How to choose a floor jack

Dear Tom and Ray: I am looking for a floor jack for my personal use and need some advice on how big a jack I need to get. I know that a two-ton jack would be plenty to work on a regular car -- e.g., a Civic, Altima, etc. However, we also happen to own a Chevy Suburban with a gross vehicle weight of 7,000 pounds. I tried calling some shops and was told by some that a one-and-a-half- or two-ton jack would be enough, since the jack will not be lifting the whole truck. But there were some that said I need to get a jack that is big enough to hold the whole weight of the truck, which would be more like three or three and a half tons. What do you recommend? If I have to get a three-and-a-half-ton behemoth, I probably would not bother working on the Suburban on my own. If I plan to work on trucks and SUVs in the future, do I need to get a jack with a higher range?

Isao

Tom: Yes, you do. Our rule of thumb is that a floor jack needs to be rated for at least three-quarters of a vehicle's gross weight. So, according to our rule, a one-and-a-half-ton (3,000-pound) jack could lift a car that weighs as much as 4,000 pounds -- or two mothers-in-law.

Ray: So, if you want to work on your 7,000-pound Suburban, you'll need to get a three-ton jack, Isao.

Tom: Here's why: It's true that a floor jack does not have to lift all of the car's weight. It has to lift half of it -- taking two wheels off the ground. But when you operate at the limit of the jack's ability, two things happen.

Ray: One is that it gets very hard to lift the car. But second, and more importantly, you leave no room for error. And unless the jack is absolutely, perfectly centered AND the weight of the car is perfectly centered (which you can't always count on), the jack's linkage bars can begin to distort under the maximum weight, causing the jack to flip and the car to come crashing down.

Tom: It's never good to operate anything at the absolute limit of its ability. For instance, some scientists say a man can go seven days without water in 90-degree heat, as long as he doesn't move. Does that mean we should all lie down and wait seven days between drinks?

Ray: Similarly, you don't want to be under a Chevy Suburban that's held up by a jack that's quavering at the limit of its abilities.

Tom: So, you have three choices, Isao. You can get a three-ton jack, or let someone who has one work on your Suburban. Or, alternatively, you can buy a set of properly rated ramps, and use those to get enough clearance to work under all of your cars.