2010 Hyundai Sante-Fe 4cyl auto

[theholycow]

Here’s why: Think about the reason cars went from BOF to unibody in the first place.

Because, in applications where it doesn't need to be built for heavy work, it can be lighter; and because the vehicle can be lower. Those motivations do not apply to trucks.

These advantages would apply equally to a small car or a large pick-up.

Pickups do not need to be low (quite the opposite in fact - if you were to sell a unibody pickup you'd have to set it at the same height as BOF pickups or nobody would buy it), and while some could benefit from weight loss (half tons used as commuter/family cars), plenty need more weight (anything used for plowing or towing).

The reason unibody never made it to large pick-ups is because they aren’t strong enough to cope with the stresses that those vehicles are built to endure.

In your previous post you conceded that unibodies “can” be built just as strong as BOF but are currently not. It's not that unibody cannot be strong enough to cope.

Most of us are looking at this discussion theoretically, talking about what “can” be done but why it is or is not actually done.

If the unibody chassis was built just as strong, it would surely be in use by now on large pick-ups and work trucks, simply because of the other advantages inherent of the design.

I'm sure I've forgotten a couple. What advantages does it have that would apply to pickups and outweigh the advantages of BOF (which, BTW, do not apply to cars)?

You talk about engineering and testing….do you really think nothing has been done in terms of engineering/testing for a pick-up frame?

I think a whole lot more engineering would need to be done to start using unibody on pickups than needs to be done to improve BOF. BOF is mature technology; once in a while someone comes up with a significant change, and of course some engineering is done all the time, but that's on a whole different level from changing to unibody would be. You'd have to re-engineer the entire vehicle, and do additional major long-term testing on the whole thing that doesn't need to be done for BOF pickups.

Marketing—nobody will buy a unibody pick-up. That’s probably an accurate statement. But think about the reason why nobody would buy one. If anyone thought a unibody pick-up would hold up, I’m sure they’d be more than happy to buy one. The fact that manufacturers don’t make unibody pick-ups just reinforces public perception that a unibody pick-up wouldn’t last very long.

Wow, talk about some circular logic.

Manufacturers don't do it because there is nothing motivating them to do so, not because it cannot be done. One of the motivation failures is that nobody will buy it. That doesn't make the general public a better engineer than than the manufacturer's engineering department; it just takes the money out of the idea.

Can manufacturers actually build a unibody chassis that would be suited for a fullsize pick-up? Absolutely.

See? We don't disagree at all.

So why don’t they do it then? Simple answer—cost. Imagine what it would cost to build that kind of heavy duty unibody chassis. My guess is that it simply wouldn’t be cost effective.

Agreed.

You still have to consider SUVs though….up until recently, there were plenty of SUVs built BOF. Do you know why? I’ll give you a hint: Many SUVs were derived from pick-up trucks, and pick-up trucks were built BOF.

I thought that was obvious enough that we didn't need to discuss it.

I have no doubt that the day will come when no new SUV will have BOF construction.

I disagree. There will always be a market that specifically wants BOF SUVs. More importantly, though, is that the engineering and design are already done for the pickup - there will always be a platform for a quick, cost-effective pickup-sized SUV design with pickup-like capabilities.

[Shadow]

Because, in applications where it doesn't need to be built for heavy work, it can be lighter; and because the vehicle can be lower. Those motivations do not apply to trucks.

So you're agreeing with me....BOF is for heavy work. That's what I've been saying all along. And height doesn't really mean anything. Cars were still low back when they were BOF.

Pickups do not need to be low (quite the opposite in fact - if you were to sell a unibody pickup you'd have to set it at the same height as BOF pickups or nobody would buy it), and while some could benefit from weight loss (half tons used as commuter/family cars), plenty need more weight (anything used for plowing or towing).

Again, height doesn't mean much unless you're talking about offroading and need the extra ground clearance. This discussion is mostly about the strength of the frame/chassis, not about vehicle height or ground clearance. If the engineers wanted to design a unibody pick-up that has the same height as today's BOF trucks, it would be very easy to do so. Take the Honda Ridgeline for example. It's a unibody truck that sits about the same height as my BOF 4Runner.

In your previous post you conceded that unibodies “can” be built just as strong as BOF but are currently not. It's not that unibody cannot be strong enough to cope.

Most of us are looking at this discussion theoretically, talking about what “can” be done but why it is or is not actually done.

Like I said, anything can be built up to any specifications. I'll say it again--a unibody chassis can be built very strong. But my point should be clear by now: BOF construction is more heavy-duty than unibody. I'm talking real world here, not what can be done. It would be silly for me to argue that it is impossible to build a unibody chassis that's as strong as a BOF chassis, which is why I'm talking about real world vehicles out on the roads today.

I'm sure I've forgotten a couple. What advantages does it have that would apply to pickups and outweigh the advantages of BOF (which, BTW, do not apply to cars)?

Research the reasons why unibody became THE choice in chassis design for the majority of passenger vehicles on the roads today. Then research the reasons why manufacturers still use BOF for their heavy-duty vehicles, including the fullsize trucks.

I think a whole lot more engineering would need to be done to start using unibody on pickups than needs to be done to improve BOF. BOF is mature technology; once in a while someone comes up with a significant change, and of course some engineering is done all the time, but that's on a whole different level from changing to unibody would be. You'd have to re-engineer the entire vehicle, and do additional major long-term testing on the whole thing that doesn't need to be done for BOF pickups.

Yet manufacturers all found the time & money to switch from BOF to unibody for the vast majority of their vehicles. Common sense should tell you that a similar switch would have been made on trucks if it made sense to do so. I can't believe you're even trying to debate this point. It should be clear to you that the reason we still see BOF on these vehicles is because they are stronger and able to cope with the additional stresses much better than a unibody design. Everyone is always trying to improve their vehicles. By now, one of these companies surely would have come out with a unibody design if it was practical and cost effective.

Wow, talk about some circular logic.

Manufacturers don't do it because there is nothing motivating them to do so, not because it cannot be done. One of the motivation failures is that nobody will buy it. That doesn't make the general public a better engineer than than the manufacturer's engineering department; it just takes the money out of the idea.

Manufacturers continually update their vehicles in order to make a profit. That should be obvious. Do you think Ford would be motivated to build a unibody F350 if it were: 1-as strong as the BOF version, 2-built as inexpensively as the BOF version, 3-as long-lasting as the BOF version? As long as buyers believed those three points, I'm sure they'd be more than happy to buy a unibody F350. I certainly would. So it's not circular logic, it's common sense and basic marketing.

See? We don't disagree at all.

I never once said it wasn't possible. I never even implied it wasn't possible. I just said it isn't the case today. And that's true.

I disagree. There will always be a market that specifically wants BOF SUVs. More importantly, though, is that the engineering and design are already done for the pickup - there will always be a platform for a quick, cost-effective pickup-sized SUV design with pickup-like capabilities.

Off the top of my head, I can think of 3 midsize SUVs that are still BOF--the 4Runner, the Pathfinder (which, interesting, went back to BOF after switching to unibody during the last generation), and the Xterra. Now I've heard rumors that the Xterra is living on borrowed time and will be going away. Oh, and the FJ Cruiser is also BOF, but that's definitely going away. So the 4Runner and the current Pathfinder (which is due for a redesign) are the only choices I can think of off the top of my head. Compare that to, say, 20 years ago when most SUVs were BOF. Do you really think BOF will survive on midsize SUVs? Sure, pick-ups will have BOF for the foreseeable future, but midsize SUVs? It's already disappearing.

[theholycow]

If the engineers wanted to design a unibody pick-up that has the same height as today's BOF trucks, it would be very easy to do so. Take the Honda Ridgeline for example. It's a unibody truck that sits about the same height as my BOF 4Runner.

I wasn't saying that it's hard to lift a unibody; rather that it's hard to sufficiently lower a BOF. Putting the body on top of the frame means the frame takes up space. Either the whole vehicle is higher or there are peaks in the floor pan (high step-over for entering the vehicle, as in my 1980 Buick with its large frame). So that is a motivation for unibody in low applications that becomes moot in truck applications (but not against either type of construction).

Like I said, anything can be built up to any specifications. I'll say it again--a unibody chassis can be built very strong. But my point should be clear by now: BOF construction is more heavy-duty than unibody.

Perhaps it would be easier to agree if you said "existing designs" rather than "construction". To me, each type of "construction" is merely a technique which gets applied in actual designs.

Yet manufacturers all found the time & money to switch from BOF to unibody for the vast majority of their vehicles.

They had motivation. What motivation would they have to do it on a pickup? That's not to say that it can't be done, but rather that there is a lack of cause to bother with it.

It should be clear to you that the reason we still see BOF on these vehicles is because they are stronger and able to cope with the additional stresses much better than a unibody design. Everyone is always trying to improve their vehicles. By now, one of these companies surely would have come out with a unibody design if it was practical and cost effective.

They would not surely have done so just because it could be practical and cost-effective; change comes from a need for something, rather than a tolerance of it. Practical and cost-effective merely mean "acceptable", not "required"...although as I previously said it would not be cost-effective.

Don't confuse "lack of a reason against" as being "a good reason for". Anyway, there's plenty of reasons against.

Manufacturers continually update their vehicles in order to make a profit. That should be obvious. Do you think Ford would be motivated to build a unibody F350 if it were: 1-as strong as the BOF version, 2-built as inexpensively as the BOF version, 3-as long-lasting as the BOF version? As long as buyers believed those three points, I'm sure they'd be more than happy to buy a unibody F350. I certainly would. So it's not circular logic, it's common sense and basic marketing.

"As long as buyers believed those three points" is not equal to "those three points are valid".

Do you really think BOF will survive on midsize SUVs? Sure, pick-ups will have BOF for the foreseeable future, but midsize SUVs? It's already disappearing.

Go back and look at your quote. You posted "no new SUV", not "no new midsize SUV". I will make no prediction about midsize SUVs since their platform-buddy the compact pickup is currently disappearing.

[Shadow]

I wasn't saying that it's hard to lift a unibody; rather that it's hard to sufficiently lower a BOF. Putting the body on top of the frame means the frame takes up space. Either the whole vehicle is higher or there are peaks in the floor pan (high step-over for entering the vehicle, as in my 1980 Buick with its large frame). So that is a motivation for unibody in low applications that becomes moot in truck applications (but not against either type of construction).

Again, BOF cars were about the same height as today's unibody cars. So I'm not sure what point you're trying to make. If you think about it, an SUV like my 4Runner is really just a "tall" station wagon with 4wd in a sense. It's not tall because it's BOF. Plenty of unibody SUVs are just as tall or taller.

Perhaps it would be easier to agree if you said "existing designs" rather than "construction". To me, each type of "construction" is merely a technique which gets applied in actual designs.

It should be clear that I was talking about today's vehicles. This whole debate started when I mentioned that I'd rather stick with my BOF 4Runner rather than a new crossover SUV. And then I mentioned my reasoning for that decision. Never was this a theoretical discussion about what could potentially be done with a unibody chassis or a BOF chassis. Rope-Pusher started generalizing, but the whole time I was discussing how I want (actually how I need) BOF for the stuff I put my vehicle through. So yes, existing designs is what I'm talking about, and the existing design on my 4Runner is BOF construction.

They had motivation. What motivation would they have to do it on a pickup? That's not to say that it can't be done, but rather that there is a lack of cause to bother with it.

The same exact motivation they had to switch over to unibody on every other vehicle they manufacture. Like I said, there are clear advantages...why wouldn't they use them instead of relying on the old BOF construction?

They would not surely have done so just because it could be practical and cost-effective; change comes from a need for something, rather than a tolerance of it. Practical and cost-effective merely mean "acceptable", not "required"...although as I previously said it would not be cost-effective.

Don't confuse "lack of a reason against" as being "a good reason for". Anyway, there's plenty of reasons against.

Exactly. And the "reason" for BOF construction is strength. There's simply no other plausible reason for them to stick with BOF construction if strength weren't the major factor here.

"As long as buyers believed those three points" is not equal to "those three points are valid".

Tell me what's not valid about those three points. What do you think buyers look for in, say, a fullsize pick-up?

Go back and look at your quote. You posted "no new SUV", not "no new midsize SUV". I will make no prediction about midsize SUVs since their platform-buddy the compact pickup is currently disappearing.

Sorry that I didn't type "midsize" in front of SUV every time I posted. I'm obviously not talking about fullsize SUVs (haven't mentioned them once) because those are still mostly based off of their pick-up truck counterparts. The 2010 Santa-Fe is a midsize SUV. My 4Runner is a midsize SUV, so I thought it was pretty clear that we were talking about midsize SUVs here. The only reason I even mentioned fullsize pick-ups was to illustrate a point about BOF strength and construction.

[Shadow]

Here's a simple question for you guys:

Below is a picture of a typical pull plow. Now tell me which of these vehicles would be more suited to pull this plow-- 2011 4Runner (BOF, live axle), 2011 Explorer (unibody, IRS), or 2011 Grand Cherokee (uniframe, IRS)



Just give me a straight answer, no "but" of "if" required. Tell me like you see it.

[theholycow]

You're talking about whole vehicles on the market, not construction techniques.

The heaviest vehicle with the best traction is going to be best for that pull plow, construction type wouldn't make a difference.

[theholycow]

Curb weights:
2011 4runner: 4400
2010 Explorer: 4628 (couldn't find 2011 Explorer 4x4 curb weight)
2011 Grand Cherokee: 4850

Unless one vehicle has better differentials or there's some severe tire differences I bet the Grand Cherokee would do the best with that plow.

[Shadow]

You're talking about whole vehicles on the market, not construction techniques.

The heaviest vehicle with the best traction is going to be best for that pull plow, construction type wouldn't make a difference.

Negative. The heaviest vehicle isn't what matters most. Weight really has nothing to do with it when you consider that all 3 vehicles mentioned can easily pull that plow. IRS and unibody chassis will not handle the stresses of a pull plow as well as BOF and live axles. If you can't understand that simple fact, then I think we should end this discussion.

[Shadow]

Curb weights:
2011 4runner: 4400
2010 Explorer: 4628 (couldn't find 2011 Explorer 4x4 curb weight)
2011 Grand Cherokee: 4850

Unless one vehicle has better differentials or there's some severe tire differences I bet the Grand Cherokee would do the best with that plow.

The Grand Cherokee, with IRS and unibody suspension (even with the "uniframe" rails attached) would be MUCH more likely to sustain damage than the 4Runner. I'm guessing you have no experience with snow plowing vehicles.

[theholycow]

I've done plenty of plowing. I had a dumptruck and plowed roads (as well as my own driveway and jobsites). The issue isn't whether the truck will break...none of them will break towing that dinky little plow over a few inches of snow. What's going to happen is the lighter vehicle will spin its tires while the heavier one keeps pulling.

[Shadow]

I've done plenty of plowing. I had a dumptruck and plowed roads (as well as my own driveway and jobsites). The issue isn't whether the truck will break...none of them will break towing that dinky little plow over a few inches of snow. What's going to happen is the lighter vehicle will spin its tires while the heavier one keeps pulling.

If you had experience plowing, you would know that unibody vehicles just aren't suited for plowing. BTW, that's not a dinky little plow. Look at it again. It's mounted to fullsize Dodge Ram and it's just as large as most front mounted plows. Yes, a Grand Cherokee probably would break rather quickly pulling that plow.

Here some quotes from a thread in a snowplow forum (www.snowplowsite.com)


Rabsparks:
I have a 1999 Jeep Grand Cherokee, and the owner's manual cautions against front mounted plows. I presume that's because of possible air bag deployment, but Jeep doesn't say. So i'm thinking about a rear mounted plow, something like the Simplicity or the Driveway SuperPlow (Latham NY).

Does anyone have any experience with the rear mounted plows?

Rick
______________________________

Mick:
Rick, welcome to PlowSite. The airbag is one reason it's not recommended, but that's not the main reason. The main reason is because the Grand Cherokee has a unibody. Even if you could mount a plow (which you can't. There have been a couple of pretty humorous threads about that.), there would be no "give" when striking an object. Your Jeep would get torn up. I think you would be ok with a rear mounted plow as long you got one that can be angled and you're only plowing a couple of inches. You'll have to plan a little more careful where you're going to put the snow, since you can only pull snow behind you instead of pushing it ahead of you. But I suppose it could be done.

_______________________________
cja1987:
western and fisher make plows for down sized suvs now check em out

I don't even think a homesteader or suburbanite would be a good idea on the Grand Cherokees, frame just can't handel it and i don't think they make a mount for the Grand cherokees.

_______________________________
Plow Meister:
That pretty much goes for all unibody constructed vehicles. I have seen many plow trucks with their back windows blown out because they get too carried away with an inferior plow vehicle. Grands are great SUV's and can go off roading with the best of 'em but they do not make adequate plow vehicles.

[Rope-Pusher]

Shadow - It's not plain to me that live axles and unibodies are inferior to IRS and BOF. Maybe if pick-em-ups had D-Pillars, they would be better candidates for unibody construction and would have migrated that way years ago.

If THC and I can't tag-team rassle you over to looking at this issue from our side of the ring, let's just agree to disagree.

[Shadow]

Shadow - It's not plain to me that live axles and unibodies are inferior to IRS and BOF. Maybe if pick-em-ups had D-Pillars, they would be better candidates for unibody construction and would have migrated that way years ago.

If THC and I can't tag-team rassle you over to looking at this issue from our side of the ring, let's just agree to disagree.

I'm not saying BOF is superior; I'm saying it is stronger (in the context that I've mentioned over and over again already). I've also said several times already that unibody has its advantages, which should be evident by the fact that the vast majority of vehicles on the road today are unibody.

I think what happened here is that THC dug himself into a hole and was just getting deeper and deeper into it. I'm quite sure that both you and him know and understand the fact that BOF construction is inherently stronger and a more heavy-duty compared to unibody. Again, this isn't about what "can be" or "might be" in the future. I'm talking about the "here and now", not what might be some time in the future. So when someone says that a fully boxed ladder frame is the strongest chassis construction on a modern vehicle, there's simply no denying that. It's beyond silly to even try to debate something so blatantly obvious.

But if you guys want some sort of empirical evidence, I can only tell you to take a hard look at the most heavy-duty vehicles (all kinds of work trucks and work vans, etc..) available today and ask yourself why they are built BOF. Just don't come to the lame conclusion that THC did and say "because they have no reason not to be". That's like asking why my lollipop is red and answering because it's not green. LOL.

[theholycow]

*sigh* I was going to just let it drop. I have plenty of responses to your previous posts but there is no point to continuing. There is nobody interested in this discussion other than the three of us and we will not accomplish anything by continuing. Yet you have motivated me to respond once again.

I've also said several times already that unibody has its advantages, which should be evident by the fact that the vast majority of vehicles on the road today are unibody.

You have failed to deliver a suggestion of these advantages, and you have discounted the ones I proposed. Telling me to research it is a cop-out; this isn't a college course, it's a person-to-person discussion. You have to back up your own arguments.

I'm quite sure that both you and him know and understand the fact that BOF construction is inherently stronger and a more heavy-duty compared to unibody. Again, this isn't about what "can be" or "might be" in the future. I'm talking about the "here and now", not what might be some time in the future.

Take out "inherently", replace "construction" with "vehicles", and I agree. "BOF construction is inherently" is the opposite of your next statement that you're not talking about what could be.

BOF vehicles on the market tend to be stronger and more heavy-duty compared to unibody vehicles on the market. BOF construction is not inherently stronger.

But if you guys want some sort of empirical evidence, I can only tell you to take a hard look at the most heavy-duty vehicles (all kinds of work trucks and work vans, etc..) available today and ask yourself why they are built BOF. Just don't come to the lame conclusion that THC did and say "because they have no reason not to be". That's like asking why my lollipop is red and answering because it's not green. LOL.

Reason to change is required. Change is expensive and risky. However, I already stated other irrefutable reasons and you even agreed.

[Shadow]

*sigh* I was going to just let it drop. I have plenty of responses to your previous posts but there is no point to continuing. There is nobody interested in this discussion other than the three of us and we will not accomplish anything by continuing. Yet you have motivated me to respond once again.

I'm perfectly content with debating this topic, even if you are the only one interested. I don't need an audience. In fact, I sent my buddy (he's an automotive engineer who works mainly on chassis design) a link to this thread because I thought he'd get a kick out of it. So maybe you have a bigger audience than you think.

You have failed to deliver a suggestion of these advantages, and you have discounted the ones I proposed. Telling me to research it is a cop-out; this isn't a college course, it's a person-to-person discussion. You have to back up your own arguments.

Failed to deliver a suggestion of the advantages? Are you serious? Okay, let me repeat it again, since you seem to have such a hard time comprehending my words. Strength. There, that's it, plain and simple. THAT is the advantage of BOF. The reason I'm telling you to research is because you obviously have a lot to learn and I don't have the time or resources to educate you. The information is out there, you can find it on your own. BTW, it is your argument that goes against the status quo, not mine. A simple Google search will bring up thousands of web pages where BOF is compared to unibody in the type of applications we are discussing here.

Take out "inherently", replace "construction" with "vehicles", and I agree. "BOF construction is inherently" is the opposite of your next statement that you're not talking about what could be.

BOF vehicles on the market tend to be stronger and more heavy-duty compared to unibody vehicles on the market. BOF construction is not inherently stronger.

Okay, are you playing the semantics game now? The fact that "BOF vehicles on the market tend to be stronger and more heavy-duty compared to unibody vehicles" supports the idea that BOF is inherently stronger than unibody. Notice that we're not talking about two specific vehicles, but rather two distinct chassis/frame designs.

Still though, you're contradicting yourself now. First you tell me that a Grand Cherokee would be the best vehicle for a pull plow (because of curb weight), but now you're admitting that a BOF vehicle tends to be stronger and more heavy-duty than a unibody vehicle. So tell me again, is my 4Runner (with it's live axle rear and BOF) built more heavy-duty than the Grand Cherokee (with its IRS and unibody chassis) or am I missing something in your theory?

Reason to change is required. Change is expensive and risky. However, I already stated other irrefutable reasons and you even agreed.

I already told you that most of the same reasons to change apply to trucks and SUVs. There are lot of advantages to unibody chassis design. If we were to list them all, the majority of them would in fact still be advantageous to trucks and SUVs. And that's exactly why so many modern vehicles are unibody. The vehicles that aren't will remain BOF for good reason.