[condor]

Originally Posted by fighterace

The logic he gave was the the very act of pressure check .. is stressful for the valve/valve stem. So one bumps up the pressure at one go, and lets it slowly leak to whatever level is unacceptable over time..

Hope you didnt buy it.

[a4anurag]

Originally Posted by fighterace

The logic he gave was the the very act of pressure check, esp. at a petrol pump, is stressful for the valve/valve stem.

A wrong logic I say. Don't buy such logic. Your risking your life.

Please don't over full the tyre for checking the leaks of the stems or longevity of the stem. Since it leaks it means it is not in a good condition so in our state of roads during a bump or a pot hole or on a highway cruising if that weak valve stem gives way, you are in trouble. Get that reburied ASAP.

Originally Posted by fighterace

So one bumps up the pressure at one go, and lets it slowly leak to whatever level is unacceptable over time.

Bump it to 100 psi or the maximum it can hold on to and forget the tyre. It will slowly leak and come to nil again. Why fill the air every week. One time job. Fill it, shut it and forget it logic.

Anurag.

[iVento]

The prescribed PSI for Wagon R New is 32 (cold pressure)
Rajesh, You can also consider filling the tubes with Nitrogen. Search TBHP for details.
My Waggy tubes are Nitro filled. I experience only 1 or 2 PSI pressure loss when I take the vehicle for top-ups once in two months. My usage around 500 KM per month.

[fighterace]

Originally Posted by condor

Hope you didnt buy it.

No, I didn't. Given the cost of petrol vs the cost of valve stems, I'd rather top up at least twice a month. besides, those things shouldn't be so damn fragile in the first place. But what I quoted is the gyan any tyre seller will give you- got it from two independent places. Which makes me wonder where the stems are coming from.

[aniketi]

Recently I faced a strange question from my cousin to which I couldn't answer. Story goes like this -

My cousin was over to my place and we were planning to go somewhere in his car, Eeco. When we came down, we noticed that one tire has very less air in it and we suspected its a puncture. So we went to nearby puncture shop to get it rectified. As expected it has one small puncture. Now as we were getting puncture done, we were chatting. It goes like this :

me: how often you fill the air in tires?
cousin: never !
me: hahaha
cousin: I am serious.
me: don't fool me.
cousin: why should I ?

Now little background. My cousin is around 45 years old and a little strange guy. He always has his own logic for everything and trusts on that. It takes effort to convince him or prove him wrong. He is a mechanical engineer and does small trading business, so basically he is a technical guy. He is using his Eeco for his business purpose and has done running of 28 K in 2 years when this discussion happened. His car has Apollo tubeless tires, company fitted.

Conversation continues:

me: you mean you never check or fill air in tires??
cousin: No
me: but why?
cousin: no need
me: what do you mean?
cousin: How air will leak from tire without any puncture? If there is no puncture, pressure will remain more or less same. No need to fill the air. So i never do it. Never filled air in tire for last 2 years !!! Never faced any issue in last 2 years. This is the first time puncture has happened. No issues at all so far.

Now i don't have any logical answer to convince him on this. But one thing is sure that he is not telling a lie, i can assure you on that. He uses his car almost daily for his business purpose. Sometimes he carries load of 300 - 500 KG in the car as well. He does mix of highways and city running, 80:20. Is this possible? Can somebody live without checking tire pressure at all? Is his logic true that without puncture there can't be leaking of air from tire, so no need to fill more air? Your opinions please.

Please note: Cousin confirmed that he is not sure if service center guy's has filled air in tires for him when he gives it for servicing. He has done normal servicing for last more than 2 years. I highly doubt if service center guy's checks tire pressure when we give it for servicing. My experience is they never check, mostly. Please note that i checks tire pressure in my car once in 3-4 months. I don't find any issues by doing so.

[Grr7]

Originally Posted by aniketi

Now i don't have any logical answer to convince him on this. But one thing is sure that he is not telling a lie, i can assure you on that. He uses his car almost daily for his business purpose. Sometimes he carries load of 300 - 500 KG in the car as well. He does mix of highways and city running, 80:20. Is this possible? Can somebody live without checking tire pressure at all? Is his logic true that without puncture there can't be leaking of air from tire, so no need to fill more air? Your opinions please.

Should tyre loose air?
Theoretically: No
Practically: Yes

When we study all those scientific phenomenon theoretically, there is a perfect summation for everything. But as soon as we move to the worldly practical aspects, there are very many factors that gets involved.
Right from the construction of rim to the rubber of tire. Every little bugger comes into play with its own whims and fancies.

That being said, your cousin's car's tires must have definitely lost some part of the air(that might be minuscule like 2-3 psi drop). Besides, its not easy to tell by the naked eyes if the pressure in tire is 28 or 30 or 32.

The best way to find out is to take a good calibrated tire pressure measuring device and take reading of the individual tire.

Keep us updated of the findings(including the pressure in spare tire).

[schakravarthy]

In a perfect world, yes; what your cousin says holds water ( or, air should we say? ). But alas, the world isn't perfect, is it?

Air can 'leak' from punctureless tyres during various instances. Some reasons I can think of are:

1) Remember, when the tyres are inflated the pressure in the tyre is more than the atmosphere. Air has funny ways of escaping back to its natural habitat, through the tiniest of pores if need be so! Every time you go over an object, brake or corner hard you are only adding that much more pressure on the tyre.

2) the valves are another culprit. A slightly loose or damaged valve is another happy passage for the air to escape out!

3) aging tyres can also aid the freedom struggle. The disintegrating rubber, as it loses strength, gives the 'struggle' more impetus.

4) damaged rims are also another possible cause for the air pressure to decrease. Land the car hard on a bump or in a dump, and you can have a damaged rim. The more the 'bend', the more is the 'leak'.

5) And also to be noted is the fact that the seal between the bead of the tyre and the rim is never perfect in real world, even when there is no apparent 'bend' in the rim. So air does escape out of that, albeit slowly. And here, pure nitrogen will escape just as much as normal air would because the gap will be far bigger than the size of the molecules

Its a safe practice to check the tyre pressures every week ( at least I do so ). Better safe than sorry, anyone?

[Nissan1180]

Air diffuses through the tire walls. No matter how good your tire is, there will be a very small quantity that will diffuse out of the tire.
If you put in Nitrogen the diffusion rate will be lower because the molecules of nitrogen are larger than Oxygen, Carbon dioxide and noble gases (traces) which are present in the air.

[srinath.s]

I may be wrong, but I think rubber cannot be 100% impermeable. There will always be that tiniest bit of space between rubber molecules through which air can escape. Although the rate at which this happens is very very low.

Tangentially, there are people who claim that frequent pressure checks can be avoided by filling nitrogen as nitrogen molecules are larger in size (that air itself is >70% nitrogen is another matter ).

Gurus, please correct me if I am babbling.

Edit: Noticed Nissan1180's post with respect to Nitrogen only after posting my comment.

[svsantosh]

Loss of air from a tyre can occur even when parked for long duration.

1) Osmosis - air molecules escape through rubber (tube or tyre, any)

2) Rim beading (again because metal and rubber are different compounds)

3) Filling valve

As to why the OPs Eeco doesnt need air over a few years - is because (may be) during every service at a A.S.S the final check is to fill air during alignment/balancing. So it holds good till the next service - as in - Eeco needs 34-36 Psi IIRC, so it may gradually reduce to 30 over 4-5 months of regular usage. Visually wont make a damn difference. They look the same even at 20ish Psi. So keep a handy Psi meter and check after a few weeks of usage without topping up.

PS - Even 100's of Kms of highway runs (under heavy loads) wont do much harm w.r.t tyre pressure as to few kms of really bad, patchy, mud roads, mumbai monsoon roads, etc.

[aniketi]

Team-BHPians, its not that i don't agree to what you are saying. Question is he can live without filling air in his tires. No harm is done to tires or to the car. Even with load its performing well, i mean as expected.

As far as i know, when temperature increases volume of air also increases. So due to his regular use i guess car tire gets heated regularly which causes to maintain the air pressure in the tire. Just a wild guess guy's as i don't have any technical answer for this. Other thing is my cousin is a very sedate driver and maintains constant speed of below 80 generally. He generally gets slow on bad roads and avoid pat holes. So bending of rims has never happened. As i said, its a strange question which has no technical or logical answer. Point is he is using his car without any issue. Tires are pretty normal and has normal wear and tear till date. Visually tires looks ok and don't look like it has less pressure. Back to square guy's

[anuragn]

He must have visited the service center thrice during the first year and, probably once in the second year (assuming he bought a new car).
I am sure the guys would have topped up the pressure while carrying out wheel balancing/alignment. Atleast, my experience with Maruti is that they do top up the tyre pressure and actually, they fill it more than the recommended value. So all this could explain running of the car without bothering for air pressure.

[sridhar-v]

Normally on new tyres air loss is negligible. Also service centres do tend to check air during maintenance.

If he has not filled air in between services, he is lucky. However on low pressure the tyre will flex more, heat up for prolonged driving & one will feel, visualy, that pressure is ok. One needs to examine the tyre wear pattern to see if it is underinflated or over inflated.

Improper tyre pressures are a major reasong for tyre bursts during highway driving. So ask him to be careful.

[Gansan]

I check the pressure on my car every two weeks and bike every week. Every time there is a slight drop in pressure. It is only logical more pressure will drop with longer intervals.

But a neighbor of mine who has joined Michelin India was sent to France for 12 months on training. He left after disconnecting the battery of his Vento, after just covering his car. It is parked open to sky, and I expected the tyres to become flat gradually.

But it did not happen. They lost some pressure, that much was visible. He returned after 14 months, the service centre guys came with a can of petrol, poured it in the tank, connected the battery, started the car and drove it to the workshop for a "wake up" service!

[schakravarthy]

Since we're heading for a stalemate, a few pics of the tyres, esp showing the thread wear, might help the cause of this thread.

Edit:
Or, you could drag your cousin to the nearest tyre air-filling station; ask the fellow there to check the air pressure; when the gauge shows a lesser pressure, shout out " Aha! I told you so! "; chide him and then enumerate the benefits of maintaining the proper tyre pressure and be done with it.