EBB Frame Shell Modification

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The Problem

After modifying the EBB of my Zion frame to reduce weight, I will now cut the shell of the frame down to 2 3/16" from 2 3/4" to match the new width of the cam. This is a lot of heavy steel that is not being used for anything.

The Cam

The Eccentric Bottom Bracket Modification cam is 2.1875" wide.

The EBB Shell

The original shell. 68mm 2.677" 2179 grams with headset cups.


Centered on the DRO


A boring bar was used taking about 4 passes to face the shell down. This was because it would take too much time to fixture up a nice ridged set-up.

If I had not reamed the shell bore round and fit a shim already, I would use this set-up to bore the shell bore round and to a usable size.


The final pass of the first side about to happen.


One side done.


second side done.


The bolt bosses are cracking at the weld. The weld may be cracked, but it seems to have plenty of strength for what it is doing. I will repair this when it fails.


The shell mod complete. 2.250" wide & 42 grams off the frame.


The finished mod. 96 grams gone. That is almost a quarter pound. I should drill some holes in the shell.

It looks so cool now!