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Old 26th December 2007, 17:01   #16
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I did this a few days back as i always had a doubt if the guages in gas stations are OK.
I checked it when cold in a BP station.......30psi.
5 min later,checked in an IOC station.........34 psi.
10 min later,checked at another BP station.....28 psi.
5 min later,checked at shell station............30 psi.

Now,which one is right ?
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Old 26th December 2007, 17:24   #17
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Originally Posted by chandan View Post
I did this a few days back as i always had a doubt if the guages in gas stations are OK.
I checked it when cold in a BP station.......30psi.
5 min later,checked in an IOC station.........34 psi.
10 min later,checked at another BP station.....28 psi.
5 min later,checked at shell station............30 psi.

Now,which one is right ?
Man, you are in a real fix!! Best option available is to take the average of the 4 readings
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Old 26th December 2007, 17:36   #18
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This is very true.

I filled air in the tubeless Potenza GIIs from the petrol bunk in Bangalore's residency road to 30 psi and immediately felt that the air pressure was too high. However, the car was zooming even at a slight tap on the accelerator)

Didn't check it for a while and then drove to Palakkad last Sat.. Believe me, I reached palakkad (410+ kms) in less than 14.62 litres, that too, after detouring in Coimbatore city! That was an awesome 28 kmpl (Maruti 1996 carb model, with 2 people and very little luggage). One should note that the road from Bangalore to Krishnagiri is downhill and requires hardly any braking. However, there were some really bad stretches as well.

I then got it checked at palakkad and the air pressure was 38 psi (thank God, the tyres didn't burst). Brought it down to 30 psi immediately and then checked it at Madurai the next day (yes, had a long long drive last weekend) when the system there showed 28 psi which was increased to 30psi... Checked at Salem the next day when the meter showed 38 psi!!! 'Reduced' it back to 33 psi to fit his reading (I knew that his digital meter was wrong). Got it again checked the same day at Dharmapuri and it was showing 22 (the reason for the sluggishness!) and filled it back to 30 psi (now the ride is alright).
God knows why there is so much of difference. However, trust me, the mileage was awesome while running on 38 psi!
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Old 26th December 2007, 17:45   #19
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Quote:
Originally Posted by Jeep View Post
This is very true.

I filled air in the tubeless Potenza GIIs from the petrol bunk in Bangalore's residency road to 30 psi and immediately felt that the air pressure was too high. However, the car was zooming even at a slight tap on the accelerator)

Didn't check it for a while and then drove to Palakkad last Sat.. Believe me, I reached palakkad (410+ kms) in less than 14.62 litres, that too, after detouring in Coimbatore city! That was an awesome 28 kmpl (Maruti 1996 carb model, with 2 people and very little luggage). One should note that the road from Bangalore to Krishnagiri is downhill and requires hardly any braking. However, there were some really bad stretches as well.

I then got it checked at palakkad and the air pressure was 38 psi (thank God, the tyres didn't burst). Brought it down to 30 psi immediately and then checked it at Madurai the next day (yes, had a long long drive last weekend) when the system there showed 28 psi which was increased to 30psi... Checked at Salem the next day when the meter showed 38 psi!!! 'Reduced' it back to 33 psi to fit his reading (I knew that his digital meter was wrong). Got it again checked the same day at Dharmapuri and it was showing 22 (the reason for the sluggishness!) and filled it back to 30 psi (now the ride is alright).
God knows why there is so much of difference. However, trust me, the mileage was awesome while running on 38 psi!
OMG...!!! U got 28 kmpl with GIIIs (assuming those are 165/60-12) upsized tyres.....
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Old 26th December 2007, 17:56   #20
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Thumbs down Accutire gauges

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Originally Posted by k36 View Post
I've recently ordered the Accutire MS-4021B Standard Digital Tire Gauge for USD 7.94 through a friend who is returning from the US in a couple of weeks. Finalized on the model based mostly on customer reviews. Once I get and try it out, it I'll update this thread.
Sorry to burst your bubble k36 but I've owned two Accutire gauges and they were both lousy.

Two years ago I bought a key chain type Accutire gauge from Canadian Tire. It was the cheapest of the entire range that they had. Brought it back to India, used it for about 4 months and then it stopped working. I didn't think much of it since it was cheap - $2-3 Canadian.

Then this year I picked up another Accutire gauge from the same shop. This one was better built, bigger with a handle - like your picture, and more expensive about $8-10 Canadian. This one lasted me even less. I used it once. The next time it was dead.

Maybe the batteries have run out in both - but I find that to be too much of a coincidence. Within a few months they both died with hardly any use. I hope you have better luck. And by the way, in the more expensive gauge, the plastic of the nozzle has deformed a little from pressing on the tire valve!

In my opinion, the build quality of Accutire gauges is really bad.
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Old 26th December 2007, 17:59   #21
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Arrow Can a Parrot pick the correct pressure?

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Originally Posted by vnabhi View Post
Man, you are in a real fix!! Best option available is to take the average of the 4 readings
I loved this option............

You can also write the 4 values on 4 chits and tell a parrot (the one you see on the roadsides with astrologers) to pick one?

--Ramky
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Old 26th December 2007, 18:13   #22
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28kmpl! My GOD! If you were able to run all the way to Palaghat, then I do not think that you need to worry about the tire bursting; if it was to be then it would have bursted!

Go and fill it to 28PSI and enjoy the mileage!
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Old 26th December 2007, 19:04   #23
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@kpzen and @HappyWheels
Yes the tyres have lower profiles 165/60

I usually get around 22 kmpl while going from Blore to Palghat and about 19-20 while coming back (not sure why, may be Bangalore is 'elevated' or may be the car becomes 'heavier' while coming back from home ).

I drive with a moderately light foot and slow down early at lights/humps/traffic jams to minimise braking. With spirited drivers (my bros who took it to 110+ enroute to Madurai from Palakkad), and correct pressure, 30psi as indicated, the mileage dropped to 19 kmpl.

The problem was, nobody except my brothers believed the mileage figures, and my dad ridiculed me :(.

Even on slightly bad roads, the suspension cried for mercy when the pressure was 38 psi...

Question: If I can put in better/stiffer suspension, is it safe to inflate to,say, 34 psi and run continuously? I think I should go for higher profile tyres then to reduce the load on the springs? Also, wouldn't it create a stiffer ride and ultimately the car will rattle more?
I wonder what figures a 5-speed MPFI would have given!
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Old 26th December 2007, 20:24   #24
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Quote:
Originally Posted by Jeep View Post
Yes the tyres have lower profiles 165/60

[...]

Even on slightly bad roads, the suspension cried for mercy when the pressure was 38 psi...

Question: If I can put in better/stiffer suspension, is it safe to inflate to,say, 34 psi and run continuously? I think I should go for higher profile tyres then to reduce the load on the springs? Also, wouldn't it create a stiffer ride and ultimately the car will rattle more?
I wonder what figures a 5-speed MPFI would have given!
I used to drive a 1995 Maruti 800 (carb) with cross-ply tyres; mine was the standard non-AC model. I found that the car bounced around a lot on bad roads even with recommended tyre pressures. The suspension was pretty bad and around corners on even slightly bumpy roads, the car handled very poorly at higher speeds; there was a lot of understeer as per my recollection and the rear used to slide. The high-speed braking was inadequate and I remember one emergency braking at 90 kmph ending up with my car at about 45 degrees to the road.

To answer your question, you need to have no fear of tyre burst at a higher pressure of 34 psi. The main issue would be how your car handles and brakes on bumpy/wet roads. Do you have alloy wheels or the stock 4J steel rims? For 165 mm width tyres I think you should have at least 4.5J wheels. I would say start with 34 psi (set when tyres are cold) and if you find the ride to be too bouncy on bad roads with bad handling around corners and/or poor braking, then drop the pressure to 32 psi. I don't think you need to go below 32 psi, assuming that the recommended tyre pressures are 30 psi. Also on wet roads, higher tyre pressures may adversely affect handling/braking and with 165 mm width tyres, you should be aware of the possibility of aquaplaning, especially as the tread wears out.

For my old Santro, I have 5J alloys and stock-size 155/70 R13 Bridgestone Turanza ER-60 tyres. I set the tyre pressures to 35 psi (5 psi above recommended) mainly because of my high-speed driving on the Mumbai-Pune route. The wider wheels and the grippy H-rated tyres compensate for the higher tyre pressures and provide more than adequate grip, even in wet conditions. With Speed 97 thrown in, the pickup and the high-speed handling/braking are quite good and the car consistently hits 140+ top speeds. On bad roads the car does bounce around a little, and some caution would be required while cornering fast on bumpy stretches. But I still find the car's handling on wet/bad roads and cornering/braking to be much better than with the stock setup of 4J steel rims and tubetype tyres at 30 psi.

For M-800, which does not have as good suspension and handling as the Santro, I would say experiment and then settle for what suits you best. You should be aware of your car's limitations and drive accordingly.
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Old 26th December 2007, 21:22   #25
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Originally Posted by spadival View Post
I go to the same petrol pump (Sai Express Way near the Expressway exit - Pune) every time to fill fuel and air.. And almost EVERY time he takes out air instead of putting in more !! i.e. the pump gives a reading of around 34-35.
To add to what I said earlier, take a look at this website:

They're Black and Round | Mazda Australia Zoom Zoom

Quote:
Tyre Pressures should be checked ideally every two weeks and must ALWAYS be checked when the tyres are COLD.

Warm tyre pressures can be 20-30kPa (3-4 lb) above the recommended cold pressure. NEVER LET AIR OUT OF A WARM TYRE TO SET IT AT THE PLACARDED FIGURE, IT WILL RESULT IN SERIOUS UNDER-INFLATION.

As petrol station tyre gauges are notoriously inaccurate, where possible, always use your own good quality gauge.

Never rely on appearance; modern tyre belt construction techniques prevent tyre distortion being easily seen, even though it may be significantly under-inflated.
As for bench-marking tyre pressure gauges, I use the simple method of cross-checking the trusted gauge with another one. I have a trusted digital gauge with a 5-year guarantee on the accuracy. My air compressor has an analog gauge which consistently reads about 4 psi below the digital gauge. As long as this difference stays the same I am confident that my digital gauge is doing fine.

Last edited by rks : 26th December 2007 at 21:24.
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Old 26th December 2007, 21:27   #26
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In Chennai at the moment there is a 20-degree difference between night and day temperatures; perhaps in some places the difference may be even greater.

Is this a serious factor, or does the road friction temperature rise make the ambient temperature irrelevant?
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Old 26th December 2007, 21:48   #27
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Originally Posted by Thad E Ginathom View Post
In Chennai at the moment there is a 20-degree difference between night and day temperatures; perhaps in some places the difference may be even greater.

Is this a serious factor, or does the road friction temperature rise make the ambient temperature irrelevant?
I am not too sure of this. But from my experience, my guess is that the ambient temperature is more of factor with tubeless tyres, as I found the tyre pressures to vary noticeably with significant changes in ambient temperature. For some reason, I did not find the same variation with tubetype tyres.

I prefer to set the tyre pressures early in the morning, around 7-00 AM when the ambient temperature is still low. I don't care if the tyre pressures rise 1-2 psi in the afternoon; there is really no danger of tyre bursting due to high pressures as most modern tyres are built to handle much higher pressures than the maximum marked on them (usually 40 psi or 44 psi). Most of the tyre bursts occur due to under-inflation which causes excessive sidewall deformation and consequent heating up of the tyres.

I set my tyre pressures early morning in Pune and then I drive to Mumbai where the temperture can be significantly hgher. Once I had to leave the car at National Motors in Mumbai for service and they told me that the tyre pressures were found to be 37 psi (I set it at 35 psi in Pune). This difference could also be due to other factors than ambient temperature, such as difference in pressure gauge or the tyre being warm when these guys measured the pressure.

Last edited by rks : 26th December 2007 at 21:49.
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Old 27th December 2007, 11:36   #28
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I am not too sure of this. But from my experience, my guess is that the ambient temperature is more of factor with tubeless tyres, as I found the tyre pressures to vary noticeably with significant changes in ambient temperature. For some reason, I did not find the same variation with tubetype tyres.
Change is 20 deg C will have about 2% change in pressure (about 2 psi on 30 psi tyre pressure).

If you have filled up tyres in the early morning (about 22 deg C)when temp is very low and drive the whole day on highway (road temp about 65 deg C) at high speed (additional rise of 10 deg C), means the tyres are really going to face a rise in temp of 40~50 deg C.

Since tubeless is sealed by rims, therefore with drop of pressure, the sealing may be affected also (but I am not sure) and hence your observation.
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Old 27th December 2007, 13:11   #29
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Thanks, guys, for your thoughts on this.

I am very bad at regular pressure checking, really should do so much more often.
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Old 27th December 2007, 13:22   #30
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Here is the gauge I use to measure the Air Pressure in my tyres:





Cost of the Gauge: 0 Ahh the benefits of being a tyre dealer!

Ok jokes apart, this is a good gauge that I got complimentary from my dealer & it has turned out to be pretty accurate & much better than the ones that are there on the Petrol Pumps & Roadside puncture repair shops. I personally, only rely on the gauges of good Tyre shops since they are of high-quality & are regularly calibrated/maintained as the machine's are serviced from time to time. Any other's are simply not worth trusting IMO.
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