Scout camper feel too heavy?

[rruff]

You justified that a semi is legal and has long stopping distance, so it’s not a problem to increase your vehicle stopping distance by a lot.
My thinking is that first, it’s not because something is legal means it’s a good idea to do it.

How about this, then. The Tacoma with a 3k lb load will stop faster than a F250 diesel with a 3k lb load... because the F250 is much heavier. True. So getting a bigger truck makes it more dangerous to others.

Context is important, and "compared to what?"

The real problem is that heavy vehicles have a long stopping distance vs a car... and the more weight the bigger the danger to other traffic in collisions. A small car does fine in the "slamming into walls test", but the fatality rate in collisions vs full size pickups is ~3x higher. We are a big threat to cars, and bigger trucks are a huge threat to everyone.

The only logical conclusion is that we should all stay home in our padded cells...

 

[jaywo]

How about this, then. The Tacoma with a 3k lb load will stop faster than a F250 diesel with a 3k lb load... because the F250 is much heavier. True. So getting a bigger truck makes it more dangerous to others.

Can you send proof of that?

As an engineer, here is what I think: more weight increases the downward force on the tires which increases the coefficient of friction. You will have more grip on the F250 as a result, so the braking power is what will make the difference.
If you double weight, you get approximately double the grip (it's not perfect, friction per unit weight decreases as you add load of course) but you also need approximately twice the breaking power because inertia doubles. Since these scale together, braking capacity is your factor. Also, brakes must convert kinetic energy into heat. More weight = more energy to dissipate. Undersized brakes for a specific load will overheat (fade).
Try to take that Tacoma with 3000lbs load down 10 miles of steep downhill and let me know how it feels when you rear end a family because your brakes faded so much you might as well not have had brakes. That's also when that V8 Diesel will help you with engine brakes, compared to that poor undersized Tacoma engine doing what it was not designed to do.

So the more weight you add to a Tacoma relative to its stock weight, the more it will stop slower in comparison to a heavier vehicle such as a F250 to which you add that same load, assuming that heavier vehicle has larger brakes (which it does).
Is that limit crossed at 1000 lbs, 2000 lbs or more I cannot tell you. We would need to know exactly how much more braking power a F-250 has versus a Tacoma and then it would be easy to calculate the point at which it becomes safer to switch vehicles.

Personally, I would much rather drive a F-250 under GVWR, than a Tacoma thousands of pounds over GVWR, to go downhill a mountain (which anybody overloading does at some point).

 

[rruff]

Can you send proof of that?

I did the analysis based on braking test data from C&D awhile ago on here. A year or two? As I recall, I started with the assumption that both trucks' brakes were just able to skid the tires at GVWR. The Tacoma was over GVWR so I assumed it was brake limited, but it still stopped in a shorter distance. Single panic stop.

Every time I've slammed on the brakes in my truck (usually from a deer jumping in my path) the ABS kicks in, indicating that traction is the limit. And that is with big tires and a load.

As an engineer, here is what I think: more weight increases the downward force on the tires which increases the coefficient of friction. You will have more grip on the F250 as a result, so the braking power is what will make the difference.

If the friction was proportional to weight, then both vehicles should stop in the same distance... higher momentum of the large vehicle and higher friction would cancel each other. This tends to be true if the contact patch increases at the same rate, but it doesn't. Stock tires on the F250 will be slightly larger, but not much. They handle the weight by increasing psi, which increases the load per area of the rubber on the pavement, which reduces the friction coefficient.

Try to take that Tacoma with 3000lbs load down 10 miles of steep downhill and let me know how it feels when you rear end a family because your brakes faded so much you might as well not have had brakes.

If that is how you drive, then you need a driving lesson. Gear down and go slow if necessary... minimal brake use. I live in the mountains so have plenty of practice on long winding descents of 10% grade or more. No issues exceeding the speed limit and I rarely use the brakes at all.

Brake fade should not be an issue unless you are racing.

 

[Gravelette]

No issues exceeding the speed limit and I rarely use the brakes at all.

I might have missed it, maybe in another thread, but how much over payload are you? Would you suggest a number of pounds that is OK or would you use a percentage?

 

[jaywo]

I did the analysis based on braking test data from C&D awhile ago on here. A year or two? As I recall, I started with the assumption that both trucks' brakes were just able to skid the tires at GVWR. The Tacoma was over GVWR so I assumed it was brake limited, but it still stopped in a shorter distance. Single panic stop.

Every time I've slammed on the brakes in my truck (usually from a deer jumping in my path) the ABS kicks in, indicating that traction is the limit. And that is with big tires and a load.

If the friction was proportional to weight, then both vehicles should stop in the same distance... higher momentum of the large vehicle and higher friction would cancel each other. This tends to be true if the contact patch increases at the same rate, but it doesn't. Stock tires on the F250 will be slightly larger, but not much. They handle the weight by increasing psi, which increases the load per area of the rubber on the pavement, which reduces the friction coefficient.


If that is how you drive, then you need a driving lesson. Gear down and go slow if necessary... minimal brake use. I live in the mountains so have plenty of practice on long winding descents of 10% grade or more. No issues exceeding the speed limit and I rarely use the brakes at all.

Brake fade should not be an issue unless you are racing.

You conveniently quote and leave out parts of my messages to make up an answer that does not make sense. You say I am mistaken about proportionality yet you remove the part where I explain how it's not exactly proportional.

You say I need a driving lesson because one should gear down driving downhill, yet you conveniently remove the part where I say "that's also when that V8 Diesel will help you with engine brakes, compared to that poor undersized Tacoma engine doing what it was not designed to do." It's a fact that the F250 Diesel engine will do a much better job downhill than a Tacoma with 3000 lbs on it.

Bad faith is common on forums, but I think it is used unecessarily here. I always like a debate, a bit less so when misinformation is said (such as there is no brake fade unless racing... wow this is the main point of having larger brakes: better heat dissipation. Brake fading with a heavy load is likely to happen even with just stop and go traffic. This is well documented), and even less so when bad faith comes into play. So thanks for the debate and we will agree to disagree!

 

[rruff]

You conveniently quote and leave out parts of my messages to make up an answer that does not make sense.

Your answer is right above my reply. Anyone can read it. Your conclusion was wrong, because your assumptions were wrong. The change in psi is not trivial, it's in fact the main reason why heavier vehicles take longer to stop. I had no intent to mislead anyone.

Gearing down works very well on a gas pickup, so a diesel having better engine braking isn't relevant.

I always like a debate, a bit less so when misinformation is said (such as there is no brake fade unless racing... wow this is the main point of having larger brakes: better heat dissipation. Brake fading with a heavy load is likely to happen even with just stop and go traffic. This is well documented), and even less so when bad faith comes into play. So thanks for the debate and we will agree to disagree!

Speaking of bad faith, I never said "there is no brake fade unless racing". I said it shouldn't be an issue... like going down hill shouldn't be an issue. If your brakes are fading in stop and go traffic, then make sure that is covered in the driving lesson as well.

I might have missed it, maybe in another thread, but how much over payload are you? Would you suggest a number of pounds that is OK or would you use a percentage?

I don't know what it weighs. I thought about hitting a CAT scale but haven't yet. WAG ~7,600 lbs, and I'll add more weight... and be over 8,000 before I'm done. GVWR is 7,200 lbs with a 5,800 lb curb weight. I initially thought I'd be able to stay under that, but there is just no way... not if you are loading for a months long trip. The "stuff" adds up...

I investigated my particular truck. I bought in 2016 and the truck hadn't changed much since 2007, so there was a lot of high mileage and high load anecdotal experience, with way more weight than I'm carrying. I concluded that buying a domestic 3/4 ton would have been riskier...

So, I'd suggest investigating forums, mostly concerning durability. Even if you are under GVWR, it's a very good idea to upgrade tires and suspension so it will handle the load better.

 

[tacollie]

Personally, I would much rather drive a F-250 under GVWR, than a Tacoma thousands of pounds over GVWR, to go downhill a mountain (which anybody overloading does at some point).

I've had the privilege of getting to drive overloaded Toyotas all over Colorado for 20 years before I decided to get an F-250. The biggest problem with Toyotas is you have to modify them for them to be suitable for carrying weight. When you're running heavy things wear out faster so you have to be more on top of maintenance. I never had a single failure. My buddies that had failures it was due to lack of maintenance. Never a brake failure but broken leaf springs and other suspension components. I'm sure I had to replace brake pads and rotors more often. You are stuck in the right lane going up passes. Engine braking was always adequate. The nice thing about the F-250 is we installed camper on it. I didn't have to worry about modifying anything. Just drive.

Whether you over gvwr or not, if you're carrying a camper you should slow down a little. Overweight or not speed breaks things.