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September 12, 2008

Tire Pressure: How Low Can You Go?

By John Coyle


As I wrote on Monday, last weekend Jen helped me get my old XJ6 back on the road. I was super stoked to hear it fire up, and I was even more stoked to see that the junkyard alternator we put on was alternating like a champ. But even after that success, we weren’t out of the woods. Since the car had been sitting for so long, the tires had lost a bunch of pressure—one of them was down to a scant 12 pounds—and since we didn’t have any way to pump them up, I had to drive to a gas station. Of course, there aren’t any gas stations in downtown Seattle, which meant I had to travel a little bit to get properly inflated. Jen followed in her Escort as I limped along, and as you can imagine, it was a pretty tense trip. Even though I kept my speed below 20MPH for the entire 2.5 miles, the tires were squealing so badly that I was afraid they were going to roll right off the rims. Fortunately, even though the first place we went had a broken air machine—yikes!—I managed to make it to a 7-Eleven—oh, thank heaven—and get the tires all squared away. The whole ordeal made me wonder exactly how low tire pressure can get before it renders a car impossible to drive, and if any CarDomain members have had a similar experience. So how about it? Has anyone else done anything this sketch?


12 VoLt ShOcKeR
Sep 15, 2008 at 12:32 am

I Run 3 to 5psi in our rock crawler! and drive home on it if needed…
My wifes car had a bent rim and it would leak till it was down to 20 psi and then stop….. Had to have the rim fixed to correct it…

Gary Faules
Sep 13, 2008 at 3:16 pm

Nails and screws are so common in tires that I can usually find them in at least one out of four tires. Not all of them leak but many of them create very small leaks. Just one more reason to check your tire pressure reguarly.

Sep 13, 2008 at 5:32 am

I was at 13 lbs. once on a motorcycle, rear tire. Turned out to be a bad valve stem. Good thing about a bike is that if the pressure gets too low and you’re not too far from an air pump… you can get off to lessen the weight and push it there, observing the tire most of the time if it’s real low.
Turned out to be a bad valve stem seal. I got one off a tube at the service station and was back on the road in 15 minutes for $3.00.

Sep 13, 2008 at 4:02 am

comin from a tire expert who works at discount tire gary purtty much nailed it on the head, haha way more explained than i would have put it but he is 100% correct

Sep 13, 2008 at 2:58 am

I drive a Ford Escape at work (inside a plant, 15mph or so) and the rear tires are constantly low, one time I checked them during our weekly inspection and they were only 10psi!, so that’s nothing new to me, we all hate that thing because there is always something wrong with it, but at least its still better than driving one of the Rangers or worse a minivan.

Gary Faules
Sep 13, 2008 at 1:55 am

Driving on a tire that is almost flat even at slow speed is an accident just waiting to happen. If tire pressure is too low too much tire surface can touches the ground which increases friction and wears the tire and the result is not only does your tire wear prematurely but they are also overheating. Overheating can cause tread separation which can result in a blow-out. What’s bad about this is, you may look at the tire and think it’s fine simply because it looks fine or because it’s holding air. Many times when a tire is driven on while way too low (NOT talking about a few pounds) it results in broken or separation of plys and cord. What’s bad is that this typically gets worse while driving at higher speeds and can end in a blowout. In now way should this condition be compared with a “wrinkle-wall” racing slick as tire design and cords are entirely different.

I am amazed how many people including surprisingly enough, mechanics and even guys working in tire shops, use the tire pressure they find on the side of the tire. That IS NOT a recommended tire pressure. That pressure is a MAXIMUM tire pressure safety rating and NOT INTENDED for a recommended tire pressure. Generally recommended tire pressures should be found in the handbook, glove compartment or door post. Keep in mind, tires build pressure when hot. A car that has the correct tire pressure on a hot day in July may be 20 pounds too low in December.

Tire pressure is critical in tire wear as well as gas mileage but if you don’t think tire pressure is critical to performance then just ask someone who races cars how critical it is. One pound can make the difference between being a hero or a zero.

Sep 13, 2008 at 1:34 am

My tires where at 15PSI. I think that’s the lowest I have ever had them.

Sep 13, 2008 at 12:37 am

That’s pretty low John.
You risk splitting the side wall doing that.
I would have borrowed a portable inflater or bought
a cheap one.
I wouldn’t have driven that way, even for 2.5 miles.

Paul Huizenga
Sep 13, 2008 at 12:35 am

Psssht… 12psi? 20mph? I run my back tires at 13 psi, and do more than 100 mph in the process. Of course, they’re drag radials, but still…

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