RoadTarmacTec

Tarmac: Front Derailleur and Chain Catcher

Now for the Front Derailleur paired with a Chain Catcher design for a SRM Powermeter. I grown to like a Chain Catcher, especially in climbing situations – no more inside chain drops during a downshift!

My choice on this is the  K-Edge SRM Pro. Nice, slim design and adjustable apart from the derailleur mounting screw. K-Edge also cooperate with SRM for their Powermeters. This is superb because the SRM Origin still needs a cadence magnet which must be mounted/glued to the frame under the bottom bracket area… no-go.

These tools are needed:

  • Bike Stand
  • 2mm Allen
  • 4mm Allen
  • PH-1
  • Torque Wrench
  • Chain Offcut
  • 1-Cent (Coin)
  • Loctite 222 (purple)

Official Service Manual:

Service/Spare Part:

  • Shimano Dura Ace FD-R9100-F
    • I-FDR9100F
  • K-EDGE SRM Pro Road (black)
    • K13-602
  • Custom Titanium Screw (black anodized)

Related Post:

Post as guidance? No warranty in ANY case of damage!

First of all the the weight check. The cleaned derailleur comes in with 66.4 grams, the K-EDGE SRM Pro with 23.3 grams.

Now the installation. The Tarmac is a brazed-on style for the front derailleur whereas the Allez is a clampy-style. I personal prefer the braze-on type because of possible frame scratches and tears plus the benefit of weight saving.

First is to mount the front derailleur loose to align everything. Only additional thing is the mounting post for the chain catcher… which I forgot to anodize :/

Everything must be aligned with the large chain ring, so it needs to go outwards. The low-limit screw needs to be turned clock-wise until the cage is aligned with the 53er cog.

Now for the adjustment. Part one is the height. The correct height between the Chainring and the cage should be around 1-3mm (Pro-Tip No.1: Use 1-Cent). Second part is to align the the outer cage parallel to the chain ring (Pro-Tip No.2: Use an allen key).

The final position of the derailleur will be secured with a torque 5-7NM.

Time for the chain catcher. To make the alignment a chain offcut is very handy. It will be placed on the inner chainring.

Before the chain catcher is mounted, the weight comparison of the Titanium screw will be done. OEM 1.3 grams versus Titanium 0.6 grams.

Also we need a drop of Loctite 222 (purple) on the new screw to secure it.

Now for the installation… finally. First Loctite 222 (purple) to secure the screw. Then just set the chain catcher on its mounting post.

To set the correct distance between the chain and the catcher the 1-Cent will help me again. The catcher screw will be set to 2NM.

In the last step it is possible to align the cadence magnet towards the inner spider of the SRM Origin Powermeter.

And it is done… super nice.