Weighing for side to side weights

[howardwheeler]

If I weigh my truck and trailer (2017 F350 srw 6.7 and 2003 Alpenlite Portofino Villa) with one side of all axles on the scales and one side of all the axles off and then do the same with the other side, can I add the two together and get an accurate total weight? I did it to see if my drivers side, which has four large batteries and two slides on it plus the fridge, was significantly heavier than the passenger side. I know I can just go back and reweigh with all axles on scales but it’s an interesting question also that I’d like to know the answer to. My drivers side was indeed 1180lbs heavier than the passenger side. But is there going to be a difference between adding the two sides together versus weighing all at once because one side of the truck and trailer is always 90% on the scale and the tires on the other side are barely off the scale? I venture to say the two will be the same. What do you say?

[4x4ord]

Try standing on your bathroom scale with on foot off and see what you come up with.

[stripit]

>>I've read on rv forums how a trailer had one wheel several hundred lbs different than the one in front or behind it. I asked my DOT guy who carries portables how this could happen. His comment was that it could have been a bad reading or a multi axle trailers side links may have got flipped at the equalizer bars or the truck or trailers brakes were locked up with the tow vehicles auto tranny still in drive or reverse. Good scale reading comes from tranny in neutral with no brakes applied.<<

I no longer have my weigh sheets, but seeing different weights on axles next to each other was common. Weight transfer from front to back or back to front is easy depending on how level the rig is. Or how the trailer was designed or built. What someone is carrying or where that stuff might be and move weight too. If a truck squats and the trailer noses down the weights can and do transfer forward. As for the scale having poles to center the rigs on the scale, that was what I was told by the fellow working on the scales.Is it accurate? Maybe not, I had no reason to doubt him as that was something he worked on and I did not. I do know I was not able to get correct readings when I side stepped the scale. Getting a repeatable scale reading is what is important, knowing where the weights are and how your rig is carrying them is what you need to know. Folks with scales that weigh rv's can attest to the varing amounts of weights axles can and do carry. Getting weighed opens many peoples eyes as to why tires fail, rigs handle poorly or "feel" heavy.

[JIMNLIN]

Talking to a CAT scale repair man, he said the scales are platform scales and are designed to have a amount of weight across the platform of the scale. When only one side has weight it will read incorrectly. As it did in my test. He said why do you think we invest the costs of poles or curbs at our scales? to keep the dummys from driving off center and getting a wrong scale reading number. Makes sense.

This comes under old wives tales or CAT scale operators/repair sales or repair people, and isn't true at all for all modern single platform scales.

The CAT scale near me says the poles are their to prevent drivers from crossing the scales at at angles as they maneuver around the parking lot.

My certified for commercial use small town grain elevator scales has no poles on the sides. I can get any weight combo I need and they all add up to w/i 40-60 lbs.
Same with my companies loading yard platform scale where we could get our combo or truck or trailers gross or one side axle or one set of axle weights.

I've read on rv forums how a trailer had one wheel several hundred lbs different than the one in front or behind it. I asked my DOT guy who carries portables how this could happen. His comment was that it could have been a bad reading or a multi axle trailers side links may have got flipped at the equalizer bars or the truck or trailers brakes were locked up with the tow vehicles auto tranny still in drive or reverse. Good scale reading comes from tranny in neutral with no brakes applied.

[howardwheeler]

As soon as it dries out around here, I’ll pull out the trailer and go to the scales.

[fj12ryder]

howardwheeler wrote:
So according to stripit, my “one side then the other” weights might not be the same when added together as weighing the whole thing at once. Am I understanding correctly?

That was the way I understood it, and I can see that those scales are for very heavy weights, and having smaller weights offset may affect the accuracy.

That was why I mentioned about not knowing how the scale is set up. But give it a shot and see what you end up with. It's gonna be close and you'll only be out a few bucks.

[howardwheeler]

So according to stripit, my “one side then the other” weights might not be the same when added together as weighing the whole thing at once. Am I understanding correctly?

[CA_Traveler]

stripit wrote:
Talking to a CAT scale repair man, he said the scales are platform scales and are designed to have a amount of weight across the platform of the scale. When only one side has weight it will read incorrectly. As it did in my test. He said why do you think we invest the costs of poles or curbs at our scales? to keep the dummys from driving off center and getting a wrong scale reading number. Makes sense.

I've wondered about that possibility which is why I use level scales with one RV side in the middle of the scale.

Oregon has numerous scales, free, many unmanned and they are on 24/7. I use the ones that are level off to the sides. I used one manned one when there were no trucks. Basically Oregon wants truckers to know their weights and it's a refreshing approach.

I've also wondered about accuracy on lighter weights like one toad axle. And in order to weight the drive axle vs tag I have to be on one end of the scale. However having weighted on several scales they are consistent.

Plus I weight with full fuel, water, propane, cargo, etc and use those weights to set tire pressure.

[stripit]

Used to own scales and weighed rv's by wheel position when I was a full time traveler. This question came up often, so I tried it with my rig at a scale where I could side step the platform scale.Very hard to find a scale with flat surfaces on both sides and no curbs/poles. Drove on with all the wheels on the scale segments and got that number for the truck and trailer hooked up. Was within 50 lbs of my scales I used to weigh each tire position. Backed up and side stepped the scale with only the driver side on the scale so I could weigh and get those numbers. Then drove off and side stepped so the passenger side was on and got those numbers. Guess what, they didn't add up correctly. The left side number and the right side number was well over 800 lbs more than the actual weight I got with the whole rig on the scale. Talking to a CAT scale repair man, he said the scales are platform scales and are designed to have a amount of weight across the platform of the scale. When only one side has weight it will read incorrectly. As it did in my test. He said why do you think we invest the costs of poles or curbs at our scales? to keep the dummys from driving off center and getting a wrong scale reading number. Makes sense.
Just for your info, my 2004 Mobile Suites 36 ft trailer was 1,100 lbs heavier on the driver side than the passenger side. And the front axle was carrying about 400lbs more than the back axle and the rig was level when moving down the highway.

[howardwheeler]

That makes sense: level is the key. On the CAT scale that use there just enough room to do it. Thanks.

[fj12ryder]

I would think as long as the trailer is level side-to-side you'd get the same results as weighing all at once. But without knowing how the scale actually is set up, there's no way to tell until you try it.

The local Cat scale won't allow you to do that because there are posts that preclude pulling up with part of the trailer off the scale. YSMV.

[CA_Traveler]

They will be the same if the rig was perfectly level in both cases. Many areas on the side of the scale are not level.

I've weighed the total axle and then one side when the area is level. Then subtract for the other side.