this post was submitted on 18 Jul 2024

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The age old tire pressure question (lemmy.world)

submitted 5 months ago* (last edited 5 months ago) by [email protected] to c/[email protected]

14 comments fedilink hide all child comments

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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[–] [email protected] 13 points 5 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.

[–] [email protected] 12 points 5 months ago* (last edited 5 months ago) (1 children)

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.

[–] [email protected] 8 points 5 months ago (1 children)

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

[–] [email protected] -1 points 5 months ago (3 children)

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

[–] [email protected] 14 points 5 months ago (1 children)

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.

[–] [email protected] 3 points 5 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.

[–] [email protected] 12 points 5 months ago

It gives you a fairly small gain in fuel mileage, but comes with several downsides.

For one, it's harder on your suspension system and gives you a rougher ride. This will wear out your struts faster, which is kind of expensive.

Next, it lowers the footprint of the tire with the ground. This means that you have decreased road grip and it will take longer to stop in an emergency.

Lastly, it means your tires won't last as long. The tread will wear uneven and it may cause tires that should last you 50,000 miles to only last 35,000, for instance. A rather large waste of money due to how expensive tires are, now.

[–] [email protected] 3 points 5 months ago* (last edited 5 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.

[–] [email protected] 4 points 5 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.

[–] [email protected] 3 points 5 months ago (1 children)

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.

[–] [email protected] 2 points 5 months ago

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

[–] [email protected] 1 points 5 months ago (1 children)

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.

[–] [email protected] 9 points 5 months ago (1 children)

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

[–] [email protected] 6 points 5 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.