Tire PSI

[iamwiz82]

Originally posted by: 0roo0roo

Originally posted by: rh71
I've found that the recommended 30 PSI causes my Accord's tires to bulge out... people have told us we have a flat while waiting at a red. It's kinda comical...

heh, some tires have sidewalls that bulge more. doesn't mean much though. only thing that matters is that the tread is totally flat against the ground. u can sorta test this, shoe polish a stripe across tread to see if wear is even.

I use chalk, but the result is the same.

Draw a line on the tire at your current pressure and drive a little bit. Check the line. If the outer edges are more faint than the inner, your tire is under inflated, if the inner is more faint than the outer, it is over inflated. If one edge is more faint than the other, you have an alignment issue.

Also make sure you are checking the pressure of all the tires at one time, either all hot or all cold.

 

[woowoo]

Originally posted by: Smaug
Yes 42 now how do I drop it?

With a knife.......

 

[flot]

Let some air out. Run the recommended pressure.

Odd anecdote, I had a tire that had gone a little flat one evening (no idea why), and I was in a hurry to get somewhere, so I just pulled into some gas station off the highway... those $0.50 air pumps are pretty hit and miss in terms of how efficient they are.. so I measured the pressure using its' built in gauge, put some air in, showed like 17 psi... put some more air in, showed 20 psi.. put some more air in, and some more, finally it looked about right (car was on an incline sloping downward, at night, so was hard to tell) and the gauge read about 30 psi so I figured screw it and hopped back in the car.

Well the whole way there I noticed that the ride was ridiculously bumpy. In fact, even my passenger mentioned something about it. Next day (50 miles later) I thought about it and went and checked the pressure with my own gauge... I think it was somewhere right around 70-75 psi.

Moral of the story - pay the $15 for a good pressure gauge and use it.

 

[Carbonadium4]

There are many articles that discusses over inflation, unless you're living in a pot hole free world, its more easy to blow or damage a tire that is over inflated. So you're willing to bet his life on over inflated tires ? especially if he goes long distance ?

tire care

add/remove air - see that for releasing air.


If your tires are overinflated, they could be damaged more easily when running over potholes or debris in the road. Higher inflated tires cannot isolate road irregularities well, causing them to ride harsher. However, higher inflation pressures usually provide an improvement in steering response and cornering stability up to a point.

Tire footprint and traction are reduced when van, pickup, or RV tires are overinflated for the loads carried. In particular, tires with aggressive tread patterns may contribute to over steer or "roadwalk" if inflated beyond the inflation pressure specified in the owner's manual and vehicle placard for standard or customary loads. Over inflation also increases the chances of bruise damage.

Most car are between 30-35.. u should lower it.. it may explode..

You're kidding right? He just told you the tire was rated to 51 PSI.

Tires (like many other things) are overengineered to withstand the idiocy of the average user. That 51 PSI limit is probably closer to 100 PSI for an actual rupture.

Example: Elevators have a posted weight limit (like 3000 lb or something). What they don't tell you is that there are at least 6 safety cables holding the elevator up in the event of a failure. Moreover, those cables are engineered so that only one can support a fully loaded elevator.

Back to the tire issue--tire pressure depends a lot on tire size. On my A4, the stock 16" tires were inflated to a recommended 32 PSI. When I went to 17s (225/45 17), the recommended pressure increased to 35. Right now I have 18" wheels on the car, and the tires (225/40 18) are inflated to 38 PSI. So saying that 30-35 is the proper PSI is jumping to the wrong conclusion. It's like telling someone they have pneumonia if they have a cough.

 

[Eli]

Originally posted by: Smaug
My car has a recommended PSI of 30 on every wheel, max PSI on the tire is 50, and the current PSI is 42. Is there an advantage or disadvantage to this?

jeebus! :Q

I ph33r your tires.

 

[Zenmervolt]

Start with the recommended and go from there. I tend to like my rear tires inflated a little more than the fronts (for a RWD car) just because it creates a handling feel that I like better.

ZV

 

[isekii]

Originally posted by: Zenmervolt
Start with the recommended and go from there. I tend to like my rear tires inflated a little more than the fronts (for a RWD car) just because it creates a handling feel that I like better.

ZV

Yea the car feels more nimble.

 

[waggy]

heh my sister-in-law (19) had her tires inflated to 60+! she said they looked low so put some in.

I was shocked that she didnt have a blow out.

 

[isekii]

Originally posted by: waggy
heh my sister-in-law (19) had her tires inflated to 60+! she said they looked low so put some in.

I was shocked that she didnt have a blow out.

Anyone reason why women shouldn't drive or touch cars.

 

[Zenmervolt]

Originally posted by: isekii

Originally posted by: Zenmervolt
Start with the recommended and go from there. I tend to like my rear tires inflated a little more than the fronts (for a RWD car) just because it creates a handling feel that I like better.

ZV

Yea the car feels more nimble.

It reduces rear grip slightly, counteracts the engineered-in understeer I think. IIRC my 924S is at 28 front and 32 rear.

ZV

 

[Beau]

Originally posted by: iamwiz82
I use chalk, but the result is the same.

Draw a line on the tire at your current pressure and drive a little bit. Check the line. If the outer edges are more faint than the inner, your tire is under inflated, if the inner is more faint than the outer, it is over inflated. If one edge is more faint than the other, you have an alignment issue.

Also make sure you are checking the pressure of all the tires at one time, either all hot or all cold.

great idea!

My car manual says to use the tires' recommended pressure which is 45psi (max 55)... but I'll check it with the chalk too, cuz I've always been worried about that.

 

[Apex]

Originally posted by: Beau

Originally posted by: iamwiz82
I use chalk, but the result is the same.

Draw a line on the tire at your current pressure and drive a little bit. Check the line. If the outer edges are more faint than the inner, your tire is under inflated, if the inner is more faint than the outer, it is over inflated. If one edge is more faint than the other, you have an alignment issue.

Also make sure you are checking the pressure of all the tires at one time, either all hot or all cold.

great idea!

My car manual says to use the tires' recommended pressure which is 45psi (max 55)... but I'll check it with the chalk too, cuz I've always been worried about that.

White shoepolish works pretty well too.

 

[ucdbiendog]

eleventy billion might be too much =\

 

[TechnoKid]

Originally posted by: DingDingDao


Back to the tire issue--tire pressure depends a lot on tire size. On my A4, the stock 16" tires were inflated to a recommended 32 PSI. When I went to 17s (225/45 17), the recommended pressure increased to 35. Right now I have 18" wheels on the car, and the tires (225/40 18) are inflated to 38 PSI. So saying that 30-35 is the proper PSI is jumping to the wrong conclusion. It's like telling someone they have pneumonia if they have a cough.

You are correct in stating that tire presure depends on the size, however, usually larger tire sizes have a higher load rating, and so they have higher tire pressures so those loads can be obtained. A tires' reccomended pressure is a factor of many things, but it is mostly based on load and comfort to the driver. You'll notice that the MAX load on the sidewall of the tire is only true at a given PSI, which is usually the max PSI of the tire. (like 1360lbs at 44psi). Going to a bigger tire/wheel combo doesn't mean that you should or have to run higher tire pressures, if you want more load carrying capability, then you'd put more air in the tires. There is no way I'd ever put 100psi in a passenger tire, there's a reason why there's a max psi on there; I do know that some truck and big rig tires do get up to 100psi. Even most passaeger spare tires have inflations of about 60psi. Just like a balloon, if you put too much air into it, it will break.

In a recent Road and track test where they drove a ferrari, the inflation for the tires during the test was 32psi, and we're talking tires that are 19" and 18". At your current setting of 38psi on 18" tires, you may wearing out the middle of the tires faster than the shoulders, and are not getting an optimal tire contact patch; sure, you may have increased handling, but that also leads to a harsher ride. The best way to test this would be to get a pyrometer (about $50 to $200, Tenma makes these) and measure the temps of the treads from sidewall to sidewall and see if it is relatively the same. If the treads all have the same reading you have optimal tire tread contact and proper pressure for the load that you are carrying. If you have wildy differing temps (like say the middle is hotter than the shoulders, or the shoulders are hotter than the middle, or one shoulder is hotter than the other), you have incorrect pressure, and or have alignment problems.

 

[Calin]

Originally posted by: DingDingDao

Example: Elevators have a posted weight limit (like 3000 lb or something). What they don't tell you is that there are at least 6 safety cables holding the elevator up in the event of a failure. Moreover, those cables are engineered so that only one can support a fully loaded elevator.

While the cables are certainly over-engineered with such a great factor of error, the electric engines that operates the elevator are not so largely overpowered. So, while maybe twice the rated load might be okay from time to time, more is just a disaster waiting to happen

Calin