Front wheel locked while cycling: disc brake or mudguard?

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Diveywivey
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Joined: 28 Jun 2019, 2:13pm

Front wheel locked while cycling: disc brake or mudguard?

Postby Diveywivey » 28 Jun 2019, 2:32pm

[Subject title was changed later on to reflect that the accident described was likely caused by front mudguard.]

Hi, I went over the handlebars going fairly slowly on a tarmac cycle path the other day. Head/face first into the tarmac. I now have stitches and look like the elephant man but nothing broken thankfully due to helmet I guess. I'm trying to understand what happened. It felt like I'd hit a breeze block, front wheel suddenly and completely locked up in a instant, no time to do anything.

A guy at A&E said it had happened to him due to grit jamming between pad and disc. That's what it felt like. However my family noticed the front mudguard had kind of folded back on itself and the folded up plastic could have ridden up and jammed itself at top of fork? No idea how that might have happened, stone/branch bouncing up in between wheel and mudguard ? Other info is that it was the first time I'd been out on it for several months (due to a different, non biking, injury).

Basically I want to know the likelihood of it being due to grit in disc brake or something else. If grit can do this I'd be very nervous about trusting them ever again, it hurt :? Cheers.
Last edited by Diveywivey on 28 Jun 2019, 11:25pm, edited 2 times in total.

alexnharvey
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Joined: 10 Jan 2014, 8:39am

Re: Can disc brakes lock up while cycling?

Postby alexnharvey » 28 Jun 2019, 2:57pm

Diveywivey wrote:Hi, I went over the handlebars going fairly slowly on a tarmac cycle path the other day. Head/face first into the tarmac. I now have stitches and look like the elephant man but nothing broken thankfully due to helmet I guess. I'm trying to understand what happened. It felt like I'd hit a breeze block, front wheel suddenly and completely locked up in a instant, no time to do anything.

A guy at A&E said it had happened to him due to grit jamming between pad and disc. That's what it felt like. However my family noticed the front mudguard had kind of folded back on itself and the folded up plastic could have ridden up and jammed itself at top of fork? No idea how that might have happened, stone/branch bouncing up in between wheel and mudguard ? Other info is that it was the first time I'd been out on it for several months (due to a different, non biking, injury).


I would bet £100 on the mudguard. This is a well-known (at least on this forum) problem that has previously resulted in rider death. Your mudguard stays should have automatic safety releases to prevent this happening.

https://www.cyclinguk.org/article/techn ... ard-safety

Diveywivey
Posts: 11
Joined: 28 Jun 2019, 2:13pm

Re: Can disc brakes lock up while cycling?

Postby Diveywivey » 28 Jun 2019, 3:20pm

Wow really, I can see that's probably what happened tho I've never heard of it. So there's no real evidence of the disc brake theory you know of then ?

The mudguards were fitted at my request by the shop I bought it from a couple of years back. I'd noticed that they were quite close fitting to the wheel too. No sign of a quick release fitting but I'll look more closely sometime. When I feel up to it I'll fit something better myself. The disc is a bit bent and rubbing but that was probably as a result of the accident.

Thanks very much. It gives more confidence about getting back in the saddle.

alexnharvey
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Joined: 10 Jan 2014, 8:39am

Re: Can disc brakes lock up while cycling?

Postby alexnharvey » 28 Jun 2019, 3:27pm

Well, something theoretically could get stuck in the discs and jam them but I think it's much less likely, the discs and caliper are further away from any potential jammers by virtue of being at the centre of the wheel.I do not see it regularly reported as a problem whenever i visit MTB forums. Any disc jams tend to be for other reasons than foreign body, problems with cables and hydraulics.

Whereas the mudguard jam is initiated by some small item lifted by the tyre and then becomes self propagating as the guard itself is dragged round into the wheel fork gap. The mudguard entry is back from the tyre-road contact point whereas the disc is directly above it. The forward motion of the bike means that most items thrown up are going to moving towards the rear of the bike.
Last edited by alexnharvey on 28 Jun 2019, 3:31pm, edited 1 time in total.

Diveywivey
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Joined: 28 Jun 2019, 2:13pm

Re: Can disc brakes lock up while cycling?

Postby Diveywivey » 28 Jun 2019, 3:31pm

I'm sure you're right, looking at the mudguard. I'll invest in some safe ones when I have recovered a bit. Thanks very much for the help and quick response. Scary tho that this can happen, it was so instant. Cheers again.

alexnharvey
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Re: Can disc brakes lock up while cycling?

Postby alexnharvey » 28 Jun 2019, 3:34pm

Yes, I'm glad to hear you're OK. Get well soon.

If you bought the bike with the mudguards fitted you should also let the bike shop know. It's illegal in Germany to sell a bike like that now I think.

Diveywivey
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Joined: 28 Jun 2019, 2:13pm

Re: Can disc brakes lock up while cycling?

Postby Diveywivey » 28 Jun 2019, 3:42pm

I will do, I wouldn't want it happening to anyone else. Hopefully they'll pay attention except they may be more worried about getting sued! It's certainly proven the worth of a helmet to me as well. It would have been more than soft tissue damage without one, thought I was a gonna at the time.

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kylecycler
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Re: Can disc brakes lock up while cycling?

Postby kylecycler » 28 Jun 2019, 3:45pm

The safety release clip alexnharvey referred to is on SKS mudguards, not sure about the rest - if you look closely at the front mudguards in the link below you'll see them. They're just clipped into the ends of the metal stays so if you get a stick or stone or whatever else caught between the tyre and the mudguard they should release, break the connection and prevent the mudguard locking up the wheel.

https://www.sjscycles.co.uk/mudguards-full/?brand=sks

They can be bought separately and fitted, even retrospectively, to other front mudguards.

https://www.sjscycles.co.uk/search/?term=sks%20secuclip

Hope you recover and get your confidence back. Could happen to anyone.

reohn2
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Re: Can disc brakes lock up while cycling?

Postby reohn2 » 28 Jun 2019, 3:51pm

alexnharvey wrote:I would bet £100 on the mudguard..........

I would add a nought to that and bet £1000 on it!

BTW I/we've been riding discs for over ten years in all kinds of conditions both on and off road and have never ever experienced a brake locking up,and have never heard of it either.
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Diveywivey
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Re: Can disc brakes lock up while cycling?

Postby Diveywivey » 28 Jun 2019, 4:06pm

Thanks everyone, I'm convinced. Attached photos, it looks obvious now. Fairly cheap, non quick release guards too I guess.

E07405C2-B02E-4CB4-9B45-52AA58672AC6.jpeg

D3AC1D8C-A8B2-4DAD-AE0C-6A61B4906E3C.jpeg

9B5A4706-37A3-481C-AC7D-EC2AA1574B0D.jpeg

reohn2
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Re: Can disc brakes lock up while cycling?

Postby reohn2 » 28 Jun 2019, 4:13pm

If those forks are carbon fibre I'd have them assessed for safety by a competent cycle mechanic.
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alexnharvey
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Re: Can disc brakes lock up while cycling?

Postby alexnharvey » 28 Jun 2019, 4:24pm

If the bike was sold to you like that it was arguably a potential deathtrap, 'unsafe at any speed'.

Brucey
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Re: Can disc brakes lock up while cycling?

Postby Brucey » 28 Jun 2019, 4:50pm

the mudguard looks as if it was set too close to the tyre at the bottom, too; this may have helped precipitate the accident.

This is a secu-clip;

Image

this or similar ought to be fitted to a front mudguard, especially if the mounting eyes are set low down like yours are.

cheers
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~~~~~~~~~~~~~~~~~~~~~~Brucey~~~~~~~~~~~~~~~~~~~~~~~~

scottg
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Re: Can disc brakes lock up while cycling?

Postby scottg » 28 Jun 2019, 5:51pm

The fender stays are mounted the drop out, so when you get a jam,
the fender rotates into the tire, jams and folds.
So you need some sort of safety release, the geometry of your fender
attachment is working against you.

British bikes had mid fork mounts, so when the fender jammed,
the fender would be moving away from the tire.
Also celluloid fenders are quite frangible, so the fender itself
tended to disintegrate.
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horizon
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Re: Can disc brakes lock up while cycling?

Postby horizon » 28 Jun 2019, 10:23pm

This is a very useful, illustrative thread. I wonder if the OP would object if the mods changed the title to reflect the mudguards content?
Let's just get Brexit done so that we can get on with the important job of re-joining the EU!