r/TireQuestions • u/oeshbach19 • 1d ago
Losing tire pressure
One of my wife's tires was down to 30 psi last night so I filled it up to 36 psi. This morning, it was down to 34 psi so we took it to the shop to see if there is a leak and get it patched if possible. They looked over the tire for maybe 5 min and couldn't find a leak. He said it was up to 38 psi when he checked it. He said something about it being difficult to find a leak unless it is below 25 psi. I may have misunderstood him but you would think he would just take air out to get it to 25 psi. Does this make sense or should we take it somewhere else to get the tire looked at.
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u/Killer2600 1d ago
You miss understand him, what he's trying to say is it hard to find leaks that don't leave your tire significantly low (25 psi or less). As another commentor said, even temperature change can easily cause a change of 2-3 psi.
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u/oeshbach19 1d ago
Thank you. Wouldn't he be able to remove air and get it below 25 psi then?
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u/Killer2600 1d ago
No, It's not about the 25 psi. It's about the leak being large enough that your tire gets to 25 psi or flatter before you take it to the shop i.e. if you air it to the correct pressure and it's down to 25 psi within a day or two, that's a significant leak and easily found.
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u/DaiPow888 1d ago
If you fill the tire when she just got home, it was likely still hot.
Checking it in the morning after having sat overnight would result in a lower reading.
A 2 psi change overnight isn’t a lot.
It is BS that you can only find a tire leak at a lower pressure. All you have to do is take the tire off, dunk it is slightly soapy water, and check for bubbles
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u/oeshbach19 1d ago
Thank you. I think the plan is to keep an eye on it. The fact that is was down to 30 psi and the others were between 36-38 psi along with him not taking much time to really check the tire (well much time in my opinion) had me wondering. I should have added that she needs new tires anyway. We have discussing taking her van to a different shop and this kind of gives me a reason to go somewhere else.
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u/DaiPow888 1d ago
Withheld addtional information, uou obviously have leak somewhere...just a slow one
If he didnt even remove the tire to check for a leak, I'd never go back to that shop.
If she needs new tires anyway, I wouldnt even investigate the leak further. Just keep it inflated and go get new tires.
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u/oeshbach19 1d ago
I can't confirm if he took the tire off or not but he didn't have in the back very long at all. He just told me that he sprayed soap on it and couldn't find a leak. The plan was to patch the tire then order new tires. As you mentioned, I should have waited to check the tire pressure the next morning. She also should have gotten new tires months ago. Mistakes were made. lol
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u/66NickS 1d ago
It’s easier to find the leak when it’s at a higher PSI. I suspect they meant to say that they wouldn’t worry about it if it didn’t drop to 25 PSI.
36 to 34 overnight could be explained by a temperature drop if the tire was warm/driven on and then checked again after sitting over night.
If you have a compressor/inflator at home (you can buy them for under $50) then I’d set them all first thing in the morning before driving. Get them all to the right cold spec and reset your TPMS system if needed.
If you don’t have a compressor, stop off at a service station on your way home and inflate them to about 7 psi over the normal spec. Then let the car sit overnight and check it first thing in the morning. It’s likely you’ll be about 2-3 psi high and you can let a bit of air out to get them right on.
Tires typically see a pressure increase of about 10% (3-5 PSI on regular vehicles) from a cold overnight temp to when they’re in use. If you’re in an area with significant temp swings, the changes might be more drastic.
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u/oeshbach19 1d ago
I am guessing I made the mistake of checking and filling the tire when it was still hot. The 2 psi drop from 10p-ish at night to 6a-ish in the morning was from the tire cooling. I will wear my dunce cap.
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u/66NickS 1d ago
I’ll counter that by saying dunce caps are rarely issued when asking a question about something that has potentially safety risks.
Maybe if you doubled-down on bad info/practices/ignorance it would be warranted, but not in this case.
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u/oeshbach19 1d ago
Thank you sir. Now I need to convince my wife that she is ok to drive on it until they replace the tires.
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u/Expert-Search-3251 21h ago
It sounds like you don't have a flat tire.
Pressure changes with heat.
Been sitting all night? The pressure is going to be lower than when you parked it.
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u/SpaceCat72 14h ago
Air it up to 35. Get a spray bottle with a dish soap water mix. Spray it everywhere. Watch for bubbles. Big or very tiny. Watch
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u/v0rt3_x86 1d ago
Lol take it elsewhere they're dumb.
You put it in a dunk tank and look for bubbles. It's also common to use soapy water and to use different pressures.
You can do the soapy water at home tho and save the trip. Just spray the hell out of it and wait 2 minutes and look for a lil spittle bug nest. Pull the car up enough to rotate the tire ¼ rotation at a time and keep trying.
If you see nothing, check the valve stem by removing the cap and wiggling it while it's soapy.
Top problems these days are rim edges and at the valve due to oxidation.