Convertible roll-over protection?

[Norm Peterson]

Very few cars roll in an everyday situation without the driver driving like an a..hole
Drive like you should and you will never need to worry about it. This is not an SUV that has a high center of gravity.

In street driving, you're not likely to roll it unless the car gets 'tripped' by something fixed (like a curb), by the wheels digging into soft ground, or by sliding down into a drainage ditch.

On level ground, it takes around 1.5g cornering to completely unload the tires on the inside, where most cars in normal street trim can barely reach 1.0g. So you could say you've got a 50% margin.

At the track, it's different. Tires get hotter (and grippier) and you probably made other mods to improve your car's cornering performance. On true street tires (Michelin PSS), I have measured cornering g's beyond 1.25 in my very lightly modified '08 GT. That 50% margin I might have in street driving just dropped to something less than 20%, without changing a thing. It should be apparent why track day groups (and autocross sanctioning bodies, at least for race tire classes) require rollover protection for convertibles.

FWIW, I have seen a car at autocross roll over onto its roof (small Ford sedan) due to just a bunch of bad stuff combined (bad car setup in particular). Thankfully it was a low speed slow-motion roll, and I don't recall either of the occupants being injured beyond bumps/bruises/shaken up.


Norm

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[paul123]

I would have to look at the stats, but I think people get hurt more in regular cars than Verts, probably because they feel safer, so they take more risk. IIHS hasn't measured roof strength on the regular Mustang, so even that is unknown. Some cars can hold 5x their weight, and some only 2x.

As an example, Dodge Ram Pickups look like tanks. Get in one of those, set the cruise control at 90mph, no worries. But IIHS measured the Ram roof strength as "Marginal". Trucks are relatively easy to roll but its best not to roll this truck at highway speed :

2016 Dodge Ram 1500
http://www.iihs.org/iihs/ratings/vehicle/v/dodge/ram-1500-crew-cab-pickup/2016
Applies to 2009-16 models
Curb weight 5,186 lbs
Strength-to-weight ratio 2.97

 

[cyberbro]

In street driving, you're not likely to roll it unless the car gets 'tripped' by something fixed (like a curb), by the wheels digging into soft ground, or by sliding down into a drainage ditch.

On level ground, it takes around 1.5g cornering to completely unload the tires on the inside, where most cars in normal street trim can barely reach 1.0g. So you could say you've got a 50% margin.

At the track, it's different. Tires get hotter (and grippier) and you probably made other mods to improve your car's cornering performance. On true street tires (Michelin PSS), I have measured cornering g's beyond 1.25 in my very lightly modified '08 GT. That 50% margin I might have in street driving just dropped to something less than 20%, without changing a thing. It should be apparent why track day groups (and autocross sanctioning bodies, at least for race tire classes) require rollover protection for convertibles.

FWIW, I have seen a car at autocross roll over onto its roof (small Ford sedan) due to just a bunch of bad stuff combined (bad car setup in particular). Thankfully it was a low speed slow-motion roll, and I don't recall either of the occupants being injured beyond bumps/bruises/shaken up.


Norm

Very interesting info, but wouldn't this be more for a roll cage vs street car debate then a hardtop vs vert ?

If your going to track your car then take the needed steps for safety.


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[paul123]

...
For those that bought the convertible, has this thought ever crossed your mind? I can't imagine Ford not implementing an auto pop up roll over design as the majority of other manufacturers had. Is the windshield really reinforced in a way that they do not need these bars?

I am curious about this.

I googled this, and someone on stangnet was asking this same question in 2006.

I would like to see statistics comparing crash test data for cars with and without. Would auto pop up roll bars hold in rollovers at 30 mph, 60 mph? etc

 

[paul123]

this is that stangnet posting:

http://www.stangnet.com/mustang-forums/threads/convertible-roll-bar.587567/

http://www.autosafety.org/safety-loophole-ragtops-escape-roof-crush-rules

"The 94 fatalities attributed to 87 convertibles that rolled over in 2004 accounted for fewer than 1 percent of about 10,000 U.S. rollover deaths last year."

Probably similar numbers today.

I would like to see a breakdown of the 94 (or whatever the number is today), by make & model.

I think a large majority of the 10,000 involved alcohol, speeding, failing to buckle up, etc. Basically people feeling secure, and assuming more risk

 

[Norm Peterson]

Very interesting info, but wouldn't this be more for a roll cage vs street car debate then a hardtop vs vert ?

Yes and no.

On the one hand, it's why rollover protection for convertibles gets mandated for motorsports activities, at least at some point.

On the other, it was a back-of-the-napkin estimate of how close to rolling over a car might be on the street (not very), with the track estimate being strictly for comparison.

If you manage to stay on the black stuff, don't find anything big to trip over, and keep your cornering g's under, say, 0.5g (which is higher than what most folks normally corner at), there's plenty of margin against going shiny side down. Even at the limits of street tire grip under street driving conditions, you're still quite a long way away from rolling when the tires simply let go and slide.

Even on the track with hot street tires and over 1.2g grip available there's at least a little 'headroom' still left. Typical speed for me in my '08 through there is ~75 mph, with about 0.8g - 0.9g cornering all the way through that curve when I'm doing a better job of driving. The tracks you see in the still are where I went off, taken from my video of the next session (after I'd cleaned most of the mud off of the wheels and taped my brake ducts more or less back together).

[ame]



Norm

 

[Norm Peterson]

this is that stangnet posting:

http://www.stangnet.com/mustang-forums/threads/convertible-roll-bar.587567/

http://www.autosafety.org/safety-loophole-ragtops-escape-roof-crush-rules

"The 94 fatalities attributed to 87 convertibles that rolled over in 2004 accounted for fewer than 1 percent of about 10,000 U.S. rollover deaths last year."

So what percentage of the total number of cars on the road were convertibles? If this was less than 1%, those stats would argue that the risk is relatively higher (fewer than 1% of the cars resulting in more than 1% of the fatalities). If more than 1% were convertibles, at least the risk of getting into a rollover situation was lower (for any number of reasons, including greater driver caution/skill/experience).


Norm

 

[paul123]

.... If you manage to stay on the black stuff, don't find anything big to trip over, ...

cool video

I have only done that in Forza. Well one time on snow / ice, in my old car, < 20 mph. Car did a 180, hit a curb and bent an axle. I now have a better appreciation for A/S vs. winter tires.

If is the key word above. This car slid sideways on the pavement, dropping much of its speed before hitting the grass again, tires rolling with the grass. if it slid perpendicular to the grass at any significant speed, I bet it trips.

I saw a sedan rollover, < 10-20 mph. Slow speed t-bone at an intersection by a van, pushed it into a curb and over it went. Passengers hanging by their seat-belts.

I also saw the aftermath of a small pickup rollover on a tollway. The roof had totally collapsed. This was many years ago. Truck roof strength may be better these days. 2015 F150 (crew cab) is the only truck that I am aware of that is IIHS TSP, including roof strength.

Also, both of these were back before ESC. Not sure if that would have made a difference.

 

[paul123]

This is German content. Popups can help, at least for low speed rollovers. Not as much for the front seat passengers. At least in this case.

I would be interested to see what Volvos solution to the problem looks like

https://www.adac.de/infotestrat/tes...ponentId=208289&SourcePageId=31799#tabid=tab1



Opel Cascada - ADAC Rollover crash test
[ame]


Volkswagen Golf Cabriolet - ADAC Rollover crash test
[ame]

 

[paul123]

One scenario that would cause me concern is driving two lane roads. If someone in coming traffic (70mph) crosses the center line, it might result in either a small-overlap crash, or swerving / leaving the road. Of course this is a bad scenario for any car.

 

[lawprofs]

Sold my Harley. Used the proceeds to help pay for my GT convertible. Feeling pretty safe!

 

[cbrookre]

So what percentage of the total number of cars on the road were convertibles? If this was less than 1%, those stats would argue that the risk is relatively higher (fewer than 1% of the cars resulting in more than 1% of the fatalities). If more than 1% were convertibles, at least the risk of getting into a rollover situation was lower (for any number of reasons, including greater driver caution/skill/experience).


Norm

Also Convertibles will have a lower center of gravity, though in a serious accident that may be in the noise. Cannot recall where I read it but fatalities per miles driven is not statistically different either. Regardless, in crash serious enough to roll the vehicle, it is a bad situation either way. I prefer to live my life, not recklessly, but not afraid to enjoy living either. When it comes down to it all cars would be safer with helmets, 5 point harnesses and full roll cages. But it is not practical and will only make a difference in a small percentage of situations.

 

[jtmat]

Right as I was seriously considering trading my car in for the convertible version, I have my mind now stuck on the roll-over protection. I realize that the probability of rolling over in this car is probably not probable, but it seriously has me thinking...

For those that bought the convertible, has this thought ever crossed your mind? I can't imagine Ford not implementing an auto pop up roll over design as the majority of other manufacturers had. Is the windshield really reinforced in a way that they do not need these bars?

It is such a shame that these cars don't get tested for roll overs..

Get a convertible and get struck by lightening and then roll it over.

Now that should scare you...

All jokes aside, I have thought about rolling it, but immediately figured I'd die.... so I went faster. Seriously.

Heck, a lady got killed when concrete from a bridge fell on her car... that was about three miles from my house. Her luck...

Hit a deer doing 70... bad day for you. Say you make it okay, you get out to see if the deer is okay and then get struck by lightening.

Roll over, be okay but find your face in a red ant hill. Crap...

All sorts of stuff can happen.

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