weight of trailer, tractor and truck

[George2615]

George,
Take a truck and trailer to a scale. Park the trailer on the scale, but leave the truck off the scale. Drive a tractor onto the scale and look at the weight it shows with the tractor on the back of the trailer. Then drive the tractor across the trailer towards the truck. Drive over and past the trailer axles. The scale will show a decrease in weight as you get closer to the truck because the weight is being transferred to the tongue. That is why the rear of the truck goes down. It is carrying more weight and the trailer is carrying less weight. Try it.

I guess you learn something new everyday.

 

[JB4310]

Find my loaded gun under the seat and maybe focus on that instead.

That would be a serious offence in my state, we have a concealed carry permit, you can have it on your body but not in your car, kinda of a gray area since you are in the car. we are talking hand guns?

 

[KAB]

George,
Take a truck and trailer to a scale. Park the trailer on the scale, but leave the truck off the scale. Drive a tractor onto the scale and look at the weight it shows with the tractor on the back of the trailer. Then drive the tractor across the trailer towards the truck. Drive over and past the trailer axles. The scale will show a decrease in weight as you get closer to the truck because the weight is being transferred to the tongue. That is why the rear of the truck goes down. It is carrying more weight and the trailer is carrying less weight. Try it.

Moss,

You are absolutely correct. There is still one possible problem with your view. If the trailer is rated at 7000# and there is 7000# over the axles (would have to be 3500# on each axle, as the weight is moved forward, would the front axle have more weight on it than the back axle?) the trailer is still overloaded (assuming tongue weight is greater than 0#). In the case that the OP has listed he would need a trailer rated at 7850# (If I used the correct numbers). When I was searching for a trailer a few years ago, there were only 7000# trailers no trailers that took the recommended tongue weight as part of the GVWR. Concidering that it is not unusual to see improperly loaded trailers (excessive rear weight), I don't think that most manufacturers would take on that liability.

If I remember correctly, most truck (1/2 ton) towing numbers will be close to payload - 150# for a driver and assumes a tongue weight of 10%. This of course is a ballpark number. Somebody told me that when Nissan first came out with the Titan it only allowed for a 25# driver assuming 10% tongue weight. (I never verified this.) I have seen 15% tongue weight but I always back into the number to make sure. (I only work with current model year vehicles, so I can get most of the manufacturer specs).

Kurt

 

[RobS]

Moss,

You are absolutely correct. There is still one possible problem with your view. If the trailer is rated at 7000# and there is 7000# over the axles (would have to be 3500# on each axle, as the weight is moved forward, would the front axle have more weight on it than the back axle?) the trailer is still overloaded (assuming tongue weight is greater than 0#). In the case that the OP has listed he would need a trailer rated at 7850# (If I used the correct numbers). When I was searching for a trailer a few years ago, there were only 7000# trailers no trailers that took the recommended tongue weight as part of the GVWR. Concidering that it is not unusual to see improperly loaded trailers (excessive rear weight), I don't think that most manufacturers would take on that liability.

If I remember correctly, most truck (1/2 ton) towing numbers will be close to payload - 150# for a driver and assumes a tongue weight of 10%. This of course is a ballpark number. Somebody told me that when Nissan first came out with the Titan it only allowed for a 25# driver assuming 10% tongue weight. (I never verified this.) I have seen 15% tongue weight but I always back into the number to make sure. (I only work with current model year vehicles, so I can get most of the manufacturer specs).

Kurt

The "equalizer" link (don't know the proper term) between the springs will mostly balance out the load between the axles.

My camper is a good example of the tongue/axle weights. Kind of freaked me out when I first noticed this but it has two 3500 pound axles. It's a fifth wheel and the GVW of the camper is 8100 pounds. I thought it was a mis-print but they do figure on a certain amount of weight on the hitch. Of course, with a fifth wheel or GN, that percentage is more but the idea is the same.

 

[KAB]

The "equalizer" link (don't know the proper term) between the springs will mostly balance out the load between the axles.

My camper is a good example of the tongue/axle weights. Kind of freaked me out when I first noticed this but it has two 3500 pound axles. It's a fifth wheel and the GVW of the camper is 8100 pounds. I thought it was a mis-print but they do figure on a certain amount of weight on the hitch. Of course, with a fifth wheel or GN, that percentage is more but the idea is the same.

Yes, I agree that it would probably help. But, in the case that we are talking about, will the axle rating be exceeded? With conventional (weight distributing hitch included) towing and a flat trailer that is easily mis-loaded, exceeding the GAWR should still be a concern.

In my earlier post, I probably should have mentioned conventional towing. When you switch to GN/5th wheel your recommended pin wight should be between 20 - 25% total trailer weight. In your case 6500# on the axle and 25% pin weight puts you at 8125#, 25# overweight. At 7000# on the axle and 20% pin weight you would be at 8400#, 300# overweight.

Also, quite often if you read the owners manuals, you will see listed with the payload capacity a note reminding you "Properly Loaded". Example that I use the most is the guy going to the local lumber yard and getting a some 80# bags of sacrete. Where is it loaded? The lazy person places it at the back of the bed. Since the weight is placed behind the rear axle, the rear axle becomes a pivot point, it the removes weight from the front axle and re-applies it to the rear axle. If the total weight of the sacrete (and driver) maxes out the payload, the truck's Rear axle rating could very easily be exceeded, even though the GVW was not exceeded. To understand this, picture 2 kids (same weight) on a (centered) teeter totter. The kid up high will remain there until the kid at the ground pushes up. Why? Center of gravity has moved adding weight to the lower kid. If this was not the case, why wouldn't the teeter totter just not return to center?

Kurt

 

[Highbeam]

RobS brough tup the "equalizer link" between the axles and I think KAB mistook that for the equalizer hitch brand of weight distribution hitch. The tandem rear axle setup for the typical trailer includes this goofy pice of linkage that almost equals out the load on both axles and keeps the loads pretty constant as the terrain changes. Consider a speed bump where there might be a time when all of the weight would be on one of the two axles without the goofy linkage piece. Pretty slick really.

The center of gravity for the loaded trailer will be ahead of both axles but behind the ball hitch. Free body diagram time. Moments about the center of gravity sum to zero else the trailer would rotate about the COG. The rear axle has a longer moment arm so its force(load) will always be more, less, or the same as the front axle?

 

[KAB]

RobS brough tup the "equalizer link" between the axles and I think KAB mistook that for the equalizer hitch brand of weight distribution hitch. The tandem rear axle setup for the typical trailer includes this goofy pice of linkage that almost equals out the load on both axles and keeps the loads pretty constant as the terrain changes. Consider a speed bump where there might be a time when all of the weight would be on one of the two axles without the goofy linkage piece. Pretty slick really.

The center of gravity for the loaded trailer will be ahead of both axles but behind the ball hitch. Free body diagram time. Moments about the center of gravity sum to zero else the trailer would rotate about the COG. The rear axle has a longer moment arm so its force(load) will always be more, less, or the same as the front axle?

Highbeam, You are correct I was not referring the equalizer between the axles. I was once again thinking about the original post. With the vehicle he is using, a WD hitch is require by GM. (yes, you can tow without it, but I will keep my responses to the manf. requirements. Explaining to a LEO (lawyer, or whoever might care) that somebody on TBN said it was fine, probably will not cut it )

There have plently of post on TBN about WD hitches and how they work and what they do. Bottom line to me is that it moves some of the tongue weight back to the trailer axles. So, figuring that tongue weight is moved to the truck is inmaterial when a WD hitch is used since some of that weight is moved back to the trailer axles.

Kurt

 

[heehaw]

the sticker on the door of my truck says GVWR of 7000: a GAWR of 3925 for the front axle and 4000 for the rear: now about the WD hitch: i have always been under the impression that a WD hitch puts part of the weight on the front axle: "years ago" when the front wheel drive Tornodo came out: they where advertised, pulling an Airstream camper, with no back wheels/tires: by using a WD hitch. and i don't carry unloaded guns.
heehaw

 

[JB4310]

So heehaw,
By your figures, your at 13,560 lbs combined weight, have you found out the GCWR (gross combined weight rating for your truck with trailer).
If it's as was discussed: curb weight of 5,740 + max trailer rating 7,000 + 150 lb driver = 12,740 lbs.

If so then your over by the difference of 820 lbs.
Hmmm, that seems to simple just the exact same amount the trailer is over!!!

So all the talk about deducting the tongue weight from the trailers GVW has no legal benefit/merit if the trailer's GVW is the same as the trucks max trailer tow rating. It would only be helpful if the trailers GVW was less than the trucks tow rating.
JB,

 

[MossRoad]

I guess you learn something new everyday.

I learn lots of stuff new all the time. It's the showing other folks how stuff works that I do not get to do very often. I've learned a lot of stuff here. The knowledge in this bunch of folks is increadible. All walks of life, that's for sure.