[boba-fett]

I have a very very slow puncture, I had not used the car for two weeks and I noticed it was low, so I added air to the correct PSI. That was about 10 days ago, and after the first 2 to 3 days I kept checking it and all seemed fine, however a week later and just noticed its low again in fact almost flat. Its about a 500 mile old tyre.

I checked everywhere to see if I can see/hear where the air is escaping but it must be so slight that its barely noticeable. I can fix a puncture if I can find where it is, and I know I probably need to take it somewhere and get the wheel and tyre in some water, but thats just a ball ache, but will do if I have to.

Just wondering if I put some tyre seal in it, like MTB tubeless tyre gunk, would that mess up the tyre pressure monitors? Anyone had this issue?

[Pond]

If it's quite new, it could be the schrader valve isn't 'nipped up'. If you don't have a 'schrader key', a small flat bladed screwdriver is good as long as you are careful not to damage the valve.

A big lump of spit over the valve opening should tell if it's weeping.

If it's not that, take the wheel off and look at the tyre all over. A wet rag with a bit of washing up liquid on over the surface of the tyre should give indication if there are any leaks as it will bubble.

[Kendo67]

Squeezy bottle with diluted washing up liquid and liberal applications around the rim / valve and tyre should see a few bubbles where the leak is.

K

[crAbb]

Originally Posted by Kendo67

Squeezy bottle with diluted washing up liquid and liberal applications around the rim / valve and tyre should see a few bubbles where the leak is.

K

Ah. You're a gas fitter

[boba-fett]

Cheers guys, thats what ill do next.

Done the gob on the valve, its not that Pond, but thanks for the reminder!

[Pond]

Originally Posted by crAbb

Ah. You're a gas fitter

Despite there being a myriad of proprietary 'leak detection sprays' available for any pressurised gaseous pipework, washing up liquid and water is still the best and cheapest.

[Allworth]

+1 to soapy water. If you can submerge tyre in some container with water it should be even easier to find a leak.

[M80]

Originally Posted by Pond

Despite there being a myriad of proprietary 'leak detection sprays' available for any pressurised gaseous pipework, washing up liquid and water is still the best and cheapest.

As my gas fitter mate used to say (it got a bit boring after a while...)
"No bubbles, no troubles"

[Rukka]

Have the tyre filled with Nitrogen. Less prone to pressure loss. My local Quick-Fit does it for about a fiver a tyre. A tad expensive but might save you a headache.

[Pond]

Originally Posted by Rukka

Have the tyre filled with Nitrogen. Less prone to pressure loss.

How does that work, then?

[JustChris]

I’ve literally just had on Tess.

Tyre pressure is 2.9 and it lost about 0.3 a week.

Reported to EV scheme and new tyre fitted The culprit was a small nail apparently.

Kiwi Fit remote so didn’t even leave the house and zero cost to me.

_

Absolutely if it was my money and tyre I’d try alone first and be asking for a repair.

[TurboWeasel]

I've had similar slow leaks a few times over the years. No air bubbles spotted when dunking the wheels in the bath, and no foreign objects found in the treads/carcass.

Turned out it was tyre fitters not bothering to wire wheel the old bead residue off the rims first, so the seal was slightly compromised. It wasn't a major leak, 2-3 psi a fortnight kind of thing.

[Rukka]

Originally Posted by Pond

How does that work, then?

Nitrogen molecules bigger than air molecules so less likely to leak.

Someone once went into a lot more detail but can’t recall the full reasoning. It did stack up though when I googled it

[TurboWeasel]

I believe Nitrogen is more consistent as well as it doesn't expand as much as it heats up?

[NanasBack]

Changing to using nitrogen would surely be problematic.

If there is a hole in the tyre, when the nitrogen molecules are forced through (during pressure surges when going over road humps, pot holes etc), they will make the hole bigger.

So you'll likely still loose pressure.

Unless you carry a cylinder of nitrogen with you, if you top up using a normal pump, the tyre will deflate quicker, because there is a bigger hole now.

????