Derailleur Bolt Replacement (M10x1.0 mm)

For singlespeed bike conversions, I like to use a bolt-on chain tensioner. They often work by using a bolt to secure the device to the derailleur hanger.

The Problem

The problem is the bolts are cheap and wear out over time. Either they rust or the hex socket head becomes rounded over time. The bolt-on chain tensioner is still good, but these bolts aren’t a common thing to find at the LBS. Surely these bolts can be easily replaced?

The Solution

Well according to specifications, most derailleur bolts have been standardized to a thread of M10×1.0 mm.

As a result, a trip was made to the local hardware store to find the bolt. Alas, all they had were M10×1.0 × 30mm hex head bolts which were too long. Nonetheless, they were cheap and could be cut to length.

To cleanly cut the bolt to length, the following supplies were gathered:


  • Hacksaw
  • Metal cuttingblade for hacksaw
  • M10×1.0 die (a M10×1.0 nut will also work)
  • Vise

Then following steps were performed:


  1. Thread the die or nut to the desired length of the M10×1.0 × 30mm bolt. In this case, it was threaded all the way.
  2. Secure the bolt into a vice.
  3. Saw off the excess bolt with the hacksaw while using the die or nut as guide.
  4. Unscrew the die or nut from the bolt to clean the threads.

End result was a new cleanly cut M10×1.0 × 10mm bolt that fits the derailleur hanger.

In this case, M10×1.0 × 30mm bolts with hex heads were all the hardware store had, so an extra stubby wrench is carried on MTB rides. The one benefit is the hex head won’t wear out as quickly as the hex socket.

Derailleur Bolt-M10x1-01-thumb.jpgDerailleur Bolt-M10x1-02-thumb.jpgDerailleur Bolt-M10x1-03-thumb.jpg