By: Phillip Stevens
Note YMMV. It works for me, it may not work for you. Particularly note: both Sheldon "nervous" Brown and Andrew "chary" Muzi don't like the idea of having two inners going to one clamping bolt. If you have a problem with that, forget this fix. The issue is that if one cable slips, then the other will be loosened in the clamp and will probably slip too. You've been warned!
It is also possible to use a "London mod" which does a similar thing to my mod. The London mod puts a bolt in the calliper upper arm, and passes two cables AROUND the arm. I don't like that solution because it creates a triangle of tension forces which strains (twists) the brake calliper unnecessarily, and doesn't fix the two cable under one bolt issue. See photo here
First, at the LBS (with B as in BMX not Bike), find a SST ORYG giro upper cable as the basis (but it would work with the Odyssey giro upper too).
The right piece is a "giro upper cable". Differentiating it from the lower cable is a barrel adjustment to allow fine tension adjustment on the brake lever on the single cable end. This barrel adjustment bolt is the same diameter and threading as that on the upper arm of the brake calliper. See photo here
Cut off all the cables on the giro upper cable. Crack open the hard plastic doubler; its two halves are only pressed together. Remove the blob of cast metal containing the cable remnants.
Drill out the hollow barrel adjustment bolt using successively larger diameter drills until two brake cable inners run freely through it. I think it was 3.5mm from memory. Because there's already a hole through the centre, its really easy to keep the drill straight. Then using a large drill, 6mm from memory, drill into the head of the bolt to remove the head. All that is left is a hollow screw.
Screw this hollow screw back into the plastic doubler thread till it stops. I put the ugly drilled end in first. Remove the fine adjustment from the brake calliper arm, and screw the end of the doubler into the calliper.
Cut the outer cables from both levers to fit. Feed both inners through the doubler and press the two halves together again. I've pulled the two inner cables under the same side of the calliper retaining bolt.
IMPORTANT: Put a star washer (not a flat washer) on first under the cable inners. This will increase the bite on the cables, and prevents them from slipping. Do up the retaining clamp bolt tightly.
VERY IMPORTANT: Test this fix properly. Squeeze one lever harder than
ever need. Then the other. Then both at once. Check that nothing's
Test this to fix to death. If you don't test and something is not
then yours may follow..