Is being a little over GVWR no worse than doing 60 in a 55?

[Joel_T]

We're struggling between a Lance1985 and a 2285 and to add to that struggle are concerned about our RAM1500 tow capabilities. Many, maybe a majority, are pulling 1985s and 2285s size TTs, 4500 to 5000lb dry weight, 6K max, with half tons. I'd be well under axle loads and tow max but only slightly under GCWR. But, I figure I might be over GVWR 2 to 400lbs, not much but....

I'd wager many are over GVWR if they load their 1/2 tons with anything at all yet claim "great" towing, Is being a little over GVWR no worse than doing 60mph in a 55?

[blt2ski]

A little of what Mkirsh says, IE the speed of which you travel is true!! altho frankly, to me slowing from say 60mph on a typical 3-5% freeway mtn grade is not a big deal to me. BUT, as noted before, when I can not get up a given grade in 1st or reverse, still under gcwr etc. NOW I have an issue. As I can not GET TO the end place I am trying to get to.

Being over a gcwr is generally speaking, nothing unsafe per say. You only slow down, or may not meat the engineer minimum max grade one can go up before literally stalling out. For the new SEA specs, this is a whopping 12%. My sister has an 18% side road in front of her house. I have a client with a 30% grade driveway from a water front home on Lake Washington. So I am under gcwr by a few hundred lbs at the bottom of either dead end place. Only way out is up, BUT, I can not pull the grade with the trailer/load at hand! If you are an out of the way forest service road camper, unlike a lot of folks that are only on asphalt or concrete. you could be REALLY SCREWED in a situation like this!

This is not so much a total HP or torque issue as it is how low an overall low first or reverse you have. Some can be helped with 4lo. BUT, if your grade to get out of, is a rake roughed up concrete 25-30% grade with a few hairpins, you've now blown up a transfer case or equal!

For me it is NOT the freeway grade slowing down, but as it was with the examples I gave earlier, not getting up the hill in first! After that incident, I figured out, one can find formula's for how steep a grade you can go in low gear based on power, turns out torque is used in this formula. If you want to know how fast or fastest you can go on say a 5% grade, that will be based on HP. There are a number of other factors to be included. Wind-age, frontal area, aerodynamics, tires as in number of them, type ie bias vs radial and traction vs a hwy and st 75-85% sidewall to tread width ratio vs lower profile in the 50-75 range. Lower profile gets more hp to the ground, as does radial to bias, and a hwy tire uses less HP than a traction tire. Using AC, or for that matter, JUST having an AC pump uses 5 or so HP at the flywheel. A single wheel rig with 20" of tire per side, uses less HP than an equal dually, as a 20" wide single weighs less than two 10" tires on rims totaling 20" of tread width to the ground.

If you go to some of the truck manufactures that build MD to HDT trucks, you can find the formulas to figure this out. It is not just an engine axel ratio that can make a difference as the LD truck manufactures, and some members of RV net will lead you to believe.

The first thing I do when specing a truck, is get the payload needs I need, then spec the drive train to HOW I am going to use the rig. Not how some engineer in Detroit thinks I should be speced. My 96 6.5td could pull a 20K load up a 30% grade. My 2005 dmax, with 50% more hp and torque, might make it up a low to mid 20% grade before stalling out at 20K lbs. Yet the 05 is rated some 10Klbs MORE than the 96. All because the 05 at 20K on a freeway grade can go 55-60, where as the 96 was doing 40-45 or so.

Marty

Marty

[mkirsch]

cdevidal wrote:
Thanks marty. So I'm in the trailer pre-purchase stage. What are the rules of thumb if "just because you are under a manufacture rating etc, does not mean it will always work for your application"? Last thing I want to do is invest a bunch of money into something I can't use.

What I think Marty is talking about is not necessarily something breaking, but YOUR reaction to how the rig accelerates and handles. Even though you're under your limits, you may not like how the truck accelerates and maintains speed with the load.

You're not in any danger, but you may get frustrated with it sooner or later. I personally had that issue with my old tow vehicle. Even though it was rated for 6500lbs tow capacity and had well over 250HP, it could not maintain highway speeds on moderate grades with a mere 4000lb enclosed trailer. It eventually got frustrating on long trips, and I ended up shopping for something bigger and more powerful.

[transamz9]

Rule of thumb, use the same gear going down as you would going up.

[AH64ID]

Keep the rpms up, gear depends on speed. Play with it.

Just don't leave it in drive and only use the brakes!

[SlowBro]

rhagfo wrote:

cdevidal wrote:

AH64ID wrote:
compression braking does wonders. (..) Use what you have, wether it's compression or an exhaust brake. I would be less excited about decending steep grades with a diesel at GCWR without an exhaust brake thou, they are money well spent.

I have neither. Gas power. 😕

With a gasser you have compression braking, either through Tow/Haul or manual down shifting of your transmission either manual or auto.

Ok so shifting into 2nd going downhill would you say?

[rhagfo]

cdevidal wrote:

AH64ID wrote:
compression braking does wonders. (..) Use what you have, wether it's compression or an exhaust brake. I would be less excited about decending steep grades with a diesel at GCWR without an exhaust brake thou, they are money well spent.

I have neither. Gas power. 😕

With a gasser you have compression braking, either through Tow/Haul or manual down shifting of your transmission either manual or auto.

[SlowBro]

AH64ID wrote:
compression braking does wonders. (..) Use what you have, wether it's compression or an exhaust brake. I would be less excited about decending steep grades with a diesel at GCWR without an exhaust brake thou, they are money well spent.

I have neither. Gas power. 😕

[SlowBro]

blt2ski wrote:
At the end of the day, just because you are under a manufacture rating etc, does not mean it will always work for your application. I never once felt white knuckles in my 96 CC at 16 to even 20K gcw. Dispite the 12500 gcwr GM gave it. In fact, it usually out did, never stalled out on a grade compared to either the 88 or 89 454's I had with 16K gcwr's. They stalled out on any grade over 15-20%.

Just because it is rated to a given number, does not mean it will do what YOUR specs are. The specs are based on an engineer that is not using the rig as you might might. Because of my experiences with light duty truck gcwr's, I do not follow, nor believe them to be true ratings, at least as to HOW I use the trucks. A few I can believe, others, not worth their wt in gold!

marty

Thanks marty. So I'm in the trailer pre-purchase stage. What are the rules of thumb if "just because you are under a manufacture rating etc, does not mean it will always work for your application"? Last thing I want to do is invest a bunch of money into something I can't use.

[blt2ski]

cdevidal wrote:

rhagfo wrote:
Sorry, just having a little fun with the preciseness of your calculations. :B

No harm, no foul 😉

rhagfo wrote:
Towing at or slightly over GVWR and/or GCVWR, you want to be sure all braking systems are in good working order.

Under. At or slightly under. I thought I'd read earlier in the thread that being right at the limit could be a problem, but when I re-read it (see the next post I wrote above yours) I see there's no real concern.

One thing to remember about GCWR, it is generally a go power rating. So if you pull the same trailer with a smaller motor, than the larger one that is rated higher, the chassis will handle the trailer assuming everything is loaded to spec. BUT< speed up a grade will be slower than with the larger motor.

On the other hand, as happened to me back in the day. I went up a hill at 12K with a C2500 at 12K gcwr, GCWR was 8500, gvwr is 8600, Grade was around 20%. Meanwhile the almight 4bbl 454 in my C3500 dumptruck with the almighty Turbo 400, not to mention a dually! sat at the bottom of the same driveway, blowing up its tranny. Dispite a 16K gcwr, and it was combo'd at 12K also!

At the end of the day, just because you are under a manufacture rating etc, does not mean it will always work for your application. I never once felt white knuckles in my 96 CC at 16 to even 20K gcw. Dispite the 12500 gcwr GM gave it. In fact, it usually out did, never stalled out on a grade compared to either the 88 or 89 454's I had with 16K gcwr's. They stalled out on any grade over 15-20%.

Just because it is rated to a given number, does not mean it will do what YOUR specs are. The specs are based on an engineer that is not using the rig as you might might. Because of my experiences with light duty truck gcwr's, I do not follow, nor believe them to be true ratings, at least as to HOW I use the trucks. A few I can believe, others, not worth their wt in gold!

marty

[AH64ID]

Drive smart and you will be fine, no questions asked.

Driving smart also means prepping smart, and having a quality brake controller and functioning trailer brakes.. Even if you don't need them to operate at full stopping power.

Unless it's a windy road with lots of corners you may find that 6% isn't all that step and compression braking does wonders. Just be smart about your speed.

I have gone down grades where I needed to touch my brakes twice, and my buddy behind me, at 2/3 the weight, is nearly smoking.... Use what you have, wether it's compression or an exhaust brake. I would be less excited about decending steep grades with a diesel at GCWR without an exhaust brake thou, they are money well spent.

[SlowBro]

rhagfo wrote:
Sorry, just having a little fun with the preciseness of your calculations. :B

No harm, no foul 😉

rhagfo wrote:
Towing at or slightly over GVWR and/or GCVWR, you want to be sure all braking systems are in good working order.

Under. At or slightly under. I thought I'd read earlier in the thread that being right at the limit could be a problem, but when I re-read it (see the next post I wrote above yours) I see there's no real concern.

[rhagfo]

cdevidal wrote:

rhagfo wrote:

cdevidal wrote:
So reading this, I gather that being slightly under GVWR isn't a concern, even on long grades?

I calculate I'll be 28lb under the GVWRand we'll traverse I-24 one to three times a year round trip, so up to three trips per year down a 5% grade for 4 1/2 miles, and up to three trips per year down a 6% grade for 4 1/2 miles. That's the worst we expect to see.

Doesn't sound risky but does anyone disagree? I'm all ears.

Really Calculated that you will be 28# under! Hope are not too worried about being over, won't take much more that a big lunch to put you over, and the TV will start falling apart. :B

My GVW can swing several hundred pounds depending on fuel and what is in the fiver. :S

The calculations aren't as important as the question. Is there any concern on the grade that I mentioned being slightly under or right at GVWR?

Sorry, just having a little fun with the preciseness of your calculations. :B

Towing at or slightly over GVWR and/or GCVWR, you want to be sure all braking systems are in good working order.

Coming down long grades use the engine as much as possible to maintain a safe speed, Tow/Haul on a auto correct gear in a manual, same as climbing.

[SlowBro]

Yeah, I'm probably going to be just fine. From earlier in the thread:

kaydeejay wrote:
GVWR is the MAXIMUM weight at which the manufacturer will stand behind the vehicle in meeting those regs.
If you go over GVWR your truck is NOT going to fall apart but be aware of the following possible (but unlikely) scenarios:
* You may wear out driveline components faster than their designed life

My biggest concern. But it doesn't look like I have much of a choice, so I guess I'm not going to worry about it.

kaydeejay wrote:
* Your dealer could void your drivetrain & suspension warranty

I have no warranty.

kaydeejay wrote:
* If you were involved in an accident you could be cited for overloading

Such a citation (likely) wouldn't occur if I'm right at or under the GVWR. Of course I can be sued but that's not likely to be upheld if I'm at/under.

kaydeejay wrote:
* Following such an accident you insurance company could terminate coverage

Same as above.

kaydeejay wrote:
Bearing all of the above in mind, I would not get too excited about 200-400# overweight.

Ok good.

[SlowBro]

rhagfo wrote:

cdevidal wrote:
So reading this, I gather that being slightly under GVWR isn't a concern, even on long grades?

I calculate I'll be 28lb under the GVWRand we'll traverse I-24 one to three times a year round trip, so up to three trips per year down a 5% grade for 4 1/2 miles, and up to three trips per year down a 6% grade for 4 1/2 miles. That's the worst we expect to see.

Doesn't sound risky but does anyone disagree? I'm all ears.

Really Calculated that you will be 28# under! Hope are not too worried about being over, won't take much more that a big lunch to put you over, and the TV will start falling apart. :B

My GVW can swing several hundred pounds depending on fuel and what is in the fiver. :S

The calculations aren't as important as the question. Is there any concern on the grade that I mentioned being slightly under or right at GVWR?

[rhagfo]

cdevidal wrote:
So reading this, I gather that being slightly under GVWR isn't a concern, even on long grades?

I calculate I'll be 28lb under the GVWRand we'll traverse I-24 one to three times a year round trip, so up to three trips per year down a 5% grade for 4 1/2 miles, and up to three trips per year down a 6% grade for 4 1/2 miles. That's the worst we expect to see.

Doesn't sound risky but does anyone disagree? I'm all ears.

Really Calculated that you will be 28# under! Hope are not too worried about being over, won't take much more that a big lunch to put you over, and the TV will start falling apart. :B

My GVW can swing several hundred pounds depending on fuel and what is in the fiver. :S