Advice re rim damage please

[nickyboy]

This morning I suffered a broken spoke. No big deal, took it to the LBS who replaced it for me. At the same time, they noticed a crack in the rim at a different spoke. Wheel is Campagnolo Khamsim

I took this to the retailer this afternoon (Decathlon). They have said that it is not covered under warranty as this type of damage can be caused by something as simple as going over a speedbump or hitting a shallow pothole. Their opinion was that that's what has happened on the opposite side of the wheel to the crack, the force being transmitted via the spokes to the side with a crack now in it.

I'd appreciate any comments regarding whether this is just one of those things (and I'll just have to buy a new wheel) or whether this is something that is not a normal occurrence and should be dealt with under warranty

Decathlon offered to return the wheel to the Campagnolo UK dealer but I've kept it and will contact them directly myself. Looking for some input from CCers before I do so

Thanks

 

[dan_bo]

It's broke that.

 

[Yellow Saddle]

Change bike shops. That guy/gal doesn't know what they're talking about.

Firstly, that's a fatigue crack, not an overload crack. In overload, aluminium will stretch plastically. In fatigue, it cracks like that.

Secondly, when loaded, spokes opposite the contact patch (called the load affected zone) do not increase in tension but remain exactly the same. Only the spokes in the load affected zone LOSE tension. In other words, no spoke increases in tension when a wheel is loaded. This is counter-intuitive to most people who don't understand the concept of a pre-stressed structure. I don't expect every bike owner to understand that but I do expect mechanics to get their heads around these things and not talk rubbish.

Which brings us to whether that is a warrantee claim or not. It may be if the wheel is still under warrantee. A rim has a limited fatigue life and the manufacturer understands that and will adjust the warrantee length accordingly. It is a matter of checking your purchase date and the manufacturer's warrantee.

It is worthwhile understanding how fatigue cracks happen. The spoke is in tension and that tension pulls on the rim. Imagine for a minute that the rim is made of rubber and the spoke pulls via an eyelet installed on the rubber. In your mind you now see a little volcano/teat with a spoke coming out the centre. Now, each time that spoke enters the load affected zone, the teat RECEDES. That's because the spoke loses a bit of tension at that point. That cyclical up/down, up/down, up/down of the spoke area eventually causes metal fatigue around the spoke. When metal fatigues, it becomes brittle. Think about this next time your plane lands and you see the wings wobble.

So, technically potholes do contribute to fatigue but just riding along with your wheel turning and each spoke going in and out of a tension cycle with each revolution, is far more significant that the one pothole/speedbump you hit per month.

The more spokes in your wheel, the more areas on the rim share the same load and the smaller the fatigue cycle is and the longer your rim lasts. There really is wisdom on 32 or 36 spoke wheels and very little in boutique wheels with stupid-few spokes.

 

[nickyboy]

Change bike shops. That guy/gal doesn't know what they're talking about.

Firstly, that's a fatigue crack, not an overload crack. In overload, aluminium will stretch plastically. In fatigue, it cracks like that.

Secondly, when loaded, spokes above the contact patch (called the load affected zone) do not increase in tension but remain exactly the same. Only the spokes in the load affected zone LOSE tension. In other words, no spoke increases in tension when a wheel is loaded. This is counter-intuitive to most people who don't understand the concept of a pre-stressed structure. I don't expect every bike owner to understand that but I do expect mechanics to get their heads around these things and not talk rubbish.

Which brings us to whether that is a warrantee claim or not. It may be if the wheel is still under warrantee. A rim has a limited fatigue life and the manufacturer understands that and will adjust the warrantee length accordingly. It is a matter of checking your purchase date and the manufacturer's warrantee.

It is worthwhile understanding how fatigue cracks happen. The spoke is in tension and that tension pulls on the rim. Imagine for a minute that the rim is made of rubber and the spoke pulls via an eyelet installed on the rubber. In your mind you now see a little volcano/teat with a spoke coming out the centre. Now, each time that spoke enters the load affected zone, the teat RECEDES. That's because the spoke loses a bit of tension at that point. That cyclical up/down, up/down, up/down of the spoke area eventually causes metal fatigue around the spoke. When metal fatigues, it becomes brittle. Think about this next time your plane lands and you see the wings wobble.

So, technically potholes do contribute to fatigue but just riding along with your wheel turning and each spoke going in and out of a tension cycle with each revolution, is far more significant that the one pothole/speedbump you hit per month.

The more spokes in your wheel, the more areas on the rim share the same load and the smaller the fatigue cycle is and the longer your rim lasts. There really is wisdom on 32 or 36 spoke wheels and very little in boutique wheels with stupid-few spokes.

Thank you very much for such a comprehensive reply. I won't pretend to understand everything you have said but I think it will help a lot in my discussions with Campagnolo. It was Decathlon who said it was impact damage and I wasn't happy for them to handle the warranty issue with Campagnolo when they had already reached a conclusion in their own mind that it was just "one of those things".
Decathlon offer 2 year warranty on all parts except cassette, chain, jockey wheels etc so based on what you say it should be covered.

 

[Yellow Saddle]

Thank you very much for such a comprehensive reply. I won't pretend to understand everything you have said but I think it will help a lot in my discussions with Campagnolo. It was Decathlon who said it was impact damage and I wasn't happy for them to handle the warranty issue with Campagnolo when they had already reached a conclusion in their own mind that it was just "one of those things".
Decathlon offer 2 year warranty on all parts except cassette, chain, jockey wheels etc so based on what you say it should be covered.

It's a pleasure. If you point out the mysterious bits, I'll try and rephrase. I think it is important that you are well armed when you march in there claiming your warrantee. They will try and bamboozle you. Not because they are dishonest, but ignorant. They genuinely believe potholes cause instant fatigue in metal.

 

[Yellow Saddle]

One more thing I can add. If someone claims that is caused by an overload, take a new wheel off their shelf, ram a hammer handle in between two spokes at the cross and push hard towards the wheel. This has the effect of violently twisting the cross and upping the tension in the spoke by a huge margin - far more than you can when turning the nipple all the way in. This violent action will NOT rip the spoke out of the rim or damage the wheel but it is so graphic that anyone who sees it has to rethink their old wisdom.

 

[nickyboy]

Quick update

I emailed that photo to the importer. They called me back to confirm that providing there is no obvious impact damage to the wheel they are happy to replace under warranty. There is no impact damage (and according to @Yellow Saddle it shouldn't be as a result of an impact anyway) so shouldn't be a problem.
Took it back to Decathlon for them to send back and the same "expert" who told me it was impact damage was there. He was very quiet when I told him it was a warranty return

 

[Yellow Saddle]

Quick update

I emailed that photo to the importer. They called me back to confirm that providing there is no obvious impact damage to the wheel they are happy to replace under warranty. There is no impact damage (and according to @Yellow Saddle it shouldn't be as a result of an impact anyway) so shouldn't be a problem.
Took it back to Decathlon for them to send back and the same "expert" who told me it was impact damage was there. He was very quiet when I told him it was a warranty return

Nice outcome. Thanks for the feedback.

 

[ColinJ]

Quick update

I emailed that photo to the importer. They called me back to confirm that providing there is no obvious impact damage to the wheel they are happy to replace under warranty. There is no impact damage (and according to @Yellow Saddle it shouldn't be as a result of an impact anyway) so shouldn't be a problem.
Took it back to Decathlon for them to send back and the same "expert" who told me it was impact damage was there. He was very quiet when I told him it was a warranty return

Excellent!

Did they hand you a replacement wheel so you will be ok for Saturday's forum ride?

 

[Spoked Wheels]

This morning I suffered a broken spoke. No big deal, took it to the LBS who replaced it for me. At the same time, they noticed a crack in the rim at a different spoke. Wheel is Campagnolo Khamsim

I took this to the retailer this afternoon (Decathlon). They have said that it is not covered under warranty as this type of damage can be caused by something as simple as going over a speedbump or hitting a shallow pothole. Their opinion was that that's what has happened on the opposite side of the wheel to the crack, the force being transmitted via the spokes to the side with a crack now in it.

I'd appreciate any comments regarding whether this is just one of those things (and I'll just have to buy a new wheel) or whether this is something that is not a normal occurrence and should be dealt with under warranty

Decathlon offered to return the wheel to the Campagnolo UK dealer but I've kept it and will contact them directly myself. Looking for some input from CCers before I do so

Thanks
View attachment 89638

What? No, that's not caused by a few speedbumbs or potholes. A deep pothole, at speed, can damage the rim beyond repair but it wont look like that. I'm sure you have seen pictures of wheels involved in accidents.... where the spokes bend and rim deforms but no cracks.

I don't follow that part where the hit hsppened on the opposite side.... my guess he is just bs...ing you.

I would be asking for a new wheel if I were you.