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Old 21st July 2009, 13:38   #1
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Question Why is 30 the default pressure in petrol stations?

I have noticed that the default pressure in almost all petrol bunks is '30'(psi) and most of the cars that check pressure would have come driven for sometime, i.e the tyre pressure when they are filling air to the tyres are not in the recommended cold state as specified, but 3-4 psi more. Most drivers don't seem to bother to even look what the air pressure is, that is being filled in their car.

I have to each time ask the attendant to increase the psi according to my running, he would do it with a strange look in his face, a condescending look.

Does this mean that most of the cars that are running around are under-inflated?
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Old 21st July 2009, 13:56   #2
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What do you mean by default pressure? Most guages have buttons by which the pressure can be adjusted to suit the specifc vehicle's tyres. So don't really understand your question.

Are you saying that the pump attendants set the guage at 30 psi and fill up all the cars that come there without adjusting the pressure to suit the specific vehicle?
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Old 21st July 2009, 14:06   #3
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Quote:
Originally Posted by gpa View Post
What do you mean by default pressure?
Are you saying that the pump attendants set the guage at 30 psi and fill up all the cars that come there without adjusting the pressure to suit the specific vehicle?
Yep, that's just what I mean, they don't seem to adjust the setting at all and the most drivers don't seem bothered too. Strange.
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Old 21st July 2009, 14:26   #4
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That is what most petrol stations/tyre shops do.

Because you can never be too wrong with 30 for 99% of the people. Of course, some people who have fiddled a bit may find that they need a little bit more or a little bit less. But for most people, 30 is a sweet spot. The tyre isnt underinflated nor overinflated.
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Old 21st July 2009, 15:11   #5
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Quote:
Originally Posted by anandtheleo View Post
I have noticed that the default pressure in almost all petrol bunks is '30'(psi) and most of the cars that check pressure would have come driven for sometime, i.e the tyre pressure when they are filling air to the tyres are not in the recommended cold state as specified, but 3-4 psi more. Most drivers don't seem to bother to even look what the air pressure is, that is being filled in their car.

I have to each time ask the attendant to increase the psi according to my running, he would do it with a strange look in his face, a condescending look.

Does this mean that most of the cars that are running around are under-inflated?
Have noticed this many times. Most people do not bother with such things. I'v often seen fully laden 4 wheelers... like 5 passangers with luggage and all, with all the passangers inside, getting air filled. Goes without saying that they would be filling up warm tyres. They just fillup whatever pressure the tyre guy fancies.

Now add to this, most pressure gauges are anyway incorrect.

So what do you expect?

I'm inclined to think that all these pressure increasing factors and the pressure reducing factors kinda cancel themselves and they get something close to what the pressure should be...

If not, may God save them and their tyres...

Last edited by Raccoon : 21st July 2009 at 15:13.
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Old 21st July 2009, 15:41   #6
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Quote:
Originally Posted by Nikhilb2008 View Post
That is what most petrol stations/tyre shops do.

Because you can never be too wrong with 30 for 99% of the people. Of course, some people who have fiddled a bit may find that they need a little bit more or a little bit less. But for most people, 30 is a sweet spot. The tyre isnt underinflated nor overinflated.
i agree with this point. tyre pressure guages in most of these bunks are not accurate , so there really is no point in trying to worry abt 1-2 psi this way or that way.
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Old 16th March 2010, 19:42   #7
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Pardon my Ignorance, but how does it matters? I have tubeless and I am among the people you guys are talking about. I fill 30 ALL the time
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Old 17th March 2010, 01:23   #8
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^^^It certainly matters. But don't worry, you can always pretend that it doesn't.
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Old 17th March 2010, 01:39   #9
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I go by the book --- or, rather, by the numbers on the label on the door post. I have to put my reading glasses on, and it is still a strain to read them. Then I need my wife to translate into Tamil.

Then I thought to write on a paper like <---36 33---> to show to the guy (the actual numbers are something like that, but I have numlexia, so have to look it up every time).

I do take liberties with the interval between fillings, and can confirm how much better the car feels when pumped up properly.

I would not settle for 30-all-round.
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Old 17th March 2010, 07:19   #10
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For my Scorpio (2004), the door panel says 29 for the front and 31 for the rear (strangely, for both laden and unladen conditions!)

So I have been filling 30 all round, as this does not make much difference.

Another puzzling thing is that the Scorpio is front heavy (at least when unladen, I assume), yet the recommended unladen pressures are lower for the front when compared with the rear!

Technical gurus, please correct me if I am mistaken in my assumptions
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Old 17th March 2010, 08:07   #11
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For my WagonR it says 33 pounds; however I assume that Maruti has recommended this pressure guage under standard testing conditions (means more mileage) at the cost of road grip; So I tend to fill in like 31/32 most of the times;

Once or twice I tried filling in like 35 & the ride was real smooth, little noisy & shaky. But on other occassion I found the wheels getting locked & skiddy when braking, it was then I decided to fill in little less. IMO, 33 is also fine.
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Old 17th March 2010, 11:14   #12
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Quote:
Originally Posted by aargee View Post
....however I assume that Maruti has recommended this pressure guage under standard testing conditions (means more mileage) at the cost of road grip; So I tend to fill in like 31/32 most of the times....
Tyre pressure should always be checked in cold condition, irrespective of the vehicle; I guess that means before the vehicle has run more than 1-2 kms. But not many people have access to a petrol pump/tyre shop with a reliable & accurate gauge within this distance from their home/office - at least I don't!

That's why I started using a digital tyre inflater a few months ago. It's a little expensive, but enables me to keep my vehicles tyres inflated according to my comfort level (a bit less than the mfg'ers recommendation), which in turn translates to a very comfortable ride and decent FE.

Here's the link, if anyone's interested. Not sure if this is available outside Pune.

Link Image Makers (India) Pvt. Ltd.

Cheers,
Vikram
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Old 17th March 2010, 11:50   #13
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^^^Looks cool; but at what price? Can you share some more details like the battery life & how it works etc?
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Old 17th March 2010, 12:03   #14
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Most of the prople dont care how much air goes into the tyre. I have noticed that only at Shell bunks, the attendants ask the recommended pressure.

A coupla days ago i had a heated argument with the manager, attendants and even some customers of a BPCL bunk near my place. Their machine was not calibrated. I asked the attendant to topup to 35psi in my bike rear tyre. The machine showed the current pressure as 22 although i filled it a week ago. I even asked the atendant if the machine was ok. I went on my way and realized that the ride was hard and bumpy. Came home and checked with a guage and it showed 50psi. Went to shell and it showed 49.x psi. I went back and asked the manager to shut down the pump. A few people came and started arguing, the 17-18yr old attendant abused me in local lingo and tried pushing me and walking off.. I caught his arm and squeezed it very hard till he howled. Big mistake on my part. This was followed by threats of calling the cops. I told them to go ahead and call them and made myself comfy there after shutting down the pump. Needless to say everyone went their way. Before all this i had asked the manager for the Phone # of the regional inchage office which he refused to give.
2 yrs ago they had filled excess air in my new wagon r due to which a tyre burst at over 100 and the car toppeled over. It was a wrieoff and seatblets made sure my bro and parents came out without a scratch. I had given a complaint to the manager in regards to this and they never got back to me. I didnt followup either.
I had visited the bunk after 2yrs thinking they may have changed! I was mistaken!
The owners dont care bout this and support their men. I want these people to be taken to task. But What do i do? I can lodge a complaint with bpcl but i dont have the attendant or managers names.
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Old 17th March 2010, 12:04   #15
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The tyre pressures set by the manufacturers are based on the weight of the vehicle etc., We should never under-inflate them compared to their set limits.
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