XTR Rims Warranty???

[Guest Big H]

Yup, the pic now makes sense!!!!!!!

 

But what is that funny mark..... looks like quite a ding..... at the bottom of the picture????? .......... could that be another crack faintly visible down the centre and right next to Christie's annotation?????

[AndreZA]

 

 

I want to know if you've been riding on the rim or used steel tyre levers on the poor rim. Just look at how it's scrathed.

 

Okay, I guess it's got nothing to do with the arrows or cracks.

 

 

[SwissVan]

Bit off topic' date=' I read somewhere today that the little hole some people drill in the BB shell to drain water can cause the BB shell to crack???? Is this possible???

[/quote']

 

Yes, drilling a hole through metal creates rough edges or very small nicks on the edges, these are usually invisible to the naked eye and they can propagate into cracks depending on the amount of movement of the metal around the hole. Its good practice during the manufacturing process to ?de-burr? any drilled holes especially aluminum that experiences stress or flex.

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As JB said the area in the BB where drain holes are drilled is unlikely to crack, unless drilled with a really blunt drill and operated like a egg beater....

 

The valve hole in the supplied picture does not look like it was de-burred during the manufacturing process (shimano probably thought shot peening the metal was sufficient). The rim probably experienced sufficient flex resulting in a crack (cracks) from a jagged valve hole edge.

 

 

[Johan Bornman]

If I owned an XTR wheel I would immediately inspect the valve hole and clean up if any burrs are present. These things have a habit to hit the fan seconds after the guarantee expires.

[Odion]

 

[Odion]

just another angle, as you can see there are no dents on the rim itself. I haven't ridden on the rim or used metal tyre levers.  The only thing that possibly could have led to the crack is the "burr" on the side, but once again I wouldn't have expected it to lead to a crack unless the rim was originally flawed or compromised.

[SwissVan]

 

You would be suprised how much the metal portion that is exposed to air pressure can flex between 0 pressure to the normal operating pressure. Repition of this cycle (every time the tyre pressure drops and when you subsequently pump it up again) would be enough to generate a crack from a weak point (burr).

 

 

[Johan Bornman]

I had a good look at a piece of XTR rim yesterday. I was lucky to find the valve hole section. The hole in that rim was perfectly de-burred and the hole was anodised on the inside.

 

Odion, your rim looks like it was modified for a Schrader valve and the burr left on. Am I right?

 

 

Edit: Stupid thought. You had a tubeless valve in there. In that case I'd say it was a defective rim that wasn't finished off properly at the factory.

Johan Bornman2009-01-01 23:52:28

[Guest Big H]

How do you de-burr a drilled hole that is encapsulated within a hollow formed section? The deburring tool is normally conically shaped and has to fit through the hole to remove the burrs on the inside?????

[Johan Bornman]

How do you de-burr a drilled hole that is encapsulated within a hollow formed section? The deburring tool is normally conically shaped and has to fit through the hole to remove the burrs on the inside?????

 

Hooi Hendrik. Ek sien daai ? sleutel op jou sleutelbord sit nog steeds vas. Maak hom reg man. Dis maklik.

 

How to deburr blind?

 

Use one of these:

 

 

 

Every machinist worth his salt will have one of these. It's a hook-shaped affair that allows you to deburr from the inside.

 

However, a small rat-tail file will also work if you only want to do your own wheel.

Johan Bornman2009-01-02 02:56:29

[SwissVan]

How do you de-burr a drilled hole that is encapsulated within a hollow formed section? The deburring tool is normally conically shaped and has to fit through the hole to remove the burrs on the inside?????

 

These rims are surely mass produced and the deburring would have been done by a machine of which there are numerous clever designs for drilling and deburring.

 

None are fool proof and even the best de burring tool cannot garauntee that a crack wont form at some stage.

 

Looks like a good case for warratnty, unless of course the valve hole was tampered with....

 

 

[Guest Big H]

How do you de-burr a drilled hole that is encapsulated within a hollow formed section? The deburring tool is normally conically shaped and has to fit through the hole to remove the burrs on the inside?????

 

Hooi Hendrik. Ek sien daai ? sleutel op jou sleutelbord sit nog steeds vas. Maak hom reg man. Dis maklik.

 

How to deburr blind?

 

Use one of these:

 

 

 

Every machinist worth his salt will have one of these. It's a hook-shaped affair that allows you to deburr from the inside.

 

However' date=' a small rat-tail file will also work if you only want to do your own wheel.

[/quote']

 

Hooi Johan!!!!! Voorspoed vir die Nuwe Jaar vir jou en die Gesin ook hoor!!!!!!!

[Mellow]

my first impression

 

someone used a vice grip(or similar) when working on the wheel and clamping around the hole.... pulling the valve through?

 

 

 

 

 

[Dirtbreath]

Is there any way the tension on the spokes or lacing pattern used on these wheels that could cause a crack like this, or on any other rims for that matter?

[Johan Bornman]

Is there any way the tension on the spokes or lacing pattern used on these wheels that could cause a crack like this' date=' or on any other rims for that matter? [/quote']

 

 

No.

[GoLefty!!]

Jeeez I go do some river rafting and this is what happens in the mean time..

 

 

 

Scandium alloys are mostly used in forged components when cooling is well controlled and post machining operations are monitored with enthusiasm.

 

I've seen these types of cracks on rocket motor casings, usually when holes have been drilled for connected the casing to a bulkhead or other component.

 

I doubt the "impact" marks have anythin to do with the crack.

 

 

 

This looks too me to be a manufacturing defect during the extrusion of the rim. The hole drilling merely exasserbated the fault.

 

 

 

Scandium is a grain boundary refiner. All it does is make the grain boundaries between aluminium and it's alloying material longer, therefore stronger so than the material is tougher and has improved fatigue life and ductility (to a lesser degree).

 

The post machining operations have to be conducted with utmost care or local heating breaks down the grain boundaries and he purpose of scandium is defeated.

 

 

 

That's what I think happened here. Probably a combination of ;

 

1) a new die and therefore the thinnest rim wall thickness in that batch.

 

2) a botched (rushed, probably made on a friday) shot peening exercise,

 

3) too little lubricant during the drilling process resulting in excessive heating of the thin wall of the rim, causing a higher embrittlement than usual.

 

 

 

Vibration and flexing during normal usage is enough to allow the crack to form along the weakened grain boundaries. Add the 3bar of tyre pressure which wants to "burst" the rim apart and add these factors up and hey presto, you have a crack waiting to occur.

 

XTR components carry a 3year warranty against manufacturers defect. I'd say that this falls under this category.