I accidentally drove 25 minutes at highway speeds on 1 year old Michelin XIce3 with one of the tires only having 7psi in my 2010 prius (the shop which mounted my winter wheels forgot to inflate it). A local mechanic removed/inspected/remounted the tire and said it looked fine (had a valvestem leak which he fixed). Can I trust that this tire is safe to drive or is there a significant likelihood that there is damage that can’t be detected on inspection which makes the tire unsafe? Thanks!
If they didn’t find any damage by inspecting them, likely folks on the internet will not be better able to inspect the tire. The thing about winter tires is they’ll be worn out in a season or two anyway so no problem with using them. As long as you didn’t ride them on the rims it should be OK. 7#s is enough to keep the rim off the ground and about what a lawn mower tire would normally use. Might have generated a little heat but they should be replaced at 50% tread anyway next season.
What Bing says sounds reasonable to me. But… after my own experience with a bad valve stem (2 of them actually, in one drive 
) I never trusted the tire again and it ate away at me every time I went out. Finally, for my own peace of mind I replaced them.
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Driving with a low tire for an extended period of time can damage the structural integrity in the sides of the tire. If it’s weakened damage is already done.probably won’t notice any performance problems, but may be more susceptible to blow out. If it was me, I would assume no damage was done, cause I wouldn’t think 25 minutes is an extended period of time.
At the very least, you’ve used up a significant portion of the tire’s durability – in engineering terms, its fatigue life. That means the tire will not be able to go as far before it fails. Hopefully you’ll wear the tire out before that happens, but:
Look for a different color to the tire – likely blue, although I have seen red. It will only be a slight change, and hard to detect. It may appear as a circumferential ring in the upper sidewall or in the outer tread area. If you have that, then the tire has definitely been damaged, but as of yet hasn’t failed.
Take a gloved hand and rub the surface of the tread – 360 degrees. You are looking for a bulge. If you find one, change out the tire immediately.
Be aware that a bulge could occur later. It will start as a small vibration that gradually gets stronger over the course of several hundred miles. Don’t wait. Get it changed immediately.
You would be well served to schedule a “rub” about once a month or so - as a precaution.
And as has been said above: The safest thing is to change it out.
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If you are a scientific type you could pretty easily rig up a way to test if the tire was bulging in either the sidewall or the tread area. Jack up the wheel so you can hand-rotate it. Figure out a way – like clamping to a chair – to position the point of a screwdriver, nail, pencil, anything w/a sharp point , position that point as close to the sidewall as you can, without touching. When you rotate the tire you can see if that distance changes with the rotational angle. It shouldn’t, or at least not much. If in doubt compare the same experiment done on a tire that didn’t suffer the damage. Same idea can test for bulging in the tread area.
If I had that problem and I routinely drove the car at freeway speeds I’d just replace the tire, why worry about it, use the old one as a spare If you want. A compromise might be to make sure that tire is always on the rear. At moderate speeds, less than 40 mph, it’s a pretty good bet a blow-out will still result in manageable handling until you can get the car to the side of the road. At freeway speeds not so much, especially if the blow-out occurs on a front tire.
I don’t thinkj that I would trust that tire. Twenty five minutes of highway speeds with only 7 PSI can easily ruin the sidewall in that length of time; or even less.
About 15 years ago my wife was working nights. Unknown to her a right rear tire (all almost new) had picked up a nail and she drove 30 miles home on a tire with about 12 or 13 PSI of air in it. It butchered the sidewall in the tire.
“Looked fine” is in the eye of the beholder and may not mean much of anything.
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Thanks all for the insight. My first time using this forum, very helpful!
Trust but verify, which I don’t think is really an old Russian proverb. I don’t trust anyone else’s work, at least not if I can check it myself (did the surgeon really remove my appendix: let’s look!), so I check fluids, air, presence and tightness of nuts & bolts, presence of allegedly-replaced part… myself.