20x4 Fat Bike puncture-proof foam

Size

20x4 anti-puncture foam liner, for a 20 inch by 4 inch tyre. This is the size used on compact and folding fat bike electric bikes.

How it works

The foam sits inside the tyre, between the tread and the inner tube. It absorbs foreign objects — nails, glass shards, thorns — before they reach the tube.

The inner tube remains essential: it holds the air and provides the pressure. The foam does not replace it, it protects it.

What it changes in the workshop

Punctures become rare, without giving up inflation or pressure adjustment. This is the argument for exposed use: worksites, tracks, debris-prone areas, rental fleets.

In return, the assembly is heavier and fitting takes longer than a standard tyre.

Fitting

Place the foam inside the tyre, then insert the inner tube over it. Inflate the tube slightly before inserting it to avoid folds, and make sure it is not pinched between the foam and the bead before bringing it up to pressure.

Sold individually: allow one foam liner and one tube per wheel.