Dartmoor Chain Tensioner Lite - chain tensioner 10 mm (1 pc) black

Dartmoor Chain Tensioner Lite – 10 mm axle chain tensioner

A 10 mm axle chain tensioner keeps chain tension on frames with horizontal dropouts that have no derailleur or built-in tensioning mechanism – typical on singlespeed, dirt, street and pumptrack builds. The Dartmoor Chain Tensioner Lite body has CNC-machined cutouts that bring the weight down to 24 g without touching load-bearing areas. Four mounting screws (5, 10, 15 and 20 mm) are included, so the tensioner bolts onto virtually any dropout.

Why a chain tensioner instead of a derailleur

On a bike without a derailleur (singlespeed, fixed, most dirt/street frames) chain tension is set purely by sliding the rear wheel in the dropout. On a horizontal dropout that slide alone isn't enough. Chain pull would otherwise drag the wheel back on its own. The tensioner bolts to both sides of the dropout and locks the axle in place, so chain tension stays stable through a full ride in rough terrain.

Installation and matching parts

The four screws of different lengths cover both thinner and thicker dropouts without extra shopping. On bikes being converted to singlespeed or a dirt setup, the tensioner is typically installed together with a singlespeed conversion kit (e.g. Dartmoor Singlespeed KIT HG) – the kit handles the single-gear drivetrain, the tensioner holds the resulting chain tension.

Full technical parameters are available in the Specification tab on this product.

Frequently asked questions

What's the difference between a 10 mm and a 14 mm tensioner?

They differ in the bore diameter for the hub axle. 10 mm axles are typical on lighter singlespeed and dirt hubs, while 14 mm axles are more common on heavier-duty dirt/BMX setups.

Do I need a chain tensioner if I already have a derailleur?

No. A tensioner only solves bikes without a derailleur, where chain tension can't be taken up by the rear mech. A bike with regular gearing and a vertical dropout doesn't need this part.

How many screws are included and why different lengths?

The package includes 4 screws in 5, 10, 15 and 20 mm lengths. The different lengths cover different dropout thicknesses and shapes, so you don't need to source hardware separately.

Is the Chain Tensioner Lite sold as a pair?

No, the package contains 1 piece. If you need a tensioner on both sides of the dropout (common on BMX builds), order two units.