Do heavy duty after market suspension coils increase your GVW?
- Thread starter TCM
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Like Dave In Denver I too have weighed my rigs to establish a baseline, then again with mods to establish their new wet weight baseline, and before trips to know the loaded weight with a certain load or trailer combination. Doing so helps me run appropriate tire pressure and know how much capacity I have for future trips or where I should cut back. Since I load similarly with each trailer or set-up, once I have established a baseline I don’t need to weigh each time before I leave town as I already have a very good idea of what the truck weighs and can make adjustments for additional loads if necessary. I sometimes weigh large items before loading them into the back so I know how much weight I’m adding above my baseline when loading for a trip.
Even more important than knowing my vehicle's gross weight is knowing the split between the front and rear axles/tires and not overloading the axles/tires. It would also be nice to know the side-to-side weight balance, but that is a bit more difficult to measure and I have yet to do this (though I should because I think my car is left side heavy).
Though technically not 'increasing' the gross vehicle weight rating, I think in practical terms, heavier & appropriate suspension modifications will allow one to carry a full Gross Vehicle Weight Rating (GVWR) load safely, and even exceed the GVWR a bit. The operator of the machine is a CRITICAL part of the wear & tear/risk assessment. In theory a vehicle that is operated at full load most of the time is working harder than one that is lightly loaded, and in general this is true. Though proficient operation of a fully loaded vehicle can result in less wear than aggressive, inefficient operation of the same platform lightly loaded. For ‘inefficient operation’ think of a ‘typical’ aggressive-driving commuter who accelerates and brakes hard with little regard for fuel economy, wear on their vehicle, or courtesy for their fellow travelers.
An example of this type of operation and low wear is my old 1996 F350 Power Stroke pickup. I purchased the truck new, and almost all of its 125,000-miles have been logged by me. The truck’s brakes are not as good as the new, 4-wheel-disc brakes on more modern Super Dutys, but they are good enough for the vehicle to be operated at GVWR (and above). It has a 5-speed manual transmission and still has the original dics/pads, drums/shoes. Most of the time I drove it in a manner to preserve the vehicle (which doesn't mean it was never worked or used hard) and the brakes were maintained/serviced even though they didn’t need repair. Though the F350 has seen many miles loaded, pulling and 4-wheeling it has also seen many miles unladen because it general I have excess capacity. This is in contrast to my 4Runner.
My 2006 4Runner is very heavy, at 5,500-lbs wet/empty everyday. Add two people and a couple hundred pounds of cargo for a trip and we are right at the GVWR. Add a couple hundred additional pounds for my Chaser's tongue weight and we are a bit over GVWR (still within gross axle weight rating/ GAWR). To carry this load I have the appropriate OME springs front and rear and have run air overload springs on the rear axle to help support the weight.
Each platform is different and my 4Runner is much happier and safer at GVWR than my 05 TJ Jeep was. I can't analyze the strength or structural integrity of the frame but the modified 4Runner's brakes are better at slowing and stopping the modified Toyota than the Jeep when still stock. I’m not bashing the Jeep, it was simply a different platform with different specifications and it performed as designed.
Your mileage will vary.
Even more important than knowing my vehicle's gross weight is knowing the split between the front and rear axles/tires and not overloading the axles/tires. It would also be nice to know the side-to-side weight balance, but that is a bit more difficult to measure and I have yet to do this (though I should because I think my car is left side heavy).
Though technically not 'increasing' the gross vehicle weight rating, I think in practical terms, heavier & appropriate suspension modifications will allow one to carry a full Gross Vehicle Weight Rating (GVWR) load safely, and even exceed the GVWR a bit. The operator of the machine is a CRITICAL part of the wear & tear/risk assessment. In theory a vehicle that is operated at full load most of the time is working harder than one that is lightly loaded, and in general this is true. Though proficient operation of a fully loaded vehicle can result in less wear than aggressive, inefficient operation of the same platform lightly loaded. For ‘inefficient operation’ think of a ‘typical’ aggressive-driving commuter who accelerates and brakes hard with little regard for fuel economy, wear on their vehicle, or courtesy for their fellow travelers.
An example of this type of operation and low wear is my old 1996 F350 Power Stroke pickup. I purchased the truck new, and almost all of its 125,000-miles have been logged by me. The truck’s brakes are not as good as the new, 4-wheel-disc brakes on more modern Super Dutys, but they are good enough for the vehicle to be operated at GVWR (and above). It has a 5-speed manual transmission and still has the original dics/pads, drums/shoes. Most of the time I drove it in a manner to preserve the vehicle (which doesn't mean it was never worked or used hard) and the brakes were maintained/serviced even though they didn’t need repair. Though the F350 has seen many miles loaded, pulling and 4-wheeling it has also seen many miles unladen because it general I have excess capacity. This is in contrast to my 4Runner.
My 2006 4Runner is very heavy, at 5,500-lbs wet/empty everyday. Add two people and a couple hundred pounds of cargo for a trip and we are right at the GVWR. Add a couple hundred additional pounds for my Chaser's tongue weight and we are a bit over GVWR (still within gross axle weight rating/ GAWR). To carry this load I have the appropriate OME springs front and rear and have run air overload springs on the rear axle to help support the weight.
Each platform is different and my 4Runner is much happier and safer at GVWR than my 05 TJ Jeep was. I can't analyze the strength or structural integrity of the frame but the modified 4Runner's brakes are better at slowing and stopping the modified Toyota than the Jeep when still stock. I’m not bashing the Jeep, it was simply a different platform with different specifications and it performed as designed.
Your mileage will vary.
R_Lefebvre
Expedition Leader
I am/was an automotive engineer, and so have some insight into how these specifications are developed. Typically, target specs are developed by very early in the process by a shadowy group of figures I've never seen. Then the engineers go to work designing all the parts with those specs in mind. Then, more engineers test that the vehicle meets requirements for those targets. Read between the lines, and you'll see that the published figures are not necessarily the actual physical limits, they are merely the limits that the vehicle was tested to. They don't actually test to failure. They don't keep adding weight till something breaks. They use the weights that were set out from the beginning, prove that it can do it, and then the design is done. The actual limits may very well be higher than the specifications, but again, they don't test to failure.
A good example of this is transmission cooling, which I can speak of with authority because that was my job. The transmission cooling system on Fords is designed to pull a GVW vehicle, with a maximum trailer weight trailer, up "Davis Dam". Davis Dam is something like a 10% grade, 10 mile pull. In 100+ degree heat. That's the test that the cooling system has to pass to be signed off. There's also Las Vegas Traffic testing. This is a test to make sure that when sitting stopped, in drive, in very high heat, with no airflow, that the system can still cool. This is the real reason for the plastic shrouds on the cooling system, and less so for a "ram air" effect. The shrouds prevent recirculation of hot air due to the fan.
Anyway, so you can see, the design limits are often established with testing that is much beyond anything that most of us would eve do. I live in Canada, it's not 100 degrees here, and I just don't have any hills like that. I have taken my fully loaded Focus wagon with a trailer up a 1 mile steep hill. I shift down to 3rd and take it up nice and easy, and don't worry about it.
Another example of this... the Focus Zetec engine is "rated" at 130hp. Mine currently makes about 240 with the help of a turbo, and the engine is otherwise stock. All the internals are fine, and were obviously underrated. I can race it around a race track for 30 minutes in hot weather making all the heat from a 240hp turbo application, with no overheating. The stock radiator is obviously much bigger than it needs to be.
This type of thing is prevalent in the industry. It's not like the aviation industry, where, if something exceeds requirements, it must be overdesigned, and thus overweight, and gets redesigned. That being said, lately that type of thing has happened due to cost. If something is overdesigned, and they can redesign it to save money, they will.
What am I getting at? I have never weighed a vehicle. I KNOW I've overloaded my Focus wagon on several occaisions. I also know that as long as you drive sensibly, it'll probably be fine. Maybe you'll need to replace the wheel bearings a little early. Maybe I should change the transmission fluid instead of going with Ford's "filled for life" plan.
I just try to keep things reasonable, and drive sensibly, and don't worry about it.
If my truck sits well and drives well with the load, and the OME suspension helps that, then I go with it.
A good example of this is transmission cooling, which I can speak of with authority because that was my job. The transmission cooling system on Fords is designed to pull a GVW vehicle, with a maximum trailer weight trailer, up "Davis Dam". Davis Dam is something like a 10% grade, 10 mile pull. In 100+ degree heat. That's the test that the cooling system has to pass to be signed off. There's also Las Vegas Traffic testing. This is a test to make sure that when sitting stopped, in drive, in very high heat, with no airflow, that the system can still cool. This is the real reason for the plastic shrouds on the cooling system, and less so for a "ram air" effect. The shrouds prevent recirculation of hot air due to the fan.
Anyway, so you can see, the design limits are often established with testing that is much beyond anything that most of us would eve do. I live in Canada, it's not 100 degrees here, and I just don't have any hills like that. I have taken my fully loaded Focus wagon with a trailer up a 1 mile steep hill. I shift down to 3rd and take it up nice and easy, and don't worry about it.
Another example of this... the Focus Zetec engine is "rated" at 130hp. Mine currently makes about 240 with the help of a turbo, and the engine is otherwise stock. All the internals are fine, and were obviously underrated. I can race it around a race track for 30 minutes in hot weather making all the heat from a 240hp turbo application, with no overheating. The stock radiator is obviously much bigger than it needs to be.
This type of thing is prevalent in the industry. It's not like the aviation industry, where, if something exceeds requirements, it must be overdesigned, and thus overweight, and gets redesigned. That being said, lately that type of thing has happened due to cost. If something is overdesigned, and they can redesign it to save money, they will.
What am I getting at? I have never weighed a vehicle. I KNOW I've overloaded my Focus wagon on several occaisions. I also know that as long as you drive sensibly, it'll probably be fine. Maybe you'll need to replace the wheel bearings a little early. Maybe I should change the transmission fluid instead of going with Ford's "filled for life" plan.
I just try to keep things reasonable, and drive sensibly, and don't worry about it.
If my truck sits well and drives well with the load, and the OME suspension helps that, then I go with it.