Does my K5 really weigh more in the back?

[imiceman44]

I don't think that's the best force diagram to apply. You should show a 5940lb center of mass and then two distances from the axle centerlines to the center of mass. Then you can show how the weights would change on an incline. Now if I was accelerating or braking during the measurement that would skew the numbers, but I think it would also tick off the scale operator.


Something I forgot is there is a crossmember and anti-wrap setup back there.

Well considering what you have in the back, I would say you are probably closer to 50-50 than we might have thought.
And like you said the platform is supposed to be accurate no matter where the load is, but I have had 200-300lbs difference when I was close to the edge, last time I came back from Boise ID, I weighed my truck consecutively in 3 weigh stations including the shipper and the numbers were off by 500lbs, and they were all within 100 miles, and the wieght wasn't going down accounting for loss of burnt fuel but was going up like the first scale was off.
As I said I wouldn't take any numbers as gospel until I corroborated them with back and forth weigh ins.
But the main thing is you have a truck that weighs 6k and half of it on each axle, that is good enough to know if you want to tow it or tow with it.

 

[Blue85]

I want front end weight for suspension design purposes.

 

[ktmoutfront]

A friend who runs a scale in Ca. said the scale is the issue. Not designed to weigh just on the ends. Will always show heavy. True axle weight needs to be done with 4 plates or running through a DOT axle scale.

I hauled mine to Ca. Speedway to get it weighed.

 

[owenst7]

A friend who runs a scale in Ca. said the scale is the issue. Not designed to weigh just on the ends. Will always show heavy. True axle weight needs to be done with 4 plates or running through a DOT axle scale.

I hauled mine to Ca. Speedway to get it weighed.

I wonder if the load cell is centered and sensitive to the balance of the plate then. It probably puts bending stress on the load cell(s) if the force isn't centered on the plate.

If that's the case, you'd probably see the weight go up as the rear tires got closer to the edge of the plate.

I kinda wonder though, if this scale is made for medium-heavy duty trucks, the inaccuracy of doing individual axles is probably pretty insignificant. Like issam said, it could be off by a hundred pounds, but in the big picture of weight distribution, its close enough.

To throw this out there, my buddy has a certed scale at his shop that I ran over on the way out to wheel a while back. I had 25 gallons in the tank, back seat, tools...basically fully loaded with the top for camping/snow wheeling. Its a 76 k5 with AC (oba), m8000 winch, plate bumpers, sliders, 1 tons, 40" pitbulls, 350/th350/np203. It was 6440 total with me and 2 50 lb dogs. Front was 3280 and rear was 3180. That's with the front moved forward an inch and rear moved back 2", total of 109.5" wheelbase.

 

[Jester1]

Was just trough the scales myself at the scrap yard today. I watched as the scale changed just floating a couple feet forward and back. The rear of your vehicle is lighter than measured because you are in fact creating a folcrum with your front axle (scale moves earth dosen't) even if it is flat, level, no lip whatever. If you measure the front seperatly you will more than likely be heavier or close to 50/50 and the two numbers added together will if fact weigh more than total weight of the vehicle. Not to mention the point of distace of your rear spare to axle and potential preload of suspention. The only true measurement for weight balance on a vehicle is load sensors (scale) under each tire. Ever seen a truck scale at a nascar race.

Sorry thought I would throw in my .02

 

[6.2Blazer]

We have multiple sets of certified scales at work ranging from a 4 pad 100,000 lb. truck scale (You can pull the steer axle on one pad, left drive axle on one, right drive axle on one, and trailer axles on one), 4 pad (each individual tire) for cars, all the way down to 200 lb. platform scales. A fairly modern and quality scale should not have any significant difference in the weight regardless of where the weight. I use the 200 lb. scales all the time and verify them by using a pair of 50 lb. calibration weights. I can put a 50 lb. weight right in the middle, or on any of the extreme corners.....and it always reads 50 lbs.

There is no law of physics that makes some sort of fulcrum point when only one axle is on the scales If the scales and surrounding ground are flat and the total vehicle weighs 6,000 lbs. with a true 50/50 split, it should show 3,000 lbs. if only the rear axle is on the scale and it should show 3,000 lbs. if only the front axle is on the scale. Using the above example of of multiple scale pads, you could never use those to get an overall vehicle total.

In any case, my '90 K5 with a 6.2 hanging over the front when basically stock had almost a perfect 50/50 weight split. Hanging a heavy rear bumper and 37" tire with H1 wheel and the other stuff could definitely cause a K5 to be heavy in the rear.

 

[Deuling]

Gas tank with gas adds some weight

 

[ktmoutfront]

When I weighed my semi I watched the scale as I drove on. It showed 10xxx and as I drove farther on it went down. Stopped before the rear axles got on and it showed 7,562. The CDOT scale that is 12 feet long on highway 25 showed 7,430. Might be the cheep scale at the landscape yard that needs the weight centered.

The Jimmy ened up at 100lbs heavier on the front. Untill I put the winch on it.

 

[6872xtc]

Plus keep in mind that any weight added behind rear axle centerline will transfer some weight off of the front axle onto the rear also. That lesson is remembered from lots of years of a KW wrecker!

Nice K5 there Blue85!