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Old 12-03-05, 01:07 PM   #1
kdh344
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Brand new bike..BB spins..WTF??

i was standing trying get up a hill and my brand new scalpel, made this weird noise. like zzzzttt. i was at the top of a pedal stroke getting ready to rank down and the cranks just spun all the way down making that weird noise. what is it? my bike has 20 miles on it.
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Old 12-03-05, 01:11 PM   #2
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Sounds like the pawls (ratchets) in the rear wheel's freehub aren't engaging 100% of the time. Was it cold out? Sometimes the lube in the freehub stiffens up enough to do that if it's cold. Or it might be faulty.
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Old 12-03-05, 01:32 PM   #3
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Quote:
Originally Posted by mechBgon
Sounds like the pawls (ratchets) in the rear wheel's freehub aren't engaging 100% of the time. Was it cold out? Sometimes the lube in the freehub stiffens up enough to do that if it's cold. Or it might be faulty.
My guess also -rear wheel. Your bb spins freely both directions.
The rear wheel spins free one direction, reversed as stated^ the pawls should engage -turning the cluster\wheel.

Since it's new, return the wheel to the lbs for repair rather than DIY.
The wheel is new also?
Dirt, dirty grease can effect the pawls engaging.
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Old 12-03-05, 01:39 PM   #4
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The other one I can think of is if the chain manages to sit on top of the teeth of the chainring, sort of inbetween the rings, rather than meshing with them. That can produce a ZZZZZTT noise up front at the cranks, as the chain skates on top of the teeth.

edit: pic of "chainskate" attached now
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File Type: jpg chainskate.jpg (43.7 KB, 40 views)

Last edited by mechBgon; 12-03-05 at 02:05 PM.
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Old 12-03-05, 02:23 PM   #5
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Originally Posted by mechBgon
The other one I can think of is if the chain manages to sit on top of the teeth of the chainring, sort of inbetween the rings, rather than meshing with them. That can produce a ZZZZZTT noise up front at the cranks, as the chain skates on top of the teeth.

edit: pic of "chainskate" attached now
wha would cause the chain to do this? and it being a BRAND NEW bike, more than likeley which problem wold it be?
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Old 12-03-05, 02:27 PM   #6
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wha would cause the chain to do this? and it being a BRAND NEW bike, more than likeley which problem wold it be?
If you downshift from a larger ring and the chain doesn't mesh with the next-smaller chainring, then that's just One Of Those Things That Can Happen To You™. The chain being narrow enough to fit in that position can be a contributing factor, though.

I like jeff williams' point: it's a new bike, so lean on the shop that sold it to you and have them check it out.
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Old 12-03-05, 02:29 PM   #7
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yeah, that would be the easy, least cotly thing to do BUT the lbs is 3 hours away.
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Old 12-03-05, 02:31 PM   #8
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I see. Practical advice for the moment: don't try out-of-the-saddle stuff until you can get that checked out. Was it cold outside when this occurred, by the way?
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Old 12-03-05, 02:35 PM   #9
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no, not cold at all. i dont understand how the cranks can spin up front if the problem is at the back??
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Old 12-03-05, 02:51 PM   #10
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Originally Posted by kdh344
no, not cold at all. i dont understand how the cranks can spin up front if the problem is at the back??
Think of coasting, pedaling backward....the cranks spin both ways -the clockwise rotation engages the pawls in the rear hub causing the wheel to be rotated foreward by the chain.
Counterclockwise, the pawls do not engage and the cluster spins backward free -not turning the wheel.
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Old 12-03-05, 03:09 PM   #11
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Another example would be a car with a manual transmission. If you put the car in 1st gear, and let in the clutch as you press on the gas pedal, and the engine redlines but the car doesn't move, it isn't the engine's problem. It's the clutch. And in your case, the "clutch" is in the rear hub.
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Old 12-03-05, 03:11 PM   #12
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What model of bicycle do you have?
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Old 12-03-05, 04:39 PM   #13
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the bike is a 2001. it was special ordered for a customer that backed out of the purcashe. its been sitting on the rack ever since .cannondale scalpel 2000
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Old 12-03-05, 08:00 PM   #14
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Quote:
Originally Posted by mechBgon
The other one I can think of is if the chain manages to sit on top of the teeth of the chainring, sort of inbetween the rings, rather than meshing with them. That can produce a ZZZZZTT noise up front at the cranks, as the chain skates on top of the teeth.

edit: pic of "chainskate" attached now
I vote for the same thing. Of a lot of possibilities, it's the most likely thing.
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Old 12-03-05, 08:08 PM   #15
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Quote:
Originally Posted by kdh344
i was standing trying get up a hill and my brand new scalpel, made this weird noise. like zzzzttt. i was at the top of a pedal stroke getting ready to rank down and the cranks just spun all the way down making that weird noise. what is it? my bike has 20 miles on it.
Ok, so you were riding up a hill, the chain was engaged and the bike was working fine and suddenly the cranks spun all the way down. The chain skate theory is possible if this had occured immediately after a shift when the chain may have gotten hung up between rings. Did you just shift the front derailleur before this happened? If not, it is improbable that the chain would ride up between the chainrings while it was under tension from your pedaling. More probably, the rear cassette pawls are gummed up after sitting on the sales floor for years and you need to get your rear wheel serviced. Actually, any bike that has been sitting for years should be completely overhauled. Good Luck.
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Old 12-04-05, 08:20 AM   #16
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Originally Posted by shiftinjon
Ok, so you were riding up a hill, the chain was engaged and the bike was working fine and suddenly the cranks spun all the way down. The chain skate theory is possible if this had occured immediately after a shift when the chain may have gotten hung up between rings. Did you just shift the front derailleur before this happened? If not, it is improbable that the chain would ride up between the chainrings while it was under tension from your pedaling. More probably, the rear cassette pawls are gummed up after sitting on the sales floor for years and you need to get your rear wheel serviced. Actually, any bike that has been sitting for years should be completely overhauled. Good Luck.
yep, thats correct. but it didnt do that UNTIL i really put some power into it. just normal out of the saddle riding didnt do it..what im gonna do just to be CERTAIN, is ride it again and see what happens. any suggestions as to what i might ry to diagnosis the problem??? i dont think i was shifting at the time. this bike has only 2 chain rings which forces you to ride 95% of the time in the biggest one. "completely overhauled" as in EVERYTHING??

Last edited by kdh344; 12-04-05 at 08:33 AM.
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Old 12-05-05, 12:05 PM   #17
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any ideas?
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Old 12-05-05, 09:00 PM   #18
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Originally Posted by shiftinjon
Actually, any bike that has been sitting for years should be completely overhauled. Good Luck.
Stuff and nonsense. I agree that the freehub pawls might be a bit sticky or otherwise reluctant to engage, but the idea that simply sitting around is bad for a bicycle is patently absurd, especially if the bike has been indoors for most of its life. Parts are overhauled as preventive maintenance against wear incurred by mileage, not time. Sometimes grease gets gummy with time, sometimes it doesn't. The pawls might be the problem due to stickiness. This doesn't mean that the hubs, BB and headset need to be taken apart as well! Good grief!
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Old 12-05-05, 09:11 PM   #19
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Well - let me start by saying that I'm no cycle mechanic, but I think I've encountered the same thing, but after twice repeating the problem, I recognized it for what it was - popping the chain off the chainring due to flexing whilst slightly crosschained.

In my case, it was when I was getting ready to climb a really steep driveway, so I dropped into the granny on the front, but was still in the 5 or 6 position on my cassette. When I went to stand and hammer up, the flex in the frame/BB allowed the chain to touch the outer stop on the FD - and off she popped. It dropped right back on as soon as my weight was relieved from it. I then failed to figure it out, and proceeded to repeat as soon as I tried it again. After shifting the rear down a couple of stops, (well OK, all the way to the lowest gear) I was able to scale the hill without incident.

It's a possibility - especially if it only happened when hammered hard, and immediately self-corrected.
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Old 12-05-05, 09:53 PM   #20
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Quote:
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Stuff and nonsense. I agree that the freehub pawls might be a bit sticky or otherwise reluctant to engage, but the idea that simply sitting around is bad for a bicycle is patently absurd, especially if the bike has been indoors for most of its life. Parts are overhauled as preventive maintenance against wear incurred by mileage, not time. Sometimes grease gets gummy with time, sometimes it doesn't. The pawls might be the problem due to stickiness. This doesn't mean that the hubs, BB and headset need to be taken apart as well! Good grief!
"Stuff and nonsense"? Oh please...

This is probably exactly what happened. Grease does get old, especially when it sits, and the only way to fix it is to R&R (that's remove and replace). Do you think the bike has different types of grease in the other parts?

You have strong evidence that this is the problem; why ignore it ("chainskating" notwithstanding...)?
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Old 12-06-05, 12:02 AM   #21
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I would check that the front chainrings are both perfectly true. If you were in your middle chainring, and its bent, it can cause the chain to ramp up onto the inside of the big ring without fully engaging and therefore slip causing the symptoms you describe. I've seen it on a number of Cannondales and other bikes out of the box--usually only happens under load on hills as you describe too, and the bike typically works fine in the stand.
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Old 12-06-05, 01:33 PM   #22
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Originally Posted by fholt
Well - let me start by saying that I'm no cycle mechanic, but I think I've encountered the same thing, but after twice repeating the problem, I recognized it for what it was - popping the chain off the chainring due to flexing whilst slightly crosschained.

In my case, it was when I was getting ready to climb a really steep driveway, so I dropped into the granny on the front, but was still in the 5 or 6 position on my cassette. When I went to stand and hammer up, the flex in the frame/BB allowed the chain to touch the outer stop on the FD - and off she popped. It dropped right back on as soon as my weight was relieved from it. I then failed to figure it out, and proceeded to repeat as soon as I tried it again. After shifting the rear down a couple of stops, (well OK, all the way to the lowest gear) I was able to scale the hill without incident.

It's a possibility - especially if it only happened when hammered hard, and immediately self-corrected.
ok, so how do i determine which problem it is. i was looking down at the chain ring the last time i test rode it but couldnt really tell where the problem was coming from.

seely, on this bike there is no middle chain ring..there are only 2. neither one appeared to be bent. if this is an "out of the box" problem, how can it be fixed? ANOTHER THING...some of the the big chain ring teeth are pointed..they look almost worn out. i asked the shop owner about that he said "all high end bikes are that way..it enables the chain to move easily back and forth from the small CR to the larger CR." ever heard of that?????????????
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Old 12-06-05, 01:59 PM   #23
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ANOTHER THING...some of the the big chain ring teeth aren't pointed..they look almost worn out. i asked the shop owner about that he said "all high end bikes are that way..it enables the chain to move easily back and forth from the small CR to the larger CR." ever heard of that?????????????
He's not making it up as he goes along. Look at a brand-new Shimano mountain-bike crankset for an example of what the special shapes, ramps, hooks and gouges look like that assist shifting.
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Old 12-06-05, 02:33 PM   #24
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the bike is a 2001. it was special ordered for a customer that backed out of the purcashe. its been sitting on the rack ever since .cannondale scalpel 2000
My vote goes for the freehub assy, I own a 2005 Scalpel and the freehub seized after roughly 20 hrs of use. Damn Cannondale propietery( SP) crap............
C/Dale replaced the freehub but not the hanger,rear mech or cogset which were all destroyed.
Luckily my LBS stepped up..
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Old 12-06-05, 02:39 PM   #25
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If it's a non-Shimano hub, then I'm with roadrasher, never did like the endless variety of Taiwanese Shimano-wannabe hubs posing as something special. DeoreLX rear hub, stat!
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