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How to fix leaky tires after 2 shops couldn't

Ever since I bought my car new I have had one tire that goes to 20psi every 30 days. Discount tire said theres no leak, but obviously something is wrong. Any idea what I can do?

2009 TSX.

Afer a 3rd trip to the mechanic (2nd at dealer) they found a nail in my tire. Apparently the submersion test still didnt help at 70psi inflation. But, he said he found it visually and had nearly missed it again.

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  • The most important thing with the submersion test is patience. I have seen so many people put the tire in the tub and take less than 5 minutes to say they can't find a leak. Put it in the tub and let it sit there for a few minutes just staring at the water looking for bubbles, turn the tire a quarter of a turn and repeat. – Move More Comments Link To Top May 22 '11 at 16:56
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Chances are you have a poor seal between the tyre and the rim. This is normally caused by slight corrosion in the Alloy which then leads to a rough surface which won't seal properly, allowing air to very slowly seep out - It is likely that this won't cause air to escape fast enough to be obvious in a bubble test - after all you're only losing 10psi a month...

The solution is to have the tyre removed and re-fitted with a smear of sealing compound around the edge of the rim, which will help to fill in the rough surface and seal it properly.

edit: While the tyre is off, clean up the beading surface of the rim as well, this will help smooth off the surface and remove any loose dirt or corrosion that has built up around it.

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  • +1 @Nick C - This is more what I was looking for. Discount tire told me they did the submersion test and see no bubbles. I also realize 10psi/month is not a severe leak. Its just annoying to hit the gas station every month and air up my 1 tire. Especially because this has happened since I bought the car brand new... – P.Brian.Mackey May 17 '11 at 15:23
  • Wow. Does this imply air penetrates rubber? – sharptooth May 18 '11 at 7:23
  • @sharptooth - no, it seeps through the imperfect seal between the rubber of the tyre and the alloy of the wheel. – Nick C♦ May 18 '11 at 18:37
  • @Nick C: I wlways thought a tire consists of two layers - the harder one which is cut out where it is in contact with the rim and the soft one which is like a donut and actually holds compressed air. Where am I wrong? – sharptooth May 19 '11 at 6:12
  • @sharptooth - You're thinking of a tubed tyre, as fitted to push-bikes, which have an inner tube (as you say, donut shaped) that holds the air. Modern Car tyres don't have a tube, and rely on the seal to hold the air in. The Car Bible website has quite a good guide to tyre construction: carbibles.com/tyre_bible_pg2.html – Nick C♦ May 19 '11 at 14:01
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Put soap and water in a spray bottle, spray it on the tire and rim, look for bubbles. Also spray on the valve stem as the valve can leak as well.

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As an alternative to what user Larry suggests in his answer you can go the bicycle way - detach the wheel (together with the rim) and submerge it into water. This will surely show whether there's an air leak.

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