20-08-07

top pull road front mech

One way to save weight is using a road front mech on a MTB. Especially when running a 2x9 drive train. One of the downsides is that roadmechs are only available in down pull versions (cable coming from underneath the mech), however many MTBs have a top pull cable routing.

I started of with a old Shimano Ultegra mech and decided to modify it to a top pull mech. The conversions consist of turning around the front part of the parallellogramme. To do this the mech is first separated by loosening the two 3mm hex bolts.

5 rear view
Then the rear part of the bushing is carefully filed away so that it can be removed with a punch. The front part ca now be detached from the cage.

1 parts
2 parts

Then the front side of the part is filed down and a recess is filed in the part to clear the back part (see pics).

3 recess

4 recess
The front part is then reinstalled with in reverse sense. The bushing is punched back into place (securing is by tapping the open part of the bushing with a conical punch). The 3mm hex bolts are put back in place. I drilled out th bolts to save additional weight. The mech can be mounted on the bike.

10 front view
This is my first attempt and prototype. Further steps: polish surface, bolt tuning (al & ti), finding a light clamp, test it in the field.

If all works ok I will see if I can do the same with a Dura Ace and source a light carbon fibre collar.

weight after modification: 109g including collar

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