An Introduction to the Pre-Tensioner

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What is a Pre-Tensioner?

The pre-tensioner acts as an attachment point between the gearbox and shifter.

This splits the gear cable and is useful for changing shifters, internal cable routing, and for protecting the gearbox internals.

It's 100mm long x 8mm in diameter, and made from lightweight aluminium alloy.

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Determining your Pre-Tensioner Position:

Consider the pre-tensioner position along the cable run relative to any frame fixing points and tight bends.

If the application is a folding or adjustable bike, ensure that the bike is at its highest or longest setting before taking measurements.

When considering internal cable routing, ensure the distance from the gearbox to the pre-tensioner will fit outside or through any existing cable entry or exit points.

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Calculating Your Pre-Tensioner Position:

Measure from the centre of your bottom bracket to your shifter position, along any planned cable routes to find your total length. Then use the calculator to determine your ideal position by entering in your total length.

You can slide the pre-tensioner left or right to determine where your pre-tensioner will be relative to your gearbox.

Alternatively, enter your desired Gearbox to Pre-tensioner length, or Pre-Tensioner to Shifter length, to calculate your total length.

The calculator will automatically factor the gearbox and Pre-Tensioner lengths into the equation.