Dave Plowman (News) wrote:
In article ,
Bill wrote:
I may be about to buy, from a scrapyard, a set of 5 replacement wheels
for the recently purchased car to get a spare wheel, proper sized tyres
and wheels that fit the wheel nuts.

In the past, I've often been told that the reason for a slow puncture
was that the alloy wheels had gone porous.
More recently, I've been told that the cylinder head on a certain
vehicle had gone porous and that was why it chuffed when cold.

I have always wondered whether this is a standard get-rid-of-him phrase
taught as part of the Car Mechanics PhD (Hons) course, or whether alloy
does actually start to leak.

Does anyone know? Is there any sort of standard test, like wheel
tapping, that can detect this sort of rot?

Alloy wheels are generally painted (or coated with something similar to
paint). If the paint is damaged where the tyre meets the rim they are more
likely to leak. As they will often corrode where the paint is damaged.


I have some that got scratched by some weights that were crimped around
the rim, instead of glued, like they seem to be now; and this is where
they have corroded and now leak slowly.