Heidenau Inner Tube 21 D Cross – 34G Valve

Heidenau Cross 21D fits tyres in the 3.00, 80/100, 90/100, 90/90, 100/90, 120/70 size range for 21-inch rims — the standard front wheel size on most enduro and cross motorcycles.

The wall is thicker than on a Standard tube — 2.5–3.0mm against 1.5–2.0mm. A thicker wall copes better with loads during fitting and demanding riding.

Material and durability

Heidenau Cross 21D is made from natural rubber: the material resists mechanical stress better than synthetic compounds and retains high elasticity even after prolonged use. On hard hits to the front wheel from stones and roots, this reduces the risk of tube damage.

The trade-off with natural rubber: it loses pressure slightly faster than synthetic rubber, so check tyre pressure with a gauge before riding rather than by eye.

Valve and fitment

Heidenau Cross 21D comes with a 34G valve — straight-stemmed and threaded for a standard cap, fitting enduro and cross motorcycle rims.

Application

Heidenau Cross 21D suits enduro and cross motorcycles with a 21-inch rim — the standard front wheel size on most such motorcycles. The Cross class carries road approval and is used both for competitive riding and long-distance touring.

In Kazakhstan's climate, natural rubber retains elasticity better at low temperatures, but ages faster than some synthetic materials during prolonged use in high heat. It's worth checking the condition of Heidenau Cross 21D regularly in summer.

Fitting recommendation

When fitting Heidenau Cross 21D, use a new rim tape of the correct size and follow the motorcycle manufacturer's tyre pressure recommendations. Pinching the tube with tyre levers remains one of the most common causes of premature tube failure.