A Case of the Flats – and Why

  • February 18, 2024

Have you had the problem of a tire that won’t hold air? It doesn’t go flat outright, just slowly – as the air bleeds out over time. You may not even notice it until it’s almost flat, because it takes a keen eye to be able to tell by looking that a modern, short sidewall tire that is supposed to be inflated to 40 psi is only holding 22 psi.

Many people don’t look – much less check – because they have been conditioned to rely on their car’s tire pressure monitoring system to let them know (via a light in the gauge cluster) when a tire is running low. These tire pressure monitoring system have been federally required for many years now, in the wake of the  Ford Explorer/Firestone tire debacle, which you may remember. People drove their Explorers on under-inflated tires at high speeds; the resultant tire failure resulting in barrell-rolling Explorers and a number of injuries and deaths.

The tire pressure monitoring systems were supposed to correct the problem of people not checking their tire pressure and driving around on dangerously under-inflated tires (low air pressure increases friction which causes increased hear build-up and that can lead to tire failure; under-inflated tires also affect handling/braking performance).

The problem is the “check tires” warning light that’s supposed to motivate people to check their tires’ inflation pressure is regularly ignored, in part because the light not uncommonly comes on when the tire pressure is fine. After a while, people stop paying attention to it – even if it’s on all the time.

But why are the tires losing air?

It may not be for the usual reasons, such as a nail in the tread. It is now common for sound-seeming tires to just slowly lose air for no apparent reason. It is not uncommon, when this happens, to have to manually check the tires every week or two – which people ought to be doing regardless – and fill the tires back up to the specified pressure. Which they ought to not have to do, unless there is a nail in the tread or some other kind of damage to the tire or the valve stem.

Often, there isn’t.

What there is, on the other hand, is corrosion on the bead surface of the wheel. This is a common problem with the aluminum wheels almost all new cars now come standard with (and have come standard with since roughly the early 2000s). Aluminum wheels have a number of virtues, the chief one being they’re much lighter than steel wheels and that lowers the curb weight of the vehicle as well as decreases rolling resistance, both of which improve fuel economy and performance. Aluminum wheels are also attractive; they can be cast in all kinds of different styles and – unlike the plastic hubcaps that used to come with steel wheels – they don’t lose their hubcaps in the curves.

But they do corrode.

And that is why your tires may be leaking air.

It’s not the tires’ fault at all. The problem is that the seal between the tire and the wheel isn’t air-tight, on account of the corrosion that built up on the wheel that the shop you paid to install the tires didn’t grind off the wheel. The reason they didn’t being it takes effort and time and that detracts from getting your car in and out of the shop as quickly as possible.

Now it’s on you to make sure you’re not driving around on under-inflated tires. The problem there is you probably will, because it’s easy to forget to check (and fill) a tire that is constantly losing air. Inevitably, you’ll drive around for awhile with it down five, maybe ten pounds – or even more. Then it will wear unevenly or more quickly – and when you try to get warranty action, the tire store will deny it and tell you it’s all you’re fault because you abused the tire by not maintaining proper inflation pressure!

This is why it’s good to know about aluminum wheel corrosion – and what it does unless the corrosion is removed before a new tire is installed.

. . .

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The post A Case of the Flats – and Why appeared first on EPautos – Libertarian Car Talk.

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