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10-22-2021, 06:57 PM
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#1
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Junior Member
Join Date: Oct 2020
Posts: 12
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CAT scales seem inaccurate
Have any of you ever found CAT scales to be slightly inaccurate? In my quest to get my new Flagstaff 526RK to ride the smoothest I made a trip to a nearby CAT scale at Love's. I weighed my rig, then unhooked and weighed the truck, then rehooked and made some adjustments and got 2 more reweighs. The first gross weight was 18320, the second two were 18260. That's 60 lbs. lighter and nothing was removed from the rig. Not a big deal but it changed my pin weight by about 1/2% point. Just wondering how consistent these scales are?
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10-22-2021, 07:36 PM
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#2
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Senior Member
Join Date: Jan 2012
Posts: 996
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According to the laws, scales must be accurate to 1/10 of 1% of the capacity of the scale. Back to that in a moment. Highways scales in most locations are either 200 or 300,000 pounds capacity. So multiply that capacity by the accuracy and it means the scale is only accurate within 200 lbs.
Also, did you set your parking brake when you were on the scale? If you stay on the brake pedal before the scale settles and reads, it will shift the weight to other axles.
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10-22-2021, 08:22 PM
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#3
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Senior Member
Join Date: Nov 2015
Posts: 26,820
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Good enough for gov'n work
After all they are intended for Semi tractor trailer combos
Us light weight 5th wheelers can get close enough weigh tickets for checking axle weights
__________________
I took my Medication today. HAVE YOU?
Dodge 3500 w/Tractor Motor
US NAVY---USS Decatur DDG-31
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10-22-2021, 10:08 PM
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#4
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Senior Member
Join Date: Sep 2013
Posts: 1,500
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Sometimes wind can be a factor .
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10-23-2021, 04:08 AM
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#5
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Senior Member
Join Date: Dec 2019
Location: NC
Posts: 1,487
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Please explain. The only thing I can think of is a tornado lifting it off of the scale.
__________________
2010 Chevy G3500 6.0 Vortec
2015 Puma 30RKSS
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10-23-2021, 05:46 AM
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#6
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Senior Member
Join Date: Apr 2004
Posts: 2,244
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Quote:
Originally Posted by Toby Dog
Please explain. The only thing I can think of is a tornado lifting it off of the scale.
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High sided vehicle catch the wind which pushes against the truck/trailer causing the scale readings to change , depending on wind direction against the vehicle.
Thats why dot will sometimes shut a scale house down when winds get gusty or above a certain wind speed.
__________________
'03 Dodge 2500 Cummins HO 3.73 NV5600 Jacobs
'98 3500 DRW 454 4x4 4.10 crew cab
'97 Park Avanue RK 28' 2 slides
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10-23-2021, 06:30 AM
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#7
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Senior Member
Join Date: Oct 2019
Location: Buena Vista, Baja California Sur
Posts: 797
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Interesting conversation. Learn something new everyday.
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Mark & Jen Rayor, Baja Ca Sur, Mexico
04 Prevost H3 45 Liberty Elegant Lady 24V
toad, Jeep Willys Wrangler
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10-23-2021, 03:17 PM
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#8
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Senior Member
Join Date: Feb 2017
Posts: 1,037
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Quote:
Originally Posted by rollondown
Also, did you set your parking brake when you were on the scale? If you stay on the brake pedal before the scale settles and reads, it will shift the weight to other axles.
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I think if you've properly stopped moving it makes no difference whether you're on the service brake or the emergency/parking brake.
__________________
'20 RAM 3500, '20 Heartland Road Warrior 430 https://thecastle.blog/ Also: Eagle Cap 950 Before:'17 Berkshire 38A class A https://dragonship.blog/ '11 Heartland Cyclone TH, '11 Lance TC, '05 Keystone TT, '76 Coachmen class A and a '16 DIY Transit conversion........
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10-23-2021, 07:00 PM
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#9
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Senior Member
Join Date: Apr 2004
Posts: 2,244
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Quote:
Originally Posted by oscarvan
I think if you've properly stopped moving it makes no difference whether you're on the service brake or the emergency/parking brake.
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Yeah it makes a difference with a auto tranny left in gear with a foot on the service brakes.
First lesson learned is shift the auto tranny to neutral then apply a brake or with a std tranny shift to neutral.
Generally scale are level to the world and applying a brake may not be necessary.
Oh yeah....don't make jack rabbit starts and don't make jerky stops.
__________________
'03 Dodge 2500 Cummins HO 3.73 NV5600 Jacobs
'98 3500 DRW 454 4x4 4.10 crew cab
'97 Park Avanue RK 28' 2 slides
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10-23-2021, 08:34 PM
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#10
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Senior Member
Join Date: Feb 2017
Location: Denver, CO
Posts: 1,527
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Right after I bought my truck I went to the CAT scales and the ticket was 4K for a 2018 F-350. The manager scratched his head and said to go reweigh and it was 7,200. Yes, they can be wrong.
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2022 Winnie Forza 36H
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10-23-2021, 08:43 PM
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#11
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Senior Member
Join Date: Nov 2015
Posts: 26,820
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Quote:
Originally Posted by BirchyBoy
Right after I bought my truck I went to the CAT scales and the ticket was 4K for a 2018 F-350. The manager scratched his head and said to go reweigh and it was 7,200. Yes, they can be wrong.
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OP is questioning a 60# difference not 3200#
__________________
I took my Medication today. HAVE YOU?
Dodge 3500 w/Tractor Motor
US NAVY---USS Decatur DDG-31
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10-24-2021, 06:53 AM
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#12
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Senior Member
Join Date: Sep 2018
Posts: 1,944
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Quote:
Originally Posted by rollondown
According to the laws, scales must be accurate to 1/10 of 1% of the capacity of the scale.
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I haven’t been able to verify that, but I did find discussion of CAT scales where they claim +/- 0.2% accuracy, applied to the load being weighed. Mettler Toledo also claims the same, with the usual verbiage about striving to narrow that to a smaller tolerance. That would mean the OP’s rig should weigh 18,000 lb +/- 36 lb.
I could not find actual truck scale accuracy tolerances by state or by any other standard.
__________________
Tom & Jeri
2018 Coachmen Galleria 24T Li3
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10-24-2021, 07:43 AM
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#13
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Senior Member
Join Date: Aug 2013
Posts: 1,463
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Quote:
Originally Posted by KanzKran
I haven’t been able to verify that, but I did find discussion of CAT scales where they claim +/- 0.2% accuracy, applied to the load being weighed. Mettler Toledo also claims the same, with the usual verbiage about striving to narrow that to a smaller tolerance. That would mean the OP’s rig should weigh 18,000 lb +/- 36 lb.
I could not find actual truck scale accuracy tolerances by state or by any other standard.
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Well if at 18,000# combined one is worried about 36#, you already have an issue!
I have always weighed at ODOT (Oregon DOT) closed weight stations, the displays are always left on. The display only displays in 50# increments, so they must not get into the nity grity of a couple pounds.
Interesting that our 2016 Ram Laramie 3500 DRW had a curb weight of 8,589# when it left the factory, and the last couple times we scaled it at a weigh station with full fuel and DEF, and ready to tow scaled 10,000#. This is the part that many when looking at yellow sticker payloads forget, that is the deductions before hooking up the trailer.
Wife and I are not skinny, but also not obese, I do have a standard 5th wheel hitch and picture frame adapter, and an in bed tool box with stuff in it, seems some heavy stuff.
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Russ & Paula, Portland, OR. The Beagle Belle.
2016 Ram Laramie 3500 DRW Aisin 4X4 14,000# GVWR.
2005 Keystone Copper Canyon 293FWSLS Rear Kitchen 12,360 GVWR
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10-25-2021, 09:53 AM
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#14
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Junior Member
Join Date: Mar 2016
Posts: 24
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Quote:
Originally Posted by rollondown
Also, did you set your parking brake when you were on the scale? If you stay on the brake pedal before the scale settles and reads, it will shift the weight to other axles.
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Can you explain how the brakes change the weight? That doesn't make sense to me.
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