Overinflation question
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AudiWorld Member
Joined: Mar 2016
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From: Maine, USA
Overinflation question
Local tire shop installed new Michelin Sport 4 summer tires (18 inch wheels), and I thought the car was behaving a bit squirrely.
I drove more than 300 miles before deciding to check the inflation. I figured they were overinflated a bit. Well, three were inflated to 40 -- and one was at 50!! That's the max on the sidewall.
Obviously I think the tire shop guys are knuckleheads. Any cause for worry?
I drove more than 300 miles before deciding to check the inflation. I figured they were overinflated a bit. Well, three were inflated to 40 -- and one was at 50!! That's the max on the sidewall.
Obviously I think the tire shop guys are knuckleheads. Any cause for worry?
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From: San Francisco Bay Area
You'll be fine. Not enough miles to cause worrisome wear at the center of the tire due to overinflation. Needless to say find a better shop next time. The techs at a tire shop have one job and these guys failed it. I would also check the wheel bolt torque. If they can't even properly inflate the tires, I'd be worried about what else they screwed up.
Thread Starter
AudiWorld Member
Joined: Mar 2016
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From: Maine, USA
Thanks all. I just went for a drive. The car is more settled and there are way fewer rattles, haha. I'll just keep on trucking.
And yeah, I have a torqure wrench. I'll check that next.
And yeah, I have a torqure wrench. I'll check that next.
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From: Saskatchewan Canada
Did you test hot or cold? If the shop set the pressure to 35 psi (factory spec for my alroad) in a cool shop and you tested outside on a hot day after driving a bit they could easily reach 40 psi. OEM pressure specs are based upon tires that have not been driven and have not been sitting in the sun - cool tires for the current environmental conditions. The 50 psi would appear to be an error.
OEM tire specs are for OEM supplied tires on OEM sized rims. Different tires and wheel sizes may benefit from different pressure settings. If you are prepared to get a tire thermometer and experiment you may find a better tire pressure. However, better is relative. Better may be less squirrelly; but, higher tread wear.
OEM tire specs are for OEM supplied tires on OEM sized rims. Different tires and wheel sizes may benefit from different pressure settings. If you are prepared to get a tire thermometer and experiment you may find a better tire pressure. However, better is relative. Better may be less squirrelly; but, higher tread wear.
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AudiWorld Member
Joined: Mar 2016
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From: Maine, USA
Good points. They were cool when I checked them, so I shudder to think what the psi might have reached while I was cruising on the highway at 80mph.
I'm running them at 34 psi now That's actually a bit higher than the owners manual recommendation, which seems skewed toward comfort. Seems like a decent compromise.
I went with the same OEM replacements that came on the car.
I'm running them at 34 psi now That's actually a bit higher than the owners manual recommendation, which seems skewed toward comfort. Seems like a decent compromise.
I went with the same OEM replacements that came on the car.
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For example the PS4 you fitted probably has a load index of 97. So that means at the 50 psi indicated on the sidewall it can carry 1609 lbs. That's its maximum carrying capacity, but that's way more than you need. Your car weighs around 4000 lbs empty, so each tire only has to carry about 1000 lbs (front tires a bit more than the rear tires), hence you don't need 50 psi for that. The recommended psi gives the tire the necessary load carrying capacity for your specific car. Nothing bad happens if you inflate them higher, other than poor handling and wear because it lifts up the shoulders unless you weigh down the car accordingly. This is why you have to increase the tire pressure to the max load recommended pressure if you load the car full with passengers and cargo, or inflate the front tires higher than the rear tires, because they have to carry the engine.
Last edited by superswiss; May 11, 2023 at 02:06 PM.
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