Need help deciphering CAT results [Archive]

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Getn off

10-01-2018, 03:49 PM

Fishsizzle

10-01-2018, 04:10 PM

Hello.
Got my new F350 TV weighed. Came in at 8900 which included a full tank of gas (48), wife, dog, bag, and hitch (~400). Truck sits at ~8500 alone.
I weighed the truck and 5er together and asked to have each axel weighed. I believe I followed her directions correctly, but I cannot make heads or tails of the report. Obviously the combined truck and rv weight is 21,080. Rv would be 12,180 which included 81 gals of fresh water, 80 lbs of propane, and most everything ready for camping. Numbers seem right. But I am confused about each axel weight. Do they make sense? I am not sure what the 9640 and the 11,340 numbers mean. Did I park wrong on the scales or does this make sense. Any help would be appreciated.
Troy

2018 F350 Lariat Dually 6.7 Powerstroke, 4.10 rear
Demco 21k hitch with Ford oem puck kit
2018 Sprinter 3551fwmls

Doesn’t. Make much sense. First, it would be nice to know your steer and rear axle separate from each other without the Trailer.. So that way you would know exactly what your Trailer weighed, as the rear axle weight with the trailer attached and the Trailer axle combined would let you know the full weight of Trailer.

Also, why your steer axle is 100 lbs is not clear.

Getn off

10-01-2018, 04:17 PM

The truck was weighed first by itself. Then I weighed truck and trailer. I subtracted truck weight from total weight...so I do know what the trailer weighs total. I just would like to know how much weight each axel is supporting.
The 100 lbs was me standing on part of the front scale by accident.
Troy

fjr vfr

10-01-2018, 04:24 PM

You parked wrong. Where you were standing you should have had the front axle there.
The scale weighs three axles. You standing was one of them. Obviously part of you anyway.
The weights you got was the truck...total and the trailer wheels.

cabldawg

10-01-2018, 04:32 PM

Yep you parked wrong. Steer goes over the first plate. Drive on the next and trailer on the next set wherever it falls. Just make sure that each set is on a different plate. Weigh the truck first. Get a steer and drive weight. Then weigh with the trailer. You'll then be able to subtract the total truck weight from the total truck & trailer weight to get the gross weight of the trailer. The truck and trailer scale ticket will have more weight on the steers too. That's trailer weight being transferred to the front axle through the frame of the truck.

Wyldfire

10-01-2018, 05:06 PM

https://catscale.com/how-to-weigh/

Wyldfire

10-01-2018, 05:17 PM

https://youtu.be/ixK9BTAXqyY

Getn off

10-01-2018, 05:23 PM

jsmith948

10-02-2018, 06:37 AM

Ahh. I think I understand what went wrong. I need to “split” the weight. Steer axel on first pad, drive axel on second. Then (after confirmation) move forward so that the front rv axel on second pad and rear rv axel on third pad.
I didnt understand because the truck and rv wouldnt fit with the two rv axels split on the 2-3 pads. Didnt realize I had to move.
Thanks for rhe clarification gents.
Next trip is in 2 weeks and will try again then.
Troy

That will give you the weights of each trailer axle.
Just pull onto the scale - place your steering tires on the forward section. Place your drive axle so it is on the center section while the trailer axles are on the last or rearmost section. This will give you the weight on the steering axle, the weight on the drive axle and the weight on both trailer axles as a "group".

JRTJH

10-02-2018, 08:02 AM

^^^ What jsmith948 said. All the CAT scales I've used are "slightly elevated" so weighing individual trailer axles is an estimate not an accurate weight. What I mean by that is this: When you are on the 3 pads, front axle on #1, drive axle on #2 and trailer axles on #3, the rig is level and straight. That weight is accurate (assuming the scales are calibrated). If you pull the tow vehicle "off the pads and it starts down the exit slope, then when the trailer axles are on pads #2 and #3 (one axle on each), the truck and the front of the trailer are already "sloped downward" and slightly off the "straight/level attitude". So, there will be some weight difference based on the trailer no longer being level.

Does it matter??? This is my opinion, so take it for what it costs you (time to read).... No it does not matter that much. Essentially, given that all trailer axles are joined by equalizer systems, there's a significant "averaging of weight" that's already influencing individual axle weights, so weighing individual axles doesn't really give you much "important information".....

What is important, and it can't be weighed at a CAT scale, is the individual wheel weights on an axle. There is no "equalizer" between the ends of an axle, so no weight is being "shifted left or right" and that's a bigger problem than most realize. Installing a refrigerator on the road side, directly over the axles may overload the roadside tire. None of that weight is "shifted to the curb side tire, but part of that weight is shifted to the other wheel on the road side via the equalizer which sits between the axles.

So, for most of us, weighing the trailer axles on pad #3 is sufficient information and trying to pull off the scales to "jockey the trailer axles onto different pads, for typical rigs, isn't going to reveal much information that would be useful. YMMV.

MattE303

10-02-2018, 09:14 AM

yup, truck front axle on pad 1, truck rear axle on pad 2, and both/all trailer axles on pad 3. Not sure about bumper pulls, but for 5th wheels, you will probably find that the truck front axle weight is pretty similar with or without the trailer (mine was exactly the same). Subtracting the difference between the truck rear axle weights (with and without the trailer) gives you your trailer "pin" weight.

Getn off

10-02-2018, 09:43 AM

That makes sense. I totally forgot about the equalization setup. Guess I am good to go.
Thanks for help.
Troy

cookinwitdiesel

10-03-2018, 01:56 PM

Here is what I worked up in Excel to plan for my weigh session. This is planning for a CAT scale with 3 weight pads.

This is for a Truck with a travel trailer (Weight distribution hitch = WDH).

If you have a fifth wheel, there is no difference between the top 2 scenarios with the trailer.

This will give you the weight of the truck total, front and rear truck axles, both trailer axles (as a group). As mentioned, subtract truck total from truck+trailer total to get the trailer weight. Compare the 2 truck rear axle readings to determine what your hitch/pin weight. In my case, I have a WDH so I am curious to weigh with and without the spring bars installed to see how weight is shifted around.

Hope that helps some.

K_N_L

10-03-2018, 03:27 PM

What is important, and it can't be weighed at a CAT scale, is the individual wheel weights on an axle. There is no "equalizer" between the ends of an axle, so no weight is being "shifted left or right" and that's a bigger problem than most realize. Installing a refrigerator on the road side, directly over the axles may overload the roadside tire. None of that weight is "shifted to the curb side tire, but part of that weight is shifted to the other wheel on the road side via the equalizer which sits between the axles.
.

So here a question for you John - On our last long trip (5K) I loaded my Harley over to the driver side of the garage so we could get in /out of the garage door easier between stops and boondocking. When I serviced my trailer axles, I swear it seemed the right rear tire was slightly more worn the right front. Sound logical? I rotated the rear up to the front just cuz, We were definitely rolling heavy with water, food, coolers, bike, generator gas and the like. Thanks btw!

JRTJH

10-03-2018, 06:14 PM

Tires wear unevenly, even with an equalizer between the axles. There are a lot of factors in tire wear. Consider the angle of the trailer (nose high, level or nose low), the axle alignment, potential bent axle hub or possibly an axle with incorrect camber, just to name a few.

I'd watch the tire that you rotated to that position as well as the tire that was unevenly worn. I've had a couple of trailers that would "eat the right rear" tire, no matter what I did to the axle. My "fix" was to keep rotating the tires onto that position. Usually they time out even before they all wear to a point of needing replacement.

When our trailers are built, Lippert builds the frames in a jig, hopefully they are straight. The axles are installed at Keystone and they use a jig to align them, although that may or may not mean the alignment is correct. If you continue to have abnormal wear on one tire position, you might consider having an alignment done at a trailer repair facility that specializes in trailers and suspension issues. I wouldn't let an RV dealer do it, usually they just don't have the equipment or expertise, although there are some exceptions. I'd put my money on a reputable trailer repair facility or a suspension shop that knows how to align a travel trailer.

Getn off

10-21-2018, 03:51 PM

Went on our second voyage this weekend. Pretty uneventful...which is good!
Weighed her again. This time I made sure the whole truck was on the first pad, which only gave me a couple inches for and aft as buffer! The trailer was on the third. Truck was full of gas and same gear as before so truck should still be about 8900. Using 20% pin weight worked out about right this time. I did not have any water this time, but did replace my tires which are about 40 lbs more each (Sailuns).
Side note. Wife was doing dishes last night and the sink (rear) wouldnt drain. I started to get pissed thinking she had been letting all sorts of crap down the drain thinking she was at home with a disposal! Then it dawned on me to check the water levels. Bingo! Lol! Rear grey full! Been trying to use only tank water this trip to make sure it all works too. I know many just leave the grey open while docked, but I actually wanted to make sure no leaks up high and such. Good lesson really!
Troy

fjr vfr

10-21-2018, 05:26 PM

So why didn't you park the rear wheels on the second pad? How do you know how much weight is on each axle?

Getn off

10-22-2018, 01:36 AM

Wasnt interested in each axel. Absolutely no way is this 350 gonna be in jeopardy there. Wanted just a weight of truck with hitch, and a trailer axel weight.
Troy
Also, the staff said to make sure that my whole truck was on the first pad. I’m new to this so did what I’m told!

JRTJH

10-22-2018, 08:04 AM

Well, they told you wrong and you really do need to know the weight that's on your rear axle. You need to know that for two reasons. First, it is possible (although not likely) to overload the rear axle. Secondly, and more important, you need to know what air pressure to run your rear tires. Knowing the weight on the rear axle when towing vs not towing will give you two tire pressure requirements. Knowing and following those pressures will give you more even tread wear and will probably extend the life of your tires.

You are correct in assuming that you probably won't overload the rear axle, but you just don't know what you don't know. Weighing the truck with the front axle on pad one, rear axle on pad two and trailer axles on pad three, then pulling off the scale, unhitching and reweighing the truck with the front axle on pad one and the rear axle on pad two is the correct procedure. That way you know the "loaded weight with trailer" and you also know how much of that weight is on each axle of the truck. You also know (by using addition/subtraction/simple math) the pin weight of the trailer. That pin weight is an indicator of proper/improper loading and should be between 15-25% of your total trailer weight. If it's less than 15% you could have overloaded trailer axles (depending on how close you are to your trailer GVW) and if it's greater than 25%, you could be close to the pinbox rating, something that few of us ever consider, but overloading the front of a fifth wheel can lead to cracked welds, damaged FILON siding and may lead to catastrophic frame failure.

So, while weighing your truck the way you did will give you the limited information you were seeking, truck weight with hitch and trailer axle weight, it's only a small part of what you "ought to know".....

Getn off

10-22-2018, 11:22 AM

Thanks John, great info.
Next time out I may give her another shot. Wifey is less than impressed with waiting around for a third weigh! Could I just fill my truck and weigh it with front axel on number 1 and rears on number 2 and just subtract my hitch weight from this weekend? I would think the trailer axel weights and pin weight would be the same...just take the diff from gvw of truck with rv hooked up (~11k) and the gvr of truck (~8.9), which yields around 2.1 (pin weight). Now, weigh truck on both scales and add 2.1 to the rear axel weight. This seems like it will give me a fairly accurate rear axel wt.
Troy

KSH

10-22-2018, 11:37 AM

No. You'll want it all hooked up. Front axel on front pad rear axel on second pad, trailer on third pad.

fjr vfr

10-22-2018, 03:03 PM

It's only $2 more for the re-weigh. When you drive back on the scale tell them it's a re-weigh and give them the ticket number from the previous weigh.
And just leave the wife at home while doing it before your trip.
You can not have too much information when it comes to both safety and reliability of your truck and trailer.

Even if you are within your capacities proper loading is just as important.

Getn off

10-22-2018, 10:39 PM

Easy if I lived near a scale. All day event for me to take the trailer out, run to scales, and repark it back at home down a very long curvy driveway that I must back down!
I may stop by a scale and have my truck axels weighed and use math. I fail to see how a reweigh of the whole thing with produce different numbers that I cannot decipher from using simple math.
Or, I may give it another shot our next venture out...thanksgiving weekend, if wifey lets me!
Troy

mazboy

10-23-2018, 05:01 AM

you are over thinking the whole thing. you are just good to go.

JRTJH

10-23-2018, 09:19 AM

I disagree. It is NEVER "overthinking" to know what your rig weighs......

That said, if you reweigh your truck with the hitch in the bed, you should be able to get "pretty close" to the axle weights and using math, get close to the pin weight. Keep in mind that without your DW in the truck, you're going to be "off a bit" based on her weight and anything else that might have been unloaded or used (fuel, etc).

Ideally, weighing at the beginning of a trip will give you an "exact weight", but that will only be valid for that "moment in time" as holding tank contents, propane, food, cargo in the bed of the truck, fuel in the truck will all change with every mile you travel down the road.... Nobody tries to get an "exact weight" every trip, and most "survive" with weighing once and never weighing again. Heck, there are some who have no idea what their rig weighs, but "it doesn't sag or lean" so it must be good.

I'd say that using your known weights from the "strangely conducted weigh" and reweighing your truck so you know what's on each axle, you'll be able to deduce close approximations. That'll give you a good idea of where you stand.

My suggestion would be to draw two outlines of your rig. On the top one, write the weights under each axle as it was done on the first weigh, then, on the bottom one, write the weights on the truck axles from the reweigh. Then use "algebra to solve for X and Y" (trailer pin weight and truck rear axle weight)....