Cycling and bicycle discussion forums. 
   Click here to join our community Log in to access your Control Panel  


Go Back   > >

Bicycle Mechanics Broken bottom bracket? Tacoed wheel? If you're having problems with your bicycle, or just need help fixing a flat, drop in here for the latest on bicycle mechanics & bicycle maintenance.

User Tag List

Reply
 
Thread Tools Search this Thread
Old 07-04-11, 05:29 PM   #1
sknhgy 
Dirt Bomb
Thread Starter
 
sknhgy's Avatar
 
Join Date: Aug 2006
Location: Illinois
Bikes:
Posts: 2,658
Mentioned: 7 Post(s)
Tagged: 0 Thread(s)
Quoted: 374 Post(s)
Chain suck problem

A month or two ago I bought a new 2011 Rockhopper. After some ongoing chainsuck issues the LBS replaced the bike.
I've had the new one for about a month. I've been careful with the shifting and had some minor gliches with the shifting but nothing too bad.
Yesterday, the new bike started sucking the chain when downshifting from the middle to the smallest chainring.
So. I'm pedaling up a very slight rise and I downshift from the middle to the small chainring and the chain, while in the process of shifting from the middle to smallest ring, starts to stick and wrap itself around the smallest chainring. I immediately stop pedalling and I stop the bike to have a look at what's going on.
What I found was the section of chain that was bridging between the chainrings was firmly stuck. This segment was about 3 inches long. One end of the segment was stuck to a tooth on the middle ring, and the other end of the segment was firmly stuck to a tooth on the small ring. This segment was under noticable tension. It took some prying to get it unstuck.
I was not pedalling hard when this happened. In fact, I have never really put a lot of torque on the pedals of this bike. It's nearly new and it hasn't seen much off-road use. It's been ridden rather mildly.

Has anyone ever seen this kind of condition, or know why it could be doing this?
I'm guessing that one or both chainrings could be out-of-spec, with excessively deep valleys between the teeth, or the teeth could be too tall. I don't see how else the chain could get trapped while straddling the two rings.

This is the second identical Rockhopper that has done this to me. I talked to a customer rep when the first bike acted this way and he said he knew of no ongoing problems with 2011 Rockhoppers.

The LBS was closed today and it is about an hour's drive away. Looks like I have no choice but to return this bike also.
__________________
more cops have been killed by donuts than guns in chicago it is a medical fact ask any doctor.
sknhgy is offline   Reply With Quote
Old 07-04-11, 05:36 PM   #2
lvolpe
Member
 
Join Date: Nov 2006
Location: Stamford, CT
Bikes:
Posts: 44
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Try this, it solved my problems with one of my kid's mountain bike.

http://www.gvtc.com/~ngear/whatis.html

Edit: On second thought, I think that you are speaking about something else and this would be no help to you.

Last edited by lvolpe; 07-04-11 at 05:40 PM.
lvolpe is offline   Reply With Quote
Old 07-04-11, 06:06 PM   #3
MudPie
Senior Member
 
MudPie's Avatar
 
Join Date: May 2004
Location: Southern California
Bikes:
Posts: 1,874
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
This may not qualify as true chainsuck, which occurs when the chain jams between the chainstay and chainring.

Your chain is doesn't seem to like the distance between two chainrings. Perhaps one of the chainrings is installed backwards, providing more space than designed. Or you might have a bent or hooked tooth which is not allowing the chain to disengage properly during the shift. Just guessing...
MudPie is offline   Reply With Quote
Old 07-05-11, 06:32 AM   #4
sknhgy 
Dirt Bomb
Thread Starter
 
sknhgy's Avatar
 
Join Date: Aug 2006
Location: Illinois
Bikes:
Posts: 2,658
Mentioned: 7 Post(s)
Tagged: 0 Thread(s)
Quoted: 374 Post(s)
bump
__________________
more cops have been killed by donuts than guns in chicago it is a medical fact ask any doctor.
sknhgy is offline   Reply With Quote
Old 07-05-11, 08:14 AM   #5
cyccommute 
Mad bike riding scientist
 
cyccommute's Avatar
 
Join Date: Nov 2004
Location: Denver, CO
Bikes: Some silver ones, a black one, a red one, an orange one and a couple of titanium ones
Posts: 18,295
Mentioned: 14 Post(s)
Tagged: 0 Thread(s)
Quoted: 409 Post(s)
Chain suck is almost always related to a bent or damaged tooth on the chainrings. And the damage can be quite small. Sometimes almost too small to see The chain hangs up on the tooth and won't release which is what happened to you.

Bent and damaged teeth aren't the manufacturers fault and are almost always related to operator error. A bad shift where you are grinding the rings or a shift made under too much tension can put a very small burr on the tooth. Look for scrape marks on the inside of the ring and then feel for protrusions. You can file them off and the chain suck should stop.

I suspect that you may need a cable adjustment too. It's been about a month and I'll bet you've had some balky shifting from the inner ring to the middle one. The kind where the chain just doesn't seem to want to go up to the middle ring. The chain just grinds against the ring and then finally jumps up. It may go the other way too, where the middle ring just doesn't want to let the chain move over and the chain is hovering on the edge of the middle ring. All this grinding can put a burr on the ring and lead to chain suck.
__________________
Stuart Black
New! Pokin' around the Poconos A cold ride around Lake Erie
New! Dinosaurs in Colorado A mountain bike guide to the Purgatory Canyon dinosaur trackway
Solo Without Pie. The search for pie in the Midwest.
Picking the Scablands. Washington and Oregon, 2005. Pie and spiders on the Columbia River!
Days of Wineless Roads. Bed and Breakfasting along the KATY
Twisting Down the Alley. Misadventures in tornado alley.
An Good Ol' Fashion Appalachian Butt Whoopin'.
cyccommute is offline   Reply With Quote
Old 07-05-11, 08:33 AM   #6
bobn
Senior Member
 
Join Date: Mar 2005
Location: South Florida
Bikes:
Posts: 726
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 1 Post(s)
You should have brought the bike back with the chain in the "stuck" condition so the LBS could see it for themselves.
bobn is offline   Reply With Quote
Old 07-05-11, 08:44 AM   #7
FBinNY 
Senior Member
 
Join Date: Apr 2009
Location: New Rochelle, NY
Bikes: too many bikes from 1967 10s (5x2)Frejus to a Sumitomo Ti/Chorus aluminum 10s (10x2), plus one non-susp mtn bike I use as my commuter
Posts: 30,837
Mentioned: 21 Post(s)
Tagged: 0 Thread(s)
Quoted: 862 Post(s)
As Cycocommute says it could be caused by a very slightly bent chainring, but there are other causes.

Given the age of your bike, and that it occurs only during the downshift, I suspect it's something else. You didn't say, but have you been riding in mud, wet or fine dust?

If so, I believe your suck is caused by internal friction within the chain, and is analogous to how fishing reel overruns the line when casting without enough reel tension.

Sorry the answer is long, but read it and you'll find the solution easy and cheap.

-----

All chains have a bit of internal friction, and wouldn't unwind from the bottom of the ring except for their weight and the tension provided by the RD. When you ride in mud with no lube, or dry lubes, water wicks into the spaces between the plates, carrying fine silt. Then it evaporates leaving the silt behind (think mud flats). Eventually this silt builds up enough to increase the friction between the plates making the chain stiffer.

With the added internal friction it takes greater tension in the lower loop to pull the chain off the rings. On the outer ring, the RD might provide it, but as you move to smaller rings, the RD tension is less, which is why suck is almost reported in inner chainrings.

The reason it's most likely to suck during the shift because as the section of chain in transition from the larger to smaller ring comes around and releases from the larger ring, there's extra slack generated and it takes a bit of time for the RD to take it up. With no tension to pull it off the ring, the chain stays wrapped around it - chainsuck.

Solution, remove and wash your chain thoroughly. If it doesn't have a master link, you can do it on the bike. Make sure to do a thorough job with multiple rinses until it rinses clean. Now dry it completely with a hair dryer or a solar oven (a car parked in the sun with one window cracked open 1"). Now lube your clean dry chain with a good wet lube that won't wash out. (Yes - I have a bias here, as evidenced by the site below my signature) Wet lube prevents chain suck by keeping the internal spaces within the chain filled so water can't wick in.

If you've read this far, I'll bet you 2 beers to 1 that you'll 100% solve the chainsuck problem if you follow the above wash/lube instructions to the letter. If you're near any Chain-L dealer, wash your chain, dry it and visit them for a free test of Chain-L (email me first so I can arrange it) and I'll bet 3 beers you'll never deal with this issue again.
__________________
FB
Chain-L site

An ounce of diagnosis is worth a pound of cure.

“Never argue with an idiot. He will only bring you down to his level and beat you with experience.”, George Carlin

“One accurate measurement is worth a thousand expert opinions” - Adm Grace Murray Hopper - USN

WARNING, I'm from New York. Thin skinned people should maintain safe distance.

Last edited by FBinNY; 07-05-11 at 08:50 AM.
FBinNY is online now   Reply With Quote
Old 07-05-11, 11:27 AM   #8
cyccommute 
Mad bike riding scientist
 
cyccommute's Avatar
 
Join Date: Nov 2004
Location: Denver, CO
Bikes: Some silver ones, a black one, a red one, an orange one and a couple of titanium ones
Posts: 18,295
Mentioned: 14 Post(s)
Tagged: 0 Thread(s)
Quoted: 409 Post(s)
Quote:
Originally Posted by FBinNY View Post
As Cycocommute says it could be caused by a very slightly bent chainring, but there are other causes.

Given the age of your bike, and that it occurs only during the downshift, I suspect it's something else. You didn't say, but have you been riding in mud, wet or fine dust?

If so, I believe your suck is caused by internal friction within the chain, and is analogous to how fishing reel overruns the line when casting without enough reel tension.

Sorry the answer is long, but read it and you'll find the solution easy and cheap.

-----

All chains have a bit of internal friction, and wouldn't unwind from the bottom of the ring except for their weight and the tension provided by the RD. When you ride in mud with no lube, or dry lubes, water wicks into the spaces between the plates, carrying fine silt. Then it evaporates leaving the silt behind (think mud flats). Eventually this silt builds up enough to increase the friction between the plates making the chain stiffer.

With the added internal friction it takes greater tension in the lower loop to pull the chain off the rings. On the outer ring, the RD might provide it, but as you move to smaller rings, the RD tension is less, which is why suck is almost reported in inner chainrings.

The reason it's most likely to suck during the shift because as the section of chain in transition from the larger to smaller ring comes around and releases from the larger ring, there's extra slack generated and it takes a bit of time for the RD to take it up. With no tension to pull it off the ring, the chain stays wrapped around it - chainsuck.

Solution, remove and wash your chain thoroughly. If it doesn't have a master link, you can do it on the bike. Make sure to do a thorough job with multiple rinses until it rinses clean. Now dry it completely with a hair dryer or a solar oven (a car parked in the sun with one window cracked open 1"). Now lube your clean dry chain with a good wet lube that won't wash out. (Yes - I have a bias here, as evidenced by the site below my signature) Wet lube prevents chain suck by keeping the internal spaces within the chain filled so water can't wick in.

If you've read this far, I'll bet you 2 beers to 1 that you'll 100% solve the chainsuck problem if you follow the above wash/lube instructions to the letter. If you're near any Chain-L dealer, wash your chain, dry it and visit them for a free test of Chain-L (email me first so I can arrange it) and I'll bet 3 beers you'll never deal with this issue again.
Sorry but you are way off base. Chain suck only happens on downshifts. Given that the chain is lifted off the inner gears during an upshift by the larger cog and that the chain is under tension, I can't see how you would have chain suck on an upshift even if the tooth were bent almost 90 degrees. The tooth would probably sheer off before it would grab the chain and hold it on the smaller cog. Plus you would have been experiencing chain suck on the downshifts long before the tooth could be sheered off anyway.

This is a bike that is a month old. I doubt that even in a month of hard riding in the mud, you could have the kinds of build up of debris on the chain that would cause the kind of internal frictions you are talking about. And the internal friction of the chain isn't going to be an issue with respect to the rear derailer either. The rear derailer spring on a month old bike should be able to deal with that kind of friction easily and pull the chain off. The kind of slack you are talking about generating in the chain is something that would be evident in a years old derailer, not a nearly new one.
__________________
Stuart Black
New! Pokin' around the Poconos A cold ride around Lake Erie
New! Dinosaurs in Colorado A mountain bike guide to the Purgatory Canyon dinosaur trackway
Solo Without Pie. The search for pie in the Midwest.
Picking the Scablands. Washington and Oregon, 2005. Pie and spiders on the Columbia River!
Days of Wineless Roads. Bed and Breakfasting along the KATY
Twisting Down the Alley. Misadventures in tornado alley.
An Good Ol' Fashion Appalachian Butt Whoopin'.
cyccommute is offline   Reply With Quote
Old 07-05-11, 11:50 AM   #9
FBinNY 
Senior Member
 
Join Date: Apr 2009
Location: New Rochelle, NY
Bikes: too many bikes from 1967 10s (5x2)Frejus to a Sumitomo Ti/Chorus aluminum 10s (10x2), plus one non-susp mtn bike I use as my commuter
Posts: 30,837
Mentioned: 21 Post(s)
Tagged: 0 Thread(s)
Quoted: 862 Post(s)
If you had read the post, you'd see that I said that the symptom was sucking wen shifting from large to small chainring, or downshifts.

Anyway, I've no interest in debating the theoretical, I'm not trying to convince you of anything. You have your theory & I have mine and readers are free to decide who to believe, or try both our suggestions seeing what works. As I repeat ad infinitum, the proof of the pudding is in the eating.

In any case my bet with the OP stands, My solution is free, and the most he can lose is the chainsuck and a beer. If I'm wrong he still has a problem, but the 2 beers might help it go down easier.
__________________
FB
Chain-L site

An ounce of diagnosis is worth a pound of cure.

“Never argue with an idiot. He will only bring you down to his level and beat you with experience.”, George Carlin

“One accurate measurement is worth a thousand expert opinions” - Adm Grace Murray Hopper - USN

WARNING, I'm from New York. Thin skinned people should maintain safe distance.
FBinNY is online now   Reply With Quote
Old 07-05-11, 12:31 PM   #10
sknhgy 
Dirt Bomb
Thread Starter
 
sknhgy's Avatar
 
Join Date: Aug 2006
Location: Illinois
Bikes:
Posts: 2,658
Mentioned: 7 Post(s)
Tagged: 0 Thread(s)
Quoted: 374 Post(s)
What I found was the section of chain that was bridging between the chainrings was firmly stuck. This segment was about 3 inches long. One end of the segment was stuck to a tooth on the middle ring, and the other end of the segment was firmly stuck to a tooth on the small ring. This segment was under noticable tension. It took some prying to get it unstuck.

^What would cause this?^ Shouldn't a power transmission system be designed to not let something like this happen? Makes me think that maybe the chainrings used on these bikes could be an issue.
__________________
more cops have been killed by donuts than guns in chicago it is a medical fact ask any doctor.
sknhgy is offline   Reply With Quote
Old 07-05-11, 12:47 PM   #11
FBinNY 
Senior Member
 
Join Date: Apr 2009
Location: New Rochelle, NY
Bikes: too many bikes from 1967 10s (5x2)Frejus to a Sumitomo Ti/Chorus aluminum 10s (10x2), plus one non-susp mtn bike I use as my commuter
Posts: 30,837
Mentioned: 21 Post(s)
Tagged: 0 Thread(s)
Quoted: 862 Post(s)
Quote:
Originally Posted by sknhgy View Post
What I found was the section of chain that was bridging between the chainrings was firmly stuck. This segment was about 3 inches long. One end of the segment was stuck to a tooth on the middle ring, and the other end of the segment was firmly stuck to a tooth on the small ring. This segment was under noticable tension. It took some prying to get it unstuck.

^What would cause this?^ Shouldn't a power transmission system be designed to not let something like this happen? Makes me think that maybe the chainrings used on these bikes could be an issue.
This is a different problem, not what people usually refer to as chainsuck,

When you shift under load, either the front or the rear, the chain can be forced down on the new chainring, before releasing from the older obe. This puts bigtime twisting forces on the chain an spreads the plates, which is why you have to use non-spliceable chains with any modern gated shifting system. This is one of the most common causes of chain breakage in mtb.

Most folks see this in the back, and don't notice other than maybe a loud crunching sound, because the upper loop is under tension and rips the jammed chain free. It happens less often on the front because it's harder to shift under load, but it can, and when it does the low tension on the lower loop can't pull it free.

The solution is very simple, Do not shift under heavy load, Plan ahead and shift the front while you're still running light pedal pressure, or can at least ease up for a well timed second through the shift.

BTW- I'd take a moment to run the chain through your fingers feeling, or looking for any twisted or spread links. If you see any replace the chain before it breaks.

As for designing the system so it can't happen, that's a trade off, the gated shifting (hyperglide) that makes this possible is also what makes for otherwise smoother faster shifting. Years ago, before hyperglide, this wasn't an issue, but shifting was much more sluggish, and totally impossible uder any kind of load. You win some, you lose some, but most who've seen both the old and the new agree the new is better.
__________________
FB
Chain-L site

An ounce of diagnosis is worth a pound of cure.

“Never argue with an idiot. He will only bring you down to his level and beat you with experience.”, George Carlin

“One accurate measurement is worth a thousand expert opinions” - Adm Grace Murray Hopper - USN

WARNING, I'm from New York. Thin skinned people should maintain safe distance.
FBinNY is online now   Reply With Quote
Old 07-05-11, 01:33 PM   #12
bobn
Senior Member
 
Join Date: Mar 2005
Location: South Florida
Bikes:
Posts: 726
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 1 Post(s)
This is my opinion and my opinion only. I'm not an expert, but this is what I would do.
I would NOT do any adjusting or mechanical work on this bike. You will give the LBS or manufacturer a way out. They could blame you. The bike (s) are to new to have this problem, both of them. No coincidence in my opinion. Two exact model bikes. Like I said before, bring it in with the chain jambed up so they can see first hand what the problem is. It's their responsibility to make it right.
Maybe they need to bring in a company rep. 2 bikes same shop. Strange.
It could be a bad run of chains. Stiff links etc.
Also, Google and check out the reviews on this bike. Seems like others have had this or a similar problem?

Last edited by bobn; 07-05-11 at 01:37 PM.
bobn is offline   Reply With Quote
Old 07-05-11, 01:49 PM   #13
cyccommute 
Mad bike riding scientist
 
cyccommute's Avatar
 
Join Date: Nov 2004
Location: Denver, CO
Bikes: Some silver ones, a black one, a red one, an orange one and a couple of titanium ones
Posts: 18,295
Mentioned: 14 Post(s)
Tagged: 0 Thread(s)
Quoted: 409 Post(s)
Quote:
Originally Posted by sknhgy View Post
What I found was the section of chain that was bridging between the chainrings was firmly stuck. This segment was about 3 inches long. One end of the segment was stuck to a tooth on the middle ring, and the other end of the segment was firmly stuck to a tooth on the small ring. This segment was under noticable tension. It took some prying to get it unstuck.

^What would cause this?^ Shouldn't a power transmission system be designed to not let something like this happen? Makes me think that maybe the chainrings used on these bikes could be an issue.
A twisted tooth - possibly 2 twisted teeth - is about the only way this could happen. The chain needs to release from the teeth smoothly for the chain to drop from one ring to the other. Your chain hung up on a badly twisted tooth as it was dropping and as it caught the little ring, it bound up between the rings, probably twisting and bending both rings in the process.

FBinNY is partially right - but only partially - about shifting under tension. I suspect that one of the rings was damaged when you upshifted earlier under a lot of torque - it happens. Because of the way that bicycle derailers work, it's easy to force an upshift and cause damage.

As you were downshifting, the chain released from the middle ring to the inner ring but caught on the damaged tooth. Putting tension on the chain like you are while riding up hill and trying to downshift, trapped the chain between the two rings, further bending both. Now your chain is stuck and can't go forward - i.e. release from the large ring - and can't go back - i.e. climb back up on the large ring. There's not enough tension in the rear derailer spring to pull the chain off the now bent teeth and you end up with a classic case of chain suck. Yours is just particularly extreme.

To avoid this, you should ease up on the pedal pressure slightly while you shift either up or down. It doesn't have to be much. Just enough so that things shift smoothly.

Quote:
Originally Posted by FBinNY View Post
If you had read the post, you'd see that I said that the symptom was sucking wen shifting from large to small chainring, or downshifts.

Anyway, I've no interest in debating the theoretical, I'm not trying to convince you of anything. You have your theory & I have mine and readers are free to decide who to believe, or try both our suggestions seeing what works. As I repeat ad infinitum, the proof of the pudding is in the eating.

In any case my bet with the OP stands, My solution is free, and the most he can lose is the chainsuck and a beer. If I'm wrong he still has a problem, but the 2 beers might help it go down easier.
Perhaps you should read your own posts:

Quote:
Given the age of your bike, and that it occurs only during the downshift, I suspect it's something else.
The age of the bike has nothing to do with it.

Quote:
Originally Posted by FBinNY View Post
This is a different problem, not what people usually refer to as chainsuck,

When you shift under load, either the front or the rear, the chain can be forced down on the new chainring, before releasing from the older obe. This puts bigtime twisting forces on the chain an spreads the plates, which is why you have to use non-spliceable chains with any modern gated shifting system. This is one of the most common causes of chain breakage in mtb.

Most folks see this in the back, and don't notice other than maybe a loud crunching sound, because the upper loop is under tension and rips the jammed chain free. It happens less often on the front because it's harder to shift under load, but it can, and when it does the low tension on the lower loop can't pull it free.

The solution is very simple, Do not shift under heavy load, Plan ahead and shift the front while you're still running light pedal pressure, or can at least ease up for a well timed second through the shift.

BTW- I'd take a moment to run the chain through your fingers feeling, or looking for any twisted or spread links. If you see any replace the chain before it breaks.

As for designing the system so it can't happen, that's a trade off, the gated shifting (hyperglide) that makes this possible is also what makes for otherwise smoother faster shifting. Years ago, before hyperglide, this wasn't an issue, but shifting was much more sluggish, and totally impossible uder any kind of load. You win some, you lose some, but most who've seen both the old and the new agree the new is better.
This is absolutely chain suck. The chain sticks to the rings and is sucked into the gap between the bike frame and the chainwheels. It's not caused by the chain but by damaged teeth on the crankset that won't release the chain. if sknhgy inspects the crank where the problem occurred, he'll find bent teeth on both rings. Given that he managed to stick the chain to both inner and middle rings, I suspect that he'll find bent rings too.

You are correct about it be an issue caused by shifting under tension but you are just wrong about the specifics.
__________________
Stuart Black
New! Pokin' around the Poconos A cold ride around Lake Erie
New! Dinosaurs in Colorado A mountain bike guide to the Purgatory Canyon dinosaur trackway
Solo Without Pie. The search for pie in the Midwest.
Picking the Scablands. Washington and Oregon, 2005. Pie and spiders on the Columbia River!
Days of Wineless Roads. Bed and Breakfasting along the KATY
Twisting Down the Alley. Misadventures in tornado alley.
An Good Ol' Fashion Appalachian Butt Whoopin'.
cyccommute is offline   Reply With Quote
Old 07-05-11, 02:19 PM   #14
bobn
Senior Member
 
Join Date: Mar 2005
Location: South Florida
Bikes:
Posts: 726
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 1 Post(s)
Dumb question.
What kind of steel are these parts made of to be able to be bent and twisted under load?
I take it this is not a big box store bike, this should not happen to a quality bike.
bobn is offline   Reply With Quote
Old 07-05-11, 03:07 PM   #15
cyccommute 
Mad bike riding scientist
 
cyccommute's Avatar
 
Join Date: Nov 2004
Location: Denver, CO
Bikes: Some silver ones, a black one, a red one, an orange one and a couple of titanium ones
Posts: 18,295
Mentioned: 14 Post(s)
Tagged: 0 Thread(s)
Quoted: 409 Post(s)
Quote:
Originally Posted by bobn View Post
Dumb question.
What kind of steel are these parts made of to be able to be bent and twisted under load?
I take it this is not a big box store bike, this should not happen to a quality bike.
The parts could be steel or aluminum, depending on the component level. But the tolerances on either are pretty small. I've had chains suck on to burrs that are difficult to see. I've also folded tandem chainwheels in half because of botched shift.

In sknhgy's case, I suspect that the chainwheels may have bent because of the chain being jammed on a chainring tooth. It takes less than you'd imagine to do it. The force of the rider's weight is focused on a very tiny spot. Small area + large load = lots of local force.
__________________
Stuart Black
New! Pokin' around the Poconos A cold ride around Lake Erie
New! Dinosaurs in Colorado A mountain bike guide to the Purgatory Canyon dinosaur trackway
Solo Without Pie. The search for pie in the Midwest.
Picking the Scablands. Washington and Oregon, 2005. Pie and spiders on the Columbia River!
Days of Wineless Roads. Bed and Breakfasting along the KATY
Twisting Down the Alley. Misadventures in tornado alley.
An Good Ol' Fashion Appalachian Butt Whoopin'.
cyccommute is offline   Reply With Quote
Old 07-05-11, 03:45 PM   #16
bobn
Senior Member
 
Join Date: Mar 2005
Location: South Florida
Bikes:
Posts: 726
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 1 Post(s)
Believe me, I'm not trying to be argumentative because my experience with deraileuers is nil.
Why doesn't stuff like this happen to Lance Armstrong. These guys must beat the ***** out of their equipment?
This is not a cheap department store bike. I just have a hard time understanding and having to accept the fact that this equipment can fail under everyday situations.
It's like saying I just bought a new car, stepped on the gas to hard and the transmission fell out. Not once, but twice.
bobn is offline   Reply With Quote
Old 07-05-11, 05:06 PM   #17
sknhgy 
Dirt Bomb
Thread Starter
 
sknhgy's Avatar
 
Join Date: Aug 2006
Location: Illinois
Bikes:
Posts: 2,658
Mentioned: 7 Post(s)
Tagged: 0 Thread(s)
Quoted: 374 Post(s)
I've never had a problem like this on any other bike.
__________________
more cops have been killed by donuts than guns in chicago it is a medical fact ask any doctor.
sknhgy is offline   Reply With Quote
Old 07-05-11, 05:34 PM   #18
cyccommute 
Mad bike riding scientist
 
cyccommute's Avatar
 
Join Date: Nov 2004
Location: Denver, CO
Bikes: Some silver ones, a black one, a red one, an orange one and a couple of titanium ones
Posts: 18,295
Mentioned: 14 Post(s)
Tagged: 0 Thread(s)
Quoted: 409 Post(s)
Quote:
Originally Posted by bobn View Post
Believe me, I'm not trying to be argumentative because my experience with deraileuers is nil.
Why doesn't stuff like this happen to Lance Armstrong. These guys must beat the ***** out of their equipment?
This is not a cheap department store bike. I just have a hard time understanding and having to accept the fact that this equipment can fail under everyday situations.
It's like saying I just bought a new car, stepped on the gas to hard and the transmission fell out. Not once, but twice.
It doesn't happen to the pros because they have a factory and a bunch of mechanics backing them up. Their bikes probably never see enough wear and tear to on the components to have much damage occur. They are also all very skilled riders and know how to shift so as to not damage the equipment.

To use your car analogy, some riders - not saying you, sknhgy - drive like they got a new car, threw the shift lever from 5th at 80 mph into reverse and then wonder why their transmission is laying on the ground behind them. Then turn around and blame the manufacturer for not designing the car to go from 5th to reverse at 80 mph.

Quote:
Originally Posted by sknhgy View Post
I've never had a problem like this on any other bike.
It happens. Like I said before, you'd be amazed at how small a burr on a chain ring has to be to catch on a gear tooth. Getting the chain sucked across two rings and stuck on two different teeth is a bit rare...I haven't heard of it happening...but I can see how it could happen. And I can envision the damage to the chainrings.

Digging a bit further, the Rockhopper comes with an Alivio 8 speed crank but a 9 speed cassette. While there shouldn't be a problem with that combination, the 8 speed's teeth may be wider. That would make any burr problem worse. Talk to the shop and see if you can swap the crank or get 9 speed chainwheels. Work a deal with them but be reasonable. Since you've had this issue with another crank, it may be part operator and part equipment. See if they'll go halvsies on a new chain ring set.
__________________
Stuart Black
New! Pokin' around the Poconos A cold ride around Lake Erie
New! Dinosaurs in Colorado A mountain bike guide to the Purgatory Canyon dinosaur trackway
Solo Without Pie. The search for pie in the Midwest.
Picking the Scablands. Washington and Oregon, 2005. Pie and spiders on the Columbia River!
Days of Wineless Roads. Bed and Breakfasting along the KATY
Twisting Down the Alley. Misadventures in tornado alley.
An Good Ol' Fashion Appalachian Butt Whoopin'.
cyccommute is offline   Reply With Quote
Old 07-05-11, 10:20 PM   #19
urbanknight
In beaurocratic limbo
 
urbanknight's Avatar
 
Join Date: Mar 2006
Location: Los Angeles, CA
Bikes: Specialized Allez, K2 Razorback
Posts: 22,456
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Quote:
Originally Posted by bobn View Post
Believe me, I'm not trying to be argumentative because my experience with deraileuers is nil.
Why doesn't stuff like this happen to Lance Armstrong. These guys must beat the ***** out of their equipment?
Stuff like this DOES happen to the pros. Andy Schleck's chain got jammed in last year's Tour de France... during a crucial moment, I might add. Lance had a pedal fail on him while climbing the alps. It happens less often to them because their equipment is replaced more often, but it does happen.
__________________
"Well, I guess you can cut the arts as much as you want... Sooner or later, these kids aren't going to have anything to read or write about." (Richard Dreyfus as Glenn Holland)
urbanknight is offline   Reply With Quote
Old 07-08-11, 10:49 AM   #20
sknhgy 
Dirt Bomb
Thread Starter
 
sknhgy's Avatar
 
Join Date: Aug 2006
Location: Illinois
Bikes:
Posts: 2,658
Mentioned: 7 Post(s)
Tagged: 0 Thread(s)
Quoted: 374 Post(s)
Quote:
Originally Posted by FBinNY View Post
As Cycocommute says it could be caused by a very slightly bent chainring, but there are other causes.

Given the age of your bike, and that it occurs only during the downshift, I suspect it's something else. You didn't say, but have you been riding in mud, wet or fine dust?

If so, I believe your suck is caused by internal friction within the chain, and is analogous to how fishing reel overruns the line when casting without enough reel tension.

Sorry the answer is long, but read it and you'll find the solution easy and cheap.

-----

All chains have a bit of internal friction, and wouldn't unwind from the bottom of the ring except for their weight and the tension provided by the RD. When you ride in mud with no lube, or dry lubes, water wicks into the spaces between the plates, carrying fine silt. Then it evaporates leaving the silt behind (think mud flats). Eventually this silt builds up enough to increase the friction between the plates making the chain stiffer.

With the added internal friction it takes greater tension in the lower loop to pull the chain off the rings. On the outer ring, the RD might provide it, but as you move to smaller rings, the RD tension is less, which is why suck is almost reported in inner chainrings.

The reason it's most likely to suck during the shift because as the section of chain in transition from the larger to smaller ring comes around and releases from the larger ring, there's extra slack generated and it takes a bit of time for the RD to take it up. With no tension to pull it off the ring, the chain stays wrapped around it - chainsuck.

Solution, remove and wash your chain thoroughly. If it doesn't have a master link, you can do it on the bike. Make sure to do a thorough job with multiple rinses until it rinses clean. Now dry it completely with a hair dryer or a solar oven (a car parked in the sun with one window cracked open 1"). Now lube your clean dry chain with a good wet lube that won't wash out. (Yes - I have a bias here, as evidenced by the site below my signature) Wet lube prevents chain suck by keeping the internal spaces within the chain filled so water can't wick in.

If you've read this far, I'll bet you 2 beers to 1 that you'll 100% solve the chainsuck problem if you follow the above wash/lube instructions to the letter. If you're near any Chain-L dealer, wash your chain, dry it and visit them for a free test of Chain-L (email me first so I can arrange it) and I'll bet 3 beers you'll never deal with this issue again.
OK. The problem got worse after I lubed the chain with a dry wax lube, then spent a couple of days on the local gravel-screening covered trail. After reading all the posts I brushed the chain then lubed it with Break free. That helped, but didn't clear it up completely.
I removed the chain and soaked and swished it in a jar of mineral spirits. Then dried it. Then I soaked and swished it in a jar of laquer thinner, then hung it in the sun to dry while I went for a ride.
Then I soaked and swished it in a jar of 30W/mineral spirits mix. It is hanging now. I will put it back on the bike and take it for a ride in a day or so. Kind of busy right now. Will report back then.

Before I did all this cleaning, and after I lubed it with Break free, I did get the chain to jam up one time and I was going to take it to the LBS in that condition, but when I touched it to feel for tension the chain came free from the chainrings.
__________________
more cops have been killed by donuts than guns in chicago it is a medical fact ask any doctor.
sknhgy is offline   Reply With Quote
Old 07-28-11, 04:23 PM   #21
sknhgy 
Dirt Bomb
Thread Starter
 
sknhgy's Avatar
 
Join Date: Aug 2006
Location: Illinois
Bikes:
Posts: 2,658
Mentioned: 7 Post(s)
Tagged: 0 Thread(s)
Quoted: 374 Post(s)
It happened again - and it has happened a few times since the last post. The chain stuck like this so I walked the bike home, loaded it up, and took it to the LBS. I said enough is enough. Here's what it looks like when it happens:

I am waiting to hear back from the shop owner. He is going to contact the Specialized customer rep. I just can't understand this. I've never had a bike do this before. I currently own 2 other, much cheaper mountain bikes and both of them work flawlessly. I hate it when you spend a lot of cash to get something better but you end up with more problems.
Thanks for letting me rant.
Attached Images
File Type: jpg 001.jpg (106.7 KB, 95 views)
__________________
more cops have been killed by donuts than guns in chicago it is a medical fact ask any doctor.
sknhgy is offline   Reply With Quote
Old 07-28-11, 05:09 PM   #22
Steve530
Senior Member
 
Join Date: Jul 2008
Location: Knoxville, TN
Bikes: Klein
Posts: 911
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Yea, that's bad.
Steve530 is offline   Reply With Quote
Old 07-28-11, 10:27 PM   #23
meaculpa
meaculpa
 
Join Date: Aug 2006
Location: Pittsburgh, PA
Bikes: 07 Bianchi Volpe
Posts: 230
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
I've had this happen 3-4 times in the last 5-6 months, is this typical "chainsuck" or some severe form of the disease?
meaculpa is offline   Reply With Quote
Old 07-29-11, 07:45 AM   #24
bobn
Senior Member
 
Join Date: Mar 2005
Location: South Florida
Bikes:
Posts: 726
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 1 Post(s)
Let us know what the LBS and rep has to say.
bobn is offline   Reply With Quote
Old 08-01-11, 07:31 PM   #25
sknhgy 
Dirt Bomb
Thread Starter
 
sknhgy's Avatar
 
Join Date: Aug 2006
Location: Illinois
Bikes:
Posts: 2,658
Mentioned: 7 Post(s)
Tagged: 0 Thread(s)
Quoted: 374 Post(s)
They are putting a new crankset on it. That makes sense to me. What else can it be but bad chainrings?
__________________
more cops have been killed by donuts than guns in chicago it is a medical fact ask any doctor.
sknhgy is offline   Reply With Quote
Reply


Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off



All times are GMT -6. The time now is 10:50 PM.