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
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.
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