Incredibly ignorant automobile question, and such bad timing, too

November 22, 2007 2:54 AM

The "check tire inflation" warning light just on my dashboard is on. Am I safe to drive to Thanksgiving dinner?

As I was driving my 2007 Toyota Prius home from work tonight, I noticed a warning light on my dashboard. My owner's manual advises me to "check tire inflation". I'm pretty sure I know why... my house has an incredibly narrow driveway and I sometimes scrape the rim of my right front wheel against the curb as I pull in.

None of my tires LOOK flat at all, and my car seems to be driving perfectly. Normally I'd just take it to the Toyota dealership first thing in the morning for some reassurance and/or maintenance, but it's Thanksgiving and everything is closed. On top of that, I'm supposed to drive ~100 miles on the interstate to attend Thanksgiving dinner this afternoon. What is the likelihood that my tire will blow out on the freeway and result in my untimely death?

posted by arianell to travel & transportation (23 comments total)

Use a tire gauge to check inflation. If you don't have one, a neighbor might.
posted by Ironmouth at 2:56 AM on November 22, 2007

How a tire "looks" is irrelavent. You need to know how much air is really in there.

Spending a couple bucks on a tire gauge is your best bet. Not only will you figure out exactly how bad it gets before you get a warning light, but maintaining manufacturer's recommended tire pressure will allow you to get the most out of that hybrid you intentionally spent extra money to obtain.
posted by phredgreen at 3:05 AM on November 22, 2007

If you take it to a gas station with an air pump, it's likely that there will be some sort of crude tire pressure gauge that you can use. Pay the $0.75, inflate your tires to the recommended pressure, and then you can worry about getting it fully inspected when there are people to take a look at it.
posted by kdar at 3:07 AM on November 22, 2007 [1 favorite]

Obtaining one should be easy, even on thanksgiving. Most major grocery stores keep at least one location open on the holday. If not, then your local Wal-Mart or a gas station will have them.
posted by phredgreen at 3:08 AM on November 22, 2007

kdar has it. Go to a petrol station and use the tyre pump to inflate your tyres to the pressure stated in your car's manual.

I confess that I am bemused that this takes an AskMe question to resolve. Light comes on. It tells you to do something. You do it. Problem solved.

I'm not sure where the need to consult the internet arises?
posted by dmt at 3:32 AM on November 22, 2007 [4 favorites]

I agree that you should check it, but often those lights are just wrong. My wife just rented a Nissan Sentra and the light came on. She mentioned it to the attendant when she returned it, and he said that 80 percent of the check-tire-pressure lights in their fleet are on. They just malfunction a lot, apparently -- the feature probably helps sell the car, but the technology isn't there yet.

But do check it.
posted by futility closet at 3:47 AM on November 22, 2007

Thanks for the quick answers. I bought a cheap tire pressure gauge and found out that my tires were all equally underinflated, but not by much. Went to the gas station, inflated them to the recommended pressure, and the warning light is STILL on. Grr.

dmt, I guess I wanted to know how likely it was that the light was simply malfunctioning, as futility closet mentioned. Also, I'm a woefully ignorant teenage girl who has never owned a car before.
posted by arianell at 4:14 AM on November 22, 2007

Thirding Kdar. He's right on.
posted by sandra_s at 5:21 AM on November 22, 2007

The Prius inflation alert is incredibly sensitive - a couple of pounds low is enough to set it off. Obviously, there could be something wrong with one of your tires - the last time I couldn't get the light to stay off for very long, I had a nail in my tire.

I cannot remember if the 10,000-mile run-flat tires are standard on the Prius; I think we got them with an add-on package that included the cargo net and floor mats and crap. If you've got the tire warranty paperwork, you can check. I don't intend to run them flat, but if the feature is there you've got a smidge of insurance.

In any case, you may want to pick up a slightly nicer tire gauge (mine's a dial, which is far easier to read and was a grocery store impulse buy), check again, and check and re-air your tires after you've been on the road 20 miles or so.
posted by Lyn Never at 5:52 AM on November 22, 2007

I can't help wondering if the environmental wunderkind's inflation alert is so sensitive because underinflation means less MPG - and being all ecowarriortastic, the Prius really, really wants you to get the maximum mileage off every gallon of dead dinosaur.
posted by DarlingBri at 6:25 AM on November 22, 2007

I am driving a Corolla right now, a rental car. This light came on in the car yesterday. I called Hertz and they said they are a getting a lot calls (four that day to the same assistant) about this light malfunctioning in Toyotas. It looks like this (!) right? They said it seems to happen in rainy weather.
posted by Eringatang at 6:36 AM on November 22, 2007

On Fords at least, when you add air, you sometimes have to hold in the little stick thing that comes out of the instrument cluster to reset the (!) symbol. If it keeps coming on after you have done that, you need to have it looked at.

If you are in the US, try going to an Advance Auto Parts. They have an OBD reader that can read your engine codes (for free) and then they can tell you what the engine thinks is going on with the tires.
posted by 4ster at 8:00 AM on November 22, 2007

Sometimes temperature can kick the light off. A sudden cold night and the pressure monitor could underreport the pressure.
posted by mathowie at 8:14 AM on November 22, 2007

I was running round in a car with two tires at 20 psi before I even noticed (naughty me, I know). Low pressure alone isn't going to cause a blowout, although damage will.

As long as you don't think your tires are significantly damaged, it's always worth over-inflating them just a smidgen (perhaps 2 or 3 psi) if you're pumping them up hot, or on the nose if it's cold.
posted by wackybrit at 8:17 AM on November 22, 2007

I have a 2006 Prius and have noticed that the tire pressure indicators are very sensitive and when it gets cold (which causes the air pressure in the tire to lessen) this will come on. Don't be shocked to see it go off after you drive around a bit and the tires warm up!
posted by benATthelocust at 8:18 AM on November 22, 2007

Go about 5 pounds over the recommendation, and see if that makes the light go off. You won't have any safety issues being a little over-inflated, and your gauge may be a bit off.
posted by The Deej at 8:29 AM on November 22, 2007

I have a honda with the sensors. When it came on, I just went to the gas station and inflated each tire a bit until it went off.
posted by jeffamaphone at 8:39 AM on November 22, 2007

Be sure to check the spare tire. Some vehicles have a sensor in the spare as well which will trip this same alert. You may be just fine to drive, but with a slightly low spare.
posted by c0nsumer at 8:44 AM on November 22, 2007

Lyn Never writes "check and re-air your tires after you've been on the road 20 miles or so"

Tires should be checked cold. 20 miles is more than enough time to heat up a tire so that the gauge readings are meaningless.
posted by Mitheral at 8:59 AM on November 22, 2007

+1 on what the Deej said. More specifically, look at the recommended pressure in the car's manual, then look at the max pressure listed on the sidewall of the tire itself, and shoot for somewhere inbetween. This will make the car ride a bit stiffer, but it'll be more responsive and more efficient.

As for the spare, the Prius gives you the donut spare because it's lighter, rather than a full-on spare tire. So it probably isn't the one giving you the reading.
posted by Doctor Suarez at 10:04 AM on November 22, 2007

we just recently went through this on our prius, except that the tire had developed a leak. after a few cycles of refilling the tire at gas stations, the leak got worse, and the tire eventually blew out (shortly after we had used some of that stop-leak stuff to get us through until a trip to costco the next day).

with a new tire on it, the indicator light isn't coming on any longer.
posted by jimw at 12:20 PM on November 22, 2007

look at the recommended pressure in the car's manual, then look at the max pressure listed on the sidewall of the tire itself, and shoot for somewhere inbetween. This will make the car ride a bit stiffer, but it'll be more responsive and more efficient.


Er. Do not do this. The recommended tyre pressure is to give maximum grip/economy under certain conditions. The maximum tyre pressure is ourely related to safety in respect to the strength of the tyre itself (ir structural integrity as opposed to efficiency). Over inflation produces a very hard tyre that will not grip effectively and will give premature wear.

There are (on the charts that are at Garages in the UK) a couple of pressure listed - normal and high speed/fully loaded. Don't go over the 'fully loaded' pressures, no matter what the pressure rating on the tyre is.
posted by Brockles at 12:57 PM on November 23, 2007

I drove my mom's Nissan Sentra last week and that same light came on. I'd say a couple tires were barely a lb low but I had to add that air to make the light go off.
posted by CwgrlUp at 5:24 PM on November 26, 2007