Porous alloy wheels

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Mon 18 Aug 2008 11:27
Porous alloy wheels - Andrew-T
From time to time we hear this phrase as an explanation for pressure loss in a tyre. To me it sounds pretty improbable, and if genuine, means a serious production fault. Is there any scientific evidence for it, or is it a fob-off for the credulous?
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Mon 18 Aug 2008 11:36
Porous alloy wheels - L'escargot
Alloy wheels can be porous but I'd be surprised if they weren't resin impregnated to minimise any possible leakage paths.
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Mon 18 Aug 2008 11:44
Porous alloy wheels - jc2
More likely to be corrosion on the wheel where the tyre-bead fits.
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Mon 18 Aug 2008 12:04
Porous alloy wheels - George Porge
Quality alloys are refinished in the wheel well almost to the same standard as the outside these days.

Barcodes fitted to the tyre bead are more likelly to pass air than porous alloys.
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Mon 18 Aug 2008 13:26
Porous alloy wheels - Spospe
Take a look at:

www.dunloptyres.co.uk/ourTyres/motorsport/

Dunlop themselves say that wheels should be treated to prevent air loss, so presumably it can still be a problem.
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Mon 18 Aug 2008 15:56
Porous alloy wheels - George Porge
Hands up then, who's had their alloys "treated" to prevent leakage?

What percentage of cars leave the factory with alloy wheels 40-50%? and what percentage have problems?

Knowing the general public rarelly check tyre pressures how many car manufacturers would risk fitting alloys if there was even a tiny possiblility of them being porous.

Where there's blame there's a claim, Americans would have a field day
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Mon 18 Aug 2008 16:07
Porous alloy wheels - Andrew-T
In my OP I asked the question partly because the assumption seems to be that steel wheels are not porous. Two years ago I bought a 1989 GTi with the original alloys, one with the original (spare) tyre. Only one of them loses pressure noticeably, about 1-2 psi/week. My earlier experience with these wheels has been that corrosion at the bead is the usual reason, and I reckoned that if steel is not porous, the thicker alloy would not be either. Hence my scepticism. I concede that it might just be a problem for racing wheels, but 'normal' use? I doubt it.
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Mon 18 Aug 2008 16:55
Porous alloy wheels - jc2
I've had a steel wheel lose pressure;turned out to be the weld where it was made.As the paint got old,it ceased to seal;tube fitted.
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Mon 18 Aug 2008 18:05
Porous alloy wheels - SteVee
On one car I had about 30 years ago, all four alloys needed tubes in. I don't think they were ever meant to be airtight ! The car itself was then about 2 years old.
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