Would a tire that is losing pressure rapidly be safer on the front or back of the car?

May 17, 2009 3:10 AM

I have a tire that keeps losing pressure rapidly. In a car with front wheel drive, would it be safer to have the tire on the front, or the back? At least until the tire can be replaced.

How would this effect (or not effect) the car?

posted by Malice to travel & transportation (18 comments total)

I'd say put it on the rear wheel, since that's not driving or steering you and isn't as important for braking.

Also depending on what's wrong with it, you quite possibly could have the tire repaired for $20ish. Any place that does tire stuff will probably be happy to do so.

If you do replace it, you may have/want to replace it's opposite. I've heard from a number of sources that it's "bad" to have tires of very different tread on your drive wheels. I don't really know the details so maybe it's just hooey.
posted by aubilenon at 3:18 AM on May 17

Nthing that it's usually pretty cheap and quick to have a punctured tire plugged. Unless the tire is worn out or there's a hole in the sidewall, just get it fixed.
posted by jon1270 at 3:28 AM on May 17

If the tire has decent tread, get it repaired, some tire shops will even do it for free.

I'm assuming you have a mini-spare so you can't just throw that on?
posted by HuronBob at 3:29 AM on May 17

Normally you can go into an auto parts place and get Spare Tire In A Can.
You spray it into your tire and then go driving at about 45 for 20 minutes so all the sealant spreads out on the inside of the tire.
Costs about five bucks.
posted by dunkadunc at 3:39 AM on May 17

Note that if you use the spray-in stuff, the tire shops won't repair the tire. That stuff is to be used only in dire circumstances. There's also a good chance that the tire will be wobbly and out of balance after you put the stuff in. We have a can of that stuff in the car, but it will only be used as a last resort.
posted by azpenguin at 4:40 AM on May 17

The leak is either patchable or not. If it is patchable, that should be done pronto by you or a shop.

If it isn't patchable, you should get a new tire or eventually that sucker is going to really open up and you will get a new tire, a towing bill, and great inconvenience.
posted by samsm at 5:13 AM on May 17

When you say it loses pressure rapidly, how rapidly are you talking about?

It is always safer on the rear, regardless of drive train. also it bears saying that you should definitely not drive this car fast if there is even a slim possibility it will blow. As everyone else said, get it plugged pronto.
posted by JJ86 at 5:35 AM on May 17

You are risking your life and the lives of others by knowingly driving a vehicle with a safety problem. You might even be invalidating your insurance coverage and risking criminal charges if something happens. Get it fixed or take the bus unless you want to be eponymous.
posted by srboisvert at 5:44 AM on May 17 [2 favorites]

You need to get the tire repaired/replaced asap, if it's losing air as quickly as you say. Also, the tire itself may be fine and the valvestem may be faulty. This has become a common problem in recent years, owing to ever cheaper parts being used.
posted by Thorzdad at 7:07 AM on May 17 [1 favorite]

I've been surprised over the years at how many of my tire leaks were caused by a bad valve stem core ((and that is a very simple DIY repair). Make sure tire is properly inflated, remove the valve stem cap and apply a little soapy water. If you see bubbles, your valve stem core needs to be replace. They cost about a dime at your local auto parts store.
posted by buggzzee23 at 7:17 AM on May 17

Tire repair or replacement is one of those cases where it's actually a good idea to go to the shop, whip out your credit card, get it fixed or replaced, and worry about how you're going to pay for it later. Because the bill is the better of the possible "paying for it later" scenarios that you could encounter.

For your drive to the tire shop, it does seem like the lesser of the two evils would be to run the bad tire on the back. This is opposite of the conventional wisdom on tire tread, where the better tires should always be on the back, regardless of front, rear, or all wheel drive.

I've paid anywhere from $5 - $15 to get a tire fixed, and a repaired tire is basically as good as new. One of the few remaining great deals around.

Good point on the valve stem - I just read about a big valvestem recall, too.
posted by altcountryman at 7:40 AM on May 17

1- On the rear is best in this situation. A low tire has more rolling resistance and more grip, and that's where you'd want it. (Just like having newer tires on back.) In the front, it would cause steering issues. In almost all situations, you want your car to "understeer" rather than "oversteer" if it is going to lose traction. What that means is that if you are in a situation where you are making an emergency steering maneuver, you want the front tires to be the ones to lose grip first. If the rear tires lose grip first (oversteer), you start spinning around and this is very hard to regain control from. If the front tires lose grip first, all you do is keep going in the direction the car wants to. The slipping tires slows the car down and you quickly regain control.

2- Could well be the stem- if you go to an auto parts store, they have little valve stem "wrenches". If it's leaking, try just tightening it up. (The little spring loaded valvestem just screws into the rubber tube that sticks out of the tire rim. They can get loose and not make good contact.) Worth a shot.

3- Has it always been leaky since the tire was installed, or is this a new development? If it's always been leaky, could be just a bad job of mounting the tire. Maybe they didn't clean the sealing rim all the way, or didn't put enough of that magic sealing juice on there. Taking it to a tire place and getting the full remount, patch, test, stem replacement, etc., treatment should only cost you $25. Well worth it.

(Usually what happens is that you ran over a nail or a screw. It punctures the tire, but remains in the tire, mostly sealing the leak. One day, it works itself loose and the tire quickly loses pressure. Bad news if you are on a sweeping curve on the side of a hill...)
posted by gjc at 7:57 AM on May 17

When I had a tire that wouldn't hold air, it turned out to be a bent rim that was the problem.

The rear has less weight (assuming the engine is in the front), no drive, and no steering, so the rear is best.

But I'd only drive the car to bring it to the repair shop.
posted by winston at 8:04 AM on May 17

The rear is best, however, you should repair the tire at a shop for <> Good Luck.
posted by QueerAngel28 at 11:08 AM on May 17

Wow, I don't know why you guys seem to think having a faulty tire on the rear is best. I'm an accident reconstructionist and I can count on one hand the number of accidents caused by a faulty front tire. I can count hundreds of cases caused because of a blown rear tire.

If a front tire blows, you can still steer your car. Even if both front tires blow, you still have some amount of control. When a rear tire blows you have no control at all. Your rear end will slide around like its on ice, and point your car in any direction the wind blows.

Of course the real answer is to get the tire fixed.
posted by sanka at 3:45 PM on May 17

At pretty much everyone in this thread:

If I'd had the money, the tire would be fixed. Thanks for your concern. There is NO bus around here, I do not live in a large city. If I didn't drive, I wouldn't get to work.

In any case, I'm marking the best answer and the tire did blow out before we could get a new one, and we're currently on a donut.

It has been doing this for a very long time and has been "repaired" by NTB four times. Well, it's gone now anyway. Thanks for the answers that actually addressed the question.
posted by Malice at 11:04 PM on May 17

There was a recent problem with tire valve stems from China. It seems that the rubber did not contain the required sunscreen, so they decay rapidly in the sunlight.

If this is the case, your stem could fail completely at any time.
posted by Midnight Skulker at 7:04 AM on May 18

A low tire has more rolling resistance and more grip, and that's where you'd want it.

I'm concerned that you (Malice) marked that best answer when it is based on a fundamental flaw of reasoning. An under inflated tyre has less grip than a properly inflated tyre in normal road driving.

Any pressure over or under the nominal inflation range of a tyre produces less grip. Less or more grip for inflation pressure within the nominal range is specific to the loads and expected surfaces for an application. The sentence I have highlighted is fundamentally wrong without considering any of those provisos, especially if normal driving is being considered.

Also, despite you getting a little antsy about people 'actually answering the question' it mainly revolves around your missing their point.

It is not safe to have an under inflated tyre (especially one that keeps losing pressure) on either end of the car. and any justification for either end of the car is missing the point. I agree that the rear is less likely to cause an accident in the first stages of deflation, but I also think that it will be much more obvious to the driver when the tyre goes down if it is on the front as this will be flat sooner. In the latter stages of deflation, the rear is more likely to cause an accident. However, this is really all hypothetical, and 'safer' is not a word that is appropriate.

Basically, it doesn't really matter which end of the car it is on - if it deflates, you need to check and reinflate it at a greater frequency than that which allows it to deflate outside the requirements of the tyre. There is no 'safer or not safer ' for 'fundamentally unsafe'.
posted by Brockles at 11:38 AM on May 18