[TravelModeOn]

My parents get their DZire tyre filled at 30ps pressure every 15-18 days.
However, only one of the tyres (rear, non-driver) gets low to around 12-15ps in 15-18 days of refill cycle. Rest all 3 tyres (including the spare one lying in the boot) are found to be at 26-27ps at the same time.

1) The tyre in question has been checked twice for any minor punctures. Nothing is found. Its all perfect.
2) Mostly driven by the parents in the city, they hardly feel any issues while driving.

Any inputs on what could be going wrong?
How can the same digital pump measure (at two different reputed petrol pumps) keeps showing low pressure in only 1 tyre, and similar intact in remaining 4? What more can be checked?

Thanks

[d.w.w.]

Assuming these are tubeless tyres, have you checked for leaks on the side walls or near the rim? Often there will be leaks from where the rim meets the tyre and local shops never check this.

[am1m]

That tyre might have developed small cracks that are causing this. Exact same thing happened with our car tyres. All tyres were ok, except the left rear one, consistently used to show much lower tyre pressure when filling up. Couple of tyre centers said it was because it had developed cracks. In our case, the issue was very, very limited usage. The car was being used once in 2 months, and that too just for the sake of keeping it running.

How old are the tyres, how many km have they run? Is the car being used often?

[humyum]

Originally Posted by TravelModeOn

My parents get their DZire tyre filled at 30ps pressure every 15-18 days.
However, only one of the tyres (rear, non-driver) gets low to around 12-15ps in 15-18 days of refill cycle. Rest all 3 tyres (including the spare one lying in the boot) are found to be at 26-27ps at the same time.

1) The tyre in question has been checked twice for any minor punctures. Nothing is found. Its all perfect.
2) Mostly driven by the parents in the city, they hardly feel any issues while driving.

Any inputs on what could be going wrong?
How can the same digital pump measure (at two different reputed petrol pumps) keeps showing low pressure in only 1 tyre, and similar intact in remaining 4? What more can be checked?

Thanks

Since I am very fincky about tyre pressures and super sensitive to it too, I keep checking it once a week atleast and have figured out some pain points which causes this.

1) Usually, tyre pressures when they drop, all tyres have a drip with a maximum difference between them of 1 psi if everything is perfect.

2) When one tyre pressure is lesser by more than 2 psi consequently, something is wrong.

3) Tyre pressure is lost because of the following

a) Valve Pins being leaky or loose
b) Value base having a minor leak
c) Dirt or dust between tyre and rim. Tyre needs to be removed and refitted back after cleaning. Make sure its fit back in the same position on the rim as when removed otherwise balancing will go for a toss.
d) Minor needle type puncture which takes an expert puncture guy to find (I had one like this, use to loose 2 psi only in 1 tyre, rest were 1 psi). I kept going to punture guys and they kept saying its fine its fine but I was not happy, I went to this punture guy, we filled it to 50 psi and kept putting the water solution on the tyre for like 20 minutes until we found this small bubble which had a very half an mm type needle type long thing stuck inside which was leaking minor air.

In your case, half the air is being lost, so its definitely out of the above.

[mayankk]

Two of my cars had this issue. First was traced to a valve.

The second was traced after taking the tyre off the car, found to be a the tail of a screw embedded in a tread. Couldn't even see it, almost.

And it did not cause any bubbles when cheeked with water. But it was enough to let out about 3-4 psi over a couple of days.

[sumeethaldankar]

It is slow leak for sure somewhere. A competent tire repair shop should be able to diagnose it. Depending on your location kindly search for a tire shop on the Team Bhp directory section. If you stay near Santacruz then Trevor from Straight Line should be able to assist. Else look for a place closer.

Good Luck.

[careind]

Originally Posted by TravelModeOn

My parents get their DZire tyre filled at 30ps pressure every 15-18 days.
However, only one of the tyres (rear, non-driver) gets low to around 12-15ps in 15-18 days of refill cycle. Rest all 3 tyres (including the spare one lying in the boot) are found to be at 26-27ps at the same time.
Thanks

Rather than going to a puncture shop, visit a Tyre shop and give the faulty tyre an once over.
There could be many things like cracks/weakness due to age or use, embedded foreign object, leaky valves, fit of the rim etc. that would release the air very slowly, which a simple water immersion test might not uncover .

I had a slow leak in my XUV, like 4 psi drop in a week, and the shop technician found an embedded screw in the treads once the tyre was taken off the rim.
They would also advise you on the health of the tyre.

[autobahnjpr]

most of the times, the leak is due to faulty valves. valves are cheap to replace and is it suggested to replace the valve of that tire.

otherwise there is some minor leak which is not very visibly evident. remove the tyre and then check again for leaks with water.

[ranjeet_sam]

Originally Posted by TravelModeOn

What more can be checked?

Thanks

How old is the Tyre? I had a similar problem in my car when the tyres were around 4-5 years. There was no visible puncture as such. The issue got resolved when I changed the tyres. It may be that the air is leaking out through the side walls or from a dent/bend in the alloy/rim.

You could change the tyre or if the tyre is in good condition simply put a regular tube inside.

[NomadSK]

Even if everything is perfectly fine, the pressure drop can happen from the tyres as air molecules would gradually pass through the rubber membrane, the older the tyre, more air would pass out due to its degradation of rubber with UV light over a period of time, rubber isn't completely air-tight and this is known as permeation of air. Different types of rubber have varying permeation coefficients, the permeation of air through rubber/any material is typically described by Fick's Law.

That's why nitrogen is preferred over oxygen with bigger molecule size and relatively less rate of permeation.

[am1m]

Originally Posted by NomadSK

That's why nitrogen is preferred over oxygen with bigger molecule size and relatively less rate of permeation.

Doesn't look like it's that much bigger (and anyway we're talking about molecular sizes) to really make a difference when it comes to leakage.

Does N2 really make a perceptible difference for normal road vehicles/usage? I thought that was debunked?

https://www.team-bhp.com/forum/techn...trogen-55.html (Inflating tyres with dry nitrogen)

[Bsimhan]

Originally Posted by TravelModeOn

...However, only one of the tyres (rear, non-driver) gets low to around 12-15ps in 15-18 days of refill cycle. Rest all 3 tyres (including the spare one lying in the boot) are found to be at 26-27ps at the same time.

I had the same problem with my Innova. The rear right tyre was deflating in a couple of days. Took it to the tyre shop twice and no puncture or valve leaks were detected. Also it was not happening all the time. When I took it in for the third time, the guy suggested that we inflate the tyre beyond the maximum suggested and immerse it in a tub of water. Did this and lo and behold a very tiny leak was discovered. Turns out that a very tiny nail got into the tyre. The tyre guy told me that this was a rare case of position of the wheel at the time of parking. In case the tyre was positioned exactly pressing the ground, the air held when parked. If the position where the nail was embedded was above the ground, then a very slow leak would result. I wouldn't have believed it if I hadn't seen the nail. This issue took me months to resolve. In the interim I was thinking of all reasons of things like defective valve, improper beading of tyre etc. In the interim I was going around keeping a tyre inflator in the car. Hope you've been able to resolve the issue.
Regards, Balaji

[mm_shen]

Originally Posted by TravelModeOn

Any inputs on what could be going wrong?

Thanks

Very similar problem with my Ignis a few months back. I replaced all valve pins on all tyres. The petrol pump attendants who top up the air do not have proper training. Coupled to worn out couplings at the tube end. They press hard for the air to show pressure. This damages the valve pins.
Another reasons is if the valve caps are not present, dirt gets stuck when filling air and pressure reduces gradually.
My solution was to top up air at puncture shops rather than petrol pumps. Rather best is have a portable compressor and top up very month yourself. See that valve caps are always present. Keep a few spares in your glove box.
After this, my tyre pressure more or less remain constant every month when I check.

[NomadSK]

Originally Posted by am1m

Doesn't look like it's that much bigger (and anyway we're talking about molecular sizes) to really make a difference when it comes to leakage.

It won't look bigger, it just is at microscopic level, we are here talking about the diameter of molecules in picometers/nanometers, not measurable with naked eye and Nitrogen have bigger molecules. There are enough studies done, that tyres with inert nitrogen lose pressure slowly than filled in with normal compressed air. Also, tyres filled with nitrogen maintain inflation pressure longer & consistent than compressed air-filled tires in "fluctuating temperatures".

Does N2 really make a perceptible difference for normal road vehicles/usage? I thought that was debunked?

I don't know about perceptible difference, but one cannot debunk the science. And I gave the example of comparison between N2 and O2 and not the air, which itself contains 78% N2+ water vapour+O2.

Anyway point is one can lose pressure due to permeation whether N2 or O2 is used, only difference would be the rate of permeation.

[laferrari]

Had a similar issue with my brand new Bridgestone tyre. Pressure used to go down by about 10 psi in every 2 weeks. Multiple visits to the local puncture guy and the Bridgestone store didn't show up anything. After a few exasperated months, had the Bridgestone guys remove the tyre and completely immerse it in a tub of water with some weight on it. Lo and behold, tiny bubbles appeared just where the tread ends and the sidewall begins. No notable puncture causing elements.

It was deemed a manufacturing defect and the dealer was good enough to replace the tyre after calculating the tread wear. I had to pay some ₹500 odd.