What happened?

Your hands were on the brake lever and it moved (because it wasn't
tightened well enough) when you hit the pothole (downwards on the
handlebar) thus pulling the brake cable forward - the brake engaged
and everything else seems to be ok.

Do I win a price (if I'm right)?

On Wednesday, January 9, 2013 7:40:54 PM UTC-6, Claus Aßmann -no-copies-please wrote:
Your hands were on the brake lever and it moved (because it wasn't

tightened well enough) when you hit the pothole (downwards on the

handlebar) thus pulling the brake cable forward - the brake engaged

and everything else seems to be ok.



Do I win a price (if I'm right)?

I don't believe this would work. You can vary the position of the brake levers by, for example, tilting the bars up or down, without having to adjust the brake cable. This is because the cable follows a curved path and slight adjustments to the lever/caliper distance just make the curve tighter or more relaxed.

On 2013-01-09, wrote:

I was out riding yesterday on a bike with conventional rim brakes.
I rode through a pothole and the bike quickly came to a stop of its
own accord. First thought was: puncture. This was clearly not
the case, but the rear wheel was impossible to turn. I wondered
if it had become displaced in the frame and was rubbing somewhere.
Again, this was not the explanation. What had happened was that
the rear brake (Tektro) was firmly clamped to the brake tracks
(both sides) on the back wheel. The brake cable was not snagged
anywhere and pressure on the brake lever did not relieve the
situation. I was able to resume riding by fully opening the back
brake caliper with the little built-in lever. I had no further
issues but on returning home I needed to readjust where the brake
cable was clamped at the caliper. How do you explain this?

Nigel,

The cable housing becoming longer is about the only cause I can think
of for what happened to your bike. Check all your housing sections
to see if one of the ends has popped out of its proper place and
become wedged. This could happen at any of the cable housing stops,
including at the lever and the brake. Good luck.

--
Gregory S. Sutter Mostly Harmless

http://zer0.org/~gsutter/

On 10/01/13 13:43, Gregory Sutter wrote:
On 2013-01-09, wrote:

I was out riding yesterday on a bike with conventional rim brakes.
I rode through a pothole and the bike quickly came to a stop of its
own accord. First thought was: puncture. This was clearly not
the case, but the rear wheel was impossible to turn. I wondered
if it had become displaced in the frame and was rubbing somewhere.
Again, this was not the explanation. What had happened was that
the rear brake (Tektro) was firmly clamped to the brake tracks
(both sides) on the back wheel. The brake cable was not snagged
anywhere and pressure on the brake lever did not relieve the
situation. I was able to resume riding by fully opening the back
brake caliper with the little built-in lever. I had no further
issues but on returning home I needed to readjust where the brake
cable was clamped at the caliper. How do you explain this?

The cable housing becoming longer is about the only cause I can think
of for what happened to your bike. Check all your housing sections
to see if one of the ends has popped out of its proper place and
become wedged. This could happen at any of the cable housing stops,
including at the lever and the brake. Good luck.


Yup, that's what I thought. Maybe you explained it better.

--
JS

Guess how I know that this can happen?

After I hit a pothole my bike suddenly moved a lot slower -- because
the rear brake was rubbing the rim. It was a freshly installed
bike where I was still experimenting with the lever position and I
didn't tighten the bolts much. Moving the lever "back up" allowed
me to ride back home (being careful not to move the lever again)

On 1/9/2013 7:40 PM, Claus Aßmann wrote:
Your hands were on the brake lever and it moved (because it wasn't
tightened well enough) when you hit the pothole (downwards on the
handlebar) thus pulling the brake cable forward - the brake engaged
and everything else seems to be ok.

Do I win a price (if I'm right)?


It's possible.
With modern aero levers, the casing stays with the tape so
if the lever does move, the wire gets pulled tight.

Necessary conditions are a nice clean tight tape
installation with a sloppy brake lever installation. Knowing
the OP, I would bet against it.

--
Andrew Muzi
www.yellowjersey.org/
Open every day since 1 April, 1971

On 01-09-2013 09:39, wrote:
Possibly relevant is that I recently fitted new Microshift brake/shift levers to the bike, although I have ridden several hundred miles without incident since making that change.

The Gremlins misread "Microsoft" and figured going that long without a
crash is unnatural.

--
Wes Groleau

“Two things are infinite, the universe and human stupidity.
But I'm not so sure about the universe.�
— Albert Einstein

On Wednesday, January 9, 2013 10:25:57 PM UTC-6, Claus Aßmann -no-copies-please wrote:
Guess how I know that this can happen?



After I hit a pothole my bike suddenly moved a lot slower -- because

the rear brake was rubbing the rim. It was a freshly installed

bike where I was still experimenting with the lever position and I

didn't tighten the bolts much. Moving the lever "back up" allowed

me to ride back home (being careful not to move the lever again)

Well, I was forgetting that the brake cable housing is taped to the bars (thanks, Andrew Muzi, for pointing this out) and that this would allow what you describe to happen. It was a pretty bad pothole that I hit, so I carefully re-examined the positioning of the brake levers and it does seem that the rear one may have moved a little (and I do run the brake pads very close to the rim). So, ding ding ding, I think we have a winner. Your prize? - you don't have to waste any more time on this. (And to Andrew Muzi, I much appreciate the compliment in your most recent posting on this thread, but it seems your confidence in my mechanical skills is misplaced in this instance.)

On 10/01/13 23:26, wrote:
On Wednesday, January 9, 2013 10:25:57 PM UTC-6, Claus Aßmann
-no-copies-please wrote:
Guess how I know that this can happen?



After I hit a pothole my bike suddenly moved a lot slower --
because

the rear brake was rubbing the rim. It was a freshly installed

bike where I was still experimenting with the lever position and I

didn't tighten the bolts much. Moving the lever "back up" allowed

me to ride back home (being careful not to move the lever again)

Well, I was forgetting that the brake cable housing is taped to the
bars (thanks, Andrew Muzi, for pointing this out) and that this would
allow what you describe to happen.

So effectively the end of the cable outer was not seated at the lever end.

--
JS.

On 1/9/2013 8:18 PM, wrote:
On Wednesday, January 9, 2013 7:40:54 PM UTC-6, Claus Aßmann -no-copies-please wrote:
Your hands were on the brake lever and it moved (because it wasn't

tightened well enough) when you hit the pothole (downwards on the

handlebar) thus pulling the brake cable forward - the brake engaged

and everything else seems to be ok.



Do I win a price (if I'm right)?

I don't believe this would work. You can vary the position of the brake levers by, for example, tilting the bars up or down, without having to adjust the brake cable. This is because the cable follows a curved path and slight adjustments to the lever/caliper distance just make the curve tighter or more relaxed.

I have a bike with a hinged riser* (think very long stem), and it
applies the brakes if I tilt it far enough forward while walking the bike.

*RANS Flip-Itâ„¢

--
Tom $herman