WaltM

I hate it when I don't think things through. Especially simple stuff, like parking in a lot with a lowered car, or pulling up to a gas pump and swinging my door open into concrete island and dinging the bottom of my door.

Neither one has happened in my '05 (knock wood), but I still have lapses when I don't think about these things.

NoPonyYet

True on the leaking air and true on the nitrogen not leaking as fast, but not true on the "good idea" switch. Air is about 80% nitrogen. Sure, you might get some humidity in there as well, but the cost of nitrogen makes it not quite worth it to have someone fill it up with N2. I would say to just keep an eye on it and save the money for something else.

mot250

Sure, regular air is cheap compared to Nitrogen but for a street car it is still cheap insurance. Think of it in terms of what your time is worth and how often one should check and reinflate their tires when using run-of-the-mill comressed air. What else could you use that "banked" time for if it was not spent checking and inflating your tires? Plus, every time you top-em-off with regular air, your probably adding more moisture unless you have a drier installed in line with the compressed air.

That said, it could get expensive if you are constantly adjusting pressures for street/strip/track duty. That is the only reason I have not switched to N2. When I go to the local 1320, I air down the rears and air up the fronts. Then before leaving the strip, I've got to re-est them to normal.

RobRob

32 psi! And I thought I was pushing things by going to 30 psi.

You know, that actually makes me feel so much better about the performance of my car -- I had always been a little bummed about the gas mileage and now I may have at least a small fix -- apparently I've been riding on underinflated tires for almost a year.

...and I have detected a problem since the incident: I'm hearing a faint eek-eek-eek coming from the right rear brake when I slow down. Dammit.

Glenn

good stuff LOL

zaghloul

Yup 32, but make sure you test the inflation in the morning before you drive it, provided it hasn't been in the sun too long.

As for the pulsating break squeal (eeek-eek-eek), I had the same shiite after I foolishly took a corner too fast thinking I'm in a Porsche. My front driver side tire slammed sideways into the curb. I took it to the tire shop and they sanded my rotors down and fixed up the warping. Later that night the squeal came back again. The next day I went back and they re-sanded the rotor and realised that the wheel is also warped and warping the rotor when I break. So they hammered the wheel to get it circular again and put it on a metal lathe which cut it perfectly round. Problem was solved after that. Make sure you check both the wheel and rotor.

bob

Doesn't cost me anything on nitrogen (free at Costco even if you didn't buy your tires from them), so its a good deal all around for me, IMO people are looking for ways to reduce fuel consumption, nitrogen helps out like 5w20 does when you average it fleet wide (by simple virtue of maintaining the correct pressure longer). IMO the OE's should adpot it as the factory fill and the feds should mandate it's use for anybody who installs/services tire products. The equipment is compatively cheap, if a bit more maintence intensive (you don't have to buy nitrogen in bulk and store it, you can ****** it right from the atmosphere with a generator).

boduke0220

i did that one time in my car lol but it was wet!
i bet you wished you have tinted windows so no one could see you lol

mrkabc

32? I run mine at 35. Of course, it's SoCal here and we don't really have weather so I can get away with it.

Unfortunately my mileage is STILL around the 17.x range / 23x miles per tank though. Must be my lead foot.

8905GT

Too funny, well not really but your story telling skills are,
32 PSI on 20"s for me.

n8rfastback

each type of tire needs a different psi rating. 32 is just the most common.

zaghloul

I think you are mistaken. Each type/brand of tire has its own pressure max, and speed rating. However, the optimum running pressure for each tire depends only on the wieght of the car. It you put low profile 22's on your Stang, or high profile 14's, they both still need to be at 32psi.

theedge67

I think that is mistaken...but I'm too drunk to explain why. Maybe tomorrow.

zaghloul

I may very well be mistaken too, I've just heard that before more than once. I've been to many tire manfucaturers websites that they say to use the pressure rating on the doorsill. Also the fact that the spare tire needs 32psi further emphasized that point to me.

Steve, when you're sober can you also please explain to me something else. I've never really gotten a good answer to this, and was hoping maybe you'd shed some light on it. Why does a tire which measures, say 32psi, while its attached to the car (with all that load on it), still measure 32psi when you remove it? Shouldn't the pressure decrease when you remove the load?

To me this seems to violate the Ideal Gas Law (pV=nRT). p=pressure, V=volume, n=number of gas mols, R=gas constant, and T=temp. When a tire has a load on it, the sides bulge out, and the bottom touching the ground is flat. This deformation should change the volume and thus the pressure, but it doesn't. How is that? The n, R, and T are not changing, thus when V goes up p should go down.

theedge67

Found this. It doesn't explain why, but I'll keep looking for a good explanation of why.

"Another valuable resource is the Tire Load/Inflation Tables. Your nearby tire dealer should have a copy. Not only will this document tell you the correct tire pressure for stock sizes, but it will provide the information on optional plus sizes as well. A good example would be the findings on a Honda Civic with the stock size 185/65R-14; recommended air pressure is 28 psi. Plus one size is 195/55R-15 with a recommended air pressure of 32 psi. Plus two size is 205/45R-16 with a recommended air pressure of 36 psi. Note how the air pressure increases with plus sizing to meet the load carrying capacity for the car."

randy_tho

I know increasing the PSI can increase carrying capacity but I don't think that always plus sizing indicates a pressure increase. For instance my Dodge stealth is 32 in front and 29 in back. That is with the factory 17" and 18" tires on the TT. I think maybe also the 16" on the base model use the same PSI.

bob

Depends on the volume of air in the tire, the tire itself is basically a wrapper, the air does the work of carrying the load, the volume of air in the tire determines the amount of pressure needed, but thats only a part of it, air pressure as this thread indicates is also important as it relates to the contact patch, being both over inflated and under inflated can reduce the contact patch in wet weather (as wierd as the latter may sound). A tire that is underinflated will deform when it crosses over a patch of water (the center section is lifted and the tire rides on the edges of the contact patch) making it more susceptible to hydroplaning. This can happen with as little as a 5 psi loss in pressure.

kevinb120

That is correct, some of the ultra low profile street tires on heavy trucks can go beyond 45psi, and run-flats have their own set of rules. It all depends. For the stock Mustang tires, 17's/18's, 32(ish) is pretty much the status-quo. You really have to be on top of pressures this time of year(for the northern half) temps now varying from 60F to 20F in any given week, the pressures can get way off quickly.

samckernan

One time, this guy I know was driving around with his traction control OFF. It was a wet day out and he was just playing around having the back end slide out... just screwing around a bit.

Later, when getting on the freeway, getting up to speed, shifting from second to third, shooting over to the second to the left lane (out of four lanes) passing slower cars in the two right lanes, as soon as he shifted to third the back end started going sideways. His thought was, "TC will kick in". He forgot TC was off, so he stayed on the gas! Next thing he knows, he's doing a complete 360 on the freeway. He comes to a stop in the 3rd lane, pointed in the right direction, with the engine stalled. He fires it back up and takes off like a bat out of hell.

People behind him must have been saying, "WTF, look at that Mustang, it's doing a 360!"

He was like, "that's right, I meant to do that...", As he's shaking uncontrollably.

Lucky as hell, not a scratch, nick nor anything...

Knock on wood.

Glad your car didn't get to messed up. Live an learn.



Sam

8905GT

Hmm so I wonder whats the best PSI for 245/35/20?