V Brake failure

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Steve O'C
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V Brake failure

Postby Steve O'C » 30 May 2020, 8:42pm

Friend of mine brought her bike round because the "cable had snapped". In fact as you can see what has happened is that the bracket that the noodle sits in had bent rendering the brake suddenly useless.

For such a safety critical part the design seems to rely on a tiny tab of metal.

I know they are designed that way so that the noodle can be unhooked to open the brakes although in practice I have never been able to do that when the pads are reasonably close to the rim.

I would prefer a design where the noodle fits through a hole as I think it would be less prone to failure but I do not recall ever having seen one like that.

Steve

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Marcus Aurelius
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Re: V Brake failure

Postby Marcus Aurelius » 30 May 2020, 8:46pm

It looks like someone has tried to release the noodle without pinching the pads in first to give it some slack.

pwa
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Joined: 2 Oct 2011, 8:55pm

Re: V Brake failure

Postby pwa » 30 May 2020, 8:51pm

That is a part of the V brake system that merit's a quick inspection when the bike is being cleaned. It is quite a flimsy item and, as said, failure could be costly.

rjb
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Re: V Brake failure

Postby rjb » 30 May 2020, 9:09pm

Ive seen this a few times. Often caused by swinging the handlebars around which then puts excessive pull on the brake cable and rips the noodle out from its support, bending open the support tab as shown in the photo. Worth checking so you know if its likely to happen to yours. :wink:
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Brucey
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Re: V Brake failure

Postby Brucey » 30 May 2020, 9:25pm

yep, very common, potentially very dangerous; the endgame is that the noodle pulls through the yoke when the rider needs to be braking hard. In cheap V brakes the yoke is made of pretty soft steel and the (small) shoulder on the noodle is often soft aluminium. It is an arrangement that hardly inspires confidence and is easily damaged should the handlebars swing rightwards. Even in good quality kit the same flaw exists.

FWIW you can often reshape the yoke; typically you can clamp the yoke in a bench vice using an 8mm allen key as a spacer/former and then reshape the ends (eg with a very small hammer) so that they fit properly again. A gentle squeeze or splay to finish and make it an exact fit again. Check for cracks afterwards, obviously.

It isn't a bad idea to swap the repaired arm to the rear brake, so that you have an unmolested arm on the front of the bike for the (more safety critical, more highly loaded) front brake.

FWIW you can often help prevent a recurrence of this problem by using an M6 washer with a couple of flats filed on it to make the 'shoulder' on the noodle bigger.

cheers
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NATURAL ANKLING
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Re: V Brake failure

Postby NATURAL ANKLING » 30 May 2020, 10:04pm

Hi,
Is this an untouched bike out of the shop or has it seen repair / maintenance in the past?
Frustration in unhooking the noddle might of damaged it.
Also the fit of the noodle in the fork (damaged bit) if slack just needs a bit of a pinch in a vise etc.
They are normally strong enough, but like all stuff we don't know the history exact.

I have reasonably strong hands and use similar stuff on my bike and as long as its not mis-shapen with poor fit that's slack fit, they seem to work well.
Could be a better designed ..maybe.
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RJS
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Re: V Brake failure

Postby RJS » 30 May 2020, 10:41pm

Seen this on a bike that had been carried on a rack on the rear of a car, easily done, I think having the front brake on the right accentuates the problem, it was designed to have the cable come from the other side. Brucey will put me right if I have this wrong.
Cheers, Rob.

gregoryoftours
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Re: V Brake failure

Postby gregoryoftours » 30 May 2020, 11:12pm

Sometimes also making sure a noodle with an angle of 135° is used on the front brake (UK brake setup ie right lever operated front brake) can help to lessen the likelihood of this happening. A front brake cable outer fitted with a 90° noodle can pull upward as the brake is applied, causing the yoke to be splayed.

Brucey
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Re: V Brake failure

Postby Brucey » 30 May 2020, 11:21pm

the nature of the OP's damage is exactly as you would expect if the handlebars have swung to the right and the noodle has hit the frame. I've seen it many times before.

I agree a 135 degree noodle is probably an improvement over a 90deg one but if you want to avoid this damage (and maybe get a different sort instead...) it probably better yet to use a flexi-noodle...?

cheers
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Gattonero
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Re: V Brake failure

Postby Gattonero » 31 May 2020, 7:55am

You can reshape that part, and once you fit the noodle (flexy ones can be made with the start portion of some Jagwire cable kits, or bought as new part anyway) you can use a small ziptie to keep the end of the noodle well inline with the yoke. A noodle that's not inline will often cause this problem, altogether with poor braking and friction in the cable.
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NATURAL ANKLING
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Re: V Brake failure

Postby NATURAL ANKLING » 31 May 2020, 9:32am

Hi,
Obviously quality varies on these products.
The real cheap end of the market also has pressed tin arms as well with punched out holes, they're not aluminium solid.
On V brakes do any other designs exist apart from that pressed steel stirrup?
I'm sure there must be just haven't seen them but I don't get out a lot anyway ha ha.
NA Thinks Just End 2 End Return + Bivvy
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Please forgive the poor Grammar I blame it on my mobile and phat thinkers.

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Si
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Re: V Brake failure

Postby Si » 31 May 2020, 10:50am

I've found this problem quite a lot while doing bikeability. Often caused by the noodle not being put all the way into the hole, so that the end of the noodle sits against the 'lips' of the yoke and when the brake is pulled on it bends them.

I have seen some instructors bend them back into shape with pliers. My view is that once bent the cheap ones are weakened and may fail catastrophically, and thus fall back on the rule that instructors are not allowed to fix bikes and refuse to do it.

Steve O'C
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Re: V Brake failure

Postby Steve O'C » 31 May 2020, 12:55pm

Thanks for all the replies. The bike is at least 10 years old (it has a sticker on it from a local bike shop that closed 10 years ago). It is well used but not so well maintained.

I would be tempted to try a repair on my own bike that I could keep an eye on but as it happened I had a spare set of brakes so I fitted them.

Steve