What happened?

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? To me, it seems as unlikely as water running uphill. 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.

Any ideas?

Thanks in advance for your suggestions.

Best wishes,

Nigel Grinter

On Wednesday, January 9, 2013 8:39:38 AM UTC-6, 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? To me, it seems as unlikely as water running uphill. 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. Any ideas? Thanks in advance for your suggestions. Best wishes, Nigel Grinter

Just a guess, but is there a lip on your brake pads which dived underneath the rim and caught there? You may need to trim the pads and re-adjust the brakes.

On 1/9/2013 8:39 AM, 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? To me, it seems as unlikely as water running uphill. Possibly relevant is that I recently fitted new Microshift brake/shift levers to the bike, althou
gh I have ridden several hundred miles without incident since making that change.

Any ideas?

Thanks in advance for your suggestions.

Best wishes,

Nigel Grinter


Look at the brake pads.
Were they adjusted a bit low such that there is a lip at the
bottom snagging the edge of the rim?

Replace, or, if they are otherwise not too worn, trim away
the lip and readjust height. You might also check that the
caliper is tightly secured to the frame, another source of this.

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

CHECK WHEEL FOR AXLE WOBBLE, maybe your bearings are looe

Look at the brake pads.

Were they adjusted a bit low such that there is a lip at the

bottom snagging the edge of the rim?



Replace, or, if they are otherwise not too worn, trim away

the lip and readjust height. You might also check that the

caliper is tightly secured to the frame, another source of this.



--

Andrew Muzi

www.yellowjersey.org/

Open every day since 1 April, 1971

I don't believe that was what happened - no evidence for the "lip" on the brake pads and they are not mounted such that any part of the pad is below the braking surface. It was just as if someone had shortened the brake cable and I had to let it out a little to compensate.

On Wednesday, January 9, 2013 11:31:19 AM UTC-6, datakoll wrote:
CHECK WHEEL FOR AXLE WOBBLE, maybe your bearings are looe

I don't think so. If it were wobble, wouldn't the rim just be touching the brake pad on one side only? As far as I could see, the brake pads were firmly gripping the rim on both sides, just as if someone were pulling on the brake lever.

On 1/9/2013 5:06 PM, wrote:
On Wednesday, January 9, 2013 11:31:19 AM UTC-6, datakoll wrote:
CHECK WHEEL FOR AXLE WOBBLE, maybe your bearings are looe

I don't think so. If it were wobble, wouldn't the rim just be touching the brake pad on one side only? As far as I could see, the brake pads were firmly gripping the rim on both sides, just as if someone were pulling on the brake lever.


And this is on the entire rim, not just a spot which is dented?

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

On 10/01/13 01:39, 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? To me, it seems as unlikely as water
running uphill. 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.

Any ideas?

Is it possible that the cable outer has jumped out of its proper
position where it terminates either at the lever or on the frame somewhere?

--
JS.

On Wednesday, January 9, 2013 5:13:10 PM UTC-6, AMuzi wrote:
On 1/9/2013 5:06 PM, wrote:

On Wednesday, January 9, 2013 11:31:19 AM UTC-6, datakoll wrote:

CHECK WHEEL FOR AXLE WOBBLE, maybe your bearings are looe



I don't think so. If it were wobble, wouldn't the rim just be touching the brake pad on one side only? As far as I could see, the brake pads were firmly gripping the rim on both sides, just as if someone were pulling on the brake lever.





And this is on the entire rim, not just a spot which is dented?



--

Andrew Muzi

www.yellowjersey.org/

Open every day since 1 April, 1971

Yes, it's a new wheel and it seems perfectly true and dent-free.

On Wednesday, January 9, 2013 5:15:07 PM UTC-6, James wrote:
On 10/01/13 01:39, 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? To me, it seems as unlikely as water

running uphill. 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.



Any ideas?



Is it possible that the cable outer has jumped out of its proper

position where it terminates either at the lever or on the frame somewhere?



--

JS.

Certainly possible but I see no evidence of it having happened. The cable end is properly seated in the brake lever and everything looks normal at the caliper end.