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

A friend has a BMW Mini and the OSF tyre is losing 8 psi every 5 days and triggering a dash warning. Progress so far as follows:

1. Car taken to my local family-run tyre business. Wheel rim inspected and no kerb damage or alloy corrosion found. Cleaned nevertheless and tyre refitted. The leak continued.
2. Car taken to small, independent wheel refurbishment business. Inspected for buckling and none found. Standard powder coating refurb. carried out. The pressure loss remained.
3. Returned to tyre business. Soapy water applied to bead and some tiny bubbles noted. It was impossible to decide whether these were being created by the pump action of the water bottle or a genuine leak. The worst was assumed and the tyre was removed and refitted using bead sealant. There was no improvement.
4. I borrowed a paddling pool and immersed the wheel in water, including the valve with the cap off and pressure increased to 40 psi. Not a single bubble was seen. No defects found in the tread.

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

Simon

I dunno Simon, this will be of no help at all (more just an expression of sympathy :shrug:), but both my 75 and my mother's Focus leak constantly from the rear n/s tyres. I've had it with other cars too, and always that same wheel...



This will sound like I'm making it up, but when the front and rears have been swapped, the leak seems to stay at the rear :eek:


It's a slow thing, taking a month or so to really show, so I don't think you'd see bubbles in a tank or anything. One of the mysteries of the universe, same as why the front n/s tyre always wears more, on every car I can remember. And there are very few roundabouts where I live, so it's not that...


Good luck...

If bubbles are created after a few seconds of applying soapy water and increase in size and quantity I would go with air escaping from the tyre. I did this to find why my tyres were going down.

macafee2

I've heard talk of cases where the wheel alloy itself becomes porous, allowing air to escape. Never experienced it myself mind, so it could well be an internet myth.

I suppose, if possible, you could try swapping tyres between a couple of wheels to see if the leak follows the tyre or stays on the same wheel. The would at least narrow the source to either wheel or tyre :shrug:.

Cliff

Agreed Ian but following the application of the bead sealant there are no more bubbles! :o

That's a good idea Cliff, provided the tyre fitter is willing to do it. I'll suggest that to the car's owner, thank you.

Simon

Not a myth, my father had it with a Vauxhall Cavalier. So long ago I can't remember how it was solved.

A mate with a Peugeot had a similar problem, he would pop round most weekends for me to top one tyre up with air.


It had been on and off numerous times and no obvious punctures or defects.


Eventually he went to a different place and they stretched the tyre once removed and stretched lots of small cracks could be seen in the inside carcass of the tyre. Not visible when no weight was on the tyre but as soon as the tyre had some weight on it the cracks opened up.


This was a quality tyre and had plenty of date left on it. The tyre place said they had seen this a few times and that is why they stretch the tyres with no leaks and consistant signs of a puncture. My guess it was driven underinflated a few too many times and the combination of the heat and the flexing of the sidewalls causes it.

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

"One of the mysteries of the universe, same as why the front n/s tyre always wears more, on every car I can remember. And there are very few roundabouts where I live, so it's not that..."

I can answer this! It is down to your driving. It is quite simply based on self preservation and if you drove in mainland Europe, it would be their F/N/s tyre. On a right hand bend, the front left tyre takes the strain and likewise on a left hand bend the front right does the work. Psychologically we all drive faster round right hand bends because we see it as safer, no real danger. However, driving round a left hand bend, there is the risk of going wide and colliding with an oncoming vehicle, therefore we go slower which equals less strain on the load bearing tyre.

Many years ago this was discussed on one of my driving courses and makes perfect sense.

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.

macafee