Guess I wasn't to stupid to fix the tube after all...
I wrecked my RydeANDRA40, probably by using too much pressure on cobblestone and pothole ridden roads.
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I wrecked my RydeANDRA40, probably by using too much pressure on cobblestone and pothole ridden roads.
Fatigued metal is weaker than it was before. It’ll work, but it’ll never be the same and keep happening easier and easier. There’s some stuff that just can’t be fixed, must be replaced. A rim is one of them.
I’m not planing to repair it. A new wheel is already ordered, since the bearings are also in need of replacement and overall repair costs of changing the rim an the bearings are not worth it. This post is about trying to fix a small reoccurring damage and finding something way worse upon taking a closer look.
I‘m curious though… Would it be theoretically possible to fix this?
It would be quite difficult, to say the least. Fixing this part of the rim would first involve removing the bottom of the rim, then some very fiddly TIG welding to refit new metal. And do that while keeping the rim spacing identical. And also making sure the rim is still balanced.
Given that aluminum rims are extruded and then turned into a circle and the ends welded together, it would actually be easier and stronger to cut out a whole sector from this rim and then replace with a new sector from a good rim, welding it in and at least then there would only be one additional weld seam.
But that means having a new section of rim, so might as well just replace with the new rim anyway. I'm of the opinion that this sort of repair is only pursued if the existing rim was a nonstandard construction where there is no real prospect of getting a new rim or even a section thereof.
Also, rims are under unique tension in multiple directions at once. Shoring up the part which broke doesn't mean another tension direction won't break later, after a fix. That said, I'm no expert on aluminum failure modes, so I wouldn't assume that the visible damage is necessarily a shear failure or even a tensile yield, since it could also be chemical/galvanic in nature.
Thank you for the extensive explanation! The only thing I know about aluminum is that unlike steel it doesn’t bend, it just breaks. I learned this the hard way.
Twice…
I wonder if your scenario would be aided by not having any spoke access holes at all. That way, the inside of the rim would have no gaps at all, except for the air valve. I understand this is common for carbon fiber rims.
Though that only helps if the issue was a fatigue fracture (eg induced due to loose spokes that turned the rim into an oval with every rotation). If the problem was due to outright overloading (rare on a non-cargo bicycle), then closing those holes doesn't help much.
And if the issue was a galvanic interaction between the aluminum rim and some other metal, then this also doesn't help at all. And indeed, neither would a steel wheel. In this situation, probably only carbon fiber would be a true fix. But that must mean you ride in some horrific conditions for a bicycle, mechanically-speaking.
It’s a cargobike and I‘m 15 kilos below maximum driver’s weight and even further away from the maximum weight, but there’s nonetheless a high probability for a fatigue fracture. I forgot to open my lock before pushing my bike more than once, so there could have been loose spokes.
The guy from my local cargobike shop^tm^ said the wheel he ordered for me is a bit more robust and I will take better care of my spokes. So I hope, this won’t happen again…
Cheap aluminum rims don't even have a second wall...
Fun fact: aluminum has a limited number of stress cycles it can go through before breaking due to metal fatigue. Unlike steel -- which will bear its designed load an infinite amount of times if you never exceed its strength -- aluminum's failure is eventually inevitable. Even very light loads can break aluminum after enough repeated cycles.
For a part that goes through a stress cycle every single time your wheel turns around, I wonder if that could have actually been a factor here. You're putting it through thousands of stress cycles every time you go for even a short ride.
Wait how much pressure are we talking about? Looks more like corrosion of some kind. Were you riding tubeless? Or seeing a lot of salt.
4,5 Bar/ 60 PSI the maximum the tire could take. It has seen a metric fuckton of salt because my city went a bit overboard with it this winter. But does aluminum corrode this much because of salt?
Well. It’s more that a rim will almost never fail in this way when overpressuring your tires (the sides are more likely to fail) and 4.5 bar is nowhere close to overpressure for an aluminum ryde rim. Salt can corrode aluminum yes. A more common occurrence is people riding their bike on a hometrainer and the handlebars breaking due to the corrosion caused by the sweat from their hands.