So I was cruising a long last night and went over a pothole not any more gnarly than any of the hundreds I've gone over before and then all the sudden something clearly had gone terribly wrong. I was only able to keep the bike up for like another 30 feet before going down. When I got up, the front rim was in like 6 to 7 pieces. Anyone know why the would happen? It hurt quite a bit and in a worse situation could have hurt a lot more, so I'd like to avoid experiencing this again...
Epic rim failure. Why?
- Thread starter Rifle
- Start date
recumpence
1 GW
Way too heavy a hub motor mounted to a way too wimpy rim.........
I'd guess that a wider, tougher rim would have been better. That is a rather wide tire for the skinny rim.
Ever get pinch flats from the tire basically bottoming out on the rim? because i'd imagine if that happened often enough, the rim was taking some serious hits and weakening over time.
Ever get pinch flats from the tire basically bottoming out on the rim? because i'd imagine if that happened often enough, the rim was taking some serious hits and weakening over time.
spinningmagnets
100 TW
Hard to say, a multiple spoke failure could have also contributed...Are all the spoke heads, spoke shafts, and nipples intact?
That's still fairly wide for what looks like a 19mm wide rim.
19mm is 0.748 inches.
I'd imagine that a tire that's balooning outwards so far would be more vulnerable to smashing up against the rim when you hit a pothole. This is more likely to happen, the lower the tire pressure is. In extreme cases, a wide tire on a narrow rim like this runs a risk of literally popping off the tire, allowing the rim to take the force directly and break.
19mm is 0.748 inches.
I'd imagine that a tire that's balooning outwards so far would be more vulnerable to smashing up against the rim when you hit a pothole. This is more likely to happen, the lower the tire pressure is. In extreme cases, a wide tire on a narrow rim like this runs a risk of literally popping off the tire, allowing the rim to take the force directly and break.
Hillhater
100 TW
Hmm ? Not sure I agree with that.neptronix said:
Most pro DH mtn bikers run 2+ inch tires on narrow rims with little trouble.
I have always run similar 1.95 a 2.2 inch tires on narrow rims SPECIFICALLY to reduce flats from pinches and sharp object cuts etc, and allow enough flex to iron out rough surfaces.
The trick is in using correct pressure,.. Too low will lead to pinch flats,...too high with make them prone to punctures from sharp edge objects.
The tire was basically the same width as the rim. There was no noticeable ballooning.
I might check on that when I'm less sore tho I think a lot of the spokes took quite a beating in the crash. I thought I maybe heard a strange ping come from the front wheel earlier in the night, so there could have been maybe one spoke that slipped loose or something.
spinningmagnets said:
I might check on that when I'm less sore tho I think a lot of the spokes took quite a beating in the crash. I thought I maybe heard a strange ping come from the front wheel earlier in the night, so there could have been maybe one spoke that slipped loose or something.
I'm really confused as to how the front rim could be the one to fail on me. The back rim is just from some $150 Shopko bike and obviously there's way more weight back there since there's no suspension back there and I have a 20lbs battery on the rear rack. And the rear tire has gotten way more flats, including a pinch flat or 2, so it's definitely been subjected to more abuse. I guess it doesn't get the acceleration/deceleration forces tho the front is subjected too tho, so I guess those must have contributed to weakening the front rim.
Hillhater said:
Yeah, but downhillers usually don't have 10-20lbs of unsuspended weight in their wheel. That's a big factor. Unsprung weight is a killer.
But that tire looked a lot wider than the rim. Even if you inflate it a lot and it kind of balloons upwards.
Another theoretical problem could have been due to using standard 14 gauge spokes. Not sure if ebikes.ca ever spoked things up like that, but that does look like a pretty old motor to me.
Just theories.
I remember that! yeah, you've been rocking the same setup for too damn long, buddy! :lol:
Hope you weren't hurt, that looks nasty.
Aluminum bits do have a finite lifespan. I've done a lot of riding very fast with a hardtail and a lot of potholes while i eas as heavy as you remember me and never had that happen with my MAC, which i had for 4 years.
What motor are you thinking of next? or will you just respoke the thing?
Hope you weren't hurt, that looks nasty.
Aluminum bits do have a finite lifespan. I've done a lot of riding very fast with a hardtail and a lot of potholes while i eas as heavy as you remember me and never had that happen with my MAC, which i had for 4 years.
What motor are you thinking of next? or will you just respoke the thing?
Rifle said:
Thud
1 MW
Looks like a lot of galvanic corosion on the nipples & in a couple of the breaks. Could have been multiple stress fracturs that finaly met the pothole that broke the camels back.
The fingers
10 TW
Wow, that's harsh. 
Drunkskunk
100 GW
I'm betting it was one of the stock Clyte rims, which were thick, heavy, and not exactly first world quality. It probably had many minor stress fractures and that bump was the last one it could take. That would account for the multiple brakes. Extra thick spokes would have only accelerated the problem by not distributing the load as evenly as a thinner spoke with more give. Being an extra heavy motor means the wheel needs to handle more of the impact before the suspension can take over.
Check the edges of the brakes. if they are bright and shiny, they're new. if they are dull grey in appearance, or dirty, then the cracks had been there for a while.
Check the edges of the brakes. if they are bright and shiny, they're new. if they are dull grey in appearance, or dirty, then the cracks had been there for a while.
neptronix said:
Hurt enough I can't go out and have fun tonight, but seems to just be a bunch of contusions at the moment. Probably won't feel good to sleep on my left hip for about a year, but whatever. Only concern I have is that maybe something happened to my left rotator cuff, but I already had surgery on that capsule, so it should be good and tight. Probably just some swelling going on.
I've been wanting to do another build for about a year, was planning on it this spring, but kept having expenses with a house I bought, so I decided to hold off. I'd like to go with disc brakes and a rear motor for the next one, but that puts a lot of weight in the rear unless I drop mad money to get the new battery I want that will fit in the triangle. I'm thinking I'll probably lace it into a new rim to get through the rest of summer/autumn. Seems the quickest way to get back up and running. I guess the lesson here is to treat yourself to a new ebike build every 4 years :lol:
Drunkskunk said:
The edges looked shiny as far as I could tell, but I couldn't get a look at all of them and I did manage to keep upright for at least like 30ft after the initial break(s) which I imagine could be enough to cause fresh breaks on an already cracked rim. I sent Grin an email about this, so maybe they'll have some insight to offer.
999zip999
100 TW
Were the spokes loose ? When was the last time you had tighten the spokes ?
Get a bag of frozen peas and ice it down.
You should feel lucky as it could have been lot's worse.
Get a bag of frozen peas and ice it down.
You should feel lucky as it could have been lot's worse.
Okay, I think I know what happened, spokes got loose. There had been a subtle noise coming from the front that I thought was maybe due to worn out bearings, but now I realize it was probably the rim shifting a little due to the spokes being loose...
Never realized it was so important to check on the spoke tension every so often. I thought worst case it just gets out of true or you break a spoke. Whoopsie.
Never realized it was so important to check on the spoke tension every so often. I thought worst case it just gets out of true or you break a spoke. Whoopsie.
dnmun
1 PW
Al is subject to metal fatigue and if you look closely at the ends where it broke you can see that the cracks started at the holes as the spokes were able to twist it more, and if you take a magnifier and strong light you may be able to see evidence of the cracks having been there for a long time until one failed and then the others failed as the rim got hung up on the fork while rotating.
John in CR
100 TW
Hitting hundreds of potholes with a front DD hubbie is sure to have that result eventually. Get a better headlight and dodge the potholes.
bowlofsalad
100 kW
What was your typical average speed with that setup?
How much does that hub weigh?
How much does that hub weigh?
John in CR said:
I'd imagine it'd be more accurate to say I had hit thousands. It is not really reasonable to avoid them here due to the quantity and having to share the road with other traffic. That being said there are some large enough that must be avoided or the result would be a crash regardless of the bike holding together or not. So yeah, I do avoid those and basically anything more than an inch or 2 deep. This failure occurred after hitting one that was only an inch or 2 deep though.
With proper tire inflation and spoke tension I believe it would hold up fine. I believe the spokes just got far too loose. Since I recalled the slight noise I had been hearing I have became quite confident this happened due to under tensioned spokes. Will know more for sure once I can confirm the noise doesn't exist when the motor is re-laced.
bowlofsalad said:
28mph WOT cruising speed.
About 10 lbs I believe.
Sounds like you need a dual suspension bike with 29er tires next at the least.
Best of luck with healing up, sir. I went airborne 2 years ago at 20mph onto pavement due to a railroad track and it's been a very slow recovery for me. I know that pain!!!
Best of luck with healing up, sir. I went airborne 2 years ago at 20mph onto pavement due to a railroad track and it's been a very slow recovery for me. I know that pain!!!
Have to agree with the others, that rim probably had accumulated a lot of stress cracks over time. We've had posters before who have had rims disintegrate over time, or gone to change a tube and found cracking. Still 10/10 for the result - most totally destroyed wheel I've seen! 
I'm not sure I quite buy the "heavy motor kills wheel" theory. In a suspended fork, yes it does increase unsprung mass, which may have a small affect. But compare that to a rigid fork, where the unspring mass is the whole weight of the bike and rider.
I'm not sure I quite buy the "heavy motor kills wheel" theory. In a suspended fork, yes it does increase unsprung mass, which may have a small affect. But compare that to a rigid fork, where the unspring mass is the whole weight of the bike and rider.
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