Tires: Alloy tires leaking 5psi/week, alloy rim, alloy rims

Question
Hello. I have OEM tires (alloy wheels) on my '01 Forester. 2 of them leak 5 psi/week, the other 2 leak 3 psi/week. The car is garaged and very low mileage, under 20k.

They have been like this for at least a year if not 2. I'm in NY and do drive during the snow/salt winter time... but not a lot. The tires look fine.

Do you think I need new tires? Or maybe it's the alloy wheels (I read something about the bead problems on alloy wheels)? How dangerous is this for long drives?

Thanks in advance.

Answer
Garion,

First, driving on underinflated tires is never a good idea - and it's dangerous both from a vehicle handling perspective as well as the potential of a tire failure perspective.  I'll bet you didn't pick it up right away and that there have been many times the tires were significantly underinflated.  It doesn't matter if the tires are properly inflated at the time the tire fails.  The tire doesn't forget that it was underinflated at some point in time.

Secondly, I hope you have considered that this time of year the temperature is going down and this causes the tire pressure to go down as well - and have factored that into the equation.

My best guess is that it's the alloy rims.  Not only do the alloy rims corrode around the bead seat area, but the alloy is somewhat porous and the air could be leaking out through the rim.  That's why alloy rim are always clearcoated - sometimes this process isn't as good as it could be.

So I would first establish where the rim is leaking.  Some folks use a spray bottle of detergent to see where the bubbles form - but this doesn't always work.

An immersion test is better.  A kiddy pool works great for this but you have to use weight to hold the tire completely under the water.  This also make take soome time to be sure you've identified the source of the leak - not to mention you have to do each tire separately.

Hope this helps.