Riddle For Mechanics: Triathlon Forum: Slowtwitch Forums

Riddle For Mechanics

Nov 20, 04 13:30

problem: bike shifts through all gears fine on the rack, with no load. after suiting up for cold weather ride and negotiating the time slot with the family, i clip in, and all is not well. as soon as i put pressure on downstroke "CHUNK, CHUNK". seems to try and creep over to another cog for a couple teeth and then fall back in.

consider events: campy record 10 speed with 3,100 miles. still very clean and well lubed for the two seasons i have used it. i put new cables and housing on last week. as soon as i went out for a ride with the new cables, within the first mile, i stand up for a sprint to make a green light. i'm not a huge legged sprinter, so it wasn't extraordinary output, but a link broke on my chain. the reason i knew it happened, is because the broken link got caught in the rear-der. and my stroke stopped with extreme abruptness and likely put a big strain on it. i walked home, and since then, put a new C10 chain on.

there are no stiff links. the cables seem to be real buttery. the problem does not occur with any regularity from cadence or wheel rotations. the problem occurs in the middle 6 cogs. it only happens when material pressure gets applied. the cogs look fine. i can't tell if the rear-der. is bent, but i don't have another to compare it to. it happens from pressure, maybe 100-120 watts is when it starts. i adjusted the rear-der. in-and-out a bit, it is not a 'out-of-tune' problem.

would a broken link getting caught during a sprint effort ruin the rear-der. with no visible damage?

please... help me get rolling again. thanks in advance.

It's not easy to juggle a pregnant wife and a troubled child, but somehow I managed to squeeze in 8 hours of TV a day - Homer Simpson

Last edited by: TheMonkey: Nov 20, 04 13:35

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Re: Riddle For Mechanics [TheMonkey] [ In reply to ]

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Tom Demerly

Nov 20, 04 14:11

Post #2 of 12 (1791 views)

Hmmm. Initiate trouble shooting protocol:

1. Is rear wheel in straight?

2. Is quick release skewer tight?

2.5 Is the cogset on tight?

3. Are crank bolts and (especially on Campagnolo) are chainring bolts tight?

4. Is cable unobstructed from shift lever to derailleur?

5. Is cogset, or one specific cog that gets a lot of use, worn?

6. Is chain worn?

7. Is there a build-up of wax based lubricant?

Those are the first things I would look at.

Tom Demerly
The Tri Shop.com

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Re: Riddle For Mechanics [TheMonkey] [ In reply to ]

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just jack

Nov 20, 04 17:00

Post #3 of 12 (1736 views)

you might pull the cables from the housing and flush with solvent. if there is grease in the housing, cold temps might be thickening it.

re: damaged rear der. a bad link could twist it just enough to cause alignment problems. but you would expect shifting quality to deteriorate the most at the extreme ends of the cassette (ie the largest or smallest cogs, not in the middles).

*****
"In case of flood climb to safety"

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Re: Riddle For Mechanics [Tom Demerly] [ In reply to ]

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TheMonkey

Nov 21, 04 12:36

Post #4 of 12 (1682 views)

thanks for tip sheet.

frustration grows....

i have checked that all bolts are tight.. skewer, etc... i unclamped the cable, and it slides easily back and forth from shifter to back of bike.

i stopped by lbs today. the mechanic is 'certain' that the cogset wore down with the old chain and that the new chain was not stretched, so hence, the problem. he ordered a new record 10 speed cassette ($240), but i don't think that is going to fix it. i think it is going to be an expensive experiment.

so, the new question is this: the old chain that broke had 3,100 miles on it. i kept it super clean and always lubed. when i got back from lbs today, i measured for stretch on the old chain via the sheldon brown method (measure one foot of chain - 1/16 inch stretch is time to change, and 1/8 inch of stretch means you waited too long and the cogs are goners too). my old chain is less than 1/32 inch stretched, and the cogset is not visibly worn. chainrings still look new too.

is it possible that a chain with such light stretch creates a meshing problem between new chain and old cassette?

anyone want to bet that he is wrong and the new cassette will not work? at least bet me the premium i paid to the lbs for the cassette...

It's not easy to juggle a pregnant wife and a troubled child, but somehow I managed to squeeze in 8 hours of TV a day - Homer Simpson

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Re: Riddle For Mechanics [TheMonkey] [ In reply to ]

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jsivvy

Nov 21, 04 13:08

Post #5 of 12 (1661 views)

You definitely could have a worn cogset at 3000 miles. I have often replaced cassettes at about that time on the roadbike. I have 5000 miles on one right now and it is completely done.

However, I don't see why you should have to pay for the cassette if it turns out to not be the problem. The shops I have worked in wouldn't have charged a customer for something if it wasn't going to solve the problem. I don't see why you should foot the bill if the mechanic is incompetent.

Let us know how it works out.

_____________________________________________________
"Oh man, it's going to take days to kill all these people!" - Jens Voigt

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Re: Riddle For Mechanics [TheMonkey] [ In reply to ]

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GregX

Nov 21, 04 16:18

Post #6 of 12 (1635 views)

Thin little 10-speed cogs can wear very fast. And a worn cogset is most likely your problem. 2nd thing to check: does the derailleur keep the chain under decent spring tension (via the pivot spring and pulley spring)?

Symptoms of worn cogset: the chain will only skip on the worn cogs (usually the smaller ones, or the ones you spend the most time on when you are pushing hard on the gears). Symptoms of a chain tension problem: a saggy chain, a lot of chainstay/chain slap and bounce when you go over even smallish bumps, and/or chain skip under load when on the smaller cogs (bigger cogs tend to hold chains better even when tension is poor).

Hope that helps...

Where would you want to swim ?

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Re: Riddle For Mechanics [TheMonkey] [ In reply to ]

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sharad

Nov 21, 04 17:07

Post #7 of 12 (1606 views)

Your mechanic got it right. More then likely, that is the cause. New chain, new cassette. Almost always fixes the problem.

Other thing to check is that you didn't simply have a stiff link. That also tends to make the chain jump cogs and want to misshift.

Steve

www.aero-concepts.com

www.buytrigear.com

http://www.infinitepool.com

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Re: Riddle For Mechanics [sharad] [ In reply to ]

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TheMonkey

Nov 21, 04 17:25

Post #8 of 12 (1594 views)

i hope he got it right too... i checked for a stiff link. the problem occurs the moment pressure is applied, not randomly.

i have replaced several cassettes before on shimano setups from similar symptoms, but every time there was visible wear. perhaps the 10 speed ti/steel wears without much visibility. the chain had very little stretch, so does it wear side to side? maybe my alignment from chainring to cassette is not straight enough. it's a custom steel, that's possible i suppose.

i'll know on wed when i put on the new cassette.

maybe i'm just whining because of the price of a record cassette.

if this fixes the problem, perhaps the lesson i learned is to change the chain based on mileage rather than stretch? 2k miles for chain swap?

It's not easy to juggle a pregnant wife and a troubled child, but somehow I managed to squeeze in 8 hours of TV a day - Homer Simpson

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Re: Riddle For Mechanics [TheMonkey] [ In reply to ]

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Wants2rideFast

Nov 21, 04 17:29

Post #9 of 12 (1592 views)

TheMonkey,

Use a Chorus or Daytona cassette for greater life and especially for training miles. Steel doesn't wear near as fast as titanium does. Unless you have lots of cash to just throw at your bike and enjoy doing so.

Ben Cline

Better to aspire to Greatness and fail, than to not challenge one's self at all, and succeed.

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Re: Riddle For Mechanics [jsivvy] [ In reply to ]

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TheMonkey

Nov 24, 04 13:22

Post #10 of 12 (1526 views)

shazam.

the cassette arrived today and it fixed the problem. i'm amazed. not amazed because a cassette wore out in 3k, but amazed because even holding the old cassette vs the new, the visible wear is so subtle.

i can't even use the old cassette for a paper weight because it is too light.

so, how do i get more mileage out of this cassette? swap chain at 1,500's?

thanks.

It's not easy to juggle a pregnant wife and a troubled child, but somehow I managed to squeeze in 8 hours of TV a day - Homer Simpson

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Re: Riddle For Mechanics [Wants2rideFast] [ In reply to ]

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TheMonkey

Nov 24, 04 13:29

Post #11 of 12 (1518 views)

i think you are right. when i used shimano, i used the da cranks and deraileurs, but ultegra bb and cassette. if i actually believed that the previous record cassette actually wore out, i would have gotten the chorus, but i thought it was just going to be a failed test.

spending that $ on any cassette was like having to get a new water heater or something. it's necessary, but when i thought that i already had a good cassette, i really don't feel like i gained much.

It's not easy to juggle a pregnant wife and a troubled child, but somehow I managed to squeeze in 8 hours of TV a day - Homer Simpson

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Re: Riddle For Mechanics [TheMonkey] [ In reply to ]

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jsivvy

Nov 24, 04 15:56

Post #12 of 12 (1458 views)

As someone else said, use an all-steel cassette like Centaur. It's significantly less expensive and wears much longer. Swapping chains often will help....I'm just too lazy to do that.

Happy to hear the problem was solved.

_____________________________________________________
"Oh man, it's going to take days to kill all these people!" - Jens Voigt

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