loss of power when hitting bumps

[Swellens]

I've noticed when I hit a bump in the road my power cuts out momentarily, only for about a second or two. Does anybody else have this problem?

[skymon]

I suspect gear sensor.

Are you using one? They can be prone to that especially if they are only held in place by the derailleur cable housing.

[Swellens]

I suspect gear sensor.

Are you using one? They can be prone to that especially if they are only held in place by the derailleur cable housing.

Yes ,I am using one and yes, it's held by just the cable. I will disconnect it and see it the problem goes away. Thanks

[Swellens]

that was it. Thanks for the help.

[skymon]

My pleasure. (Finally got one :)

[PatrickGSR94]

This is one reason I opted against the gear sensor, that and I didn't feel like cutting my RD cable. I just give a slight tug on the front brake lever when shifting, which works fine. Sort of feels like I'm operating a motorcycle clutch lever.

[Rodney Bush]

likewise, i was suspecting that as well although mine is secured. and know what you mean about the MC feel. will check it out disconnected.

[73Eldo]

You think its the derailer moving around and slacking the cable which the sensor is picking up as a shift? Or just cables and housing flexing around giving enough movement to the cable that it thinks it was a shift?

I never took one apart to see whats inside but I'm assuming its a little zig zag block in the center that the cable runs though and lightly grips on with some sort of spring loaded switch(s) on each end keeping it centered when the cable isn't moving. You shift it yanks that block into the switch before it slips back to the center rest position.

[Rodney Bush]

my problem was more pronounced during off-road riding, particularly down hill. my gear sensor is secured with wire ties. replaced tired old shimano XT rear derailleur with a new advent 9 speed derailleur with clutch and seems to have virtually eliminated the problem.
very pleased

[Tonerider]

Is your bike full suspension? Try mounting the sensor to a solid non moving frame member.

[Rodney Bush]

I also used some double sided tape on the underside of gear sensor against the frame along with the wire ties. works good for me.

[mathias5171]

I had this problem, thought it might be the cable thru the gear sensor, but then I realized that my fingers were resting on the brake lever, which when going over bumps, would trigger the lever just enough to cut the motor for a millisecond. Took my fingers off the lever and problem went away.

[Tonerider]

Also, if your chain is too long, it could trigger the gear sensor as well.