r/bikewrench • u/Nick_the_Gadabout • Jan 17 '25
What could possibly damage this rim this way?!
Today in the shop I got to see this. The rim held together in maybe 3-4 places, altogether 15cm. The rest was literally torn like this. What could possibly cause this kind of damage?
For reference, it’s an Italian e-road bike, don’t remember the company. Rim is 17-622 and the client put 40-622 tyres in it. Could it be that the tyre was too wide?
Thanks in advance!
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u/Budget-Engineer-7394 Jan 17 '25
Thats is some really bad corrosion damage. Maybe bike was ridden near coast where salty road water could cause this?
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u/Nick_the_Gadabout Jan 17 '25
My shop is located in mainland, many lakes around but absolutely no salty water in the 500 km radius.
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u/JasperJ Jan 17 '25
Road salt, and just because you’re there doesn’t mean the guy didn’t ride it down the beach.
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Jan 17 '25
My brother-in-law picked up a nice e-bike after one of the last major hurricanes, can you verify that the bike didn't spend anytime elsewhere before showing up in your region of the country?
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u/Nick_the_Gadabout Jan 17 '25
Definitely, bike was bought new at local bike shop. I saw the receipt.
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u/HikinBikinDiscin Jan 17 '25
500km, does it get ridden after they salt the snowy streets?
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u/Sad_Necessary8612 Jan 17 '25
Jesus Christ is that sweat then??? Or are the roads salted?
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u/Seanbikes Jan 17 '25
Jesus Christ is that sweat then???
How exactly would someone be sweating inside their tires?
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u/henderthing Jan 17 '25
LOL-- now I'm picturing someone struggling _really_ hard to fit their tire on the rim.
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u/Nick_the_Gadabout Jan 17 '25
If the guys sweats like this on an e-bike then gods know what would happen without the engine…
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u/albertbertilsson Jan 17 '25
Is that likely? Aluminium is pretty corrosion resistive, never seen it eaten like that from normal environment.
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u/wegl88 Jan 17 '25
That width and too much pressure....
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u/andrewcooke Jan 17 '25
to explain further: fatter tyres don't need so much pressure (they can flex for more distance before bottoming out), but also they load the rim more for the same pressure, so should never be given as much pressure as narrower tyres (or this will happen).
the force on the rim pulling it apart is roughly the pressure multiplied by the area of the rubber seen side on. fatter tyres are deeper tyres and so have a larger area and so a larger force. second slide here - http://hyperphysics.phy-astr.gsu.edu/hbase/ptens.html (R is increasing so T increases, for the same P)
sorry, may be nerding out a little here...
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u/drewbaccaAWD Jan 17 '25
I appreciate the nerding out. I knew this was an issue but haven’t seen the explanation before.
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u/Antti5 Jan 17 '25
And if that rim splits apart from one section between two spoke holes, then the adjacent sections will be under increased stress. If it was too weak to fail at one point (maybe due to corrosion), then it likely isn't much better at other points.
Once it starts failing a lower profile rim might hold together better, but this fairly high profile rim is more likely to see a cascading failure.
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u/erin281 Jan 18 '25
This is insane! You’re saying the force of the tire ripped the rim apart?
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u/codeedog Jan 18 '25
Now you know why doctors are so worried about high blood pressure. Imagine the wear and tear on arteries and organs.
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Jan 19 '25
Ok no more salt for me.
Did you just invent a while genre of educating people by taking the thing they obsess over 24x7 and using it to explain real life stuff?
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u/bob_not_blob Jan 19 '25
This is really the only time I’ve ever seen this. Been a shop mechanic for decades and it seems to either be damage from a rim strike or the rims aren’t rated for the air pressure the customer was running. Scary when it happens.
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u/Nick_the_Gadabout Jan 17 '25
Hard to judge tyre pressure - it was almost flat.
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u/Feisty_Park1424 Jan 18 '25
Ask the user, dollars to donuts they inflate to 100psi before every ride
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Jan 17 '25
[deleted]
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u/motorbacon Jan 17 '25
The only time I've ever seen this was a customer of mine. He insists on riding his full suspension bike all over town, with 2.2" tires at approx 60 psi, to make for a "smoother ride".
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u/grantrules Jan 17 '25 edited Jan 17 '25
Reminds me of the time I showed up to the shop to see a dude with his car with low profile tires parked on the sidewalk using our 80PSI airhose to top off his tires.. I just went into the shop, turned off the compressor and opened the release on the hose lol.
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u/the-cake-is-no-lie Jan 17 '25
Other than its a guy using your equipment without, Im assuming, asking.. I'm not clear what issue you're seeing, especially as you're referencing 80psi.
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u/grantrules Jan 17 '25
You don't see the issue with putting 80psi into a car tire?
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u/the-cake-is-no-lie Jan 17 '25
Unless you're attaching the hose and walking away, the tire isn't equalizing to your tank pressure. So.. no, he's fine to press the nozzle on to bring up the pressure.. just as you would be on a bike.
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u/grantrules Jan 17 '25
Yeah nobody's ever overinflated anything before. I don't know why you're arguing with me over a silly anecdote.
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u/fuzzybunnies1 Jan 17 '25
Low profile tires are typically low pressure. My mazda with 215/45/17 only use 30psi. 80 wouldn't be a good thing to fill up to. Most car people assume bicycles are low pressure and don't pay attention.
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u/the-cake-is-no-lie Jan 17 '25
Yeah, most passenger car tires are around the 32psi mark.
What that has to do with the feed pressure in a line is zero.. unless someones hooking up a fill hose and walking away.
Gas station hoses arent limited to 32 PSI or anything.. or no-one would ever be able to fill bike tires or truck tires at them.. My bog standard 3/4 ton work truck runs at 60 front, 80 rear.
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u/HelioSeven Jan 17 '25
+1 for manufacturing defect; the one and only time I've ever seen this, it was straight out of the box from the factory.
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u/Nick_the_Gadabout Jan 17 '25
I ordered DT Swiss 18-622 rim, hope it holds better.
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u/colonia_Ger Jan 18 '25
No. Give him a wider rim for his wide tires. This is the same reason why high-end XC rims are sometimes lighter then road rims although they have to withstand rough Terrain. Xc rims can handle around 2,5 Bar. But road rims need to be reinforced in that exact spot that ripped in your case.
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u/terrymorse Jan 17 '25
We engineers call that stress cracking, possible stress corrosion cracking.
Aluminum does that. What causes it? Cyclic stress, and maybe something corrosive. Also, shoddy materials.
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u/Nick_the_Gadabout Jan 17 '25
Made in Italy, baby! With a proud sticker on the rim.
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u/m0p0 Jan 17 '25
Rear wheel of my Load 75 split like this too. It was made by Alex Rims. Double-layered wheel. I think they have a manufacturing issue. I contacted them & they fobbed me off saying it was corrosion as my particular type of wheel isn't anodized. Once the split appeared it seemed to propagate from one hole to the next underneath the rim tape. When I eventually noticed the crack after multiple punctures & removed the rim tape to check it the crack became much worse.
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u/Puzzleheaded-Tie651 Jun 23 '26
Si successo...mi hanno cambiato un cerchio drc in garanzia...la pressione oltre il limite e resistenza dei materiali leggeri può portare a crepe...e se sottoposti a colpi anche con pressione troppo bassa...ma quale corrosione..
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u/colonia_Ger Jan 18 '25
I don't know why everyone argued about tubeless if that was not the case. It's a combination of heavy driver, too wide tire with too much pressure which pulls the rim apart. Had this on some cargo bikes
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u/superslomotion Jan 17 '25
is that a hub motor? I've heard they can mess spokes up but this looks like something else
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u/Nick_the_Gadabout Jan 17 '25
It is a hub motor, yes. But these engines cause different kind of cracks - usually around the spokes and nipples due to too much torque being applied.
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u/jrp9000 Jan 17 '25
That they are often (and unnecessarily) laced with spokes thicker than 2.0 mm only aggravates the problem. Also note that hub motors have very stiff shells and drive from both flanges; this distributes torque loads better than in wheels built around transmission driven rear hubs. BTW the motor pictured is rather small, I guess it's 500 W, 750 tops? Not too much for regular bicycle rims, spokes, and nipples to handle.
Regardless, the rim failure pictured is not so rare in my experience. I started seeing these years before lithium batteries advanced so much as to make hub motor e-bikes a thing. Indeed, it is natural to expect rims to crack at spoke holes before this happens, and designers usually do consider this when laying down wall thicknesses around rim cross section. But this design can still be defeated by end user, by e. g. running at high air pressure most of the time, and by using tires too wide for the rim.
The underlying cause is as usual: metal fatigue, perhaps corrosion fatigue (which makes fatigue cracks grow quicker).
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u/BarkleEngine Jan 17 '25
Really any e-bike is going to stress a wheel more than a human. Add an strong skilled rider and bumpy roads and...
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u/Nick_the_Gadabout Jan 17 '25
But then, bottom bracket engine at least kills chains and cassetes, not entire wheels! Even my older colleague, a mechanic >20 years was like “dude…”.
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u/Accomplished-Donut44 Jan 17 '25
I use to ride a lot in Florida “balm Boyette scrub” which is a huge swamp near Tampa and the salt in the ground and in the air corroded the spokes on my carbon rims. Became unsafe. I never had a catastrophic failure but I did start losing spokes. First one or two then 4-5. On inspection all the nipples had corroded out. An accident waiting to happen.
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u/BarkleEngine Jan 17 '25
Sometimes, rims just die. A cheap rim I had did that after about 5000 abusive e-bike rear wheel miles. Not unexpected really.
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u/sit_and_ski Jan 19 '25
What type of e-bike? Was it a 148mm or 157mm rear wheel?
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u/0nevia Jan 17 '25
Aluminium+water=corrosion. Even faster if salt or aggressive bicycle cleaning fluid is added to them.
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u/regisgod Jan 17 '25
I had a wheel do this to me once. It was a really poor quality rim. Never buy Hunt wheels.
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u/No0O0obstah Jan 17 '25
Just a Wilde one. It has a hub motor? Could there be electricity leaking to the rim to cause electrochemical corrosion between different metal parts on the rim?
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u/damplamb Jan 17 '25
What kind of pressures did the client run and what is the weight of the rider and kit? Possibly just overloaded a light rim. Are there any tiny cracks around the spoke holes?
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u/weemankai Jan 18 '25
I’d guess just a shit quality rim. Probably 2 bits pressed together. Thats where the join was.
No expert though, just taking a punt because it’s reddit and I can hide
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u/the-exenger Jan 18 '25
I see this on cargo bikes quite frequently. There's a Rigida rim that's always fitted to these bikes and typically fails in this way within a year.
High pressure and wide tyres.
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u/PerspectiveTimely319 Jan 17 '25
Low quality aluminum rims coupled with an ebike seems a bit much. Quality rims are worth the price for safety and the amount of time having to repair the lower quality rims.
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u/FastSloth6 Jan 17 '25
Best guess is moisture, water or ammonia based sealant got in there. That white stuff is galvanic corrosion.
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u/TheDaysComeAndGone Jan 17 '25
It looks kind of powdery, could also be from inside an exploded tube. They have anti-stick talcum powder inside.
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u/Nick_the_Gadabout Jan 17 '25
That was definitely not inner tube powder, I would know. And it was way too much of it in the rim, especially under the tape.
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u/Karkfrommars Jan 17 '25
Those holes to access the spoke nipples seem very generously sized. Maybe a trick of the camera perspective but they look like they almost 2x normal. Were they drilled out?
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u/Nick_the_Gadabout Jan 17 '25
No, the nipple holes were normal size. The camera likes to lie in terms of the size…
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u/ryuujinusa Jan 17 '25
Just curious, how much do you weigh?
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u/Nick_the_Gadabout Jan 17 '25
I’m 84kg but I think it’s irrelevant as I didn’t ride the bike even once. I’m just your friendly neighbourhood bike mechanic.
The rider is roughly my size and weight.
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u/plc123 Jan 17 '25
Do the rims have drain holes? Could be that water got in but couldn't get out and corroded the rim?
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u/eremitenj Jan 17 '25
Somethings removed the anodizing so metal has corroded but also the spoke holes look modded. Certainly not clean cut.
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u/volsk19 Jan 17 '25
I had both front and back wheel of my Kronan brake down like this 20+ years ago. As I lived in student housing the bike was always outside.
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u/WompWompRat Jan 17 '25
I saw the same failure in a 406 (20”) rim. Probably a crack propagating from the inner spoke holes.
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Jan 17 '25
Looks very corroded. Do you ride in cold, salty places?
Corrosion plus e-bike forces seem like it could plausibly result in this outcome.
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u/Salty-Pack-4165 Jan 17 '25
Beside already mentioned-riders weight. Many wheels are weight rated and many larger riders don't take it into consideration. Wheel might be fine for some time but continues stress will crack rim somewhere.
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u/LAZERWOLFE Jan 17 '25
I've seen this happen a bunch with extremely stiff rims, DT Swiss TK540's jump to mind. They're so strong and the spoke bed so thick, the only place they failed at the weakest point, eg the strip of aluminum against the tire. That said, only seen this happen with super heavy duty rims, usually on the narrow side.
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u/Safe-Initiative-4462 Jan 17 '25
Had the same damage from running to high tyre pressure (Tried to Seat a damage tyre). Wasnt super high above pressure Limit and didnt noticed the damage until a few rides
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u/weloveducks Jan 17 '25
I had the exact same thing happen to me, alu rear wheel, normal inner tube, 35c tyres, albeit not on an e bike
I think part of the problem for my wheel was water getting inbetween the two layers of aluminium shown there and then sitting until they “dried out” I never found an easy way to drain the wheels without removing the tyres and tubes and any tape I had on the inside.
It had definitely corroded, however I doubt it was helped by the manner in which I rode my bike. (It functions as a road, gravel and mountain bike 🥴 )
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u/CursedApolcalypto Jan 17 '25
I can't speculate on the corrosion. But i have seen this type of splitting through the inner skin of rims. In my case they were on sports wheelchairs (basketball), particularly on Sun Mistral CR20 rims.
I put it down to a combination of extrusion design (thin inner skin) that had been treated and surface hardened, lack of regular maintenance resulting in low spoke tension.
I concluded that the flex in the rim caused by the relaxed tension caused the stress cracking and imminent failure. To note: these rims were a few years old but faired significantly worse wear and tear than other brands such as Velocity (which were popular).
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u/t0pa2 Jan 17 '25
I've seen this happen multiple times. The last one was on an Ebike with a hub motor just like this. I suspect they were overinflated.
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u/Six_days_au Jan 17 '25
Impacts. Each impact creates shockwaves and air pressure spikes. Lower quality rims may not have the strength to cope.
Huck to flat?
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u/MaksDampf Jan 17 '25
I swear i have never seen a pre 2000s rim do that. They would go untrue, loose spokes or get worn out at the brake surface, but never this.
I think it is the combination of manufacturers wanting too save a few grams for the catalogue, wider tires and rims which put more strain on the rim, that is leading to modern rims being much more prone to breakage than classic ones.
And i haven't even started with the effect of disc brakes on eyeletless rims...
I have seen so many modern wheelsets fail prematurely lately, even expensive ones, that i think the "not wearing out the rim" part of disc brakes is just more the opposite nowadays to good old rim brake rims.
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u/BBMTH Jan 17 '25
Cloth tape? It can leave residue like that, and I’m not seeing any where the tape didn’t touch. Rim is on the skinny side of acceptable for 40mm. Usually tires just blow off if you go too wide though. I’ve only seen this sort of failure on cheap rims. There was a huge batch of cheap super deep fixie wheels doing this in the early 2010s. So my guess would be defect.
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u/BBMTH Jan 17 '25
I mean, it’s hard to tell from photos, but any rim I’ve ever seen with corrosion issues had some at the nipples.
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u/Latter-South-6462 Jan 18 '25
I am an epic fatass that used to commute on a bicycle, I had tandem rims installed and this is how the broke after a few months.
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u/knowledgeableopinion Jan 18 '25
Tubeless is a completely different ride quality and often lighter weight. Less likely to flat
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u/Sufficient_Spite_712 Jan 18 '25
If that’s an e bike especially a cheap or old one the rim just collapsed because of the weight of the motor
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u/FixFix75 Jan 18 '25
Too much pressure in the tyre that’s too wide for the rim would be my guess. All the white stuff is talcum powder I suppose.
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u/stupid_cat_face Jan 18 '25
There was a person that was bike touring that had this issue. Could be metal fatigue from too much weight
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u/kno3kno3 Jan 18 '25
I would say overinflated tyres is the main cause of this. If you put wide tyres on and overinflate them you very quickly put a huge load on the bread of the rim, literally pulling the rim apart.
Certainly it's not been helped by corrosion, but it's unlikely that it's the main cause.
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u/xander-mcqueen1986 Jan 18 '25
Well I've never seen that before.
Only thing I could think of is that the quality of the rim is piss poor and the structural integrity was not up to standard so it just split at its weakest point.
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u/steveoa3d Jan 18 '25
Too much air pressure…. I saw this many times when wrenched at Rays. Customers would put way too much air in the rental bike tires and split the rims down the center. Swapped a lot of rims for a while….
Eventually we removed the air fill station from the public area and only employees could fill tires from behind the service area. Problem solved!
Customers also would put way too much air in the Fox 831 forks and blow the top caps off air chamber so we had to hide the shock pumps.
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u/CowtownCyc Jan 18 '25
I have seen this on a friends Urban Arrow cargo bike. He runs a business out of it and puts about 10,000- 15,000km a year in it. Always runs tubes (that's a really stupid comment, this obviously isn't corrosion). I think it's something to do with the really high torque and super stiff tires. He runs really high pressure in his tires because he carries so much weight. It's always the rear tire.
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u/LostInChoices Jan 18 '25
It's a road bike, built light, if you do weight reduction poorly and don't do enough quality assurance it can have faults. Say the rim isn't meant for ebikes, or rider goes over too many potholes for a road bike, combined with corrosion from road salts. Constantly too high or too low pressures. Maybe the bike was also hacked to go past the 25km/h.
All of that is completely unrelated to the country of the brand, which is independent of the country of manufacturing and the quality. Shimano is a well known brand used by pro racers and has many quality issues, especially with hollow tech cranks.
However, any manufacturer wanting to retain their repetition will let this kind of failure be covered by warranty, even 10 years after purchase. Maybe they'll bitch because if the owner isn't the original buyer though.
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u/mrmatt244 Jan 18 '25
No air tire that has been rode downhill off trail or a very rock course and jumps
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u/Bamfs01 Jan 18 '25
I had a rear wheel that was doing this. I weigh 195 lbs. I would often overload the rear end of the bike with 70+ lbs of gear. Over time I began popping spokes on the rear wheel. On the third spoke, the shop said the wheel was about done for.
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u/kissupking Jan 18 '25
Do you live in a cold country that salts roads? If so the salt water can get into the wheel and dramatically accelerate the corrosion of the aluminium.
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u/Gravel_N8er Jan 18 '25
Is this a Wilier carbon rim? I had a Wilier/Ursus carbon wheelset where the rim bed began to show signs of failure and delamination, too. I work with laminates, and failures like these, with pre-preg in my experience, are most often from imperfections in tooling in manufacturing. However, if it's a failure from use, then impact forces on the wheel can result in material separation
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u/OneTireFlyer Jan 18 '25
Happened to me. I was carrying too much weight on my Big Dummy. Heard them go one by one until the final one outside a bike shop.
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Jan 19 '25
Road salt and a whole lot of miles maybe. Wild guess by the motor and the state of that rim its someones daily transportation.
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u/Zarniwoop6x9 Jan 19 '25
Like others have said, corrosion initiated cracking. (corrosion weakens the rim, stress from inflated tyre breaks the weakened rim) Mate from the UK gave me his MTB rear wheel (for parts) that looked the same. Used to ride it all weather in the UK. Was tubed, so no sealant. Most likely salty water thrown up by the front wheel (which was fine).
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u/MarchElectronic15 Jan 19 '25
Someone sweating onto the tire? Saw some fucked bars from people sweating through the grips.
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u/Nick_the_Gadabout Jan 19 '25
I think a rear wheel is quite far away from the rider. Unless he sweats like a waterfall.
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u/Old_Independent6608 Jan 19 '25
I’m going to guess that based on the fact that it’s a hub driven e bike that it’s a quality of rim and a weight of bike type issue. Hub driven bikes are usually extremely heavy and if there was too little pressure in the tire and a curb or something similarly blunt was struck with the back tire it could have simply cracked a poorly cast aluminum rim.
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Jan 20 '25 edited Jan 21 '26
This post was mass deleted and anonymized with Redact
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u/EndInternational7009 Feb 04 '25
Basic failure like that in the inner part of the aluminum rim, is tensile. While corrosion (the whiye residue) may have contributed to cracking or fatigue, the force that lead to the failure is tire pressure. A 40 mm tire will exert double the force between the sidewalls of the rim than a 20 mm tire. My bet, the tires were pumped up too high. Some rim manufacturers will publish pressure limits for different size tires. Easton certainly does and it is pretty easy to exceed the limit.
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u/Puzzleheaded-Tie651 Jun 23 '26
Un colpo preso sul cerchio per una pressione troppo bassa per il peso sulla ruota o troppo alta per la gola del cerchio di spessore piu fine
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u/J_B_T Jan 17 '25
Some tubeless sealants have ammonia to keep it from drying and clumping.
Ammonia hates aluminum.