Very slow loss of pressure

[456GT]

I'm due to put my summer tyres back on soon and have spent the winter not fixing an issue with one of the rear wheels/tyres (the winter tyres are on their own set of wheels).

Just before I took the summer wheels off I noticed one of them was down to 9psi. I had topped them up two weeks previous. My question is: does the problem lie with the tyre or the wheel?

If it was the tyre, I'm thinking it would've gone completely flat and it wouldn't have taken two weeks over it. So should I get the wheel re-furbed? Or can slow punctures be that slow? How do I find out which it is?

Thanks.

[kambites]

Unfortunately, slow punctures can be that slow, as can wheel porosity or valve leakage.

Pump it up, stick it in the bath, and see where the bubbles come from.

[Snowboy]

Is it possible the puncture is airtight until the weight of a car is on it?

I think the psi will the same whether the tyre is on the car or not, but there's going to be some impact from the car weight.

[Dave Hedgehog]

try filling the tyre with a gas that has larger molecules, hopefully they will not be able to escape out of the hole

[rohrl]

I had a long term problem with a slow puncture which was eventually solved with a light rub-down around the sealing edge of the alloy wheel with some fine-grit sandpaper. Any corrosion there prevents the tyre from sitting cleanly against the rim.

[Ozzie Osmond]

kambites said:

Unfortunately, slow punctures can be that slow, as can wheel porosity or valve leakage.

Pump it up, stick it in the bath, and see where the bubbles come from.

Sound advice. I've also had situations where there can be a small leak where the bead seats onto the rim, especially relevant if the wheels are old and may be corroded.

[swansea v6]

rohrl said:

I had a long term problem with a slow puncture which was eventually solved with a light rub-down around the sealing edge of the alloy wheel with some fine-grit sandpaper. Any corrosion there prevents the tyre from sitting cleanly against the rim.

Just had exactly the same problem only clio

[fjord]

Both front wheels on my st220 and my 320d leak air. I assume they are corroded and they lose about 10psi a fortnight.

[speedking31]

Use Tyreweld as long as your tyre is small enough and you won't need to repair a puncture in the future. Then get it sorted properly next time the tyre is off.

[Stuartggray]

Stick an inner tube in it...

[Sticks.]

When I've not used the Z4 for a while the tyres lose pressure. Fine the rest of the time.

Other half had one tyre on her car losing pressure (regularly used). It just needed resealing by the local tyre firm and has been fine since.

[456GT]

Thanks for all the input, guys.

The tyres are three years old and will probably need changing anyway later this year. I'm guessing most tyre places can sort out a bit of corrosion on alloy wheels...?

[Sticks.]

I think that's probably what it was with OH's car, it being 8 years old. Local tyre firm sorted it for a few £.