Ok, so the old MGB has been listing lately... the left
rear tire tends to go flat after a week or two. So,
postponing work on the rally car, I decided to take a
look at it.
Took the tire off the wheel. Figured I'd clean the rim,
look for any punctures inside, and put in a new
tire valve. Tire looks intact. A little rust around
the rim (it's a steel wheel) and so I cleaned that
up with a steel brush. Cut the valve out (cut off
the mushroom end) and have a look at it. It looks
a little degraded in the seal area.
I pull out a new valve, and the two just don't even
look the same size! I measured the hole, and it's
a standard .453" hole, so I know it's *supposed*
to take the standard valve size. But the one I took
out just looks small!
Now, they don't make any "small size" in addition
to the standard size. I found this out after trips
to a couple shops. It was only after getting home
from this did I realize that my wheel hole was the
standard size and a regular size valve should fit.
Here's the data:
Hole size in the wheel: .453" (29/64ths, apparently)
Size of the old valve: .480"
Size of a new valve .590"
Amount that the old valve must have shrunk: .110"
That's nearly 1/8" of an inch!!! No wonder it would
let the air out!
At least, I'm assuming that that was the problem.
Put some goop (we all love the Rim-Ease!!!) on the
new valve, popped it in, lubed up the tire, put
that back on, pumped it up and put it back on the
car.
Quite interesting! I wouldn't have thought the
rubber would have shrunk that much, especially the
part that is not exposed to UV.
So here's hoping that the MG doesn't list anymore.
Anders
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