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In this youtube video, a Toyota FJ cruiser in Saudi Arabia drives up on two wheels while 5 people get out and remove the wheels on that side.

https://www.youtube.com/watch?v=MQm5BnhTBEQ

This turns out to be somewhat of a thing-to-do in arab nations (they call it hagwalah), and called 'high-skiing' stateside.

Wikipedia: Ski (Driving Stunt)

How to drive a car on two wheels (Car and Driver)

So here's where it gets confusing: based on everything I understand about differentials:

  • Open differentials (which this FJ comes with in most trims) allow the torque to follow the path of least resistance, which should then just spin up the airborne tires with the engine's power until the vehicle loses speed (coasting)
  • Locked differentials (which is a rear-only option on FJs) would spin both right and left wheels at the same speed, the airborne wheel would be forced to spin under engine power (unless in neutral, which would cause the vehicle to lose speed)
  • Limited-slip differentials would make the airborne wheel behave like a locker up to a torque value that is higher than the free spinnable wheel in the air could provide
  • Torsen differentials, used in some sports cars, use planetary gears to send torque to the harder-to-drive wheel, but require some resistance ('torque multiplying differentials, anything * 0 = 0) to operate so again would just spin the airborne wheel freely

The only thing I can think that would do this would be something like a parking brake on the rear wheels when in 2WD mode, but it would have to be disconnected or rendered inoperable on the side with the wheel on the ground, and I would also expect the (rear) wheel to come to an abrupt stop, which it does not.

How is it possible that this driver is maintaining speed for ~4 minutes while up on two wheels in an FJ cruiser, that is likely unmodified? There are other videos that show drivers doing this and switching sides, but for lesser time so it would be possible that they are coasting while their vehicles are up in the air.

Spend a little time watching more similar videos and you will realize that all these cars are stock. Theyre either rentals or stolen from hard working average citizens.

Source: 16 years living in Saudi Arabia >

http://www.reddit.com/r/videos/comments/18lovz/dude_changes_a_tire_while_driving_a_car_on_two/

  • The second step in the Car and Driver article you linked is to weld the differential shut. It also says "High-skiing for long distances requires specially built tires". Doesn't modificaiton seem like the most likely explanation here? (Interesting post, though, for sure!) – jscs Mar 19 '15 at 20:59
  • That's only if you're concerned with safety. The people in this video are clearly not at all, and multiple sources have indicated that these vehicles are typically rented. – Ehryk Mar 19 '15 at 21:01
3

This could work in a car with an open differential and an active traction control system.
When the system detects a wheel spin, it actively brakes (and locks out) the particular wheel, as a consequence the torque is directed by the differential to the wheel with traction (least resistance, as you noted). I do not know the details of the implementation in this particular vehicle, but since you're certain that the vehicle is un-modified, I would bet that this is what is happening.
Edit
After watching the video, I noticed that the airborne rear wheel does come to an immediate stop. The front wheel however coasts to a slow stop. I would speculate from this that the vehicle is in the rear wheel drive only configuration with TRACTION CONTROL enabled.

  • It is an AWD model, as you can see drive shafts in the front, but I believe you are spot on with the idea of traction control. It is the only way I can think of which would actually stop the wheels with enough force to allow them to break the lugs free (unless they were actually loose to begin with ... which seems stupidly feasible considering everything else these idiots are doing). +1 for a good answer. – Pᴀᴜʟsᴛᴇʀ2 Mar 19 '15 at 11:16
  • :) . Yes , it is an AWD. But what I was noting is that in this particular case, it is probably in the rear-wheel drive only configuration (I would assume it is selectable). Which is why the TCS only locks out the rear airborne wheel (as seen in the video) . The front wheel, throughout the video , seems to be free, even during wheel change. So, I guess the wheel lugs, at least on the front wheel, were pretty loose to begin with. Lack of safety precautions aside, that was pretty skillful I would say. – chilljeet Mar 19 '15 at 11:44
  • 1
    I see what you are suggesting now about driver selection of the transfer case, which could be. And yes, very skillful on the part of the driver. I'd be very nervous about not only skiing a vehicle, but doing it with people hanging out on top of it and with two wheels missing at a given point? They must have more oil than sense in Saudi ... I spent nine months in Riyhad and can actually say that statement is mostly true! ;-) – Pᴀᴜʟsᴛᴇʀ2 Mar 19 '15 at 12:27
  • FJs come three ways: RWD, Part time 4WD (selectable between 4WD and RWD), and Full time 4WD (aka AWD), let's assume this model was 4WD in RWD mode. Traction control will pulse the brakes when it detects wheelspin, but then free up to allow the wheel to come up to speed again. With TC I would expect the wheel to be spinning up again and again before the brakes engage: TC does not (and typically cannot) lock up your brakes and leave them locked. – Ehryk Mar 19 '15 at 14:50
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    Ultimately I think a preponderance of the available evidence points to a semi-engaged parking brake with the TJ in RWD. This is in keeping with the 'tradition' of renting a car and bearing on it (unmodified). I suspect they either disconnected the right side (doubtful) or they explored the effect of the parking brake exerting more force on the wheel it could stop than the one that is being forced to rotate, this the engine torque takes the path to the ground. Care to write this up as a second answer with this reasoning and process that eliminated the other possibilities? – Ehryk Mar 23 '15 at 4:35

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