So I've gotten on a kick of watching dashcam videos on YouTube. One thing I've noticed is that it seems really easy to knock the wheels off a newer vehicle.
I don't mean cracked rims, but completely separated knuckles, spindles control arms etc.

Are they intentially designed to do this nowadays? Or just a consequence of weight loss and efficiency?

Surprisingly, I even see this on trucks too.

I don't recall ever seeing stuff like that on older vehicles, at least ones that weren't completely clapped out or rolling tetanus mills.

My guess is some of both. Lighter, but also part of the "crumple zone". The energy of a crash has to go someplace; break the car before breaking the occupants.

Not 100% on the reasoning, but the suspension on newer vehicles is so easy to replace, my bet is yes, let the force destroy the consumables/sacrificial

Seems to me the wheels & tires are located further out, so to speak, more nowadays than on older cars.
Example: my '68-'69 Road Runners vs my '97 Mustang.
So the edge/corner tags the object sooner, maybe before the body depending on angle/object height/whatever.
Plus, control arms & etc are analyzed down to minimums, not the big honkin' things our older cars have.

Everything is as light (both in weight and duty) as is possible. Lots of aluminum, too. I doubt that the designers are thinking of repairability. They certainly don't think of repairability in any other areas that I can think of.

May seem like a silly example, but I remember w-a-y back when that show 'COPS' started, they'd show cars with tires blown off, rims shredded , but the suspension wouldn't just 'break away' as it was being drug down the road at high speed. It would usually ground down, until the car was stopped by something (or someone) else.

I remember one episode where a full size GM had ground thru the rotor all the way down to the control arm. Bent? Pretzeled? No doubt, but it didn't come apart.

My thinking, from a technical standpoint, I could see the advantage on having a " breakaway" front wheel assembly, and then completely negating the difficulty of preventing it being rammed into the passenger compartment in a crash, as a wheel is a relatively large robust object, so separating has upsides as I see it. Loose objects post crash in public don't seem to have the same liabilities/concerns that they do for spectators at the race track.

There are no crush zones in suspension parts, and wheels/suspensions are not designed to break away from the vehicle. I've been involved in vehicle damage claims since 1994, and vehicles now are no more or less likely to get their wheels torn off in a collision than they were in 1995. They've used aluminum in spindles, etc, for a long time now. The use of aluminum is more common than it was 25 years ago, but it wasn't as though everything was cast iron 25 years ago. Also, no manufacturer would purposely design a car to have a 100lb (or more) object intentionally separate from the vehicle and go flying into another vehicle, or a crowd of people, etc. The liability would be extraordinary.

Front wheel drive and the MacPherson Strut front suspension are the culprits. No (or a very small) upper control arm makes for a very light, efficient, and compact front suspension. But it's not nearly as robust as twin A arm front suspensions because the lower control arm must do it all.

While I would agree with the above statement that current front suspensions are not much if any more fragile than those from 1995, the MacPherson strut front suspension has been wide spread since before that time. If you go back into the 60s and 70s before MacPherson became wide spread, you don't see the type of suspension separation that you see now. At least not nearly as often.

And you don't see suspension separation on larger rear wheel drive vehicles like full sized trucks and vans even today. Those vehicles aren't suitable for MacPherson Strut front suspensions due to the heavier loads that the front suspensions must deal with. On those vehicles, the front suspensions are basically as robust and resistant to separation as their counterparts were 40 or 50 years ago.

Front wheel bearings are another casualty of lighter, cheaper, more efficient....and more fragile modern front suspension designs. The ball bearings used in most MacPherson Strut front suspensions won't tolerate much in the way of side impact. Curb one once and it will be noisy thereafter. That wasn't true of the tapered roller bearings that we have in our muscle cars. The tapered roller can withstand much more side impact with little or no problem. That was the reason Mopar used tapered rollers in our rear axle bearings rather than the ball bearings used in the 'Green' bearings that many people like to use so that they don't have to adjust preload. Ball bearings on the rear of our cars do survive better than they could in other applications because they are better supported by the axle shaft.

I think it has a lot to do with the design of new cars for easy assembly and lightweight parts.

Combine Aluminum control arms & spindles which were not the norm 25 years ago and the easy to assemble strut suspension, it becomes easy to separate the suspension from the car in an accident.

I have never replaced a broken metal control arm, I have seen them bent to a pretzel, but not broke. I have lost track of the number of snapped aluminum control arms I have seen or replaced. Combine that with struts which bend easily in an impact and only have a rubber isolated bearing at the top held in by 3 small bolts, it doesn't offer much in the terms of impact resistance. I have replaced multiple struts pulled out of the bearing mount that were not even in a serious accident.

It's just the nature of modern design.

I guess a lot would depend on the specifics of "purposely".

Any past case history on the pursued liability to the manufacturer for separated parts caused by another's negligence in an accident?

I have never heard of this concern, not saying it does not exist, yet.

I've seen plenty of trucks/vans over the years with the wheels torn off. Hit the rear wheel on a solid axle-equipped vehicle hard enough, and you'll snap the end of the shaft and the wheel will come right off.

It doesn't happen often, thankfully. Anyone wondering why a manufacturer wouldn't design a wheel/suspension to purposely come off, or even design it with the intent that it might come off, can refer back to Senna's death in F1.

That is a clumsy sentence on my part and does not reflect what I meant to say. I have a Ram here now that we replaced the rear diff in due to one side sheered off. But the point of this discussion is about today's vehicles being more prone to that than their predecessors. Not whether it happens at all. And I guess that I could have been clearer and have said that in my experience, today's full sized truck suspensions are no more prone to separation than yesteryears. And certainly not nearly as frequently as front wheel drive cars. Which is in keeping with the original subject of this thread and more in keeping with what I meant to say.

Gotcha.

Rough estimate, I probably inspected 18-20k vehicles before I moved into my cushy corporate gig ( ) and stopped getting my hands dirty, but I can honestly say I never noticed an increasing propensity for suspension separation as time went on.

Completely depends on the time frame and designs used for reference. Let's use a very popular car, say chebby Impala as an example. It is my position that a 1995 Impala with twin A arms resists separation far better than a 2005 Impala with MacPherson Struts. But the 2005 is probably about as prone to separation as a 2015. Because of the change in designs and different approaches between the '85 and the '05/'15, the suspension separation became more frequent. Just looking at the difference in suspension components clearly shows why.

And I often look at 'cripples' at the salvage auctions to rebuild. Meaning late model cars with one of the suspension corners displaced or missing. They are often a little better bargain than usual and a front 'knee assembly' usually costs $150 or so and can be changed in a few hours when the inner structure is still in it's original location. On the more substantial double wishbone front suspensions like the rear wheel drive Impala I referenced above or on any full sized truck or van, the inner mounting structure is much more likely to have also sustained damage due to the ruggedness of the suspension on those vehicles. So, on late model full sized trucks, I will consider one with a rear wheel knocked off because there is a good chance that a replacement will simply bolt in. While a front wheel knocked off more often means body and frame mounts have been disturbed. Of course, a thorough in-person inspection is absolutely necessary to determine the particular extent of the damage.

How about one last example: break an axle at the drag strip on one of our Mopars and what happens to the wheel and tire? They usually stay in place due to the way that the axle is retained by the flange at the hub. Now, break an axle on a chebby at the strip. The poor chebby guy is probably looking at a quarter panel problem, too.

Again, different designs, different outcomes in the same application.

I'll say again that I believe that the MacPheason Strut form of suspension is much more prone to separation than the older suspensions that had substantial upper and lower control arms. And as the MacPherson Strut front suspension has became more predominant in production cars, so has the suspension separation frequency.

I can understand the breakaway as a crumple zone feature but question the benefits. Often in the videos the 3 wheeler carreens out of control. Not surprising when when 25 to 50 percent of your stability disappears along with 50 to 75 percent of your braking.?

Older stuff that retains it's integrity better might have a better chance of control.

Mind you, I fully understand that driver skill is a huge variable. GM ignition switch ring any bells?

Repairability is a whole other thing, odds are the vehicle will be a total either way. There's a reason derby cars tend to be more traditional in construction, they bend but don't break.

There are no breakaway, crush zones, etc...in suspension parts. There are no parts designed to separate from the vehicle in a collision. There are no benefits to having such things. Manufacturers don't want a chunk of metal, a wheel/tire, a window, etc. flying through the air addressed "to whom it may concern."

You're right about the loss of stability and braking should the car keep moving/stay on the roadway. That does happen, but in my experience, it's the exception and not the rule.

When we raced karts we always used the lowest grade bolts as kingpins. The idea being it would bend or shear the bolt rather than damage the spindle or bend the frame. I suspect they're using this reasoning as well. Better to have a replaceable component break off than to bend a frame.

You did that because you cared about having to fix your kart, paying out of your pocket, and wanted to keep repair costs down. It makes sense in your case. However, the OEM's don't give a rat's a$$ about that. It's not their car, and they aren't paying the bill to fix it.