Smartweigh: Geekoid Nirvana
Originally posted 4/5/2013
Originally posted 4/5/2013
Had Dickens been at my Smartweigh at the Escapees North Ranch in Congress, Arizona he would have summarized it as, “It was the best of times. It was the worst of times.” Although the Smartweigh is a safety-oriented number-crunching exercise, with terms like GVWR, GCWR, and GAWR, I’ll try to make the explanation of it as understandable as possible. The Executive Summary: As far as the numbers go, I’m looking good – much better than I thought. The bummer is the remaining three “original” trailer tires themselves, and the weight distributing hitch. Even though I’m not overloading any tires, it would be a real good idea to lose some weight. I’ll show you why.
The Escapees’ Smartweigh system is much better than your typical truck stop scales, which weigh the tow vehicle, the trailer, and then both. All that does is give you a “yes, no, maybe so” result that tells you if the individual units are overweight.
For $55 for a truck and trailer weigh-in, the Smartweigh test coughs up individual loads on each tire. Because RVs typically load their tires and suspensions very near their load carrying limits, and do not distribute those loads evenly, it’s common to have an RV weigh in under the maximum limit, and yet be overloading one or more tires. In order to get “worst case” numbers, the RV is supposed to go into the test with all fuel, propane and fresh water tanks full, while all waste tanks are to be empty. This is the normal travel mode.
For the record, the majority of RVs tested so far have overloaded something beyond its limits. That presents a safety problem, sometimes a legal liability problem in case of an accident, and it accounts for many interesting, unplanned road adventures. It’s a fair question to ask why RVs aren’t delivered with higher-rated axles, wheel bearings, and tires. That way, they wouldn’t run full-time with a load very close to the absolute maximum they can carry. There would be a safety cushion of sorts.
But, you already know the answer: money. If the trailer you can afford happens to be rated at 7,500 pounds capacity, you are going to waffle when asked for an extra $5,000 for the exact same trailer which has been pumped up to 10,000 pounds capacity. From the manufacturer’s standpoint, it’s the story of The House That Jack Built. A 7,500 pound-rated trailer with a 10,000 pound suspension means that some idiot somewhere is going to try to use that extra capacity instead of leaving it as a safety cushion. Without increased frame stiffness and a higher-rated tongue jack for starters, that opens up a can of worms for liability and warranty issues. Not to mention that nobody would buy it.
But, let’s get back to Smartweigh. With a truck and trailer combination, the first thing to be weighed is the truck alone, as loaded for travel. This acts as kind of a baseline, allowing you to find out later just how the trailer’s tongue weight is affecting the truck. My Ford 2008 F-250 4×4, loaded for bear, weighed in at an astounding 9,100 pounds. That massive diesel engine in front put 5,100 pounds on the front tires, while the cargo load put 4,000 pounds on the rear tires. Side-to-side weight variation was fine. Fortunately, this particular model was delivered with a 10,000 pound rated capacity option, so I’m okay there. So far.
Step two of the Smartweigh procedure is to hitch up and weigh each of the eight tires hitting the ground. With some cipherin’, that lets you know how the individual trailer tires are loaded, total trailer weight, what the tongue weight is, and how that tongue weight is stressing the tow vehicle it’s attached to.
Thanks to a damaged and painted-over trailer ID plate, I’ll never know what the official maximum trailer weight rating is. It’s based on axle capacities, but some of the trailer’s weight is also carried on the tongue. Best conservative guess so far is at least 7,500 pounds, and perhaps as high as 8,000. Dancing down the numbers shows that the trailer alone now weighs 7,100 pounds. This would be upsetting, since its tandem axles are rated to carry only 7,000 pounds. Fortunately, 1,000 pounds of that weight is on the hitch, not the axles. Total load on the axles then, is 6,100 pounds. The rule of thumb for trailers is that 10-15% of the trailer’s total weight should be carried on the hitch. I’m at 14%, which is acceptable. A little less would be nice, but I’m okay when push comes to shove.
The trailer’s tires are rated to be able to carry up to 1,820 pounds each. The actual load on them varies from 1,400 to 1,600 pounds. The front right tire is predictably carrying the most because of the solar panels and office battery pack on that side. The front left tire is carrying the least. In theory, this was good. I’m not maxed out on any one tire. My test guy George had a case of the willies, though. He noted that I’d just replaced one of the trailer’s tires with one rated at 2,150 pounds, and strongly urged me to replace the other three with the same type of better tire. He’d be happier with a larger safety cushion than 200 pounds, especially when waste tank usage starts transferring more weight to the rear end. Me, too.
The other issue with the trailer tires which was more pressing was that, using the tires’ date codes, he knew that the remaining three tires are at least 10 years old. You’re supposed to start thinking about replacing them at 5 years of age, and to definitely replace them at 7 years regardless of the tread remaining. That 1,820 pound rating is at 60 miles per hour, with brand new tires. Go faster than that, and all bets are off.
What was giving George the creeps was that a tire’s maximum load capacity is only attained by using the maximum air pressure that it is designed to carry. In my case, that’s 50 PSI on the older tires, and it’s noted right on the sidewalls. At their age, he noted that 50 PSI may now be too much, yet if I use a lower pressure, their load-carrying ability nosedives. End result: There’s a chance that I may grenade a tire by insisting on 50 PSI, and yet if I lower it to 45 PSI, I will be overloading it. He advised that I lower pressures to 45 PSI and drive 45-55 MPH only as far as the nearest tire dealer. Hmm. These things are $120 apiece, if you can find them that cheaply. $150-$160 installed is not unusual at all. That was the first piece of bad news. Although the numbers look good, the tires do not.
But let’s go on. Hitching up the trailer to the truck definitely has an effect on its weight distribution. One would expect that adding 1,000 pounds at the rear bumper would affect things, and it does. Neither the tires nor axles are overloaded or close to it. However, once hitched up, the truck now weighs 10,100 pounds overall, 100 pounds over its rated limit. It’s a suspension and brake thing, I assume. If I dumped 12 gallons of fresh water, I’d be fine. I can do that, too. The Tankmin carries more fresh water than I can use, because I’m limited by my waste capacity.
The more squeamish issue is that hitching up the trailer actually removes 450 pounds from the truck’s front end. That’s not particularly good. The trailer should ideally add 50-75 pounds. It’s a teeter-totter effect, and the pivot point is the rear axle. It’s a theoretical negative for handling, and slightly changes the geometry of the front suspension. Think “wheels misaligned” and “tire wear”. Actual handling on the road has been pretty darned good, but running a tad above maximum weight rating while removing weight from the front suspension at the same time is not the best. The truck’s hitched weight distribution is 4650 front, 5450 rear. At night, this makes the headlights aim for the sky.
The normal fix for this is to crank up the weight distributing bars on the hitch. This can transfer some weight toward the truck’s front axle, and away from its rear axle and hitch. Without other compensating changes, it can also nose up the front of the trailer, which takes a little weight off the hitch and transfers it to the trailer’s tires. That option does not exist for me, unfortunately. My weight distributing hitch has two problems that prevent setting the bars with more tension. First, it’s been installed improperly. Second, it’s worn out.
The rear ends of each of the two spring bars end in a chain. You attach the chain to a mount that’s on the trailer tongue. Attach the chain using a shorter effective length, and it pulls up the bar so you get more tension. More tension transfers more weight. The attachment pads on my trailer tongue are mounted too far rearward, putting the chains at an angle when the truck and trailer are lined up straight. I could remount them properly (assuming their rusty fasteners don’t snap off) except that the platform holding the propane tanks is in the way. That needs to be remounted further forward, too.
Having the chains at an angle is actually a big deal. During a turn, the bars move forward and back. As you can see from the photo below, the chain on the outside of the turn is angled so much that it’s binding against the mount, placing twisting stresses on it that it’s not designed for. Oops. You may also notice that the chain looks pretty short, Tightening it by one link to get more tension would make the binding worse. I’ve tried a tighter setting, and this rather inexpensive mounting system will not take the stress. Having it snap and drop bars onto the highway would not be good. The reason the chain looks so short is because the forward, pivoting end of the bars have worn their round receiving sockets into elongated egg-shaped holes. Somebody didn’t bother greasing them, and now they’re not holding the bar down as they should. The make-do fix is to relocate the propane tank pad, and then relocate the chain mounts forward. This won’t help weight distribution a bit, but would at least address the binding problem. The real fix is to relocate the propane pad and then replace the entire weight distributing section of the hitch. Ow.
I’ll bet that the real reason the propane pad was mounted too far rearward was that the old propane hose going from the tanks to the trailer was too short even as is. They didn’t want to replace it. Too much time and trouble. So, they mounted the hitch mounting pads too far back, and saved themselves about $15 and ten minutes work. Then they didn’t lubricate anything. Ever.
One thing I noticed on the 100-mile trip to Congress, Arizona is that the new wheel bearing is running cool as a cucumber. The remaining three are warm, but not hot. When my daily drives expand from 2 to 6 hours, you can bet that I’ll regularly be groping the trailer’s wheel hubs like some kind of trailer pervert. No lady, it’s okay, really, don’t call the police!
One can sense that the opportunity to spend admirable amounts of money here is blooming like flowers in a garden. Tires and weight distributing hitch. Maybe three sets of bearings. Any expert concerned about safety would advise me to ante up. Tires right now, WD hitch later, and keep checking those wheel bearings.
But there’s that haunting, siren call of the cheapskate somewhere off in the distance. I need to lower the tongue weight. First order of call will be to rearrange the truck bed to place the heaviest items further forward, close to the Tankmin. That will help a little bit. I’ll be agonizing over the office battery pack and solar panel storage in the long term, and trailer tires in the short term. The tires have not shown any signs of running hot, but there’s no way of knowing if they are aged eggshells or still good tires.
One last note concerning my priorities. While showing my obnoxiously large solar panels to Mike, who is prepping his van for one or two, he noticed that one pair of trailer wheels appeared to be out of kilter with each other. One was vertical, and one appeared tilted. That’s easily explained when the wheel on the other end of that axle is in a hole or depression. A look on the other side showed that the wheel was lower, but not enough to justify that amount of tilt. This is a deja vu moment, since that’s close to how the wheel with the blown bearing looked in Quartzsite. Time to raise the offending wheel up, take it off, and have a look at the bearing. If I’m “lucky”, the cotter pin will be missing and the bearing nut will have merely loosened. If I’m not lucky, I’ll be looking for a local RV shop and all three old wheel bearing sets will have to be replaced. Adventure!
As you can see for yourself from the above photos, it’s a little more difficult to obsess over non-crisis mechanical problems out here. I think I’ll look up a local RV/trailer place just to know one exists, and then take a nice nap. Then I’ll see if I can join Bob on his late afternoon walk with his dog Homer. After that, if the sun hasn’t set, maybe I’ll break out the Ford’s bottle jack and see if it fits under the trailer axle. Pop that puppy open and see what’s going on. Then, a nice dinner. Life is hard.