Question tire pressure?

babyherder

Well-known member
How close to the recommended tire pressure do tires need to be? Do you fill them with air every time you drive to keep them at the right pressure?

Thanks for your help!
 
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beeman

Active member
Tire pressure should remain relatively constant unless there is a significant change in temperature or there is a leak in the tire. I usually check mine once a week with the gauge, and do a visual inspection every day. Over or under inflation will cause abnormal tire wear. Under inflation will cause poor handling, braking and accelerating, while over inflation will cause a much rougher ride. The recommended pressure is what the manufacturer feels is necessary for your vehicle and the tires your vehicle uses. I would aim to be as close to the recommended pressure as possible (less than 5psi difference), and prefer that the error is on the side of over inflation, as it will have less effect on handling :twocents: . If you need to constantly add air to your tire there is likely a leak that needs to be addressed in the near future ;) .
 

Adam's Mom

New member
Agree with previous poster. I only check mine once a month, but I also have those TPMS monitors on my car, which freaked out last week when cold weather hit. I had forgotten they lose pressure when it gets cooler out and mistakenly thought I had a flat. Took it to the dealer and felt really silly after they told me they were just low from the temperature change. :eek:
 

babyherder

Well-known member
Thanks for your help everyone! I now have new tires on my car (the old ones were about 10 years old from what I could tell) and when I checked last week they all had the correct pressure:)

Adam's Mom, I once took my car to the shop because the dash board lights were out. Apparently they were out because I bumped the switch that turns them off. Opps.
 

TechnoGranola

Forum Ambassador
I just skimmed so this may have been mentioned, but pressure should be checked when tires are cold, i.e. the tires should be at air temperature, before you have driven anywhere. They warm up when you drive and the pressure then increases so you won't have an accurate reading at that point. Driving a block or two to get to the gas station to check the pressure is fine.
 

southpawboston

New member
beeman, tires do lose air over time, even without a leak. the rubber compounds used in tires are semi-porous to air, so no tire will hold air indefinitely. this is the appeal of nitrogen. allegedly, nitrogen does not "leak" through the rubber as readily as air (even though air is mostly nitrogen :confused:).

i recommend a visual check of your tires before each ride, and a pressure readout once a week unless you have TPMS. apparently the US govt felt as strongly as i do about the importance of correct tire pressure that they mandated that all new cars in the US come standard with TPMS.
 

babyherder

Well-known member
Thanks, TechnoGranola. I check while the tires are cold but thanks for mentioning it. I would hate to have missed something like that. And its good for everyone else to know
 

Polola0628

Active member
woah, 10 years old? My DH works at sears auto center and has one of those "tread checker gauges" and checks his tread on each tire before each ride- lol! I think he'd have a heart attack if he'd read that!
 

southpawboston

New member
woah, 10 years old? My DH works at sears auto center and has one of those "tread checker gauges" and checks his tread on each tire before each ride- lol! I think he'd have a heart attack if he'd read that!

you can use a penny, too. :)

that's pretty extreme, considering that a tire essentially can not wear down measurably each trip you take.
 

babyherder

Well-known member
Well, I only checked the date on one tire and it was from 1999. I got the car used and it is from 1996. I didn't know about the dangers of old tires until I read about it here a few months ago. I spent those months convincing my parents my tires needed replaced and am now trying to convince them to replace theirs.
 

bobandjess99

Senior Community Member
I'm getting 2 new tires today, to go with the 2 we replaced thjis summer, so my car will have 4 brand new tires on it, and not 10 year old "new" tires either, LOL!!
 

babyherder

Well-known member
I'm getting 2 new tires today, to go with the 2 we replaced thjis summer, so my car will have 4 brand new tires on it, and not 10 year old "new" tires either, LOL!!

Yay! I'm hoping that after telling my parents about the dangers of old tires they'll at least check the date of manufacture on the next set they buy.
 

BigDaddy

Active member
I was thinking about starting a thread about this, but I guess this one will do. Just a few tips...

Now that the weather is changing and temperatures are dropping, everyone needs to check their tire pressure. The pressure will get lower lower as the temperature continues to go down.

The correct pressure for your tires is the vehicle manufacturer's specification, not the pressure specification on the side of the tire. You should, however, check the pressure rating of the tire to make sure that it is not lower than the pressure spec of the vehicle. If the vehicle pressure spec exceeds that of the tire, then the tire is not safe to use on the vehicle, and a different tire must be used.

Tire pressure should be checked regularly. There is generally a 3% loss of pressure per month, (but the loss can be as high as 10%) due to air permeating the rubber composition. Stand to the side of a tire while inflating it and not directly facing it, just in case it fails. If you notice a tire that is leaking at a higher rate than the others, it should be checked for leaks.
 

babyherder

Well-known member
The correct pressure for your tires is the vehicle manufacturer's specification, not the pressure specification on the side of the tire. You should, however, check the pressure rating of the tire to make sure that it is not lower than the pressure spec of the vehicle. If the vehicle pressure spec exceeds that of the tire, then the tire is not safe to use on the vehicle, and a different tire must be used.


Can you explain more about where to find the pressure specification on the side of the tire? My tires are inflated to the tire pressure recommended by the vehicle manufacturer. But I've never compared it to the pressure specified on the actual tire.
 

my2kidsSafe

New member
Can you explain more about where to find the pressure specification on the side of the tire? My tires are inflated to the tire pressure recommended by the vehicle manufacturer. But I've never compared it to the pressure specified on the actual tire.

he's saying don't go by whats on teh tire. There should be writing on the side of the tire saying the specs. But he says go by vehicle manufactuer recommendations. I know i find mine on my drivers side door. Open it up and the side that has the hinge on it says what it should be set at.
 

sirrahn

Active member
this is the appeal of nitrogen. allegedly, nitrogen does not "leak" through the rubber as readily as air (even though air is mostly nitrogen :confused:).

I thought the benefit to nitrogen is that it's drier. Regular air contains more water and that's what causes the apparent change in tire pressure with temperature. At least that was how I understood the spiel I got from the Costco tire guy;)

FWIW my nitrogen inflated tires are still showing green on my AccuPressure caps and the temp has dropped quite a bit in the mornings here. I haven't had to add any air since I bought the tires last April although I suppose they were checked and possibly adjusted when I had it in for service.
 

BigDaddy

Active member
Can you explain more about where to find the pressure specification on the side of the tire? My tires are inflated to the tire pressure recommended by the vehicle manufacturer. But I've never compared it to the pressure specified on the actual tire.
Most of the time it's down close to the bead of the tire. This normally isn't a problem unless you are using cheap tires on a vehicle that uses relatively small tires compared to it's size.. The vehicle manufacturer PSI spec is directly based on the size of the tire and the weight of the vehicle. The tire manufacturer max PSI spec is based on how much weight the tire can handle, and is usually an indication of the quality of the tire's construction.

Take a 4,000lb car for example, there are 4 tires and each one is supporting 1000lbs (assumption made that the car is perfectly balanced to simplify math). At a manufacturer spec pressure of 32 PSI (pounds per square inch), each tire has 31.25 square inches in contact with the ground. In this scenario, a tire with a max rating of 35PSI (for example) would be fine.

Now, that same size tire on a car that weighed 4500lbs would require 36PSI to maintain the 31.25 contact patch. So in this scenario, if the vehicle manufacturer spec was 36PSI, that same tire that was okay in the first scenario could not be used.
 

southpawboston

New member
I thought the benefit to nitrogen is that it's drier. Regular air contains more water and that's what causes the apparent change in tire pressure with temperature. At least that was how I understood the spiel I got from the Costco tire guy;)

i think you might be right. air theoretically shouldn't change pressure with changing temps, but moisture in the air definitely will. i never thought that there was enough moisture in the air to affect tire pressure so drastically, but apparently there is!

the compressed nitrogen tanks probably contain no moisture, whereas the pumps that you use to fill up your tires with air just pump the same air that you're breathing into your tires, along with any moisture in that air. sometimes you can even see the moisture coming out of the filler hose!
 

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