I go through a lot of used tires. To save money and add convenience, I manually dismount and mount the tires myself, using only a GM lug wrench (one end has pointed tip). This inevitably damages spots on the "bead" of the tire, resulting in leaks. I want to buy the proper tool that will prevent this damage while mounting tires for, say, around $50, if available. Can I get by with simply buying a crowbar, or are there other, more specialized tools that I can buy for less than this price?

TOM: There is a tire-mounting tool that you can buy for less than 50 bucks. It's called a visit to your local gas station, where you ask them to mount and balance the tires for you.

RAY: Actually, you could just upgrade to some tire irons. That's a set of two, or sometimes three, specialized, curved-end metal bars that serve as levers that help you pry a tire off a rim - or get it back on there.

TOM: That'll be a little better than hacking at your tires with a lug wrench (which is designed to remove hubcaps) and a hammer, which probably is what you're doing now. But it's still less than ideal. You still can damage the bead with tire irons, and it's very difficult to add the adhesive that's supposed to go around the inside of the bead to reduce the chance of leaks when you inflate the tire.

RAY: So what you really need is your own tire-mounting machine. That's a machine that does what you're now doing by hand, but it does it with consistent pressure so the tire bead doesn't get damaged.

TOM: In order to mount a tire to a wheel, you have to pull the bead of the tire (the inside edge) over the lip of the wheel. Then the tire sits inside the wheel and, when inflated, pushes out against that lip to form an airtight seal.

RAY: You're doing it the old-fashioned way, with brute force. The only problem is that sometimes you pull too hard and damage the tire bead.

TOM: Unfortunately, I doubt you'll be able to find a tire-mounting machine for $50. I think you're looking at more like 10-20 times that, even for a used one. I'm guessing $500 is the minimum you'd pay, and the price is more likely to be $1,000-plus.

RAY: And then there's the issue of balancing the tires. All new tires look perfectly round and evenly weighted, but they're not. And when they're spun at high speeds, like when you're driving 40, 50 or 60 miles per hour, those imperfections become more obvious. That's why your car probably vibrates like a bad washing machine at highway speeds.

TOM: So you need a tire-balancing machine, too. That's at least another grand.

RAY: And by then, you might as well buy a couple of squeegees, install some gas pumps, open a filthy restroom and make a few extra bucks on the weekends.

TOM: There's nothing inherently wrong with buying good used tires for your car. But they really should be balanced. That's a safety issue at higher speeds. And if you're damaging the bead and causing every new-old tire you buy to leak, you may want to consider having someone with the proper equipment mount and balance them for you.

RAY: Maybe the place you're buying the used tires from has the equipment, and can install them for you? Unless, of course, you're stealing the tires. In which case, we'd advise you to immediately start stealing the wheels with them. That way, they'll come pre-mounted and balanced.

I woke up screaming the other night, as I'd dreamed I had just pumped five gallons of diesel fuel into my Prius. Back in the '50s, I heard on the radio (maybe it was your grandfather's show, "Buggy Talk"?) that adding a gallon of diesel fuel to a full tank of gas would add "top-cylinder lubrication." I tried it several times on my '53 Plymouth on trips, with no ill effect. What would happen if I did that today?

TOM: Your wallet would be $1,000 lighter.

RAY: It most likely would ruin your catalytic converter.

TOM: That's why you got away with it in your '53 Plymouth, which had absolutely no emissions equipment.

RAY: Diesel fuel is cleaner than it used to be; you no longer see sticks and rocks and dinosaur bones in it. So it mixes easily with the gasoline, and probably would pass through the fuel pump and fuel injectors without doing harm.

TOM: But it probably would kill your catalyst, and you'd never pass an emissions inspection without that.

RAY: When a customer of ours accidentally puts diesel fuel in a gasoline car, we have him or her tow it in. We remove the gas tank and drain it completely. Then we refill the tank with gasoline, and run the fuel pump with all of the fuel injectors removed - we just let the fuel injectors spray into a container.

TOM: So that second tank of gasoline flushes out the fuel line and the injectors without running the gasoline through the engine.

RAY: There's obviously a small amount of diesel fuel that was left on the walls of the tank. But that gets dissolved in that second tank of gasoline and diluted to the point where it's harmless.

TOM: Hope that helps. Now, pour yourself a cup of warm milk and go back to sleep.

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