Mavic X138 rim crack

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9494arnold
Posts: 834
Joined: 21 Jan 2007, 3:13pm

Re: Mavic X138 rim crack

Postby 9494arnold » 5 Sep 2019, 5:00pm

I disagree with last post. The rim has lost it's integrity for whatever reason, and is no longer strong. One application if the brakes, or pot hole could cause a catastrophic failure. Or the pressure in the tyre could cause the sidewall to fail. With a Big Bang. And probably a big off .
I have been behind a Tandem when the rim let go without warning. Fortunately it was stationary at the lights.
(I say without warning, a post incident examination did reveal a fair bit if wear on the brake track which I am sure contributed ) .
I think old school rims were more designed to last whereas most Modern Rims should be considered as a consumable and need to be perioducally replaced. Some rims do have a tell tale groove, when the brakes wear the rim down so you can't see the groove it's time to replace it.

Brucey
Posts: 35201
Joined: 4 Jan 2012, 6:25pm

Re: Mavic X138 rim crack

Postby Brucey » 5 Sep 2019, 5:10pm

rim cracks like that do not cause modern rims to spontaneously fail completely.

IME (which involves seeing hundreds of similarly cracked rims) the spoke eventually pulls through the cracked rim and all tension in that spoke is lost. Quite a lot of folk then ride round for quite a long time before bothering to get the wheel fixed; long enough that they tether or remove the free spoke so that it stops rattling and doesn't get snarled up in the workings.

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

bgnukem
Posts: 176
Joined: 20 Dec 2010, 5:21pm

Re: Mavic X138 rim crack

Postby bgnukem » 6 Sep 2019, 11:27am

Have been riding a rim with similar cracks on my Giant summer bike for the summer. Just marked the ends of the cracks and monitored them for growth.

The cracking occurred after I tweaked the wheel and slightly increased the tensions, so obviously some rims are not very tolerant of increased spoke tensions!

If the cracks grow significantly or the spokes start to pull through the rim, the wheel will be going in the bin, and I'll bin it at the end of the season anyway.

Brucey
Posts: 35201
Joined: 4 Jan 2012, 6:25pm

Re: Mavic X138 rim crack

Postby Brucey » 6 Sep 2019, 11:33am

is it possible that the cracks were there already and only opened up (making them more easily visible) when the spoke tension was increased?

IME folk don't spot cracks of this sort (before they open up) unless they are obsessive bike cleaners and/or have eagle eyes; a crack that is completely closed is to all intents and purposes invisible.

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

User avatar
Sweep
Posts: 5514
Joined: 20 Oct 2011, 4:57pm
Location: London

Re: Mavic X138 rim crack

Postby Sweep » 6 Sep 2019, 11:34am

bgnukem wrote:Have been riding a rim with similar cracks on my Giant summer bike for the summer. Just marked the ends of the cracks and monitored them for growth.

The cracking occurred after I tweaked the wheel and slightly increased the tensions, so obviously some rims are not very tolerant of increased spoke tensions!

If the cracks grow significantly or the spokes start to pull through the rim, the wheel will be going in the bin, and I'll bin it at the end of the season anyway.

Interesting - I assume you are referring to my crack? - the one introduced to the thread recently rather than the original one (as I said I posted here as I thought it might create a library of knowledge/expertise).

I had assumed something dangerous might happen suddenly quite soon.

From what you and Brucey say I could keep riding the bike for a while - and the bike is at the moment mainly ridden around London so I would never be far from base.

One question though to you and Brucey - if I keep riding it aren't I likely to end up damaging that spoke, the one which is I assume on its way to pulling out? And maybe one or two others?

Whereas if I take it off the bike and rest it I may well be able to re-use all of the spokes on a new rim - which would be simpler/less fag than sourcing the relevant spokes? The spokes are decent quality I think so I was planning to re-use them.

By the bye, I have the idea that all of this might be an argument in favour of silver rather than black rims - easier to spot surface issues?
Sweep

Brucey
Posts: 35201
Joined: 4 Jan 2012, 6:25pm

Re: Mavic X138 rim crack

Postby Brucey » 6 Sep 2019, 11:57am

whenever there is an entirely unloaded spoke, that spoke can flail around and be damaged. and the neighbouring spokes see a higher load than normal too. However if you ride a few tens of miles with such a failed spoke, that increased loading etc wouldn't automatically put me off re-using that set of spokes.

It is of course a risk/consequence thing; in 'sensible' wheels a single failed spoke oughtn't be a disaster anyway, and since that is the likely worst outcome of re-using a set of spokes that is not quite perfect, I'd probably live with that risk.

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

mercalia
Posts: 11102
Joined: 22 Sep 2013, 10:03pm
Location: london South

Re: Mavic X138 rim crack

Postby mercalia » 6 Sep 2019, 2:44pm

Sweep wrote:
bgnukem wrote:Have been riding a rim with similar cracks on my Giant summer bike for the summer. Just marked the ends of the cracks and monitored them for growth.

The cracking occurred after I tweaked the wheel and slightly increased the tensions, so obviously some rims are not very tolerant of increased spoke tensions!

If the cracks grow significantly or the spokes start to pull through the rim, the wheel will be going in the bin, and I'll bin it at the end of the season anyway.

Interesting - I assume you are referring to my crack? - the one introduced to the thread recently rather than the original one (as I said I posted here as I thought it might create a library of knowledge/expertise).

I had assumed something dangerous might happen suddenly quite soon.

From what you and Brucey say I could keep riding the bike for a while - and the bike is at the moment mainly ridden around London so I would never be far from base.

One question though to you and Brucey - if I keep riding it aren't I likely to end up damaging that spoke, the one which is I assume on its way to pulling out? And maybe one or two others?

Whereas if I take it off the bike and rest it I may well be able to re-use all of the spokes on a new rim - which would be simpler/less fag than sourcing the relevant spokes? The spokes are decent quality I think so I was planning to re-use them.

By the bye, I have the idea that all of this might be an argument in favour of silver rather than black rims - easier to spot surface issues?



A good incentive to get a new rim and learn to build a wheel as I did. Mine are still going strong havent had to adjust them other than get the dishing a bit more accurate.