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Bead core
Tyre carcasses are wrapped around bead cores.
Wrapping the carcass around both sides creates
three carcass plies.
To ensure that tyres do not slip when inflated on
the rim and have an effective grip, the bead cores
are stabilised in two different ways:
1
Figure 27: Steel bead core (1) and Kevlar bead core (2)
•
with a steel wire. These tyres are called clinchers.
•
with aramid fibres (Kevlar®). These tyres are
called folding tyres. Folding tyres are about 50-
90 g lighter than clinchers. It can also be folded
into a smaller pack size.
Puncture protection belt (optional)
There may be a puncture protection belt between
the carcass and the tread.
Figure 28: Effect of puncture protection belt
Each tyre manufacturer has its own puncture
protection classes which are not on par with one
another.
MY23I0a - 42_1.0_22.01.2024
2
3.5.4.3 Rim
The rim is the metal profile on a wheel which holds
the tyre, tube and rim band together. The rim is
joined to the hub with spokes.
In rim brakes, the outer surface of the rim is used
to brake.
3.5.4.4 Valve
Each tube-type tyre has a valve. Air is pumped
into the tyre via the valve. There is a valve cap on
each valve.
The screw-on valve cap keeps out dust and dirt.
The pedelec has either a:
•
Dunlop valve
•
Presta valve
•
Schrader valve
Dunlop valve
The Dunlop valve, also known as a conventional
valve, is the most widely used valve. The valve
insert can be replaced easily and air can be let out
very quickly.
Figure 29: Dunlop valve
Description
62
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