In the past couple of years I have heard of two guys who's cars fell while working under them and they managed to get out of the way; another ended up with a broken arm. You don't realize how lucky they were until you meet one guy with a twisted body, or see him in a box, because his luck ran out just as the car fell. 

 

        This article is an attempt to prevent accidents related to the use of car jacks and jack stands.

 

TIRE JACKS:  The jacks that come with cars are intended to serve one purpose only: change a tire. Never use one to lift more than it was designed to lift, and use them only under the car they came with. If that car has 4 jacking points lift only one wheel at a time with it. When using any jack-the tire jack or a floor jack-be sure it is sitting on a firm surface or you have something under it to spread the load over a larger area than the jack foot itself. Something like a  wooden 2 X 6 board about 8 inches long works well on soft ground.  (theAutoist's Note:  The OE jack works great for the purpose it was designed; I'd agree with John that its not much good for anything else.  If you must raise the car on the side of the road for emergency repairs, don't get under the car without additional protection.  I use my spare wheel for that.  For example:  To repair a tailpipe that you just knocked loose, jack the car at its jacking point on the driver side & slide the spare wheel under the driver front tire.  That should give you enough clearance to get your arms under the car to reattach the pipe - been there, done that!  For fuel pump repairs, jack the passenger side up & slide the spare wheel under the rear passenger tire.  You can then slide underneath the car far enough to whack the you-know-what out of the pump - been there, done that also!)

 

CONCRETE BLOCKS:  Modern concrete blocks are made with a very dry mixture of cement that is vibrated and lightly pressed into a mold.  They are then cured in moderately heated "ovens". When used in any manner other than their intended use, cemented on all non exposed sides, they are very weak. Never use them as jack stands under a car, any load that is concentrated on a small area will cause them to break and crumble. It may happen immediately or more than a week after the load is applied, but be assured, they will break. I have some old "wet poured" air dried blocks I use when a car must be up for weeks or months, but you just can't find that kind any more. They are very heavy and you can't carry one very far with one hand. Even at that I make sure the floor is clean under them and span the entire top with a two inch board to avoid any concentrated load on them. To be on the safe side just don't use concrete blocks and bricks are even more brittle than blocks.

 

JACK STANDS:  Most jack stands are shipped with the top piece strapped or taped to the base. Read the assembly instructions carefully. On the side of the base, near the top, you'll find a hole with a tab sticking into it. Insert the top into the base and with a hammer and punch bend that tab inward as per the instructions. This is a safety feature and prevents pulling the top out far enough to make it become unstable in the base. Generally speaking, the higher the weight capacity of a jack stand the higher it will extend.

 

FLOOR JACKS:  About the simplest advise I can give here is: if it doesn't weigh 90 lbs. or more and have a jacking pad at least 6 inches in diameter it's not much of a jack. Floor jacks fitting this description will usually be rated at 2 1/4 to 2 1/2 tons lifting capacity. Look for flanged edges along the mainframe sides of the jack. Flanged edges, top or bottom, or both are indicative of a better quality jack. They can cost from $300.00 down to $50.00 on sale and a higher price doesn't necessarily mean a better jack. I know of a company that made floor jacks and some models went down an assembly line that split into three branches. Jacks going down one branch got painted orange, another was red, and the other was blue. The orange ones were generic and may have any one of a dozen brand name stickers on them. The red ones were a major tool company that every mechanic knows the name of. The blue ones were for a national auto parts chain. The orange ones retailed for about 90 bucks and the others were about 300.
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The rest of this article will deal with jacking a car and sitting it on jack stands.

  

        I keep the wheels on my floor jack well oiled and I never use one without first sweeping the floor. A rock or any piece of grit the size of a pencil lead tip can stop the jack and cause it to pull the car. When one end of the car is on stands and I'm jacking the other end, I always wiggle the jack handle sideways a little every few strokes just to make sure everything is settling in and staying solid. 

        When jacking the front of a car, and especially an MGB, make sure one of the tabs that stick up on the jack pad is hooked behind the rear edge of the cross member. One of the guys found out a few months ago that without doing that the car can slip off the jack and end up supported by the front anti-roll bar or the bottom of the radiator; whichever comes first. 

        When placing jack stands under the A-arms of a car ease the jack down a little and watch for the stands to begin tipping. The inside legs of the stands will raise up off the floor a little. Leave the jack in place and hit the bottoms of the stands with a hammer until they settle down and are standing solidly on all legs. Ease the jack down some more and repeat the above. When it seems everything is sitting solidly on the stands, let the jack down to where it clears your jacking point about 1/2 inch and hit the bottoms of the stands with the hammer again. If they feel solid give the car a good shake.  If, then, it feels stable it's safe to take the jack out of the way. Do the 1/2" jack clearance and shake thing every time you're putting the car on stands. NEVER set the wheels, brake drums, or brake rotors on blocks, NEVER. If you must have someone get in the car to help you do something, like bleeding the clutch, while it is on stands, get out from under the car while they get in or out. I don't care if the car feels as solid as the rock of Gibraltar, get the hell out from under while that's going on.

 

        I, and the old man who taught me, always followed these rules  Both he and I have worked under cars that were on jack stands all our lives, and we've never had one to even slip much less fall.  I hope this little piece will help you enjoy safe working conditions under your car.

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