If the jack stands are used properly, then yes, they are very safe. A couple things to be 100% sure of when using them: -Make sure they car is on level ground. This should be pavement, asphalt, or some other hard, solid surface.
Give your car a few light shoves to verify that the stands are all in place. Ensure the vehicle is level, with all stands are raised to the same height. If everything checks out, your vehicle should be safe to leave on stands indefinitely under normal conditions.
Assuming your jackstands are rated to support your vehicle's weight, the chances of them failing is very small. You are more likely to make an error in placing the stands and have the car fall or slide off them than they are to fail.
Is it safe to leave a car on jack stands overnight?
Leaving a jack up overnight is dangerous to the car and its surroundings. Not so much to the jack per se, but even the slightest leak can cause it to collapse over time. Also the jack, like a torque wrench, should be stored with the valve open and the jack dropped, to reduce issues with the spring.
When using safety stands, the capacity rating is the most important factor to consider. Typically, jack stands are rated at 3 tons up through 20+ tons. Unless stated otherwise, jack stands are sold individually, and MUST ALWAYS be used in pairs. Capacity rating is based on what the pair of them can support together.
Jack Stands: How safe are they really? (Weakest link revealed.) | Auto Expert John Cadogan
Can a jack stand fall?
Every year, thousands of amateur mechanics and automobile enthusiasts suffer severe and potentially fatal injuries when a car jack or jack stand collapses as they're working beneath a vehicle. Sometimes, car jack and jack stand injuries result from improper use.
Since the jack stands are rated for 2 tons (4,000 lbs) you should be good to go, especially since you're not technically lifting the entire weight of the car on one corner. As the others have said, you'll be fine. Personally, I bought a set of these jackstands and I'd be reluctant to use any other type now.
For as long as it takes for the body sub frame to rust and allow the engine section to fall on the floor. Depending where you have it on stands, that could be months to many years.
It is safe as long as you use a quality jack stand that can withstand the weight of the car including the passenger and also don't forget to place a concrete block or stone around the opposite tire so that your car won't slip. If it's on solid level ground, and you have a good jack. I would do it.
For most sedans and small cars, a two-ton jack will be sufficient for raising a corner. A pickup truck or SUV could require twice that rating (four tons) to give you the margin of safety that you need.
Lifting a vehicle that exceeds the jack's capacity
One of the first things you should check before attempting to lift a vehicle is your floor jack's weight capacity. Ideally, the tool should comfortably lift more than three-quarters of your vehicle's total weight.
This is especially crucial if you're trying to put all four wheels of the car in the air, as the act of jacking up one end of a car can easily cause stands already at the other end to tip forward.
Find a flat, level surface to park your vehicle. Work on a clean, paved area so your vehicle is on even ground. Avoid jacking your vehicle in a place that's bumpy, near heavy traffic, or covered in gravel. Make sure each side of your vehicle is level so the jack or jack stands can't slip out from underneath it.
It is relatively safe to use 4 jack stands at once, if they are quality stands. But I still prefer to keep one or two floor jacks under the frame someplace, just incase something DOES break. Redundancy never hurts.
4 jack stands is fine, I do it all the time. It's just as stable if not more stable as having the car on a lift. Once the car is on all (4) stands, yeah, it's fine. I think the unstable part is when it's on (2) stands and you're raising it to place the next (2) stands.
The safest way is on four stands. With all wheels off the ground (and stable) you negate the possibility of the car rolling/ moving. Even a slight movement could mean slippage off the jack stands. And you don't need that while you are under the car hustling away.
Using a car jack can be intimidating, as well as dangerous. But with the proper safety precautions and procedures, as well as plenty of common sense, you can lift your vehicle and fix a flat tire without hurting yourself or damaging your vehicle.
While ratchet jack stands are safe, pin jack stands are considered more reliable because they include a locking pin that makes it almost impossible for a vehicle to slip through the base.
For answering what size jack stands do I need the solution is a stand that is rated for the weight of your vehicle. For instance, a 2-ton car should use jack stands rated to hold 2-tons. There is also nothing wrong with using higher weight rated jack stands, as it gives extra margin of jack stand safety.
If it's road legal, then he's entitled to park it there in that manner, as long as the stands are safe, what other parking he has available doesn't change that. If it parked causing an unnecessary obstruction, that is a different matter. If that's the case, then that's fine...
It shows that you can get a lot of strength for not a ton of money, and it's worth spending $40 more on something that could save your bacon. The test also shows that expensive jack stands really do work better than the rest. Be safe, folks. Get a decent set of stands and wrench happily and safely.
Set the jack stand underneath the pinch points of your vehicle. The pinch points are located on the sides of your vehicle behind your front tires or in front of your rear tires. Slide your jack stand in from the side of your vehicle.
For example, a full-size family saloon will probably only need a jack with a 2-ton capacity to lift it. The best car jack for an SUV or 4x4, meanwhile, may need a capacity of at least 3 tons. One of the most important factors to consider is how much your trolley jack can lift.
If the jack is made up of iron then it will get rusted with constant water contact. Some rust though, don't make the material weak altogether, some are just surface rust you can just sand it of and paint over it with anti-rust paint. But if it got to the point where the rust eats the metal, then it's definitely bad.
