The mystery of the leaking tyre (not 75/ZT)

[SD1too]

Originally Posted by mileshawk56

Sounds to be a valve seating/core problem.

Thanks Chris but when the valve was submerged in the paddling pool there was no sign of air escaping from the valve. There again there's no sign of air escaping from anywhere, but escaping it is so I suppose that form of thinking is unreliable.

Originally Posted by macafee2

Simon, point 3 also says "It was impossible to decide whether these were being created by the pump action of the water bottle or a genuine leak." and it was this I was replying too.

Yes, understood Ian and the fitter did do what you've suggested, resealing the tyre with bead sealant. When in the paddling pool I reapplied soap solution and I was satisfied that the tiny bubbles were created by this process because they remained the same size and when I deflated them with finger pressure they did not reform. Thanks for clarifying your reply though.

The owner is considering Cliff's diagnostic procedure of swapping tyres.

Simon

[sworks]

Generally with gradual air loss if there’s no puncture it can only be a few things. The valve, is the core tight? You say there were no bubbles when submerged, did you apply movement to the valve whilst submerged or is it an early tpms metal type? It could be removed and a standard valve added for testing. Although the tpms light would be on in the process.
Alloy wheels can become porous but generally only old ones, back in the day an inner tube would be fitted to prove or disprove but not possible now.
Bead sealing, I’m guessing when bead sealer was used the wheel was thoroughly cleaned?
Age of the tyre, the tyre itself can become porous which Is difficult to prove but if it’s dated as an old tyre I’d probably start here as If it doesn’t fix it at least the tyres are safer

[Ducati750cc]

The best way with these slow leaks is to wash the tyre off with clean water then submerge the wheel completely including the valve in clean water, no soap, you will have to weigh it down.


Then observe over it over a day or so checking it as often as you can and you will see where the leak is.


Depending on the size of the hole, or holes, you may not see a stream of bubbles, with a very small hole what you will see is an air bubble forming on the tyre, or wheel at the site of the hole, once it reaches a certain size it detaches and floats to the surface.


Turn it over and do the same on the other side, it can obviously be time consuming but this is the only certain way of finding very small leaks, soapy water rarely shows these up.


I had a similar thing with a tubeless ride on mower wheel, losing a small amount of pressure taking around 14 days + to get really flat, normal pressure 30psi did the soapy water thing, nothing, did the quick putting it in water, nothing, increased pressure to 60psi nothing, then did the one as describes above, I put it where I would be constantly walking past and started seeing the occasional bubble surface from three areas.


It took a good magnifying glass and a good light to spot the culprits which were the tiny tips of thorns, still stuck in the holes, obviously only the minute sharp tip, literally a pin NAUGHTY WORD-NAUGHTY WORD-NAUGHTY WORD-NAUGHTY WORD-NAUGHTY WORD-, must have penetrated the inner tyre skin.


I removed them, thought a good dose of the old Slime would work, nope, Slime works by the fibres in the solution filling the hole, but in this case, with the hole being so small, the fibres were too large to enter and seal the hole.


One thing doing this did though, was show up another hole I had missed, it did this because the blue Slime fluid passes through the hole and can be seen on the surface.


I stuck a spare wheel on meaning to ream out and plug the holes with a repair kit but haven't got round to it, if I get the chance in the next couple of days I'll dig it our and take a couple of photos.

[Synchromesh]

I have same problem on a Focus alloy wheel. Sometimes pressure holds at 31psi for days, even weeks, then it drops by several psi in a day or two. I know it is leaking at the bead because I observed bubbles when I put the wheel in deep water in the bath with no soap. I cleaned the alloy rim, painted it then applied sealer but it still leaks. I wonder if the intermittent nature of the leak is down to where the wheel stops when it is parked.

[COLVERT]

Originally Posted by mileshawk56

Sounds to be a valve seating/core problem. I would replace the core first, if it continues replace the valve. ?? Chris.S.

The valve dust cap would stop any potential air leak from the valve.

[SD1too]

Originally Posted by sworks

The valve, is the core tight? ... did you apply movement to the valve whilst submerged or is it an early tpms metal type? ...
Alloy wheels can become porous but generally only old ones ... I’m guessing when bead sealer was used the wheel was thoroughly cleaned?

Thanks for your thoughts Mark.
I regret that I didn't apply movement to the valve whilst submerged.
The car does have a tyre pressure monitoring system (post no. 1).
The alloy wheel (and the car) is 8 years old so I wouldn't expect porosity.
When the bead sealer was applied the wheel rim had already been cleaned then refurbished by powder coating (post no. 1) so I think we can take it that it was as clean as clean could be.

Originally Posted by Ducati750cc

The best way with these slow leaks is to ... submerge the wheel completely including the valve in clean water, no soap ... Then observe over it over a day or so ...

Thanks Bill for this technique from your own experience with a mower wheel. Unfortunately the paddling pool's edge wasn't deep enough to submerge the wheel completely so I had to observe it in two passes. I also only had two hours (including dealing with a rusty scissor jack) as the car's owner had to depart for her second job! This BMW Mini wasn't supplied with a spare wheel either!

Simon

[Ducati750cc]

I should have added in my post that care needs to be taken with some puncture sealants in that they can block the valve core and sometimes the valve stem, not a massive problem but one you don't want if you just want to put a bit more air in.


A quick test to see if this has happened is to push down on the core as if you were releasing air, if it is stuck, or it goes down and no air is released, even though there is obviously air in the tire you will need a new core, and possibly clean out the stem bore with a suitable tool out of your bits box.


Some off road cyclist, off road motorbike/quad bike and other similar sites recommend, where possible, to have the valves at 12 o'clock when parked up/stored for a while and when inflating, deflating, if possible put the valve at 12 o'clock for a while to allow any fluid to drain out, either way at any time it's best to have the valve at 12 o'clock when inflating.

[sworks]

Originally Posted by SD1too

Thanks for your thoughts Mark.
I regret that I didn't apply movement to the valve whilst submerged.
The car does have a tyre pressure monitoring system (post no. 1).
The alloy wheel (and the car) is 8 years old so I wouldn't expect porosity.
When the bead sealer was applied the wheel rim had already been cleaned then refurbished by powder coating (post no. 1) so I think we can take it that it was as clean as clean could be.

Simon

If you can get some soapy water in a spray bottle and spray around the valve then give it a wiggle whilst looking for bubbles providing it’s a rubber valve.

[T-Cut]

Originally Posted by SD1too

Does anyone have any further diagnostic suggestions before the owner buys another tyre and we cross our fingers?

Try nitrogen? http://www.btmauk.com/wp-content/upl...-10-Mar-15.pdf
TC

[SD1too]

Originally Posted by T-Cut

http://www.btmauk.com/wp-content/upl...-10-Mar-15.pdf

That's a very interesting and particularly well-written document, thank you.

Simon