Subject: Talcum Powder for Tubes and Tires
From: Jobst Brandt
Date: November 4, 1997
I've been told since my first bike that I should liberally dust the tube in talcum powder before installing it. I've believe that this may have reduced the number of flats I've had recently.
Talcum is one of the more durable urban legends. There is no benefit in putting talcum or substitute powder on a tube or in a tire. The practice has come to bicycle tires the same way tire treads that are miniature replicas of automobile treads have... if it's good for cars, it must be good for bicycles. Trucks (and formerly cars) use talcum or graphite powder between tire and tube, because without it, the two can vulcanize from the heat of rolling. This often makes tube removal destructive, leaving tube fragments stuck in the tire casing.
Bicycles do not generate enough heat to vulcanize tubes, so they can be removed from the tire without problem. Other than that, talcum has no effect on punctures other than to release air faster when one occurs. A tube stuck to the casing will retain air for a considerable distance after a thorn penetration because the thorn that penetrates plugs the casing hole leaving the tube hole with no outlet. This is especially true for snake-bites flats. I have found such flats the day after when they have gone flat overnight. Without powder, a tube will stick adequately to most clincher tires in about 100 miles.
Cornstarch is no better than talcum powder, the only difference being that it is water-soluble, but then who cares. Talcum also cakes up when wet, although it doesn't dissolve.
A tube cannot move in a tire when inflated, regardless of what powder is used, because no translational forces exist, on top of which the holding force between tube and casing is large. That talcum prevents damage when mounting a tire is also not the case, because the pinch occurs when the last part of the bead is being popped onto the rim. This can cause a pinch with or without a tire iron, and powder will not protect a tube from lying in the gap if it hasn't been pushed into the tire adequately.
The reason inner tubes have talcum powder inside is that in manufacture, they become hot enough that, otherwise, they could become inseparably stuck when folded.
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