When new tires act old.

Dear Car Talk

Dear Car Talk | Dec 01, 1991

Dear Tom and Ray:

In August I had new front tires put on my '80 Olds Calais. The problem is they keep losing air. I have had it back to the tire company four times trying to resolve the problem, but they have checked and they say can't find anything wrong.

TOM: Well, Jo, we can look at this problem in terms of industrial stoichiometry; what goes in must either come out or stay inside. And since the air isn't staying in the tires, it must be coming out from somewhere.

RAY: There are only three possibilities that we can think of. The first is that the tires are defective. But that's not very likely.

TOM: The second possibility is that air could also be leaking out from around the valve stem (where you put the air in). But this kind of leak is relatively easy to fix by simply putting in new valve stems.

RAY: I'm going to assume that the dealer has looked into both of these possibilities already. Which means that the leak is probably coming from your rims. If the rims are bent or rusted, air could leak out from between the rim and the bead of the tire.

TOM: This kind of leak is hard to find because, usually, the air only leaks out under "dynamic conditions." That means the air doesn't come out until you're driving around--going over bumps and deforming the tires under the weight of the car.

RAY: So there are two ways to see if the rims are causing the leak. The easy way is to put on new rims and see if the leak stops. There is a more scientific approach, but it does require a lot more ef?fort. Basically, you have to recreate the dynamic driving conditions under water.

TOM: For instance, you could drive this car into a nearby river. Make sure you load it up with plenty of cement blocks to keep the tires in constant contact with the river bed. Then get under there with your scuba gear and see if there are any bubbles coming out from around the rims.

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