What is the meaning of a “pinned” speedometer? Damaged on impact and needle frozen in place? How could that accurately determine the vehicle speed prior to Launching off a 100 foot cliff? With the accelerator depressed when the wheels left the ground wouldn’t (I’m thinking) the drive wheels would significantly increase RPM having much less resistance. The vehicle has only been described as an SUV no make, model, or year disclosed. Do current speedometers still rely on wheel RPM or do they now use GPS? Or could the media be merely turning a “leaked” bit of random information into extra drama concerning this tragedy?
Computer records last period, so they can know if it was 90+ mph.
Confusing at best.
I suspect in this case pinned simply means an electronic sticky note in the PCM showing the MPH.
The vehicle left the cliff at 90 but it could be that the driver took her foot off of the accelerator just before it went airborne.
Pretty sick pair of women to take those kids with them…
I’m just not familiar with modern vehicle sensors, computers, and system recorders. Vintage vehicles with mechanical drive speedometers could have the drive wheels lifted off the ground and supported with jack stands for example. Start engine, put in gear, and depress accelerator. With drive wheels pushing zero weight the speedometer could reach 60mph in 2 seconds or less with the actual vehicle velocity at 0mph. That is why I asked about GPS which could track actual velocity regardless of the drive wheels RPM. So with the technology I am familiar with the SUV could have launched from the cliff at 60mph and spun the speedometer up to 90mph by the time of impact and if the speedometer uses drive wheel RPM to determine speed would it not record that as the speed prior to impact? I would really like to learn how this works in modern vehicles.
what goes on in the head of someone who decides that they cannot live and than make the crazy leap to include all those around them? why not let the others live?
The article is not clear whether they accessed the black box that would give speed, braking, etc. for the seconds before the crash, or just what the speedometer stopped at. I’d want to see the black box data. At any rate kind of a weird group going from demonstration to demonstration. They evidently started out in Minnesota but never heard much about them.
Still, I can’t imagine someone picking that method if that’s what they did. Gotta be easier ways. Maybe another unexpected acceleration? Who knows at this point.
No, GPS isn’t used as the primary speed measurement. It isn’t reliable enough. Some cars may have it for other reasons - OnStar and the like.
Many modern speedo’s take a signal off the transmission output shaft. It is similar to the ABS tone ring type signal - a toothed wheel - read by a hall-effect sensor. The outputs are “counts” per second. Math in the ECU determines actual speed. That math can be adjusted, if needed, for different tires, or gears. I have a programmer tool that allows adjustments to that value for my Mustang since I have shorter tires. The speedo then reads what the wheels are actually doing and it may not be the actual seed of the car.
I’d guess that “pegged” at 90 mph is the data recorder function in the car only reads up to 90 mph or the SUV has a speed limiter set to 90 mph because of the tires fitted. My SUV is limited to 98 mph (uuhh, or so I’ve heard… 
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The crash scene showed a dirt leading to the cliff. If the wheels were spinning on the dirt, 90 mph would easily be attained and maintained as the SUV shot off the cliff and dropped to the water.
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Todays up-date. Investigators think the SUV stopped 70 feet from the cliff edge then accelerated straight over the cliff. Zero to 90mph in a distance of 70 feet fully loaded on gravel? That is one quick SUV! Did they check the AA Fuel dragster box on the option list? It appears the 38 year old women chose the “Thelma and Louise” method of suicide. Why-o-why did they feel a need to take the children with them?
Thank you. So the concept is quite similar to a mechanical cable between the transmission output shaft and speedometer but accomplished electronically. That is what I suspected and you described it in language I can understand. The reason I did not mention wheel-spin on the dirt/gravel was a report that the investigators found no physical evidence of rapid acceleration/deceleration on the ground surface. What happened to “This is an active investigation so I am unable to comment at this time”?
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Yeah it sounds like the CHP is saying it looks intentional. In Minnesota the one was cited for child abuse and it sounded like they had continued the abuse as they moved. Who knows what goes through some of these peoples minds when they are on the fringe. I’ve even heard someone say they weren’t going to have kids because of the fear of climate change. People need to chill out a little.
Probably not…per the article:
“Certainly, that [speedo reading] does not mean the vehicle was going that fast,” Robertson said Sunday night.
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We can discuss the physics of the speed reading, but there’s really no way to discuss driving off a cliff and deliberately killing yourself and your family. Like Jonestown. What can you say about that? People can do amazingly bizarre and horrible things.
Maybe the person driving had their metabolism shoot through the roof as they left the ledge with their foot buried in the pedal and the rear wheels started spinning at 90 while on the way down.
Those two should not even be allowed to have a burial plot.
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If the children are all missing why is it assumed they were in the car?
Well they found three of them that had been ejected and they seemed to travel as a group. No one home so figured they were dumped in the drink and the waves carried them out. Shoulda heard by now if they had gotten away somehow but not much opportunity to jump free.
That’s a pretty remote spot, so three African-American kids walking on the road or hitching a ride would be unusual, and by now someone would have reported something. The ocean is very rough with lots of big waves, currents and tides, and pretty inaccessible. Divers can’t get near the shore at all. Bodies may show up after a while.
This Hall-effect sensor is called the Vehicle Speed Sensor (VSS).
In 1995 GM installed hundreds of thousands of defective ones in their product line, all of which failed in the first year or two but there was never a recall. The owners got to pay for GM’s mistake.
If they failed in the first year or two, they would have been covered by the new car warranty so no cost to the owner, no? That’s the purpose of the new car warranties to protect against problems with a particular part.
And GM since installed million and millions that have worked just fine. Other car makers as well. Pretty much the standard speedo sensing device. Same technology is used for ABS sensing, crank position sensing, cam position sensing and more.