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Old 03-10-10, 09:06 PM   #1
DoctorBrian
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cracked crank spider

My spider is cracked at one of the bolt holes. I've been riding on it for a while, and it doesn't seem to be too big a problem. Just wanted to get some second opinions on replacing it. Anyone else had this and kept riding on it? Cranksets are pricey, and I'd rather not get a new one if I don't have to.
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Old 03-10-10, 09:15 PM   #2
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Could be painful when the other shoe drops. A little more info would be nice. Make and model and age.
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Old 03-10-10, 09:16 PM   #3
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Where exactly is it cracked?
How badly?
How big is it?
Pictures would help alot, I can't imagine that failing catastrophically, worst case would probably be that part of the spider cracks off and you bend / break a chunk off of your chainring, the former could put a nasty ding in your frame but I doubt it will destroy anything (edit: other than your chainring and crank obviously)
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Old 03-10-10, 09:29 PM   #4
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Just replace it already. End thread.
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Old 03-10-10, 11:57 PM   #5
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Pff, I bet it lasts 50,000km. Many chainring/crank combos have a pretty tight clearance where the edge of the chainring sits on the shoulder of the spider so it isn't just the bolts taking the load.

Mind you, I've gotta wonder why it cracked in the first place...

Show us a pic.
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Old 03-10-10, 11:59 PM   #6
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Replace it.
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Old 03-11-10, 09:22 AM   #7
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pic as requested. its a bit embarrassing to share, since you can see the wear that resulted from a lazy attempt at chain alignment using spacers. im guessing thats why it cracked. not looking for critiques on that, but more advice on whether to replace the crank. mind you, im cheap, and its been fine for the last while. the other bolt mounts are fine.
crank is a truvativ elita, was on a fixed gear but now single-speed, id say its about 3.5 years old.
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Old 03-11-10, 09:53 AM   #8
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I'm sure it'll be fine. They obviously designed a crank with redundant spider arms and bolt holes. Pro racers could save a ton of weight by just omitting several chainring bolts.
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Old 03-11-10, 11:35 AM   #9
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redundant spider arms and bolt holes.
pretty much what i was thinking. just wanted some second opinions. thanks for everyone's replies.
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Old 03-11-10, 11:56 AM   #10
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pretty much what i was thinking. just wanted some second opinions. thanks for everyone's replies.
This was sarcasm.

I'm sure it'll be fine. They obviously designed a crank with redundant spider arms and bolt holes. Pro racers could save a ton of weight by just omitting several chainring bolts.

There are more than a few professional bicycle mechanics and very talented amateurs who frequent this forum and dispense some really good advice.

Operator is one of those people.

Pony up the $$$ and get a new crank.
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Old 03-11-10, 05:35 PM   #11
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Perfectly safe for coasting down hills.
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Old 03-11-10, 05:55 PM   #12
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replace. cost of quality, used cranks and if needed cartridge BB is $50 or so.

it'll be one exciting moment when the chainring folds in on itself.
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Old 03-11-10, 08:44 PM   #13
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If you are going to run one ring get a crank designed for it.
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Old 03-11-10, 08:50 PM   #14
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If you are going to run one ring get a crank designed for it.
I highly doubt this had anything at all to do with the failure, but indeed, replace the crank, A pake single speed crank costs like 50 bucks, you could probably find a good old double for even less if your really on tight budget
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Old 03-11-10, 08:57 PM   #15
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Did you drill the holes it's using? That would explain why it happened, as that one would have been off by a mm or two.

It's pretty ugly, but I reckon it'll prolly hold for a good while yet; that's the position it's settled into. Although that gap under the ring doesn't help...

However, if those are factory holes, I'd say it's seconds away from destruction.
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Old 03-11-10, 09:50 PM   #16
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It's possible that the spacers used previously as you described, scored the metal in such a way as to create a stress riser, which started the crack. I doubt that the chainring is about to "fold in on itself" (unless your real name is Magnus Backstedt)--more likely you would notice chainring wobble when this attachment lets go, although you might not notice it right away on a single speed as you don't have the front derailleur to "sound the alarm" with chain rub. If this tab has cracked, the others could also be compromised (by scoring) but not showing cracks yet, so the best bet is to replace it.

Last edited by simplify; 03-12-10 at 10:34 AM.
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Old 03-11-10, 09:59 PM   #17
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Doesn't look like a particularly pricey crankset to me. Maybe you're too cheap. bk
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Old 03-11-10, 10:25 PM   #18
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consensus seems to be that i should get a new crank. id say 'thanks' again, but i run the risk of missing some more sarcasm and looking even stupider. but thanks anyway.
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Old 03-12-10, 10:29 AM   #19
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consensus seems to be that i should get a new crank. id say 'thanks' again, but i run the risk of missing some more sarcasm and looking even stupider. but thanks anyway.
When members are unnecessarily sarcastic with you, YOU aren't the one who looks stupid.
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Old 03-12-10, 10:41 AM   #20
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When members are unnecessarily sarcastic with you, YOU aren't the one who looks stupid.
This thread was done at post #4.
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Old 03-12-10, 11:49 AM   #21
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Operator is one of those people.
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Just replace it already. End thread.
He is, but um... he can sometimes be too terse, not to mention sarcastic That can be intimidating for newbies or, on occasion, perceived unfriendly. Sorry, Operator, I don't mean disrespect, but perhaps sometimes a few more words is all it takes

Adam
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Old 03-12-10, 02:28 PM   #22
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So did you drill those holes? It doesn't look standard.
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Old 03-13-10, 12:09 PM   #23
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kimmo - no, i didnt drill them. its a goofy ring that has holes for both 130 and 110. it was all my local shop had in the size i wanted, so i tried it out. Been happy with it so far.

i know i sound cheap, but i try to do what i can with what i have. most of my bikes have been a little mickey-moused over the years, but ive never had anything fail on me (except for this crankset tab). i had a couple track cranksets that had various issues before this, so its not like i bought a double just for this bike. it was just the one that was laying around.

simplify gets my vote for most reasoned advice. im not too worried about massive failure, but i will replace it sooner rather than later. so, thanks. again.
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Old 03-13-10, 12:25 PM   #24
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Sorry I am late to the party...

Replace...
Replace OR DIE!




Well, maybe not die, but I sure wouldn't want to ride with my crank like that.
I was missing a spacer from behind the small chainring on my mtb years ago and figured there were four other bolts so it should be ok... I was picking gravel out of my face for a week.
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Old 03-13-10, 12:37 PM   #25
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lardasse - what happened to your crank? did it bend in on itself or something? maybe i can get a glimpse into my future.
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