Brake locks front wheel resulting in flying over the handlebars

[Freddy92]

Some of you will wonder why I am posting this but it will become clear later.

My youngest daughter is a student at Sussex University. She has a Dawes Ladies Bike which she loves. It is a fairly early model with centre pull brakes made of some sort of engineering plastic. One side of the front brake broke under extreme braking. Not good and I am sure the reason no one seems to make brakes out of plastic any more. Shame on you Dawes for ever choosing it. Anyway, not to prolong this, she takes her bike to a cycle shop in Brighton and asks if they can fit a new front brake which they do. Now here is the real story. Friday night she is cycling down a hill - probably rather faster than she should - someone walks across the road and she slams on the brakes. The front wheel locks up and she does a superman impression flying over the handlebars and landing on her front in the road. Luckily she does not seem to be injured other than bruises. She blames herself for 'braking too hard'. On picking her bike up she finds the front wheel will not rotate, being locked by the front brake. I say it should be impossible to apply the brakes so hard that the front wheel is permanently locked. The brakes must have been installed incorrectly by the bike shop. She keeps blaming herself.

 

[downfader]

Does sound as if a mechanical failure might be the cause. How is the front wheel? Could it have buckled upon the crash thus jamming one side? Un-clamp the brake and try and free spin it, does it wobble?

Many front brakes can lock a front wheel under the right circumstances (eg hitting a small rut in the road or a kerb at the exact moment, something I did as a kid a few times). A rider also has to learn the limits of braking and how to control their body to avoid the bike becoming unbalanced.

 

[ColinJ]

Applying the brakes should not 'jam them on' but are you sure that the brake was not damaged in the crash, with that causing it to get stuck?

It is perfectly possible to go over the handlebars with over-enthusiastic braking of properly maintained brakes, however.

Can you see why the brake is stuck on?

 

[simon.r]

It's easy enough, with a well set up brake, to lock the front wheel. Just think how easy it is to do a rear wheel skid - it's the same priciple.

Not sure what you mean by '...the front wheel is permanently locked' though? The only thing I can think is that the blocks have gone under the rim somehow? Any photos, or a better description?

 

[sidevalve]

Forgive my confusion but if you mean the wheel is permanently jammed [as opposed to just locking up when she hit the brake] then something is seriously wrong. I can only think of three things 1- lever pivot breaking sticking lever on. 2- cable sticking or 3- actual brake arm pivot bending or possibly twisting [and thus tightening up] preventing arms releasing. If the brake is still stuck on I'd go back to the shop and start jumping up and down.

 

[derrick]

If the front brake did not lock up on the mtb, i would noy be able to do stoppies. have not tried it on the road bike though.
Though they should not stay locked on.

 

[Ian H]

It's easy enough, with a well set up brake, to lock the front wheel. Just think how easy it is to do a rear wheel skid - it's the same priciple.

Hmm. I've never managed to lock a front wheel on a dry road.

Not sure what you mean by '...the front wheel is permanently locked' though? The only thing I can think is that the blocks have gone under the rim somehow? Any photos, or a better description?

That sounds like a possibility.

 

[simon.r]

Hmm. I've never managed to lock a front wheel on a dry road.

Boris can (at 51s)

 

[Freddy92]

When she picked the bike up the front wheel would not rotate. I asked the same question - is it jammed? I asked her to take pictures - the one I will upload is less than I would have liked but shows the type of brake. She took the bike back today and she says the guy in the shop did something quickly to the brake and immediately it released the wheel so it was not buckled. What has really annoyed me is he then persuaded her that she needed a full bike check for £20! I am a professional engineer and I know all the usual brake designs and I don't think any of them should jam the wheel like this. It can only happen if the brake shoes rides over the rim onto the tyre which means it was not adjusted correctly in the first place. From the picture I guess this is what has happened on the RHS.

 

[Freddy92]

As I explained in a later post the guy in the bike shop made some adjustment and all was working again so there was no permanent damage. All I can think is that either the brake shoe had ridden over the rim. This can only happen if the brake shoe was adjusted to be too high. I cannot think of anything else.

 

[simon.r]

That's a standard V brake, as you know, so enough power to lock the front wheel if applied sharply.

Did something happen to the brake as a result of the crash? If the shop guy did 'something quickly' that suggests to me that it's something like the noodle being dis-placed rather than the pads being re-aligned. Even a good mechanic will take a couple of minutes to re-align pads. TBH I think you're leaping to conclusions when you say that 'The brakes must have been installed incorrectly by the bike shop'. They may have been, but, IMO, you can't definitely state that from the information you have.

 

[boydj]

That's a standard V brake, as you know, so enough power to lock the front wheel if applied sharply.

Did something happen to the brake as a result of the crash? If the shop guy did 'something quickly' that suggests to me that it's something like the noodle being dis-placed rather than the pads being re-aligned. Even a good mechanic will take a couple of minutes to re-align pads. TBH I think you're leaping to conclusions when you say that 'The brakes must have been installed incorrectly by the bike shop'. They may have been, but, IMO, you can't definitely state that from the information you have.

Have to agree. Sounds like something fairly basic - and easily corrected - went wrong with the brake as a result of the crash. The crash itself was probably caused by over-enthusiastic braking.

 

[downfader]

..and to add, even if you're unsure of what we tell you perhaps take it to a second shop for a second opinion.

 

[HLaB]

I could be wrong but it seems to me the original brakes were pants but she was used to that and the new brakes actually worked and it simply caught her out; I'm glad she's OK though.

 

[simon.r]

A thought has just popped into my head - you say the bike originally had a 'centre pull' brake, (by which I assume you mean a cantilever), which has been replaced by a V brake:

Was the brake lever replaced at the same time? When V brakes were introduced I seem to remember dire warnings about using them with levers designed for cantis.

To quote Sheldon:

'Direct-pull cantilevers (i.e. V brakes) have a very high mechanical advantage, which makes them unsuitable for use with conventional levers. If you do use conventional levers with direct-pull cantilevers, braking may be too abrupt"

As I say, just a thought.