Spontaneous rim brake clamping Anyone?

[Tickdoc]

Had a new one on me happen on my Christmas Eve ride. I was crossing rr tracks and after bumping across them my front brake clamped down. I released it at the shifter (super record circa 2016) but it is clamped beyond the usual. Did I unseat the cable stop?

Haven’t pulled the hoods yet to check but this is a new one on me and curious what the consensus is from the experts here first.

[nublar]

Gunk in the cables or return spring?

[sitzmark]

How close do you run your pads? On some calipers the quick release cam closes the distance before opening. Cam get bounced into mid-travel position? If not your thought re: cable head in lever is a good place to look.

[Dave Wages]

I bet you hit those tracks hard enough to move the brake lever down the bar a touch. The housing stayed in place, but the lever moving would tighten up the brake.

My two cents...

[dddd]

Originally Posted by Dave Wages

I bet you hit those tracks hard enough to move the brake lever down the bar a touch. The housing stayed in place, but the lever moving would tighten up the brake.

My two cents...

Almost certainly this.^^^

I read this just as I was wondering if the handlebar had perhaps fractured, which is also not outside of the realm of possibility.

A good check here, besides checking the clamp bolt tightness, would be to place a straight-edge atop the hoods, sighting from the front or back to check that the bars are still parallel to the straight-edge.

And I would give each of the drops a solid tug, to check the bar's solidity.

Were you riding with hands on the hoods, or in the drops?

[zetroc]

Also possible that the bars rotated in the stem just enough to pull the brake cable and bind it up. That's where my money is.

[Hindmost]

Originally Posted by Dave Wages

I bet you hit those tracks hard enough to move the brake lever down the bar a touch. The housing stayed in place, but the lever moving would tighten up the brake.

My two cents...

Didn't that happen to Tony Cruz in Paris-Roubaix? He went over the bars, iirc.

"Tony Cruz: My bike broke, about two sectors before the Arenberg. I don’t know what happened, it must have been the bars, because all of a sudden my bars dropped, my brakes engaged and then I’m popping a front-wheelie down the pavé. Guys are bouncing off my hip." From Velonews.

[unterhausen]

I had that happen when I hit a giant pothole and double flatted. Never did figure out what moved. It was a bit annoying when i got the tires pumped back up and the brake was tight.

[flying]

Originally Posted by Dave Wages

I bet you hit those tracks hard enough to move the brake lever down the bar a touch. The housing stayed in place, but the lever moving would tighten up the brake.

My two cents...

Yup that is usually the case after a good bump.
The confirm is probably your front derailleur went out of adjustment too
(That is if your front derailleur is on the same lever as your front brake)

[Tickdoc]

I bet you are right as the left hood looks more inbound after but was not loose enough to move by hand. Hands were on hoods. Those tracks are angles and have taken out many a rider over the years and saddest part is they are defunct or go nowhere. We always call them out and move way over to the inside of the lane to try to cross them as parallel as possible. I noticed also that the cable housing for the front brake at the brake was squelched up or folded a bit. Hopefully the bars are ok and I’ll find out after I remove the tale and play with it. Supposed to rain tomorrow so may be a good day to play with it. Coulda endo’d easily there.