/or hitched, can flip even a heavy tow vehicle. Polar-moment-of-inertia.

Whether a trailer is used regularly or irregularly one still can make the journey more safely as well as at a reduced cost by attending to details. Ecomod as a concept is one that works here.

I like trailers very much, but only because I rarely need to use them. It allows my vehicle to stay relatively tiny (and efficient) most of the time without the added expense/maintenance of a large vehicle that would be underutilized.

Bingo! But what of when the trip is cross-country, of a weeks duration, and thousands of pounding miles on goods, tow vehicle and driver? Attending to basics -- and to fine-tuning -- pays upfront, and pays long-term.

This is like a DAH moment. :rolleyes:

If the load is within the vehicle's rated capacity, then load 'er up and go with it. The hypermiling tip is correct in saying the trailer is extra weight and etc. BECAUSE IT IS.

Overloading a vehicle is no different then overloading a TRAILER so don't do that either. :eek:

Who was talking about overloading anyway? Oh yes, that's right, nobody.

Sometimes the trailer is the best solution and sometimes it ain't. Wanna go through every possible load/vehicle/trip combo? My A.D.D. won't allow me to follow along.

http://i146.photobucket.com/albums/r...ncher/2003.jpg

Hm... where's my video of an S-10 towing a Saturn L200 on a utility trailer?

Anyone who seriously believes that safety and handling are irrelevant, please stay far away from me. (fat chance... too many idiots already out there. *sigh*)

When taken out of context, it seems like that's what the person who said that was saying. Why not quote the whole sentence?

Safety and Handling concerns are fairly irrelevant on this forum. We're probably the safest, most conscientious drivers on the road, and if you were here long enough to really have any grounds to critique any one of us, you'd already know that.

Does this thread have any significant place/relevance here? I mean, the concerns are un-informed, at best.

I'm not trying to be rude, but you're directly speaking out against a well-known tenet, teaching, and set of facts, based on contextualization of a series of words that you've obviously misunderstood in their original format.

I find it interesting that of the thousands of people that visit this forum yearly, (several of which drive trucks, large, small, or otherwise, and tow trailers) you're the only one that's ever pointed this "concern" out.

EDIT - This is in RE: to the original post on this topic.

Good point... I'm not happy with the way we're communicating in this thread. Lots of assumptions and misunderstanding. I'm gonna bow out now.

This is one premise and it's all messed up.

Nope, at least not two of those. Acceleration and deceleration depend on the total weight. Load plus trailer weighs more than load alone, therefore your A&D is going to be worse. (Braking MIGHT be a little better because of the extra tires on the trailer, but you've still got more mass to decelerate.) Handling is going to depend on trailer & load geometry. I'm no expert, but in my experience (which includes a spell driving logging trucks, among other things), in the best case handling with trailer is going to be worse than without. (This assuming the load is within the vehicle limits, of course.)

Well, that pod on the roof isn't carrying the load in the vehicle, is it?

Now a counter-example, me taking the Toyota pickup out to get firewood. So I've got the bed loaded about cab high with logs, some hanging a bit over the tailgate, and yeah, it does squat the back end down just a tad (though not enough to be unsafe), and stopping distance increases, so I REALLY like to plan ahead. Now do you want to argue that I could put the same load on a trailer, more effectively?

Now after I unload the logs, I need to go to Home Depot for a couple of sheets of plywood. Again, you're suggesting that it's more efficient to hook up a trailer for the job? I don't think so.

Now if all you have is a car, then yes, a trailer might make sense for the occasional lumber run. Though in my case the car's an Insight, which won't haul much of a trailer, maybe one to haul a couple of bikes or kayaks.

It'd help if the original post was read.

There are times when the load requires a trailer, and choosing the correct trailer for tow vehicle and load will make a difference for both safety and economy. There are times when the tow vehicle could carry the load, but it would not be in the interest of safety to do so. The fuel penalty can be minimized, and the attendant safety considerations not compromised. There are cases one can make that the trailer, carefully chosen, rigged and equipped will use less fuel in tow than heavily loading the tow vehicle driven solo. They might be rare yet they exist. I've done it.

The assumption that towing is automatically the wrong choice when fuel economy is a prime consideration has to be weighed against alternatives; especially if the alternatives just shift the burden to another. Most vehicles are capable of quite a bit, but the details must be attended to for proper performance.

I, too, have driven OTR. And heavily loaded my pickup. And used trailers to make life easier. And I can go on, refute, offer counterexample and all the rest. Whoopee. Thought maybe someone might also read that Tip and come away with the same impression: tow=bad. It isn't. There is more to it than I wrote, and I see that none of the responses so far understand how to make the tow vehicle/trailer their most efficient and not compromise safety. I'm not the one making poor assumptions, here.

I did read it. You claim that it's always better to tow something than to carry it inside, which is nonsense, expecially when it relates to performance.

Sure, there are times when towing's the better choice. I'm not, for instance, even going to try to convince my horse that she ought to ride in a pickup bed :-) And it's better to tow the occasional load - those sheets of plywood, for instance - behind a small car, than to always drive a vehicle big enough to carry them. But you're paying an additional penalty, the extra weight & drag of the trailer, in order to reduce the cost of driving all those times when you're not pulling the trailer.

I'll admit, I didn't finish it. Too much was wrong in the beginning, then it got way too long. In my experience, when it starts out bad, it doesn't get much better.

That's the way the original post sounded to me, as well.

-soD

penalty
 

The only thing I can bring to the table is my experience with the CRX.
That car has a 400-pound max. load limit.It is not rated at all for towing.
I fabricated a 1-1/8" ball hitch for it and pulled a utility trailer with only an upper body shell from the Dallas/Ft.Worth area to Los Angeles,California and back,running with a 1,300-lb load on the return leg.
MPG dropped from 52,to 50 mpg @ 55-mph.
By putting the load in the trailer I was able to run 900-lbs overweight with only a 3.84% drop in fuel economy.Of course,this was a majority of steady-state highway driving.
This an instance when the trailer offered an alternative unattainable with the tow vehicle.

Most vehicles can tow a trailer. Actually, most all, is a better way to put it. While I got off on the wrong conceptual foot in this thread, there are ways to analyse what a vehicle is capable of (axle ratings, tire ratings) that are of use. Vehicle manufacturer "ratings" do not have the force of law in any respect, they are what those "individuals" are comfortable recommending (thus the conundrum of the exact same vehicle sold overseas having the ability to tow two or three times as much).

It's reasonable to expect a 30-40% drop in mpg for a conventional, fairly large trailer. Less so the more aero is the rig along with fewer stops or hilly terrain.

An overloaded single vehicle -- we've all seen it -- where the passenger compartment and roof are jammed, crammed and tall, is the poor choice where some trailers can provide a better way to move the same load. And as cheaply in fuel, sometimes better (due to aero, COG, and fewer steering inputs).

I've done it both ways. The cost of a trailer rental was not offset by mpg that was better with the trailer, but the improved vehicle handling -- in a relative sense -- offset that to my satisfaction. It's distinctly easier for a tow vehicle to pull a load that would strain it if carried aboard.

.

towing
 

I'm really a newcomer with respect to trailers.I've enjoyed the limited exposure that I've had so far and now keep a 3rd eye open with regards to all things trailers,as so many folks I know are now dealing with them.
Most surprising of all is the limited peer-reviewed documentation on performance prediction capabilities.
With Scan-Gauge capability now,members ought to be able to construct a complete performance profile of their rig,simply by documenting observed mpg under the varied driving environments encountered during travels.
I'm having to deal with eleven simultaneous unknowns while attempting to reduce the data from my Sept/Oct trip with the Viking trailer.What a PITA!

With Scan-Gauge capability now,members ought to be able to construct a complete performance profile of their rig,simply by documenting observed mpg under the varied driving environments encountered during travels.


Predictability is everything. The problem is always: new roads, with new loads, and wacky weather/wacky traffic (outside of perceived norms).

TX_dj description of Ultra-Gauge capabilities has my attention for what I've been missing in this regard (for diesel trucks).

Outside of critical mechanical issues, the rule of thumb for a cargo trailer ought to be that the trailer is no taller or wider than the vehicle towing it. Length is where the additional cargo space can be found. Aero trumps weight in all considerations for highway use.

The first divider is occasional use versus regular use. The formers impact on annual fuel burn is minimal. The second -- as percentage of miles per year, and anticipated years of use -- is where homework needs be done. In this case, the trailer trumps the tow vehicle for order of importance. Spec trailer first, then spec & purchase tow vehicle.

As example recently came across a thread on an RV forum where the tow vehicle was a HONDA RAV-4 and the travel trailer a tiny 16' fiberglass egg CASITA. The owner reported mpg figures consistent with my 3/4-T truck solo & towing a 34' travel trailer. A better chosen TV in that instance would have seen much better fuel mileage. (His overall vehicle costs were actually higher than mine if purchased new).

I'm having to deal with eleven simultaneous unknowns while attempting to reduce the data from my Sept/Oct trip with the Viking trailer.What a PITA!

Never seen anything like it for information-collection (that thread).

Logging every trip will obviously produce a set of reliable datum. But once one changes just terrain (or climatic conditions) it all changes again. Electronic engine controls have made today's vehicles much more consistent in solo use with regard to changes in terrain, climate, and vehicle spec, but towing opens the deficiencies right back up again. A spring-like day on US-287 near Ft. Worth is one thing . . a wintry day on US-287 near Thermopolis is quite another. What is a bit of a hurt while solo is noticeable, but while towing it may mean not making ones destination on time or in budget. (This is where strict trip-planning pays off).

The more closely one can define need and use over time and miles, the better the ownership and operating costs.

.

Some good information here, but some beating the dead horse as well.

I would love to see some of your personal stats, if you would share them, about what your base empty PU mpg. empty is for long freeway cruise, with added, lets say a bumper style pull 28-32ish foot travel trailer at the same cruising situation, and your tricks to keep those 2 figures closer to together than apart.

I know different trucks are different, but in theory, what would be a good rear end diff. ratio for that 50mph long living. I have a '85 Suburban w 6.2, w the 700R 4 spd. auto. It has 3,70's, or 3.73 ish. Though a K model, it has manual hubs, and only 31's for tires so it sits almost 2wl drive low.
Alone, mid 20's-30mpg. is still possible.

Would BF Goodrich Mud/All Terrain tires change my mpg. like falling off a cliff, or not; up to 33's much difference in all at 50mph or less cruise life?

Would greatly appreciate some input.

I liked the sharing of the CRX towing example as a clue to seeing real life results.
That is the pertient info example that would help, though I do cringe at the thought of MY CRX having to tow anything.

For us mpg. people, and the general future of smaller, lighter cars in the future, do any of you think that the 1 tired cargo trailer might make a comeback???
I remember as a kid watching my Dad pull one on one of our vacations.

Obviously, design is SO important here, generally the motorcycle/bicycle people probably have much more proper application experience here.

Your thoughts, please!!
Thanks!

I would love to see some of your personal stats, if you would share them, about what your base empty PU mpg. empty is for long freeway cruise, with added, lets say a bumper style pull 28-32ish foot travel trailer at the same cruising situation, and your tricks to keep those 2 figures closer to together than apart.


Oh, boy, detail time. Below is an assumption of a pickup truck and a travel trailer (for the most part) where higher than average miles is expected (5k-plus annually). As always, vehicle specification is paramount. Nothing will overcome bad choices. Truck aero and trailer aero are separate issues. No wing or other devices on the truck will "help" the trailer as the gap between vehicles is too high (unless one lives in Sanger, Texas). FE is small changes adding up to percentage increases. Maximizing mechanical leverage details makes for a better handling, better braking, better tracking rig. Less wasted energy in forward motion.

Rolling resistance concerns are of a higher order than when solo, thus this set of posts about hitch rigging.

This is the "how to" (short version).

My numbers:

For solo, at 58-mph, 1,725-rpm cruise across Gulf Coast Texas, on 700-mile roundtrips (including traversing Houston twice each time) I never fell below 24-mpg, loaded, empty, winter or summer, rain, dark, traffic, etc. Highs of 27-mpg numerous times. Did this trip over two dozen times. Never a straight tail or head wind. And winds always shifted at the trip mid-point.

With a 34' TT (6860-lbs empty, 7,500-lbs loaded for full-timing; .94 of 8k GVWR; under 16k combined), saw from 13-mpg on hilly two lane backroads with lots of small towns, and then open flats. On the same highways as in the solo, above, saw 15+ mpg. All of this was at 63-mph, my previous cruising speed. Had I slowed to the present 58-mph, I'd have broken 16-mpg. These miles were in Texas.

The above figures are consistent with other owners of the same brand and near MY truck, plus very similar trailers (all aluminum, aero, low COG, relatively light weight, etc), some of whom do better than me. Non-Cummins powered GM pickups from the early 2000's do the same. My comparisons range across mainly RV'ers, but some commercial drivers in there too; all of them in the Southern or South Central US to keep variations for climate and terrain to a minimum.

The spread is at about 31% for this trailer type from solo to towing with a CTD or Duramax. Ford is less desirable (not just FE). The gasser range is closer to 40% when using TRAILER LIFE articles on rig performance be it 1971 or 2011.

With U-Haul's biggest enclosed trailer (12x6x6) and at about 13k GCW, saw 18/19-mpg empty and loaded on the above roundtrip routing. Saved more money by renting in one city instead of point-to-point dropoff. The other savings was in using a MASTERLOCK 500/5000 Adjustable Hitch

http://images.shopletcdn.com/product...2841AT.EPS.JPG

in order to, using a level, tilt the trailer nose just barely forward of perfectly level. I also loaded and sometimes re-loaded the trailer to get the lowest COG and have it ideally placed versus the trailer axle.

U-Haul does not have a good record in taking care of it's equipment, not at the level I think they should. So part of my inspection is to see that the surge brake fluid looks new (and have them change it if not); also to get that device hooked up appropriately (instructions online); and I also take along a torque wrench to apply correct value to lug nuts; and I want to see perfect tire inflation. I also use a flashlight to inspect the underside, not just topside plus treadwear. I also get "underneath" the coupler and clean it out, looking for cracks and galling. The coupler must not be loose (beyond normal). I use wheel bearing grease or whatever is handy to grease the ball and the coupler underside.

(Once hitched, that ball is a critical steering component. In big trucks, the fifth wheel -- as a predictor -- is, if dry, the number one cause of big truck loss-of-control accidents. Not rain, not other traffic or driver error, but a dry hitch. The same, I believe, works for small trailers as well. We want no resistance to returning to center for the trailer).

In their favor, I would love to have a trailer as well designed and built as this U-Haul trailer.

On a trailer I own Step One past purchase is to pull brakes and service wheel bearings, even if brand-new. (I am looking at "treated" wheel bearings by MICROBLUE RACING for the next trailer. Might be worth a full 1-mpg on big truck trailers). Same for axle alignment and wheel balance; the assumption is that it is off. Perfection is just acceptable for these.

Step Two is either new shock absorbers, or to add them on a conventional leaf-sprung trailer (torsion axle [independent suspension] is much superior and not included in the following). I want road irregularities dissipated as heat, not as a trailer that crow hops. A leaf sprung trailer has a high and narrow roll center. It is unstable, already. We want to minimize this.

The goal is lane-centeredness under all conditions. And, as it is difficult to have a perfectly-balanced trailer (in regards ideal tongue weight) either side-to-side, or front-rear, then shock absorbers --like tandem axle equalizers -- help with imbalances even if minor. I've pulled worn shocks off of one axle and found those on the other still good. Weighing a trailer usually reveals what the equalizer has to cope with (and there are upgrades for that component from DEXTER and MOR-Ryde and others). I also add CENTRAMATIC balancers for the finishing touch.

Alignment, wheel balance, shock absorbtion (wheel dampers and the equalizer), and ball grease all add up to a trailer that more easily follows the truck, and is less affected by tripping hazards. You'll have noticed that all too many travel trailers appear to sit two feet off the ground as it is. This high center-of-gravity [COG] is exacerbated by a crude suspension and the tendency to tip (even before wind loads from any direction are added).

Tires are always worthy of discussion in re trailers as the usual ST rating tires are essentially junk, not suitable for extended high speed travel. I'd rather have radial LT tires, for commercial use, of the appropriate rating (and American made wheels with a commensurate or higher rating) for longest service and best performance. One never wants trailer tires to run hot or to hydroplane.

A TPMS is recommended. Trailer tires are notorious for losing air. On the next trailer I plan to use epoxy paint to coat the aluminum wheel interior and to specify that bead sealant be used when the tire is mounted. Trailer tires only have their weight rating at the specified pressure. A day of running them hot, low, is enough to shorten life drastically.

Daily, the trailer needs: A check of all lug nuts for appropriate torque value (I keep a dedicated torque wrench for this), and tire pressure values. One should always check suspension components, and brakes. A hand-held IR device is handy for this. If bearings are too loose or too tight; if brakes are dragging, the IR gun will disclose it immediately. Same for tire temps. TV should have one set of temps, the trailer another. Discrepancies should be addressed ASAP.

I plan to convert the next trailer to disc brakes. I want the best performance with the coolest running when things get tough. And the shortest application time, repeatedly. This is a matter of -- for all vehicle controls -- using the least amount of time/energy to maintain lane-centeredness. Anti-lock is on the immediate horizon for trailers. Disc brakes, alone, mean a shorter stopping distance for a TV/TT combination than the TV alone. One can get there with drums, but adjustment has to be constant to maintain this. Trailer drums are usually out-of-round, even new, so balance, stopping performance, are all compromised. Tolerances in this industry are low, much lower than automotive. Disc brakes on all axles of the rig are just right.

Next post will be about Weight Distribution Hitches.

.

When towing the goal is to remain lane-centered without driver inputs (beyond what was normal for the solo vehicle). Cummins and Kenworth both use the number of steering inputs per X-miles when high as deleterious to fuel mileage.

A weight distributing hitch [WDH] is required even on 1T pickup trucks when trailer tongue weight [TW] exceeds 400-lbs. A trailer with a TW of 400-lbs may weigh as little as 2,500-lbs. The bar is low. The simplest understanding is that a WDH "returns" the Front Axle [FA] to unhitched height/weight values, and that this ensures "normal" steering and braking by so doing. The remainder of the TW is "distributed" over the Rear Axle [RA] and Travel Trailer [TT] axles. When a large force plays against both the TV and TT at slightly different times, the leverage action of the trailer tongue is spread out across all axles of both vehicles effectively dampening "problems".

Now, payload of a truck is, in a manner of speaking, irrelevant to the discussion, overall, as TW is a static measurement of a dynamic problem. That is to say, an 800-lb TW can be 12,000-lbs under the wrong circumstances. The "arm" of the trailer tongue, extending back to the center of the axle is a lever that can upset the TV, drastically. The tail wags the dog. I once watched a portable generator that I know weighs around 1,800-lbs takes a dually pickemup clean off the road. A dry road.

A download of a spreadsheet made by Nickcrowhurst on AIRforums.net showing forces acting upon the rig is here; the thread is a discussion of these factors. One can play with different trailers and tow vehicles given a handful of measurements. This, and the below, are ways of understanding how SAE looks at tow rig dynamics, the forces acting upon the tow vehicle different from solo, and how to re-establish solo handling to the best extent.

The following is chart made up by Ron Gratz a contributor on RV.net, handy for it's brevity and checks. By using a three-pad certified scale (see CAT Scale Locator, online) one can fine-tune a WDH beyond the usual measurements of before/after heights given in Towing Guide instructions by vehicle and hitch manufacturers. Specifics to vehicle ought to be followed.

For a truck, the usual result of proper hitching, today, is that once the FA has returned to the unhitched weight value that the balance of the TW will be distributed from 75-25 to 60-40 on the RA and TT axles respectively. (Copy and print a few):

Weighing #1 -- TT attached and Weight Distribution Activated

Let Front Axle Load be "FA1"

Let Rear Axle Load be "RA1"

Let TT Axles Load be "TT1"

Then, while in same position on scales, take
Weighing #2 -- TT attached and Weight Distribution Not Activated

Let Front Axle Load be "FA2"

Let Rear Axle Load be "RA2"

Let TT Axles Load be "TT2"

Then, drive off scales and drop TT. Return to scales and take
Weighing #3 -- TV only -- TT Not Attached

Let Front Axle Load be "FA3"

Let Rear Axle Load be "RA3"

From the above values, you can calculate:

TV weight = FA3 + RA3

Gross Combined Weight = (FA1 + RA1 + TT1)
- should also be equal to (FA2 + RA2 + TT2) if scale weights are correct

TT Weight = Gross Combined Weight - TV Weight

Tongue Weight = (FA2 + RA2) - (FA3 + RA3), or

Load Transferred to TT Axles
when WD System in Activated = TT1 - TT2


Once these values are established, and some subsequent ones done the same way to account for different loadings, the range of WDH adjustments are known for a given rig. Now is when tire pressures can be zeroed in as highest pressures are not always to the point in braking/handling questions. Same for alignment problems on the TV, slack in the steering gear, etc. In short, any TV shortcomings are magnified and we do not want the actions of the TT to have any farther effect. IOW, if the rigging is ideal, then the diagnosis of handling, braking and FE problems can be isolated and treated.

Now, as to type of WDH; next post.

.

VPP Hitches
 

The TV Drive Axle is the Steer Axle of the trailer. The tendency of the trailer to want to move about on its own -- to pass the TV -- is greatly reduced when the proper hitch rigging is installed correctly. Side-to-side motion of the trailer can increase to trailer sway due to all sorts of concerns: trailer design, trailer load, winds, road surface, etc. To keep this at a minimum is the purpose of trailer anti-sway. The better the anti-sway, the less wasted motion in moving forward (less drag, cleaner aero).

The function of a WDH is to spread the 12-15% of TW across the TV, thus keeping handling/braking closer to the solo norm. The addition of anti-sway devices to the WDH keeps the trailer closer to center. Some hitches are designed around a particular concept to achieve this, some have add-ons. The first is a type, a VPP hitch, Virtual Pivot Projection where design linkages simulate a fifth wheel or gooseneck hitch, each of which mounts at or barely ahead of the TV Rear Axle:

GN

http://www.gooseneckhitch.info/installation.png


Fifth Wheel

http://www.godfearingbrothers.com/im...nschematic.jpg

(A high mpg example is Kamper Bob's rig: short OAL, lightweight & and decently aero. Another is Skyking's proposed aero conversion of an Avion 5'er TT to take advantage of close vehicle coupling. The trade-off of a 5'er is the loss of the truck bed & enclosure while towing beyond high wind load and COG concerns).

For trailers starting at about 8k, and especially above 12k, a GN or 5'er is pretty well required due to TW requirements.

A VPP Hitch replicates this advantageous arrangement of keeping the pivot point of the rig at the Drive Axle. The farther back from the RA is the pivot point, the potentially worse the handling problems that arise.

The TV Drive Axle is the Steer Axle of the trailer. The tendency of the trailer to want to move about on its own -- to pass the TV -- is greatly reduced. Side-to-side motion of the trailer can increase to trailer sway due to all sorts of concerns: trailer design, trailer load, winds, road surface, etc. To keep this at a minimum is the purpose of trailer anti-sway. The better the anti-sway, the less wasted motion in moving forward (less drag, cleaner aero).

In order of performance, thus preference, the best hitches are those which we might refer to as sway-eliminating:

1] Pullrite This mounts under the truck, and that center bar pivots from a mount point to have the trailer track true in all instances.

http://www.pullrite.com/images/pullrite_160.jpg

2] Pro Pride The improved, new patent Jim Hensley design. Allows a greater range of WD adjustment.

http://www.propridehitch.com/product...39433_zoom.jpg

3] Hensley Arrow The original Jim Hensley design patent.

http://hensleymfg.com/wp-content/upl...wfullsmall.jpg

The second tier, again in order of performance, may be called sway-resisting:

4] Reese Strait-Line / Dual Cam

http://www.rvsupplywarehouse.com/con...arge/66072.jpg


5] E-Qual-Izer (and similar designs by others; preferred for surge brake applications)

http://www.grovecamp.com/wp-content/...izer-hitch.jpg

And finally, the doorstop known as a "friction device" anti-sway; to be avoided overall as one must disconnect in wet weather, etc, when most needed). This is what maybe 80-90% of folks think of when referring to a WDH (and their "understanding" that a 5'er is more stable) and the "poor performance" of a conventional "bumper pull" travel trailer.

http://mrtruck.net/h_pic/hitch2.gif

In short, the less movement by the trailer under any circumstance, the less power needed by the TV to maintain headway being lane-centered in all conditions.

Towing is a risky business, and the likelihood of an accident per mile of travel is greater than with a solo vehicle. Thus the best hitch & rigging is neither expensive nor onerous to set up.

Next post: Incidental Concerns.

.