From: jbrandt@hpl.hp.com (Jobst Brandt)
Newsgroups: rec.bicycles.misc
Subject: Re: Tube Problem or Tire Problem?HELP!
Date: 15 Nov 1996 00:18:15 GMT

Dale (anonymous) writes:

>> the tube.  Talcum has no benefits other than to make tube removal
>> from the tire casing easy.

> I would argue that it can also make the action of putting a tyre on
> much easier as well.

When WOULD you argue that, or do you mean you believe that it helps
but don't want to commit yourself to such a tenuous contention.  Maybe
you'll explain how talcum can facilitate mounting a tire.

In the days before tubeless tires on cars, automotive tubes that were
not much thicker than the heavier bicycle tubes vulcanized into the
tire from the heat of the road and would rip when forcefully removed.
For this purpose, talcum was extensively used.  Bicycles don't have
enough power not enough rolling resistance to generate vulcanizing
temperatures required to cause such adhesion so using talc has little
purpose.  You'll notice that tubes contain talcum, and that is for the
purpose of preventing adhesion in the package of two absolutely clean
surfaces.  You don't have that problem.  In fact, adhesion of the tube
to the casing prevents rapid air escape in the event of a thorn
penetration.

Talcum, like tying and soldering, will last as much as 40 years after
the last need for it vanished.  The last need for tying spokes
together at their crossings vanished with high wheeled bicycles that
threw the rider if a spoke broke and lashed about freely.  Talcum in a
bicycle tire never had a reason, it has always been done in imitation
of automobiles, but even they don't use it anymore.

Jobst Brandt      <jbrandt@hpl.hp.com> 

From: jbrandt@hpl.hp.com (Jobst Brandt)
Newsgroups: rec.bicycles.tech
Subject: Re: Cornstarch vs. Talc
Date: 4 Nov 1997 22:09:42 GMT

Dave Hamilton writes:

>> This among other things is an urban legend that won't die.  There
>> is no benefit in putting talcum powder or a substitute in a tire
>> casing.  The practice is like bicycle tire treads that are
>> miniature replicas of automobile treads... if it's good for cars,
>> it must be good for a bicycle.  Cars used talcum between tire and
>> tube because tubes tended to vulcanize to the tire from the heat
>> developed on hot roads.  Pulling the tube out subsequently tore the
>> tube and left parts stuck to the casing.

> I doubt that "powder in tires" rates the title of "urban legend".
> Bicycle tubes stick to tire casings -- not from heat, but from
> getting wet.  Powder won't prevent this after repeated wettings but
> it will definitely slow down the process.

Please explain how getting wet causes tubes to adhere to tire casings.
The tubes in my tires are as stuck as they ever will be after about a
hundred miles, in the summer with no rain.  That they stick is an
advantage as I have amply described, in that they prevent rapid air
loss from snake bites and thorns.

>> Bicycles don't get hot enough and the tubes are relatively far
>> stronger for the small contact area they have with the tire.

> I've seen ultra-light tubes stick so that they tear on removal --
> usually at a seam. Invariably, this happens 10 miles from nowhere
> when you forgot to bring along a spare tube. The problem is
> compounded because you are making a hurried repair on the roadside.

Well if you have to work with condoms, that's your problem, but I
don;t think this is reason to advise all of bicycling to put powders
in their tires.  I for one rode tubulars with no talcum for years and
never had a stuck tube.  They used condom thin tubes that required
daily inflation.

>> Talcum has no effect on punctures of any kind other than to let the
>> air out faster when one does occur.  A tube stuck to the casing
>> will allow one to ride a considerable distance because the thorn
>> that penetrates plugs the casing hole and the tube hole has no
>> outlet.  I have found thorns the next morning when I prepared to
>> ride to work, because coming home the tire had not yet lost enough
>> air.  The tube will stick to the casing of a non powdered casing.

>> The only difference it that it is water soluble, but then who
>> cares.  Talcum cakes up in the wet although it doesn't dissolve.

> There is little difference between the products, Sheldon's comments
> notwithstanding.  I didn't originate this thread but I still plan on
> using powder in tire casings.

I know and there are many riders who will continue to turn their
bicycles upside-down to change a wheel.  There is not much one can do
to help in that case... except to throw some salt over one's shoulder.

>>  Has anyone explained what talcum powder does?

> The only uses I can think are these.  It makes installing the tube
> easier -- minimizes the risk that the tube will remain twisted or
> kinked when first inflated.  Careful installation will prevent this.
> But you cannot see inside the tire to know the tube is twisted.

That is a claim I can not reconcile with my own experience and
watching others mounting a tire or changing a tube.  The problem is
that the tube gets pinched as the final section of tire is popped over
the rim.  Powder has no effect on the tire iron or the position of the
tube at that time.

> The other purpose is to ease removal of the tube at a later time.
> Powder won't last forever -- repeated wettings will defeat any use.
> However, I have seen it still working (still in powder form) after
> several years.

I'm sure I have pulled as many tubes from tires as most people, and
have never had a problem separating the tube from the tire.  If
pulling on the tube annoys you then that is a problem that I do not
share.

> FWIW, some tubes come out of the box lightly coated with powder.
> There is no consistency on this -- some manufacturers use it, some
> don't. I have never seen a comment or explanation on the box
> regarding this practice.

In manufacture, when the rubber is fresh, clean, and not oxidized,
adhesion is more possible than later.  Most of my tubes are stuck
together in the package but none are stuck inside because the heat of
manufacture requires them to have talcum on the inside.

> I also note that _Bicycling Magazine's Complete Guide to Bicycle
> Maintenance and Repair_ mentions the practice:

>* "4.  Talc.  This much overlooked substance is a _necessity_ for
>* smooth tire manipulation.  A tube without talc tends to stick to
>* its tire and is much harder to force into position..  Sprinkle some
>* into the palm of your hand and draw the partially inflated tube
>* through it.  Then dust the inside of the tire by putting some talc
>* into the bottom and rotating the casing while spreading the talc
>* with a soft brush. With many tires, the use of talc spells the
>* difference between success and failure_." [emphasis added]

There you go.  If that isn't an urban legend supported by emotional
words that are non sequiturs.  The tubes may stick to the casing, but
not on installation.  It certainly describes the ritual but is lacking
in evidence of any merit.  It sounds a lot like tire wiping to me.  It
was in print, therefore, it must be true.

> Fear mongering comes from all sides in this debate!

> In my opinion, powder won't prevent flats, minimize leaks or anything
> of the sort. It is not a necessity and will probably not spell the
> difference between "success and failure".  You can definitely live
> without it.

Then why are we propagating this urban legend?

> The only disadvantage is one Jobst suggested -- that lack of powder
> might actually discourage the leak if there was an external puncture.
> But, this would require a very tight seal between the tube and casing.

...and that seal takes place naturally in most clincher tires.

Jobst Brandt      <jbrandt@hpl.hp.com>