CRASH! front brake locked up

Marko Polo · Jun 28, 2008

Does anyone have an idea why the front brake on a dura ace brifter would lock up when going over a bump in the road?
Here's the scoop. I recently bought a new road bike, a Gunnar Roadie with a full dura ace set up. I bought the frame and components from the LBS and had them assemble it. The components were a take off from a new bike, supposedly never ridden, they look new. The frame is brand spankin' new.
I was on a group ride, cruising along about 20 mph or so when I hit a bump in the road. My front brake locked up and put me over the bars. No apparent damage to my bike but the front brake was locked up solid. When I got home, after a trip to the ER, I pulled the bike out of the van the brake was still locked up. I moved the shifter and squeezed the brake and then the brake worked fine.
I'm going to be off the bike for a while, but now I question the shifter and what recourse I have. The bike only has 160 miles on it.

-Mark

andulong · Jun 28, 2008

Are you saying that you never even applied the brake? Or are you sayin' that you applied the brake and then it locked up? I don't see how the brakes would lock up just riding over a bump. Maybe you have a defective/sticky mechanism? Not sure what sort of liability there might be? Might want to talk to an attorney if it is mechanical failure.

Marko Polo · Jun 28, 2008

I never applied the brakes, I was riding on the hoods, hit the bump and I was airborn. The bump was nothing out of the ordinary, it wasn't even a pothole, just a small dip and rise in the asphalt. I think it's a defect.

Kerry Irons · Jun 29, 2008

Lockjaw

Marko Polo said:
I never applied the brakes, I was riding on the hoods, hit the bump and I was airborn. The bump was nothing out of the ordinary, it wasn't even a pothole, just a small dip and rise in the asphalt. I think it's a defect.

Please explain in more detail. For example, were the pads clinched on the rim and the cable slack, or was the cable taught and the lever slack? Is it possible the pads are adjusted to "high" and they grabbed the tire? What did you do to free up the brakes? Have you been able to detect any stickiness in the lever action? Can you reproduce the lockup?

It is rather hard to envision how a defect in the levers could spontaneously apply enough force to the brakes to put you over the bars. Where would that force come from? What you experienced sounds a lot more like picking up some road debris and having it jam between the tire and fork.

cosmo333 · Jun 29, 2008

Since you hit a bump while on the hoods at the same time the brake locked the most likely cause would be the shift lever sliding down on the bars, the cable tightens as the lever moves down and the housing holds tight under the bar tape. Doesn't take much movement if the brakes are set tight. More common on carbon bars with a slick finish but if the lever wasn't tight enough and/or an odd placement this can happen on an alum bar too. When you moved the shifter the tension was released and the brake opened, probably nothing wrong with the shifter or brake. There's most likely a good mark on the bar from the clamp nut-inspect it.

At our shop we put carbon assembly paste under all bar clamps (carbon or alum bars) to give some extra grip and torque to spec. And check the spec for both the bar and clamp-you be surpised the varience in min and max spec for bars and shifters out there. Some bars have a max torque below the min spec of the shifter.

Marko Polo · Jun 29, 2008

Kerry, when I picked my bike up off the road the brakes were locked up tight on the rim, the wheel wouldn't move and if memory serves the lever was tight. When I dropped my bike off at my house I pulled it out of the van and the brake was still locked. My front deraillieur was in the big ring but the chain was off, I shifted to the small ring and put the chain on and squeezed the brakes and they were fine. I'll admit I didn't do any real troubleshooting as I was in some pain. Tomorrow I'll go back over to my house and take a better look and see if I can recreate the problem.

Cosmo, I do have carbon bars, so I'll check for lever movement/marks.

I've built a few mountain bikes, all single speeds, and fixies in the past but this is my first "real" roadbike that's why I had the LBS build it up.

thanks for the info

Henry Chinaski · Jun 29, 2008

cosmo333 said:
Since you hit a bump while on the hoods at the same time the brake locked the most likely cause would be the shift lever sliding down on the bars, the cable tightens as the lever moves down and the housing holds tight under the bar tape.

From what he described that would be my initial guess as well.

Camilo · Jun 29, 2008

cosmo333 said:
Since you hit a bump while on the hoods at the same time the brake locked the most likely cause would be the shift lever sliding down on the bars, the cable tightens as the lever moves down and the housing holds tight under the bar tape. Doesn't take much movement if the brakes are set tight. More common on carbon bars with a slick finish but if the lever wasn't tight enough and/or an odd placement this can happen on an alum bar too. When you moved the shifter the tension was released and the brake opened, probably nothing wrong with the shifter or brake. There's most likely a good mark on the bar from the clamp nut-inspect it.

At our shop we put carbon assembly paste under all bar clamps (carbon or alum bars) to give some extra grip and torque to spec. And check the spec for both the bar and clamp-you be surpised the varience in min and max spec for bars and shifters out there. Some bars have a max torque below the min spec of the shifter.

Could it also be the bar clamp on the stem? It's a fairly common mistake to undertighten those, and when you hit a bump with weight on the brifters, the bars will rotate downward.

ericm979 · Jun 29, 2008

Camilo said:
Could it also be the bar clamp on the stem? It's a fairly common mistake to undertighten those, and when you hit a bump with weight on the brifters, the bars will rotate downward.

That won't cause the brake to come on.

It's the brake lever clamp. Oops.

Marko Polo · Jun 29, 2008

Ok, I have looked at the bike. Both shifters are scraped up as expected. It looks as though the rear assembly stayed in place, maybe pushed up a bit. The front assembly definitely moved, down. I moved the thing up, down, in and out and the brakes work fine. I cannot get the problem to show up.

I guess my main concern is more for piece of mind. Is this going to happen again? I don't really understand how it's possible to go from apparently functioning well to locked up tight without doing anything other than hitting a bump in the road.

I ride about 3500-4000 miles a year on the trails and the road and have not had a road crash until now. I could see if it was something obvious, like a huge pothole or a sewer grate, or even tangling with another rider but a bump in the road? come on I live in Wisconsin, after this winter and spring the roads are crap, there is no such thing as a smooth road.

Henry Chinaski · Jun 29, 2008

Marko Polo said:
Ok, I have looked at the bike. Both shifters are scraped up as expected. It looks as though the rear assembly stayed in place, maybe pushed up a bit. The front assembly definitely moved, down. I moved the thing up, down, in and out and the brakes work fine. I cannot get the problem to show up.

What do you mean by "assembly"? The brifter? If so, it sounds like what Cosmo described above--did you understand what he was talking about? I'm gonna refrain from a huge anti-carbon rant, but you need to make sure the brifters will stay in one place.

Marko Polo · Jun 29, 2008

Yes, I mean the brifters. If I understand Cosmo, shouldn't I be able to recreate the brake lockup by moving the brifter one way or the other? I have tried moving the brifters around every which way and if I move them 15 or 20 degrees outward from straight I see the brakes tighten up a little bit. What I experienced was a total lockup of the brakes. No matter how I move the brifters I cannot get the brakes to lock the way they did, not even to the point of the pads touching the rim.

The bump I went over, I would equate the force to the equivilent of popping a wheelie maybe 3 inches high.

mohair_chair · Jun 29, 2008

Do you KNOW that your brakes locked up, causing the crash, or are you making the ASSUMPTION that because you found them locked up AFTER the crash, they must have locked up to CAUSE the crash. Because those are totally different things.

It would not be unusual to find your wheel doesn't turn after a crash for a variety of reasons. This could be because the brakes are locked up, perhaps due to the cable housing slipping out of a cable stop somewhere. But that doesn't mean that is what caused the crash.

FatManOnaBike · Jun 29, 2008

Something must be missing. The calipers are held open by a spring. If the brake pads
( with no debris under them ) are "clamped" to the rim so tightly as to cause the effect you described, there had to be tension on the cable substantially greater than the opening force of the spring. It appears that the bump, however minor, was enough to allow the brifter to slide down the bars driven by your body weight on the hoods. I'm simply trying to clarify what others have said. The brifter is simply a lever and a cable. IMHO it can't fail the way it has appered to.

msohio · Jun 29, 2008

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 !!

Marko Polo · Jun 29, 2008

Mohair, the brakes locked up to cause the crash. Usually when I see a bump I kind of unweight the bike to float over it. I unweighted and the next thing I knew I was slammed over the bars, no nose wheelie or anything. The bike just flipped over.

Marko Polo · Jun 29, 2008

My LBS is closed today, so I'll head down there later this week and see what they come up with. I'll post their diagnosis...

Bocephus Jones II · Jun 29, 2008

Marko Polo said:
Mohair, the brakes locked up to cause the crash. Usually when I see a bump I kind of unweight the bike to float over it. I unweighted and the next thing I knew I was slammed over the bars, no nose wheelie or anything. The bike just flipped over.

you sure a stick or rock didn't get caught in your wheel? I really can't see how a brake could spontaneously lock up without the brifter being depressed or something getting stuck in the brake.

android · Jun 29, 2008

cosmo333 said:
Since you hit a bump while on the hoods at the same time the brake locked the most likely cause would be the shift lever sliding down on the bars, the cable tightens as the lever moves down and the housing holds tight under the bar tape.

Ding, ding, ding!!

He wins the prize. The shop didn't tighten the levers tight enough.

anax.mananagat · Nov 30, 2022

"To the LBS" would have been my first response. They built it and should be answerable for it.

andulong · Jun 30, 2008

I have also seen wheels lock up after a crash because the calipers are knocked off center. This will cause one brake pad to rub the rim. Maybe the levers slid down during the impact causing you to go over the bars and it locked up during the impact by the calipers being knocked out of alignment??????

DrSmile · Jun 30, 2008

I suggest you strap a video camera to your handlebars, point it at the caliper, and go for a vigorous ride until the problem replicates itself. Why? Because I need some entertainment!

MWPDX · Jun 30, 2008

DrSmile said:
I suggest you strap a video camera to your handlebars, point it at the caliper, and go for a vigorous ride until the problem replicates itself. Why? Because I need some entertainment!

... +1

bike_guy · Jun 30, 2008

android said:
Ding, ding, ding!!

He wins the prize. The shop didn't tighten the levers tight enough.

That is my thought. Similar thing happened to me, but I didn't go over the bars. I was trying to avoid a chasing dog when I hit a pothole and the front brake locked. After coming to an abrupt stop the entire shifter had moved just enough to take up the slack in the cable causing the caliper to lock. Checked the other shifter and sure enough it was not completely tight either. I later read that some people leave their shifters a little loose in case of a crash so the lever will turn when it hits the pavement hoping that it won't completely destroy it.

android · Jun 30, 2008

Marko Polo said:
Yes, I mean the brifters. If I understand Cosmo, shouldn't I be able to recreate the brake lockup by moving the brifter one way or the other? I have tried moving the brifters around every which way and if I move them 15 or 20 degrees outward from straight I see the brakes tighten up a little bit. What I experienced was a total lockup of the brakes. No matter how I move the brifters I cannot get the brakes to lock the way they did, not even to the point of the pads touching the rim.

The bump I went over, I would equate the force to the equivilent of popping a wheelie maybe 3 inches high.

Just turning the STI levers typically won't lock up the brakes. You have to push them DOWN the handlebars while the cable housing is wrapped in tape. Think about it mechanically. That is the equivalent of squeezing the lever. You have shortened the inner cable in relation to the housing.

Marko Polo · Jun 30, 2008

gratuitous carnage picture

First photo post, I hope it works...

Here is a picture of my knee after the crash...

cmg · Jun 30, 2008

post a photo of the brakelever on the bars without the tape. we're looking for scratch marks that indicate that the brifter has moved. The photo of your knee looks bad. recommend cleaning with epson salt and water 1:4 twice a day and keep in wrapping. i landed on gravel, saw the knee cap, lots of blood, nasty fall.

CRASH! front brake locked up

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