automotive tire repair slow leak

Factual Questions
1

Is it common to have a slow leak in a car tire after getting a hole repaired? Is it anything to worry about?

I got a flat a couple months back on a nearly brand new tire. There was a screw in it and I got it repaired at a national tire manufacturer’s retail outlet. Today that tire was about 5 PSI lower than its siblings. It was at 30, the others 35. The max on these tires is 44. For all I know the guys that repaired the tire just didn’t fill it up as high as the others.

This thread makes me wonder if they only plugged the hole and didn’t patch inside the tire. It also makes me a tad nervous as the Retsin family is about to take a road trip and I don’t want to put Mrs. Retsin or the Retsinettes in any added danger. I also don’t want to deal with a blowouot on our trip. Thoughts?

Thanks dopers!

2

if the puncture was inside the tread, the risk of a blowout is low. if it was on the shoulder or sidewall, they shouldn’t have repaired it at all.

aside from your thought about it just having been underfilled, the possibilities:

  1. they plugged it, and the plug is seeping air

  2. they patched it, and the patch either didn’t adhere properly or it might have been pierced by s steel strand from the belt

  3. they patched it and the patch is holding, but R&Ring the tire from the wheel caused a bead leak. Common with old rusted wheels, or alloys.

  4. there’s another leak that they either didn’t catch or happened shortly after the repair.

if you’ve still got a little time before leaving, fill it and check it in a day and see if it’s losing.

3

This is a definite possibility. The tire place should air up your tires to the manufacturer’s recommended specs, which is usually listed on the door jam. 32 PSI is usually about the upper end for what manufacturers will recommend on a normal-sized car (there’s some that recommend higher, especially sports cars with low-profile tires, but they’re less common). Ideally, they should be checking the tire pressure of any car that comes in, but if they were busy maybe they only aired up the repaired tire to the spec and assumed the others were good.

So if I were you, I’d check what the correct pressure is, either air the odd one up to it or lower the pressure in the other three and then just keep an eye on it. Being 5 psi low won’t cause a blow-out or anything like that and if it took it a couple of months to leak that much, it won’t be a problem on your trip. Just check it regularly on your trip and if it does seem to be leaking, get it reparied at your leisure when you get home.

4

Thanks guys!

I called the place and they said they never repair with anything but a patch-plug combo. Also the hole was right in the middle of the tire. So I’m feeling okay with this now.

Thanks again!

5

I’d suspect a bad valve. The major tire chains seem to buy cheap, chinese-made valves-they must save a few cents per hundred. These valves are absolute crap-I have had to replace several.

6

Note as well, twice now I’ve been the victim of a bad seal at the bead of the tire due to a piece of errant rubber stuck in there. Once I was able to pull it out with lock-grip pliers, the other time I had to have the tire dismounted and the bead area of the wheel scraped. If they took the tire off to patch, there is a nonzero chance of old rubber not sealing…not saying it’s the most likely problem, just saying, it’s not too hard to check.

7

Would it not be pretty standard for a car tyre to drop 5psi over a number of months?

I know here we have to check our tyre pressures pretty regularly, with most filling stations providing pressure guages for drivers to top up air pressures. If I had tyres down 5psi after 2/3 months I would just top them up and drive on.

8

equally, perhaps. but if one is measurably lower than the others it’s a good idea to try to find out why.

9

There is also the possibility of a rotted or improperly installed valve stem. You should really have the valve stems replaced every time you get a new tire, and it is a common cause for a difficult to detect slow leak.

Stranger

10

I’d use a bucket of soapy water and a sponge to check for leaks around the plug and valve.

11

Ah, nope. Most of the late model cars (sedans) coming into my shop have recommend pressures of 36-38 PSI

Been there done that. Also corrosion/deposits from the previous mounting left on the lip of the rim.

Filling station gauges, pencil gauges, and many/most air line end gauges are inaccurate. Sometimes wildly.
If you are really anal about this invest in a good digital gauge (about $20) or use one and only one gauge and trust it.
A man with one watch knows what time it is, a man with two is never sure.

12

Ah, okay. I’ll admit it’s been a long time since I busted tires for a living.

13

It would appear that the tire in question was just not inflated as high as the others after the repair. The others were overinflated as a matter of fact. I should have mentioned that not just the tire is new but the entire car is under 6 months old so all the parts are new. Last night I checked the PSI again and after a week it has lost no detectable pressure.

Also FWIW this is a small SUV and the recommended PSI is indeed 32.

Thanks again all!