Cause of rim split...

[Bodhbh]

The rim of the back wheel on my MTB split recently. It was one of the mavic rims with an internal width of 19mm - a chainreaction jobbie with an XT hub. I lazily put this down to running fat tyres at high pressure (2.35 big apples at 60psi), but from where the split is, that doesn't make sense...

The split is well below where I'd expect it too occur if the tyre pressure was pushing out the wall. Is this due to over tensioned spokes, or just one of those things?

 

[Yellow Saddle]

I don't see a split? Edit: Oh, yes, I thought it was a tyre on there and the "split" was the border between the tyre and rim.

What model number Mavic is that? I want to see if I can get a better photo on the Mavic website.

 

[Bodhbh]

I'll try to find out, although my yahoo mail seems terrible for searching emails regarding orders which I never delete, but can never find either...

Sorry can't find it. I can't find it in yahoo, and chainreaction doesn't seem to have account info going beyond 2013. I'm pretty sure it's a low to mid-range mavic x19 rim. The rim itself is in the skip now, so that's no help.

 

[fossyant]

Might help if the rim was clean so we can see. How old, how much use ?

I eat through rims in 18 months on the commute.

Wear would also be my opinion.

 

[Yellow Saddle]

Worn down below safe limit by breaking is the most common cause.

It doesn't look like a rim brake wheel, does it? OP?
I assumed disc brake because he said MTB.

 

[rualexander]

It doesn't look like a rim brake wheel, but if it is, the crack is below the braking surface anyway so not likely due to brake wear, also the tyre would have distorted or blown the rim off before the crack got anywhere near that size this crack looks to be on a different part of the rim, it won't be caused by spoke tension, probably a manufacturing or design defect.

 

[Bodhbh]

Ooops, sorry it was a disc rim.

 

[Illaveago]

Is it the way that the wheel is made as it is a hollow section rim. I was wondering if that may be where the two sections join.

 

[Yellow Saddle]

Nice photos would help, but the clues are dripping in slowly. It seems as if there was a pre-existing "feature" groove at a very critical place in the rim's structure. On the Monday those rims were fast-tracked into production, all Mavic's engineers were on holiday. Unfortunately Mavic's engineers take very long holidays and many Mavic designs slip straight from a design student's desk to the factory.

 

[Bodhbh]

Oh well, doesn't matter really - rim goes in the skip, I get an excuse to buy a new wheelset, which precipitates an eBay clearout to pay for it and hopefully I stay money neutral, have more housespace and better wheels to boot.

(yeah right...I'm down on the deal)

 

[Smurfy]

I get the impression that Bodhbh is a serious tourer with heavy loads. This can give rims a hard time, and I've seen my own and a friend's rear rim crack when loaded heavily for 1000s of miles. My advice is to stay away from rims with deep hard anodising, as any cracks that initiate at the surface in the brittle, anodised layer, may then start propagating through the underlying metal.

Edit: Rim looks black, which suggests anodised.

 

[Illaveago]

What I find strange about the split is that it is parallel to the circumference as if it had been machined into the rim.

I would have thought fracturing would have a more irregular appearance.