[msohio]

bar tape on or off

When trying to duplicate it, the bar tape has to be on and tight. That's what causes the brakes to tighten when the brifters shift. The tape holds the casing and the brifter sliding forward pulls the brake cable.

When I was getting new bars set up right, it happened to me. I thought I had them set right and taped the bars. Then when I rode, they needed to be a bit lower. I loosened the clamp and slid the brifter down and forward a slight bit. Tightened it back up. re-mounted and started to pedal. Nothing. Brakes locked from the forward movement. The good news is that no one saw me do a tip over before got got my cleats out !!

 

[msohio]

It shifted forward

MP.....I can assure you the lockup was caused by the levers not being tight enough, and when you hit the bump, they slid forward. Because the outer protective cable was held in place by the bar tape, and maybe electrical tape under the bar tape, the shifter moving forward by half an inch caused the inner cable to pull outward and would be no different than pulling the brake lever to cause one half inch of pull in the inner cable and thus the brakes tighten.

You are by no means the first person this has happen to. As I said in a previous post, if you want to prove it, secure the outer cable with bar tape firmly wrapped and then loosen the shifter and slide it forward about one half to one inch. re tighten it in the new location. The brakes will probably be locked, if not the "free pull" before contact to the rim will be reduced very significantly. It has to happen that way pure and simple.