Tyre pressure drops

[thebullettrain]

I’ve a BMW 840d. It’s usually driven weekly / bi weekly for a 500 mile round trip. Tyres are 20” Potenza. All are in good shape with thread and recently gone through a BMW health check.

Over the past six weeks, the onboard system tells me that the tyre pressure regularly drops. It goes down 2/3 PSI all around. This has happened around two times.

Point to note 1

Prior to the above, the pressure would drop maybe at a tyre or two at most by around 1psi monthly or more.

Point to note 2

For a while one of the tyres valves was precious and wouldn’t latch on.

Recently (and then once again!) at Sainsburys that tyre still wouldn’t latch and two others didn’t either. I then went to another station and they latched on without a problem. The pump guy thought it could be his machine but wasn’t particularly bothered.

Point to note 3

There is a view that the tyres / valves are damaged or that it’s simply monthly osmosis. Given the long drives and colder weather.

Point to note 4

It’s a 2.3 mile run to the local petrol station (the non Sainsburys one).

Any thoughts on this?

[Bluevanman]

Some general points.
Tyre pressures drop in cold weather.
The Sainsbury's tyre inflator machine may not be very accurate
I've had wheels refurbished,they then maintain pressure for a few months and then they start to drop by a pound or 2

[Panamax]

Have you checked the tyre valve inserts are tight?

If so, and you still have leakage, a cheap and easy place to start is to replace all the inserts with new ones and see if it makes any difference. (Jack or at least prop the car first so you don't crush the tyres.)

Make sure your tyre valves have dust caps correctly fitted at all times to keep crud out of the valves. Otherwise next time you inflate you may just be blowing crud into the valve inserts which can prevent them sealing correctly.

[GreenV8S]

thebullettrain said:

Over the past six weeks, the onboard system tells me that the tyre pressure regularly drops. It goes down 2/3 PSI all around. This has happened around two times.

Have you owned this / similar car through a winter? It's completely normal for the pressures to drop slightly as the temperatures drop. A 10C drop could easily cause the pressure to drop by a couple of PSI.

If a tyre inflater doesn't connect to the valve properly that's probably because the connector is worn. It's not related to air leaks.

[Baldchap]

My B5 had the tyre warning come on last week, undoubtedly due to temperature changes.

Also, those supermarket inflators are usually fairly inaccurate due to abuse, as well as the fact you should only check cold tyres, which they aren't if you have driven to the supermarket.

[stevieturbo]

thebullettrain said:

I’ve a BMW 840d. It’s usually driven weekly / bi weekly for a 500 mile round trip. Tyres are 20” Potenza. All are in good shape with thread and recently gone through a BMW health check.

Over the past six weeks, the onboard system tells me that the tyre pressure regularly drops. It goes down 2/3 PSI all around. This has happened around two times.

Point to note 1

Prior to the above, the pressure would drop maybe at a tyre or two at most by around 1psi monthly or more.

Point to note 2

For a while one of the tyres valves was precious and wouldn’t latch on.

Recently (and then once again!) at Sainsburys that tyre still wouldn’t latch and two others didn’t either. I then went to another station and they latched on without a problem. The pump guy thought it could be his machine but wasn’t particularly bothered.

Point to note 3

There is a view that the tyres / valves are damaged or that it’s simply monthly osmosis. Given the long drives and colder weather.

Point to note 4

It’s a 2.3 mile run to the local petrol station (the non Sainsburys one).

Any thoughts on this?

You are saying the onboard thing says your tyres are going down, but you have not said they are down, or if you have even verified this reading.

And WTF is a precious tyre valve ?

[thebullettrain]

stevieturbo said:

thebullettrain said:

I’ve a BMW 840d. It’s usually driven weekly / bi weekly for a 500 mile round trip. Tyres are 20” Potenza. All are in good shape with thread and recently gone through a BMW health check.

Over the past six weeks, the onboard system tells me that the tyre pressure regularly drops. It goes down 2/3 PSI all around. This has happened around two times.

Point to note 1

Prior to the above, the pressure would drop maybe at a tyre or two at most by around 1psi monthly or more.

Point to note 2

For a while one of the tyres valves was precious and wouldn’t latch on.

Recently (and then once again!) at Sainsburys that tyre still wouldn’t latch and two others didn’t either. I then went to another station and they latched on without a problem. The pump guy thought it could be his machine but wasn’t particularly bothered.

Point to note 3

There is a view that the tyres / valves are damaged or that it’s simply monthly osmosis. Given the long drives and colder weather.

Point to note 4

It’s a 2.3 mile run to the local petrol station (the non Sainsburys one).

Any thoughts on this?

You are saying the onboard thing says your tyres are going down, but you have not said they are down, or if you have even verified this reading.

And WTF is a precious tyre valve ?

Verified at the pump.

Precious tyre valve means it’s temperamental .

[stevieturbo]

So all 4 tyres are behaving the same ? ie most likely temperature and of little real concern

Or are they all different ?

If genuinely concerned about leaks, go to a reputable tyre place and have them check them all.

[thebullettrain]

stevieturbo said:

So all 4 tyres are behaving the same ? ie most likely temperature and of little real concern

Or are they all different ?

If genuinely concerned about leaks, go to a reputable tyre place and have them check them all.

Yes, all four having the same issue.