On Sun, 1 Feb 2009 12:47:44 -0800 (PST), "
wrote:
On Feb 1, 1:44?pm, dpb wrote:
Rick Brandt wrote:
...
How exactly would you determine that? ?One would need extensive
controlled testing comparing similar wheel/tire combinations some mounted
with tire paste and some without and then periodic measuring of leakage
rates. ?Have you done this? ?Has anyone? ?
I'd certainly have expected the manufacturers, SAE, etc., to have done
quite a bit in the area, yes...
I expect that if using paste has any anti-leak properties it is largely
because the bead is not abraded during mounting, thus having a better
surface mating to the rim. ?The act of application might also be removing
some surface dirt which is also going to help the seal.
Since virtually 100% of tires that are professionally mounted will be
mounted using paste and since we have people reporting bead leakage then
the evidence seems to indicate that the sealant properties are pretty
poor if not totally non-existent.
The following is conjecture as opposed to actual research since I can't
inspect the rims of those who have complained... 
But, w/ the number of vehicles I both have now and have had over some
40+ years, I've only had one instance I can think of where leakage
around the bead was a real problem and that is on a tractor I currently
own. ?It is owing to a damaged rim which I finally just replaced last
month after being tired of fooling w/ it any longer.
I really think most problems are due to either rims being damaged
(curbs, rocks, etc., can ding up rims as well as an overly ambitious
tire shop jockey) and the problems of ensuring the rim bead area is
indeed clean and free of debris is an issue. ?Plus, there is a tendency
besides the mechanical damage noted above for steel rims to rust and pit
and alloy rims have their problems as well. ?But, w/ all that, ime it
simply has never been an issue I've seen as being frequent at all. ?But,
of course, if one counts the total number of tires, a pretty low failure
rate can still add up to quite a number of instances. ?And, it only
takes one for any individual to get the impression it's a problem.
Now, is it possible that amongst all of the varieties of tire paste on
the market that a few make claims about assisting the seal? ?I have no
problem believing that, but that would be a special formulation that
deviates from what the primary usage is for the product.
I wondered that as well and did find a couple of manufacturers who did
note it helped seal bead as well as lubricate. ?The fairly common
"purple glop" was one that did mention it. ?It isn't, however a special
formulation for the particular product, but a claimed extra advantage.
The same company (as do many others) does have a separate product which
is designed specifically to be a bead sealer as well as lubricant for
the problem cases.
It appears the most widespread lubricants are potassium coconut soaps
with ionic surfactants (wetting agents); the purple product and its ilk
claim no soaps but are very ambiguous about actual ingredients...
--
the yellow goop NTB used remained semi pliable I peeled some off but
under it was white powder corrosion of the alunimum
Rubber hardens with age, aluminum alloy corrodes from roas salt, and
steel rims rust.
All contribute to rim leakage - which is a common problem in the "rust
belt" where NaCl is heavuily used as a road de-icer in the winter.
However, this is NOTa strictly cold weather pressure loss phenominon.
Cold weather pressure loss is adiabatic? - having to do with expansion
and contraction of a gas with temoerature.
PERMANENT cold weather pressure loss is due to hardening of the bead
rubber in cold conditions and is GENERALLY worse if the tire pressure
is already low, allowing the sidewall flex to force the bead to move
against the rim. Being hard from the cold it does not readily
re-conform to the rim, particularly rims roughened by corrosion.
The yellow "goop" used as a tire sealer by many tire shops is nothing
more or less than trim adhesive and is virtually useless, particularly
on corroded alloy rims. Best solution there is a good wire brushing, a
quick application of an etchant like phosphoric acid (metalPrep) and a
good coat of an appropriate primer/paint. This keeps the "white
powder" from growing in the bead area, releasing the air from the
tire.