Car Have Become Too Complex!

[mstrjon32]

Originally Posted By: Pop_Rivit
If you're trying to apply a 20 or 30 year old skillset to any modern piece of technology you'll be out of your league. Vehicles are no exception-they have always gotten more complicated and require that you constantly improve your mechanical skillset to keep up with the new innovations.


The issue isn't skill, it comes down to the fact that modern cars require computer diagnostic equipment that just isn't available to the average DIY'er. Can I replace the TPMS sensor inside my wheels myself? Yes, I actually have the equipment and skill to do that. Can I program it to the vehicle? Nope, need the Tech II that only the dealer has.

The mechanics of the task really haven't changed in the past 50 years, but they've introduced some nice electronic barriers to keep you from doing many jobs yourself.

 

[OVERKILL]

Originally Posted By: d00df00d
Originally Posted By: OVERK1LL
If you were to fit a diesel making 600lb-ft of torque...

Sounds like you don't need me to tell you why trucks are body-on-frame, then.


Originally Posted By: OVERK1LL
A unit-body is definitely more rigid however, which translates into better handling.

...and is much lighter for a given level of strength.

Sounds like you also don't need me to tell you why cars are unibody.


Originally Posted By: OVERK1LL
In the pics I posted, the difference would have been 2-4,000lbs, with the biggest weight difference being an F-250 vs a Neon.

Sounds like you also don't need me to tell you why those trucks killed the occupants of the cars they hit.


Glad to see we're on the same page.

LMAO!, yeah, guess we are

I think a lot of people confuse rigidity with strength, which was part of the point I was trying to make.

What body on frame DOES do, as indicated by KrisZ is have an impact (no pun intended) on how the vehicle behaves in a crash; they can not have the same sort of detail engineered into the crumple zones due to the strength of the parallel frame rails. These do not have a huge bearing on side-impact though (in cars, dealing with a similar height plane, trucks are a different area here), as indicated by the Panther chassis crash-tests.

Essentially with trucks, the issue is the large parallel chunks of steel that are designed to BE strong; they have to be due to the application. They are obviously incredibly unforgiving in a front or rear-end crash. Since the body itself only crumples so much and then the frame says "no way padre", and begins hammering its way through whatever was hit, the damage is focused on the other vehicle, who's crumple zones are still giving way as the impact is occurring.

Given how the new F-150, and other trucks fare in the IIHS crash tests, there is no doubt in my mind that body-on-frame can be incredibly safe for the occupants.

The issue comes into play when a vehicle who's engineered crumple zones are designed to absorb the impact of another crumple-zone equipped vehicle or that of hitting a stationary object at speed, has a head-on or rear-end collision with a vehicle that weights 6,000lbs and only crumples so far. If the truck is moving at a considerable rate of speed, I would liken it to taking the IIHS test that the car was tested against a solid stationary object (key aspect here, as an impact with another car with equal energy absorption is going to translate into less damage) in, and then almost doubling the speed and observing the damage.

To me at least, the issue with body-on-frame is as outlined above: The damage to other vehicles is more severe in front and rear-end collisions (especially with trucks where ground clearance becomes a big issue), and the question as to how much more energy is transferred to the occupants due to the inability of the chassis to absorb as much of the energy in crumple zones as can be done in a unit-body.

If we use the F-150 as an example: It does FANTASTIC in the IIHS crash test, absolutely perfect score. But what does it do to a car, even a LARGE car, that is unit-body, in say a 50Mph head-on collision?

So, what makes the F-150 different?

The same thing that sets the other trucks that score well in the IIHS tests apart: They are the ONLY body-on-frame platform that has seen consistent R&D investment and improvement.

Cars like the Crown Vic and Caprice have not seen a whole lot changed beneath the skin since their inception some 40 years ago. They are the perfect example as to why body-on-frame is criticized in the manner that d00df00d used.

 

[d00df00d]

Good summary.

I feel like I should reiterate the point I was trying to make:

Originally Posted By: d00df00d
Compared to a unibody, a body-on-frame structure is going to be weaker, heavier, or both.


In other words:

- If it's as strong as a unibody, it'll be heavier.
- If it weighs the same as a unibody, it'll be weaker (except longitudinally).
- It could very easily be both heavier and weaker than a unibody.

This doesn't seem to be in contention, am I right?

 

[BuickGN]

I'll agree with that. What about a body on frame car with a full cage? I'm finally giving in and having a cage installed and all the other stuff to make it legal. I would hate to see what would happen if I hit a modern car with it. I forget the exact numbers but I believe torsional stiffness goes up somewhere around 1,000%. This will be very nice for many different reasons and hopefully it will stop it from cracking the roof.

Back to the original topic, I'll always own an older car. I like mine because it's from an era that had enough computer controls to make it run good but not enough to make it hard to work on.

 

[d00df00d]

Originally Posted By: BuickGN
I'll agree with that. What about a body on frame car with a full cage?

Depends how it's made AFAIK. It could easily be stiffer than a unibody, although it would certainly be a lot heavier unless you are willing to use expensive alloys and/or sacrifice a good amount of your interior to triangulate it.

 

[OVERKILL]

Originally Posted By: d00df00d
Good summary.

I feel like I should reiterate the point I was trying to make:

Originally Posted By: d00df00d
Compared to a unibody, a body-on-frame structure is going to be weaker, heavier, or both.


In other words:

- If it's as strong as a unibody, it'll be heavier.
- If it weighs the same as a unibody, it'll be weaker (except longitudinally).
- It could very easily be both heavier and weaker than a unibody.

This doesn't seem to be in contention, am I right?


Except that the opposite could also be true. Ford's old Fox platform was hardly the pinnacle of safety and a Crown Vic would fair better in a crash than a Mark VII (fox platform) and they weigh about the same.

I personally don't think the "safety" aspect is dependant upon whether it is body-on-frame or unit-body. It is the R&D and money invested in the platform itself. That's why I brought up the F-150. As I said in my previous post, the body-on-frame vehicles that are usually being compared to are cars with frame and underpinning designs that date back almost 4 decades.

There are certain things that unit-bodies are better at:
-far more rigid for a given weight
-better control of crumple zones and crash dynamics for the manufacturer
-better control of crash energy by means of chassis and zone manipulation to minimize what is transferred to the occupants in an average accident.

And certain things that body-on-frames are better at:
-better longitudinal strength
-greater weight capacity and towing capacity
-controlled-twist to handle engines with higher torque output
-better protection of the occupants in accidents of above-average speed (think F-150 and other full-sized trucks) at the expense of higher risk of fatality for those in the other vehicle.

 

[d00df00d]

Originally Posted By: OVERK1LL
Except that the opposite could also be true. Ford's old Fox platform was hardly the pinnacle of safety and a Crown Vic would fair better in a crash than a Mark VII (fox platform) and they weigh about the same.

I was assuming all-else-equal. It should be plainly obvious that a poorly constructed unibody will not compare well to an highly developed body-on-frame.

Originally Posted By: OVERK1LL
-better protection of the occupants in accidents of above-average speed (think F-150 and other full-sized trucks) at the expense of higher risk of fatality for those in the other vehicle.

I disagree on the point that body-on-frame is inherently better for the occupants. If occupants of body-on-frame trucks fare better than occupants of cars, it's because of the weight and height disparity.

And again, I have to say that my skin crawls at the idea of arguing in favor of a vehicle's safety on the basis of a design feature that risks someone else's life in a crash. I would call that a huge net disadvantage, especially considering all the methods at the disposal of a modern engineer to achieve safety without that risk.

 

[BuickGN]

Originally Posted By: d00df00d
Originally Posted By: BuickGN
I'll agree with that. What about a body on frame car with a full cage?

Depends how it's made AFAIK. It could easily be stiffer than a unibody, although it would certainly be a lot heavier unless you are willing to use expensive alloys and/or sacrifice a good amount of your interior to triangulate it.


You would be surprised at how light cages are. My car is a little over 3,000lbs right now and the cage should bring it to 3,200lbs all the while being much more rigid than a production unibody car. Don't get me wrong, I'm not trying to argue a caged car vs a production unibody car, just wanted to throw it out there to see if anyone had any comments.

 

[BuickGN]

Originally Posted By: d00df00d

And again, I have to say that my skin crawls at the idea of arguing in favor of a vehicle's safety on the basis of a design feature that risks someone else's life in a crash. I would call that a huge net disadvantage, especially considering all the methods at the disposal of a modern engineer to achieve safety without that risk.


Call me selfish but if I could put my family in a car that I knew was safer than the rest and it put others at slightly more risk of injury in the event of a wreck I would do it.

 

[d00df00d]

Yeah, I think it's safe to say you are with the majority on that one.

 

[OVERKILL]

Originally Posted By: d00df00d
Originally Posted By: OVERK1LL
Except that the opposite could also be true. Ford's old Fox platform was hardly the pinnacle of safety and a Crown Vic would fair better in a crash than a Mark VII (fox platform) and they weigh about the same.

I was assuming all-else-equal. It should be plainly obvious that a poorly constructed unibody will not compare well to an highly developed body-on-frame.

So other than trucks, what vehicles consist of a highly developed body-on-frame that you can compare this to?

They don't exist. That was the point I was making.

The only highly developed body-on-frame vehicles in production right now are trucks. And current models from all manufacturers do extraordinarily well in crash-tests.

Quote:

I disagree on the point that body-on-frame is inherently better for the occupants. If occupants of body-on-frame trucks fare better than occupants of cars, it's because of the weight and height disparity.


I have to disagree.

Lets again use the F-150.

In the IIHS tests, they run the truck at a standard speed into a stationary object and measure the damage and effects on the occupants.

This is a pick-up that tops the scales at 6,000lbs yet handles a collision with a stationary object well enough to earn PERFECT across the board in the IIHS tests.

Now, a unit-body car that does as well in this test, say a BMW 3-series, weighs in at 3,575lbs. Again, this is against the same stationary object at the same speed.

So, yes, the BMW does just as well as the F-150 in the crash test. It also weighs 2,500lbs less. If we increase the speed of impact to emulate the car weighing 6,000lbs, or add mass to it to increase momentum, would it still score perfectly? Would it still handle the impact as well?

In contrast, if we drop the speed of the F-150's impact down to emulate it weighing 3,575lbs, the damage would be far less than as tested.

If the 6,000lbs F-150 hits the 3,575lb BMW, which vehicle is likely going to fair better? Which vehicle is going to suffer more damage? Yes, mass comes into play here. Mass is always in play. Which is why testing a vehicle against a stationary object at a set speed using its own mass to determine the results is only one factor. And will NOT give you a full picture as to how the vehicle is going to behave in a collision, especially against something that is NOT stationary and weighing significantly more than the vehicle being tested.

Quote:
And again, I have to say that my skin crawls at the idea of arguing in favor of a vehicle's safety on the basis of a design feature that risks someone else's life in a crash. I would call that a huge net disadvantage, especially considering all the methods at the disposal of a modern engineer to achieve safety without that risk.


Yet people buy large SUV's and trucks for that very reason.

 

[d00df00d]

Originally Posted By: OVERK1LL
The only highly developed body-on-frame vehicles in production right now are trucks. And current models from all manufacturers do extraordinarily well in crash-tests.

Well, you were just comparing the Fox platform to the Crown Vic, weren't you?

Unibody is more expensive than body-on-frame. If it weren't stronger per pound, manufacturers wouldn't use it for ALL their cars.


Originally Posted By: OVERK1LL
So, yes, the BMW does just as well as the F-150 in the crash test. It also weighs 2,500lbs less. If we increase the speed of impact to emulate the car weighing 6,000lbs, or add mass to it to increase momentum, would it still score perfectly? Would it still handle the impact as well?

In contrast, if we drop the speed of the F-150's impact down to emulate it weighing 3,575lbs, the damage would be far less than as tested.

Of course. So what does it say that 6,000 lbs of body-on-frame metal doesn't perform any better than 3,575 lbs of unibody metal?


Originally Posted By: OVERK1LL
Yet people buy large SUV's and trucks for that very reason.

I know. Sad, isn't it?

 

[OVERKILL]

Originally Posted By: d00df00d
Originally Posted By: OVERK1LL
The only highly developed body-on-frame vehicles in production right now are trucks. And current models from all manufacturers do extraordinarily well in crash-tests.

Well, you were just comparing the Fox platform to the Crown Vic, weren't you?


Yes, as examples from the same era..... like the 80's. The Fox and Panther platforms are very similar in age. They are also similar in weight in some examples, like the ones I cited.

Quote:
Unibody is more expensive than body-on-frame. If it weren't stronger per pound, manufacturers wouldn't use it for ALL their cars.


How is unit-body more expensive? It uses less material to achieve greater rigidity (notice I didn't say strength) and has been the platform of choice for CHEAP cars since its inception.

When I think of the K-car (unit-body) I think anything but expensive. The same goes for the Festiva, Fiesta, Vega, Monza, Pinto.....etc.

In terms of material cost, you are out MORE money with body-on-frame, because you have to have all the steel for the frame and THEN a large amount of metal for the body itself. And you are then dealing with two units that need to be put together rather than a single unit with smaller separate components like a K-frame and the like.

The unit-body revolution began with small, cheaply made economy cars that were anything but expensive to build. More expensive vehicles were body-on-frame until they were eventually displaced almost completely as unit-body construction advanced.

As I said many posts ago, unit-body has undergone constant improvement since its inception and widespread adoption, whilst the only example of a body-on-frame car still currently in production is the Crown Vic, who's underpinnings date back 4 decades. Hardly a "modern" example of body-on-frame chassis and it shows.

Quote:
Originally Posted By: OVERK1LL
So, yes, the BMW does just as well as the F-150 in the crash test. It also weighs 2,500lbs less. If we increase the speed of impact to emulate the car weighing 6,000lbs, or add mass to it to increase momentum, would it still score perfectly? Would it still handle the impact as well?

In contrast, if we drop the speed of the F-150's impact down to emulate it weighing 3,575lbs, the damage would be far less than as tested.

Of course. So what does it say that 6,000 lbs of body-on-frame metal doesn't perform any better than 3,575 lbs of unibody metal?


You just missed it. COMPLETELY. If we load the 3,575lb unit-body up to 6,000lbs, it is NOT going to do as well as the F-150 at 6,000lbs.

If we drop the crash speed down on the F-150 to emulate it weighing 3,575lbs to make it emulate the BMW, it is going to do even BETTER.


Quote:
Originally Posted By: OVERK1LL
Yet people buy large SUV's and trucks for that very reason.

I know. Sad, isn't it?


To each their own. I'd never own an economy car for that very reason.

 

[JimPghPA]

Hay people, I thought this was suppose to be an oil site.

Any comments regarding older car oils vs newer?

JimPghPa

 

[StevieC]

Originally Posted By: JimPghPA
Hay people, I thought this was suppose to be an oil site.

Any comments regarding older car oils vs newer?

JimPghPa
Huh?

 

[d00df00d]

Originally Posted By: OVERK1LL
Yes, as examples from the same era..... like the 80's. The Fox and Panther platforms are very similar in age. They are also similar in weight in some examples, like the ones I cited.

I'm confused. What was your point?


Originally Posted By: OVERK1LL
How is unit-body more expensive? It uses less material to achieve greater rigidity (notice I didn't say strength) and has been the platform of choice for CHEAP cars since its inception.

My understanding is that the materials savings don't make up for the additional cost of making odd shapes (i.e. not beams) that have to bear load. Steel is cheap...


Originally Posted By: OVERK1LL
When I think of the K-car (unit-body) I think anything but expensive. The same goes for the Festiva, Fiesta, Vega, Monza, Pinto.....etc.

Those had to save fuel, so they had to be light. Since they were small and light, they also had to have high strength-to-weight ratios. Because they are small, differences in manufacturing costs between different methods are going to be relatively small as well. I don't see why those examples point to unibodies being cheaper.


Originally Posted By: OVERK1LL
You just missed it. COMPLETELY. If we load the 3,575lb unit-body up to 6,000lbs, it is NOT going to do as well as the F-150 at 6,000lbs.

If we drop the crash speed down on the F-150 to emulate it weighing 3,575lbs to make it emulate the BMW, it is going to do even BETTER.

I get what you're trying to say, and I don't think it's a good point. A fat chunk of the weight difference is in the structure of each car so it's not a good way make the point that body-on-frame construction is what makes the F-150 stronger.

 

[OVERKILL]

Originally Posted By: d00df00d
Originally Posted By: OVERK1LL
Yes, as examples from the same era..... like the 80's. The Fox and Panther platforms are very similar in age. They are also similar in weight in some examples, like the ones I cited.

I'm confused. What was your point?


That unit-body cars from the same era as the hayday of body-on-frame cars were no better safety-wise. The difference was of course that unit-body cars continued to be improved, whilst, with the exception of trucks, this was not the case for body-on-frame cars.


Quote:
Originally Posted By: OVERK1LL
How is unit-body more expensive? It uses less material to achieve greater rigidity (notice I didn't say strength) and has been the platform of choice for CHEAP cars since its inception.

My understanding is that the materials savings don't make up for the additional cost of making odd shapes (i.e. not beams) that have to bear load. Steel is cheap...


Then why are light trucks, like the Ranger, Dakota, and the Tacoma still body-on-frame?

They are not used in the same manner as as 1/2-ton + trucks, so why have these manufacturers continued to use body-on-frame if they could get markedly better fuel economy out of a lighter vehicle that is "just as strong" (going by your argument here) by making it unit-body?

Honda went that route with the Ridgeline.... and it ended up being a 4,500lb behemoth.

Quote:
Originally Posted By: OVERK1LL
When I think of the K-car (unit-body) I think anything but expensive. The same goes for the Festiva, Fiesta, Vega, Monza, Pinto.....etc.

Those had to save fuel, so they had to be light. Since they were small and light, they also had to have high strength-to-weight ratios. Because they are small, differences in manufacturing costs between different methods are going to be relatively small as well. I don't see why those examples point to unibodies being cheaper.


The cars themselves were the least-expensive available! More expensive cars were still body-on-frame.


Quote:
Originally Posted By: OVERK1LL
You just missed it. COMPLETELY. If we load the 3,575lb unit-body up to 6,000lbs, it is NOT going to do as well as the F-150 at 6,000lbs.

If we drop the crash speed down on the F-150 to emulate it weighing 3,575lbs to make it emulate the BMW, it is going to do even BETTER.

I get what you're trying to say, and I don't think it's a good point. A fat chunk of the weight difference is in the structure of each car so it's not a good way make the point that body-on-frame construction is what makes the F-150 stronger.


It weighs 2,500lbs more, yet is able to handle the impact into a stationary object as well if not better than the vehicle it is giving up 2,500lbs to. I cannot break it down any more basic than that.

That was why I used SPEED examples in my previous post as a better indicator than just adding some mass, as the manipulation of impact speed can be used to emulate weight variances and their effect.

You stated that body-on-frame was inferior to unit-body. Any of the modern pick-up trucks, and how they handle the impact of their own sheer mass into a stationary object flies in the face of that argument.

I am not arguing that they are superior per se. Just that your assertion that they were inferior was wrong.

The body-on-frame vehicles (trucks) that have garnered the same sort of attention to safety as their unit-body counterparts do just as well (and better if you factor in the mass of these vehicles) in the IIHS tests. Showing that either platform can be equally safe if the money is put into R&D to facilitate it.

 

[d00df00d]

Originally Posted By: OVERK1LL
That unit-body cars from the same era as the hayday of body-on-frame cars were no better safety-wise.

That's not a fair comparison. Body-on-frame had been around for a LOT longer by that time.


Originally Posted By: OVERK1LL
Then why are light trucks, like the Ranger, Dakota, and the Tacoma still body-on-frame?

Longitudinal strength and cost?


Originally Posted By: OVERK1LL
Honda went that route with the Ridgeline.... and it ended up being a 4,500lb behemoth.

I thought you said and we both agreed that longitudinal strength was not a strong point of a unibody. Given that, I'd imagine they had to reinforce the heck out of it to make it carry load. From Wikipedia:

"The Honda Ridgeline uses unibody architecture ladder frame/unibody hybrid chassis. Honda claims this design gives it 2.5 times more bending rigidity and 20 times the torsional rigidity than the standard ladder frame only type of chassis construction, while retaining the load carrying capacity of the traditional ladder frame."


Originally Posted By: OVERK1LL
The cars themselves were the least-expensive available! More expensive cars were still body-on-frame.

I just gave three reasons why those cars could still be unibody even if it were more expensive than body-on-frame.


Originally Posted By: OVERK1LL
It weighs 2,500lbs more, yet is able to handle the impact into a stationary object as well if not better than the vehicle it is giving up 2,500lbs to. I cannot break it down any more basic than that.

But since a good deal of that 2,500 lbs is in the structure of the vehicle, it is making the vehicle stronger than it would be if it weighed 2,500 lbs less, isn't it?


Originally Posted By: OVERK1LL
You stated that body-on-frame was inferior to unit-body.

No, I didn't. I promise you.

I made two points:

1. Unibody is stronger per pound, which based on our discussions I agree should have been qualified with "except longitudinally."

2. Body-on-frame is not inherently better for occupants (which in fact you asserted).


Originally Posted By: OVERK1LL
The body-on-frame vehicles (trucks) that have garnered the same sort of attention to safety as their unit-body counterparts do just as well (and better if you factor in the mass of these vehicles) in the IIHS tests. Showing that either platform can be equally safe if the money is put into R&D to facilitate it.

As long as there is a mass disparity between body-on-frame and unibody vehicles, that point can't be proven by looking at crash tests.

 

[BuickGN]

I was going to type up a long post but suffice to say, I tend to agree with Overkill on all points but this has been a good discussion, thoroughly enjoying it.

The Ridgeline is interesting. Unibody AND a ladder frame... Interesting.

The only thing I can contribute and it's pretty meaningless is the TL seems very solid, not rattles and squeeks. The GN even with many frame and body enhancements still twists when going up driveways at an angle or over large speed bumps. I do prefer the unibody for a daily driver.

I wonder how a unibody would do with my current engine. Right now it lifts the left tire about a foot off the ground but the right tire stays on the ground. I think if I put this engine in a RWD unibody it would either solve the problem of only the left tire lifting or it would crack the body.

 

[OVERKILL]

Originally Posted By: d00df00d
Originally Posted By: OVERK1LL
That unit-body cars from the same era as the hayday of body-on-frame cars were no better safety-wise.

That's not a fair comparison. Body-on-frame had been around for a LOT longer by that time.


The Mustang was unit-body. It was also conceived in 1964. I was comparing cars from the late 80's. Both were equally "developed" at that point in my opinion.

Unit-body construction began in the 1920's. It is not a "much newer" technology.

Quote:
Originally Posted By: OVERK1LL
Then why are light trucks, like the Ranger, Dakota, and the Tacoma still body-on-frame?

Longitudinal strength and cost?


Longitudinal strength at a given weight.


Quote:
Originally Posted By: OVERK1LL
Honda went that route with the Ridgeline.... and it ended up being a 4,500lb behemoth.

I thought you said and we both agreed that longitudinal strength was not a strong point of a unibody. Given that, I'd imagine they had to reinforce the heck out of it to make it carry load. From Wikipedia:

"The Honda Ridgeline uses unibody architecture ladder frame/unibody hybrid chassis. Honda claims this design gives it 2.5 times more bending rigidity and 20 times the torsional rigidity than the standard ladder frame only type of chassis construction, while retaining the load carrying capacity of the traditional ladder frame."


Exactly. In the case of longitudinal strength (which we agree on here), unit-body is NOT "stronger". Even for a given weight. It is more RIGID. Which is the point I've been making since the beginning! Rigid does NOT equal STRONG.


Quote:
Originally Posted By: OVERK1LL
The cars themselves were the least-expensive available! More expensive cars were still body-on-frame.

I just gave three reasons why those cars could still be unibody even if it were more expensive than body-on-frame.


From Wikipedia:

Originally Posted By: Wikipedia
In automobiles, it is now common to see true monocoque frames, where the structural members around the window and door frames are built by folding the skin material several times. In these situations the main concerns are spreading the load evenly, having no holes for corrosion to start, and reducing the overall workload. Compared to older techniques, in which a body is bolted to a frame, monocoque cars are less expensive, lighter, more rigid, and can be more protective of occupants in a crash when appropriately designed.


http://en.wikipedia.org/wiki/Monocoque


Quote:
Originally Posted By: OVERK1LL
It weighs 2,500lbs more, yet is able to handle the impact into a stationary object as well if not better than the vehicle it is giving up 2,500lbs to. I cannot break it down any more basic than that.

But since a good deal of that 2,500 lbs is in the structure of the vehicle, it is making the vehicle stronger than it would be if it weighed 2,500 lbs less, isn't it?


OF COURSE IT IS! That's the point here! It needs to be stronger, it weighs 2,500lbs more! If it weighed 2,500lbs less, it wouldn't need the same structure to perform as well in the crash test.

The mass and crash performance are linked. Though somewhat indirectly. A vehicle of less mass needs less reinforcement to do well in the IIHS crash tests. A vehicle of greater mass needs more reinforcement, which is of course going to add MORE mass, so it is a catch-22 or sorts.


Quote:
Originally Posted By: OVERK1LL
You stated that body-on-frame was inferior to unit-body.

No, I didn't. I promise you.

I made two points:

1. Unibody is stronger per pound, which based on our discussions I agree should have been qualified with "except longitudinally."

2. Body-on-frame is not inherently better for occupants (which in fact you asserted).


I agree wholeheartedly with #2. I do not agree with the use of the word "stronger" in #1, it should be "more rigid", because that is the advantage.


Quote:
Originally Posted By: OVERK1LL
The body-on-frame vehicles (trucks) that have garnered the same sort of attention to safety as their unit-body counterparts do just as well (and better if you factor in the mass of these vehicles) in the IIHS tests. Showing that either platform can be equally safe if the money is put into R&D to facilitate it.

As long as there is a mass disparity between body-on-frame and unibody vehicles, that point can't be proven by looking at crash tests.


The reason for the mass disparity is that the vast majority of body-on-frame vehicles are TRUCKS and SUV's, and the vast majority of unit-body vehicles are CARS.

What the crash tests CAN tell you is how well the vehicle is going to do against a stationary or lighter object. When you step into the "bigger than" territory, that is where the issue occurs.