Removing rear seats to increase payload capacity?

[stevo_pct]

Dude, that was awesome. I feel the case is closed!

 

[ChasingOurTrunks]

Dude, that was awesome. I feel the case is closed!

Thanks Stevo! As it turns out, I'm really quick at math. Just not accurate I've updated the math to what I think is correct; it's not as dire (240 feet instead of 460 feet) but it's still a huge difference. Timmy still dies (unless it's a Toyota as @Buddha. said! )

 

[rruff]

I'm 100% in agreement with your philosophy of wanting a setup that's safe and rides well, as that is my goal as well, and so I've tried to learn as much as I can about how weight impacts vehicles over the years. Transmissions are usually not the issue, but brakes for sure are.

But today, with Timmy's upgraded truck's better suspension that lets him cruise at 100 kph (double his speed of the other day), fully loaded with his 3,000 lbs of gear, and with Bullwinkle 100 feet away on the road ahead, Timmy has a problem. He now needs 240 feet to stop his truck (4 times the distance). Essentially, that's almost an extra football field of distance. With a total stopping distance of 240 feet, Timmy is only half of the way through his braking distance when he hits the moose -- that means it's not even close. He hits that moose at near highway speeds. It doesn't go well for Bullwinkle, but it goes a lot worse for Timmy and his dog; the moose goes up over the hood of the truck and into the cab, right beside Timmy. Timmy gets a hoof in the head from the moose thrashing around, and dies slowly on the side of the road.

Braking distance is only proportional to weight if you can't lock up the tires, making the friction between pads and rotors the limiting factor.

In this case we are looking at the difference between 6000+1500= 7500lb truck vs 6000+3000= 9000 lb truck. A 20% increase worst case.

A camper in the bed will stop better than a towed one of the same weight. The higher CG shifts weight to the front when braking. The towed camper will push down harder on the hitch, lightening the front.

Your example only illustrates why everyone should drive overloaded 1/2 tons (vs not overloaded 1 tons for instance)... because the handling is so poor that people are very cautious and drive slow... but maybe you knew that?

 

[ChasingOurTrunks]

Braking distance is only proportional to weight if you can't lock up the tires, making the friction between pads and rotors the limiting factor.

In this case we are looking at the difference between 6000+1500= 7500lb truck vs 6000+3000= 9000 lb truck. A 20% increase worst case.

A camper in the bed will stop better than a towed one of the same weight. The higher CG shifts weight to the front when braking. The towed camper will push down harder on the hitch, lightening the front.

Your example only illustrates why everyone should drive overloaded 1/2 tons (vs not overloaded 1 tons for instance)... because the handling is so poor that people are very cautious and drive slow... but maybe you knew that?

There is background information about Timmy I didn’t include. His truck is less than 5 years old so no chance of locking up the tires.

You might be right about the camper weights vs the trailer weights, and I might be wrong about the physics of it - this is how I’ve understood it but you’ve got me thinking about it. Not enough grey matter left for me right now, I put it all into crafting Timmy’s backstory. It’s an action tragedy in three parts.

But the point of Timmy’s story wasn’t to the physics of towed weight vs bed weight, as much as it was, quite simply:

Big weight = hard to stop. Buy bigger truck.

 

[skrypj]

There is always the heavy duty payload package F150 if you dont want to move up to a 3/4 or 1 ton. An XLT crew cab 4x4 with HDPP can have a legit 2500+ lbs of payload and it comes with the frame, axle, springs, etc to deal with the added weight.

 

[Porkchopexpress]

The axle ratings on the Tundra are 4000 lb front and 4150 lb rear. Not sure how the 5700 lb curb weight is split, but if it's 60/40 (3420, 2280), then you can add 580 lbs to the front and 1870 lbs to the rear to hit the axle rating.

The only axle issue I've heard with Tundras is the rear bearings, but this doesn't appear to have anything to do with load, but rather manufacturing tolerance issues (preload).

Somehow you quoted someone else's post but my user name is above it as if it is mine?

 

[billiebob]

This has a payload of nearly 1,000kg (I think it's 940kg) between unladen with me in it and GVM. Easiest way for me increase the amount it can carry is let the missus drive instead of me, and not go along - that would take the payload up to 970kg straight away.

Admittedly, it'd be slow as a sloth with a 1600cc petrol lump in it...View attachment 684862

The 2.5 diesel might be a better option.

(Helpful comments as always!)

why is it that guys who drive cheap old trucks understand GVWR but guys who spend $50K on a new truck,,,, any new truck..... act life the best 3 years of their life were Grade 8.

 

[rruff]

There is background information about Timmy I didn’t include. His truck is less than 5 years old so no chance of locking up the tires....
Big weight = hard to stop. Buy bigger truck.

If the ABS is working that means the tire traction is the limiting factor, not the brakes. A bigger truck doesn't help... it's simply heavier to begin with. That's why large RVs and trucks require about double the stopping distance.

 

[tacollie]

why is it that guys who drive cheap old trucks understand GVWR but guys who spend $50K on a new truck,,,, any new truck..... act life the best 3 years of their life were Grade 8.

It's because GVWR was low on those old vehicles with crappy brakes and crappy handling. I've seen $50k F150s rated to carry more than a some 90s 3/4 tons ?

 

[Porkchopexpress]

A camper in the bed will stop better than a towed one of the same weight. The higher CG shifts weight to the front when braking. The towed camper will push down harder on the hitch, lightening the front.

Kind of going off on a tangent, but a higher CG is not better for braking.

 

[ChasingOurTrunks]

EDIT: Based on the conversation that followed this post, I may not have had the best understanding of the contact patch issue. You shouldn't be taking the word of a stranger on the internet anyway, but it appears this is more nuanced and the rest of the discussion addresses it so read on for the full context at least a page or two of this thread. I still stand by "buy the truck that is spec'd to carry the weight" and I think my "Inspired by a True Story" about Timmy and his Dog is still accurate, but WHY it's accurate is a matter of some interesting conversation. Cheers to folks like PorkchopExpress, Rruf, and others for contributing to understanding this rather niche (but critically important) aspect of our shared hobby!

If the ABS is working that means the tire traction is the limiting factor, not the brakes. A bigger truck doesn't help... it's simply heavier to begin with. That's why large RVs and trucks require about double the stopping distance.

I might be wrong so I appreciate the conversation, Rruff because the best way for me to learn stuff is through pulling it apart and putting it back together again. I don’t disagree with what you’ve said but my understanding, and why I think a bigger truck is better for bigger loads, is a bit more related to tires and weights. I’ve now slept, though the coffee hasn’t kicked in so no promises on this post either though!

To your other point about towing vs hauling - that’s not been my personal experience. I’ve done a ton of towing and it was always much easier to drive (and stop) with big towed weights than it is with big weights in the box. These days I use a trailer brake so it’s a moot point now, and I’ve never gotten out a measuring tape and practiced my emergency breaking in both contexts but the swaying of the front end because of too much weight in the box and the subsequent poor performance of the brakes is something I have first hand experience with. When towing, I’ve never had any problems like this. Of course that assumes the trailer is loaded properly and everything is tied down. I’d be very open to understanding the huge variability in weights (1900 payload vs nearly 10,000 towing) in most trucks if it’s not the reasons I’ve stated.

Setting trailers aside and focussing in big loads, the weight shift your talking about does happen, but F = MA. Weight shifting forward and putting more downward pressure on the front tires has to be met with a corresponding easing of the pressure on the rear tires, right? Every action equal and opposite, and all that. This is a lot easier to notice on a motorbike with and without a pillion. This forward shift your talking about does indeed happen and the front dives down putting way more pressure on the front wheel, but the key part is the time it takes that shift to happen. It’s not instant and in that time the front has worse traction, and thus worse braking performance. This is because the light weight changes the friction between the tire and the ground. And once the shift happens, the rear wheel of the bike lifts and thus there is less braking performance on the rear, though this is less impactful as the front does most of the work.

So if braking is determined by friction (tire to ground), the more tire that’s on the ground, the more friction you get. Bigger trucks typically have taller and wider tires. Failing that they are heavier and cause more deflection of the tire. The end result is the same - a bigger contact patch. And this translates to better braking performance.

So all other things being equal, a truck that is built for the weight will see a less variable contact patch front and rear because the suspension and load carrying is designed to properly carry the weight with minimal contact patch variability from shifting back and forth. And, the tires are typically taller and wider, with greater overall weight causing the tire to deform which further increases the contact patch.

So big load = hard to stop. Big truck = better.

I’d like to see a head to head test — a 1500- series pickup with 3k lbs in the bed, and an HD pickup with 3k lbs in the bed. Bring them both to 100 kph and see which stops faster. Where’sthe Mythbusters when we need ‘em, eh?

Thanks again for the conversation Rruff. Always good to chat about this stuff and figure more things out.

 

[Porkchopexpress]

Weight shifting forward and putting more downward pressure on the front tires has to be met with a corresponding easing of the pressure on the rear tires, right? ...
... once the shift happens, the rear wheel of the bike lifts and thus there is less braking performance on the rear, though this is less impactful as the front does most of the work.

So if braking is determined by friction (tire to ground), the more tire that’s on the ground, the more friction you get. Bigger trucks typically have taller and wider tires. Failing that they are heavier and cause more deflection of the tire. The end result is the same - a bigger contact patch. And this translates to better braking performance.

Pretty much true except the part about "less impactful". The front does most of the work because weight shifts forward during braking and therefore manufacturers put better brakes up front. That does not mean that it is desirable to intentionally shift more of the load to the front. Ideally, the rear wheels and tires help out.

 

[ChasingOurTrunks]

@Porkchopexpress — gotcha! That was probably a poor word choice on my part. I was thinking of the 70/30 split it breaking effort (70% of effort being on the front), so a reduction of half of the traction on the rear wheel only reduces breaking power by 15%, whereas the same reduction of half traction on the front reduces breaking power by 35%.

Is that your understanding too?

 

[Porkchopexpress]

@Porkchopexpress — gotcha! That was probably a poor word choice on my part. I was thinking of the 70/30 split it breaking effort (70% of effort being on the front), so a reduction of half of the traction on the rear wheel only reduces breaking power by 15%, whereas the same reduction of half traction on the front reduces breaking power by 35%.

Is that your understanding too?

It's not so much percent traction as you either have it or you don't. Once your tire breaks loose, (skidding) you loose all traction. So the contact patch size is somewhat proportional to how much braking force the tire can hold before breaking loose. If you have more down force on the tire, it deforms creating a bigger contact patch. The converse is true in the rear as weight shifts forward.

 

[ChasingOurTrunks]

It's not so much percent traction as you either have it or you don't. Once your tire breaks loose, (skidding) you loose all traction. So the contact patch size is somewhat proportional to how much braking force the tire can hold before breaking loose. If you have more down force on the tire, it deforms creating a bigger contact patch. The converse is true in the rear as weight shifts forward.

That makes sense - thanks Porkshopexpress!