How are tubeless tyres prevented from leaking at the rim?

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Offline Atomic-S

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An Internet reference indicates that tubless tire beads are affixed to the rim by means of the internal pressure. However, if that is all that is going on, I would think such a connection would be very leaky, especially if any dirt got in there. How do they keep the joint from leaking air?
« Last Edit: 04/08/2008 09:23:05 by chris »
 

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lyner

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Re: How are tubeless tyres prevented from leaking at the rim?
« Reply #1 on: 04/08/2008 09:16:30 »
There is a lip / groove around the rim and a bead around the tyre. Both are made to a high standard of flatness. The pressure pushes the sidewall against the rim and it just beds down.
Run over a kerb and you can easily distort the rim enough to spoil the seal. In marginal cases I have seen them use a 'gunge' painted on the tyre wall to help things get started.

Why not use a tube? Tubed tyres just generate more heat through friction between tube and case; cases for tubed tyres need to have a smoother finish inside, to avoid this.