Do Tyre Valves Heal ?
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Odd one this.

Back in mid July I rolled the Motorhome down the drive and found that one of the outer rears was looking a bit flat. Further inspection reveal that the N/S inner rear was totally flat. This is a 6 wheel transit by the way.

No time to mess about changing the tyre as we were already cutting it fine for the ferry. So I just blew it up to 4 bar as normal and set off but taking it easy. Checked it several times on the way down and it seemed fine. Gave it a run at 70mph on the last 1/2 hour into Dover, no problem.

Before anyone points out the risk, each of the rear tyres is rated high enough to work on its own. Losing pressure in a single rear tyre will not cause an accident.

Once in France we realsied that we did not have the tools to change the wheel if we had to anyway. We had a metric socket set of sorts. So we bought a long 1/2" extension and a 21mm socket at a DIY store. The jack with the vehicle is a heavy duty scissor jack, but hardly up to the job.

We got down as far as the Dordogne by the next evening and checked out the pressure. It had fallen to 2.5 bar according to my dodgy old tyre inflator. Not sure what to do, we pulled into an Aire on the Autoroute that had a free trye pressure check. This confirmed that it was at 2.5 bar, so we had it pumped up and off we went again.

To cut a long story short, we kept checking as we went through the Pyrenees and then back up the Atlantic Coast before heading back for Calais. We checked it every two or three days and it did not seem to be dropping much at all. We used the old 12v tyre inflator and kept adding a little bit.

Parked it up mid-August and started to sort out 7 new tyres. They are all 8 years old but only done 27,000 miles. Conti recommend a maximum of 10 years. I was planning on changing them all in April next year, unless we change the MH in the meantime.

Anyway, we are up tut north next week, so we decided to fit the spare. Just changed them over, with some difficulty to find that the "flat" tyre still has nearly 4 bar in it after standing 2 1/2 months.

So what the hell was going on with that tyre?

Apologies for the Essay.

Saul Bellow - "A great deal of intelligence can be invested in ignorance when the need for illusion is deep."
Stephen Hawking - "The greatest enemy of knowledge is not ignorance, it is the illusion of knowledge."

Sometimes a nail or similar can go through a tyre that seals so well it barely leaks - so long as the nail is in an un-flexed bit of the tyre.
So you get three scenarios,
Parked with the nail in 90% of the tyre that isn't touching the ground and hence in an un-flexed bit = no leak.
Moving so the bit of the tyre the nail is in gets flexed once per revolution = slow leak.
Parked with the nail in the bit of the tyre in contact with the ground so is permenantly flexed = faster leak.

Schrödinger's cat - so which one am I ???

Thanks Rod.

Just checked every square cm of the tyre and cannot see anything.

Saul Bellow - "A great deal of intelligence can be invested in ignorance when the need for illusion is deep."
Stephen Hawking - "The greatest enemy of knowledge is not ignorance, it is the illusion of knowledge."

If it is a nail (or similar) you may not be able to see it from outside - the hundreds of miles you covered will have worn the "head" off in no time and the "shank" may now be pushed below the surface.

Try a spray of soapy water (from a garden type trigger spray bottle) with the tyre at its maximum inflation pressure.

Even then, I had one I couldn't find, nor could the local tyre place with their dunking tank, but as soon as they took the tyre off it was blindingly obvious from the inside.

Schrödinger's cat - so which one am I ???

The schrader valve does some times leak. They can be temperamental especially if you are using it alot such as checking the pressure or inflating the tyre. The dust cap is just that, it prevents dust getting into the valve, the cap does not act as a secondary seal. If dust does get into the valve, it can get trapped in the seal, which creates the leak. new valves can be installed, and is easy to do. Obviously if you replace the valve and the tyre still deflates, the leak is somewhere else.

The Schrader valve is notoriously bad on refrigeration systems. perfectly fine before you fit the gauges, then gushing out liquid refrigerant when you remove the gauges. God knows why they are still used in refrigeration. The company I work for still uses them on the latest high pressure refrigerants, up to 45 bar!

I usually check the tyre pressures twice a year. April before the easter break, then in July before we go across the channel.

This year I also checked them in June before we went to Somerset. Now I do remember thinking it felt a bit spongy on the way back in June.

My guess is that some crap got in the valve in June and it took several blasts to clear it.

Saul Bellow - "A great deal of intelligence can be invested in ignorance when the need for illusion is deep."
Stephen Hawking - "The greatest enemy of knowledge is not ignorance, it is the illusion of knowledge."

try checking around the rim, im a tyre fitter and that sounds like your problem

God i wish my tyres lasted long enough tonget punctures.... It may sound unbilevable but i have done repairs on tyres from thorns they dont leave any visible signs on the outside but still alow air to leak out slowly its a pita

Drives
-Ford S-max Mk2 Ecoboost
-Rover 100 VVC #2 - track project

Searching is all you need on TurboMinis

I've had valves leak at the base where they go through the rim, wiggleing them can make them seal up again

The smallest bit of dust stuck on the schrader valve seat can make it leak. Sometimes you can be lucky & dislodge it, blowing it inside the tyre when reinflating. They make dust caps for a reason.

I never knew that

Just wheeled the old gal out for a short break and the O/S inner tyre was flat.

Changed it with the spare (the tyre that went flat last year) and tried to inflate it.

The actual valve body has perished :(

So, the tyre can last up to 10 years according to Continental, but the valves they fit cannot.



I'm going to have to pay out for 7 new tyres next month before our long distance holidays.

Saul Bellow - "A great deal of intelligence can be invested in ignorance when the need for illusion is deep."
Stephen Hawking - "The greatest enemy of knowledge is not ignorance, it is the illusion of knowledge."

I bet that will cost a pretty penny.

If something is worth doing, it's worth doing half of.

Mine have leaked from around the clip on type balancing weights.

In the 13's at last!.. Just

Just got my friendly garage to change the valve.

The valve body was split on the base of the stem.

The inner rear wheels have long valve caps and it would seem that these probably induce extra stresses on the valve body.

I will have to change all 7 tyres next year. As it's not worth the hastle of changing the valves this year and then having to go back next year to change the tyres so I might as well get them done now.

Saul Bellow - "A great deal of intelligence can be invested in ignorance when the need for illusion is deep."
Stephen Hawking - "The greatest enemy of knowledge is not ignorance, it is the illusion of knowledge."

Are they bald or is this down to age Paul?

If something is worth doing, it's worth doing half of.

I think modern rubber is just crap.

Ive seen loads of proper brand name tyres only a few years old, falling apart.

Valves are the same, in fact, lots of rubber stuff.

9.85 @ 145mph
202mph standing mile
speed didn't kill me, but taxation probably will

All sorted for a mere £826.00

I'll change the valves again in about five years if we still have the old girl.

Saul Bellow - "A great deal of intelligence can be invested in ignorance when the need for illusion is deep."
Stephen Hawking - "The greatest enemy of knowledge is not ignorance, it is the illusion of knowledge."