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submitted 4 months ago* (last edited 4 months ago) by venusaur@lemmy.world to c/mechanicadvice@lemmy.world

2001 Infiniti QX4

Placard on car says 26 psi cold

Tires say 32-49

Rear tire is set to 27 cold

Does this look under-inflated? What’s the lowest I should go?

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[-] RestrictedAccount@lemmy.world 15 points 4 months ago

I would 1)go with the vehicle placard as the default and and limit driving until I 2)call a reputable dealership

I think it was the Ford Explorer that required lower tire pressure because the vehicle was a rollover threat at normal inflation pressures. But people were worried that the tires would blow out if under inflated. There were a ton of lawsuits.

They did a 60 minutes piece about Jeeps on this too.

It was a mess.

[-] venusaur@lemmy.world 3 points 4 months ago

Damn. I feel like 26 is pretty low. Some old threads about R50’s said they had a TSB raising it to 30 so that’s where I’m at now. Dealership said follow placard but the car is so old they don’t know or care

[-] Successful_Try543@feddit.org 13 points 4 months ago* (last edited 4 months ago)

If there is a minimum required pressure written onto the tire, I'd go with that one. A little more than the pressure required for the car doesn't hurt.

[-] lemming741@lemmy.world 10 points 4 months ago

They may have originally specd lower pressure for ride comfort. I agree with using the tire's minimum.

https://en.m.wikipedia.org/wiki/Firestone_and_Ford_tire_controversy

[-] Zwiebel@feddit.org 3 points 4 months ago

Why is everyone recommending the minimum here? I've always heard to go a smidge above the maximum for the fuel savings

[-] Annoyed_Crabby@monyet.cc 15 points 4 months ago

If by maximum you mean the pressure recommendation by the car manufacturer, then yeah it will help with fuel saving. If by maximum you mean the pressure provided by the tyre manufacturer, please don't do that lol. Jumping from 26psi to 32psi isn't much, but jumping from 26psi to 49psi is way too much especially for car with only 1 passenger, it's gonna wear the middle of the tyre without the weight pressing down to give it an even wear. The money you save here will be used to replace the tyre earlier than it should. Will also cause terrible braking.

[-] glarf@lemmy.world 3 points 4 months ago

Yep I have to second, you lose a ton of safety when overinflating tires like that due to the tire not gripping the road as it would if correctly inflated. Not a trade off I'd make with my life.

[-] Hubi@feddit.org 4 points 4 months ago* (last edited 4 months ago)

Because on OPs car the recommended tire pressure is lower than the minimum recommended by the tire manufacturer. Increasing it even further may affect ride quality. In most scenarios your approach is correct.

[-] venusaur@lemmy.world 3 points 4 months ago
[-] Death_Equity@lemmy.world 8 points 4 months ago

The placard on the driver's door frame is what you use.

The tire itself has no relevant information for a driver, only for an installer at a shop mounting the tire.

[-] thisbenzingring@lemmy.sdf.org 9 points 4 months ago

*as long as the tire is the same size as suggested by the manufacture

[-] Death_Equity@lemmy.world 7 points 4 months ago

Even if you have a different size than is OE. You only disregard the psi, that is based on gross vehicle weight, if you know what you are doing.

It doesn't matter if you have 265/70r16 and go to a 275/50r20, you still use the same pressure because your car still has the same GVWR.

[-] venusaur@lemmy.world 1 points 4 months ago

Thanks. What does the installer use the info for?

[-] Death_Equity@lemmy.world 2 points 4 months ago

Practically, nothing. The pressure on the sidewalk is what the manufacturer says will seat the tire on rim, but reality dictates you add pressure until the tire pops into place. That may be 40psi, but I have had to use over 100psi to get a tire to pop in place if that is what it needed and the tire lube wasn't enough and you correct to manufacturers' spec once the beat seats.

[-] venusaur@lemmy.world 1 points 4 months ago

Interesting. Thanks!

[-] zer0hour@lemmy.world 4 points 4 months ago

would you be able to post a pic where it says the minimum psi on the tire? I work with tires and wheels and I have yet to see a tire with a range of psi like what you're describing and I'm curious to see.

I would set the pressure to what is listed on the placard.

usually with an 8 ply passenger tire, you shouldn't go below 20 psi.

[-] zer0hour@lemmy.world 3 points 4 months ago

oh also, the tire in the pic doesn't look under inflated to me, but looks can be deceiving

[-] venusaur@lemmy.world 2 points 4 months ago

I’ll try to post a pic tomorrow. Just saw this on the Nokia website:

We recommend using the vehicle manufacturer’s suggested tire pressure for all season tires

Not sure what the numbers on the tire are for then.

[-] zer0hour@lemmy.world 2 points 4 months ago

they're for the technicians mostly. basically safe maximum levels to get the tire installed on the wheel and other safety information. sometimes you really have to inflate them when installing to get the tire to seat properly

[-] venusaur@lemmy.world 1 points 4 months ago

Got it. Thanks!

[-] Hubi@feddit.org 4 points 4 months ago

I agree with the other poster. You should go with the minimum on the tire because it's the manufacturer's specification. You don't necessarily see that a tire is underinflated but there can still be too much stress on the sidewall.

[-] venusaur@lemmy.world 3 points 4 months ago

Thanks. I’m compromising at 30psi

[-] Nomecks@lemmy.ca 2 points 4 months ago* (last edited 4 months ago)

The placard is useless if the tires aren't the factory type. Don't inflate tires to less than minimum pressure if you don't know that they're the right tires for the vehicle.

[-] venusaur@lemmy.world 1 points 4 months ago

Thanks. They’re the right size but what other factors do I need to account for when matching a tire?

[-] Nomecks@lemmy.ca 1 points 4 months ago* (last edited 4 months ago)

Load rating is a big one. Speed rating and number of plies can affect it too

[-] venusaur@lemmy.world 1 points 4 months ago

Thanks I’ll check those. These seem to be pretty heavy duty tires

this post was submitted on 18 Jul 2024
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