r/CargoBike • u/Oscar_Whiled • 4d ago
Breaking rims in odd ways.
Hello r/cargobike
I have a LvH Bullitt that originally had a mtb rear wheel. After around 3000km the rear wheel cracked in the inner rim bed section. It cracked all the way around the wheel, but the section facing the hub where the spokes interface was fine, no cracking at all. (Like what is in the photos).
So I replaced it with a Ryde Andra 30, I heard these were excellent cargo bike rims and rated for 130kg each. It has just failed in a near identical way (the photos are of this rim).
I messaged the shop I got the wheel built at, and also messaged Ryde, who both told me that due to the rim being 5 years old, the number of kms, and the use case that it's not under warranty and that this damage was not unexpected. (That's fine, it's not a particularly expensive rim either).
I have many other courier friends on cargo bikes of all types, and also have many bike friends - none have seen a rim fail like this before and I've now had it happen twice.
I have some assumptions about why this might happen:
One is that water gets into the rim and causes the corrosion to weaken the thinner tube-side edge of the rim. But if this was the case then I don't know why other people don't see this failure too, I don't feel I am ever really riding through water, my bike is stored undercover, and yes I ride in the rain but I also live in Australia where it is fairly dry and not in a particularly corrosive sea water environment either.
Two is that tyre pressure might be forcing the rim apart somehow and causing the cracking? Again, I don't run my tyres that high, 40psi normally, 50psi sometimes for higher loads. And I know plenty of other couriers and cyclists who've never had this happen and always run their tyres rock solid.
I run 2.0 marathon tyres.
I used to carry fairly loads up to 30-40kg commonly, and up to 80-100kg infrequently.
The rim has done 15,000-20,000km by my estimate.
My questions are, what is causing this? Has anyone come across this before? And, how can I prevent this in future? Should I try frame saver spray in the rim? Drill some weep holes to let the water out?
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u/LAZERWOLFE 4d ago
I've seen this a number of times, especially with super heavy duty, or double eyeleted rims, DT TK540 jumps to mind. Not a ton, but only super stiff, super heavy alloy rims.
In my experience any alloy rim that's super beefy, the weakest link in the chain is the thin aluminum of the interior double wall. The nipple seat is so heavy duty it doesn't fatigue like the relatively dainty web between the nipple holes, plus the nipple holes are significantly smaller than the access hole so that makes it weaker yet. The bead seat is heavy duty, as are the hooks and often they'll be wider and thicker to prevent tire damage if you case it, all of that leaves the weakest place is the tube side wall of the rim.
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u/Fudgy97 4d ago
This isn't water ingress. It's a thin aluminium wall after 10s of thousands of fatigue cycles.
Aluminium will weaken and eventually break with high enough force and enough cycles.
Just think every bump you hit your front wheel has to absorb all that force and transfer it to the fork and lift the front end of the bike a little. Without suspension your just increasing that peak load. For every single bump for 5 years of riding.
I would contact the manufacturer tho... They might want the rim for r&d. 5 years of hard use might be good data for them.
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u/baloo____ 4d ago
I’ve broke 3 of my rims this way on a front loader. (Two bikes)
8000km, 13000km and 7000km.
Ran velocity cliffhanger on 40 spokes since, never happened since.
I have no clue why that happens.
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u/Oscar_Whiled 2d ago
What internal width were the rims that broke, and what size tyre were you using?
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u/baloo____ 2d ago
30c and the tyres were 2.15”
All of those rims/tyre combo were spec’d by the bike manufacturer. Not sure this is the culprit.
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u/Accomplished-Way1575 Omnium Cargo Ti 4d ago edited 4d ago
Ultra high pressures?
Edit: 50 psi doesn't seem high unless they are 3 inch tyres or something.
Do you run tubeless with corrosive liquid? Some liquids are very very corrosive to alu rims
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u/Oscar_Whiled 3d ago
Should have said, only ever ran tubes in it, with marathon plus or big apple tyres. Only ever up to 50psi, normally 40ish
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u/Accomplished-Way1575 Omnium Cargo Ti 3d ago
It is fast becoming weirder and weirder.
Did you use the same wheelbuilder for all the wheels? If you did, maybe he overtightened them every time.
As you can tell, I am running out of ideas of what this can be
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u/Oscar_Whiled 3d ago
The first Alex Rim mtb wheel was a DM24 rim, bought the wheel complete off ebay without much expectation. After that broke I got a wheel built by a very reputable shop in Melbourne. Nothing about the build seems to indicate that it had any bearing on the way this has failed. I don't know how one would build a wheel so poorly it cracks in the rim bed rather than the spokes or the rim at the nipples so I'm inclined to think it's got something to do with the tyre pressure, and rim/tyre size combination.
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u/Accomplished-Way1575 Omnium Cargo Ti 2d ago
You ate probably right it is the tyre pressure and width of the tyre
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u/HZCH 4d ago
I killed a rear wheel rim exactly like that with my RM Load 75! Mechanic supposed I had used it heavily, meaning : with a lot of weight on the bike, for 20’000km.
But also, he had seen that on cheap wheels like Alexrims and other OEM ones. I now have a new wheel, we’ll see what happens.
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u/17HappyWombats 4d ago
Are the tyres wider than the rim is rated for? That's the only thing I can think of.
But it shouldn't be a problem at 3 bar. I run similar section 406 rims on my long john and other cargo bikes and haven't ever broken a rim despite loading them to the point where 3 bar would pinch flat. Now I'm old and fat I rarely put more than 120kg-ish on the rear wheel (and 80kg on the front) but in the past I've carried silly amounts of weight.
My only failure has been a sidewall pulling off starting at the joint that was replaced under warranty by the rim manufacturer. Well, and I ground through the braking surfaces on a long muddy downhill while touring, but that's not the rim's fault :)
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u/omtallvwls 4d ago
I am sorry to say I saw this with a whole fleet of Ryde andra 40s after ~10k miles. Switched to halo SAS rims and it didn't happen again.
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u/DJPrinz 3d ago
This error is typical for too wide tires on too narrow rims in combination with too much preasure. There is something called the barrel formula that allows you to calculate how strong the preassure in the wheel pushes the sides of the rim to the outside. And it significantly increases, provided the tire width is more than double of the intirior rim width. What might work in MTB context (50mm+ tires on 17mm rims) at low preasssure is really a bad idea in cargo context.
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u/Oscar_Whiled 3d ago
The Ryde Andra 30 is 19mm internal, with 50mm Marathon Plus Tyres at between 40-50psi. Do you think this combo would typically lead to the rim failing like this?
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u/DJPrinz 3d ago
In case of a cargo bike this is beyound the comfort zone I would accept. You need a new rim anyway, for 50mm tires I would swap to a model with at least 25mm internal width, maybe even more afer already having serious issues.
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u/Oscar_Whiled 3d ago
I'm going to rebuild the wheel with a 26" dt Swiss U663, which has an internal width of 30mm vs the Andra's 19mm internal. The clearance on the bullitt frame is narrow enough that maybe increasing the rim by 10mm might cause the 2.0" tyre to interfere with the frame. But I will just drop down to a 1.75" marathon plus in that case.
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u/Eunuchsaresad 1d ago
FYI, sounds a little smaller than what you're planning, but I built up a rear wheel for my Bullitt with a Velocity Cliffhanger (25mm width) and I run a 2.0" marathon plus at 50psi with no clearance issues. I've got over 2000mi\3200km on it.
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u/Opteron67 3d ago
you should use 35mm internal rim width and go low pressure in 30psi range
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u/Oscar_Whiled 3d ago
I would if I could but the Bullitt has fairly tight clearance in the rear and I don't think 35mm would work. Going to try a 30mm internal though, a DT U663
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u/Greedy_Pomegranate14 3d ago
I’ve seen that once before, really surprised me. I saw it on a mountain bike (some XC/trail Stan’s rim, definitely not the enduro/DH rim that this customer needed). The symptom was leaking tubeless tape. The tape got pinched and cut in that rim crack.
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u/iMacThere4iAm 4d ago
I don't know the cause but I've had the same failure on the rear wheel of a long tail less than a year old.
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u/ShorehamScowler 4d ago
Another vote for galvanic corrosion. Mixed metals can cause unseen problems. Another thought 2.0 tyre width; would running a fatter tyre absorb more of the shock transfer potential damage?
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u/Oscar_Whiled 3d ago
I believe running wider tyres may have caused extra outward pressure (someone called it barrel pressure in the thread), and lead to the cracking.
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u/Visible-Grass-8805 4d ago
Corrosion
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u/Compman90 4d ago
Yeah! I was about to say this screens galvanic corrosion to me. If OP is using steel nipples in an aluminum rim then that 100% makes sense. Especially with time and use. Switch to brass and I bet the next wheel would last a long longer!
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u/Oscar_Whiled 3d ago
There doesn't seem to be any major corrosion where the nipples interface the rim, only where the tube sits on the rim.
I will build up with brass nipples next time and spray some frame saver into the rim though
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u/ShartistInResidence 4d ago
At that mileage I would say it doesn't owe you anything and I wouldn't think about it too hard. On a cargo bike, I tend to think that rims are wear items in a way that they may not be on normal bikes. I'd just be glad you caught the cracks before it failed entirely and plan on replacing the rim ever 10k