I fixed my problem...but did I damage my bike?
08-27-05, 07:44 PM
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I fixed my problem...but did I damage my bike?
I had a problem about a month after getting my new bike. I couldn't shift to the smallest and second smallest gears without the chain rubbing up against the front derailleur cage.
My LBS solution was to not use those gears because he said not all gear combinations can be used even though they're available.
Not satisfied with his response, I did some research on the net on how to adjust the front derailleur.
So what I did was I loosened both screws on top of the front derailleur until the chain was not rubbing up anymore against the front derailleur guard anymore for those small gears.
Then I tightened both screws one full turn and gave it another test run. I continued to do this until the chain started rubbing again. Then I loosened the screws 1/4 turn and gave it another test run. I repeated the 1/4 turns on both screws until the chain stopped rubbing.
My question is this. Did I fix my bike correctly? Or did I do something terribly wrong but still managed to correct my original problem.
My LBS solution was to not use those gears because he said not all gear combinations can be used even though they're available.
Not satisfied with his response, I did some research on the net on how to adjust the front derailleur.
So what I did was I loosened both screws on top of the front derailleur until the chain was not rubbing up anymore against the front derailleur guard anymore for those small gears.
Then I tightened both screws one full turn and gave it another test run. I continued to do this until the chain started rubbing again. Then I loosened the screws 1/4 turn and gave it another test run. I repeated the 1/4 turns on both screws until the chain stopped rubbing.
My question is this. Did I fix my bike correctly? Or did I do something terribly wrong but still managed to correct my original problem.
08-27-05, 09:18 PM
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Hi Fretman -
Sounds like your adjustments came out all right -- if you're satisfied with the way the gears shift now, and the chain never falls off the front chainrings, then declare victory and leave the set screws where they are. Once the set screws are adjusted the way you want them, you'll rarely need to touch them again. The derailleur cables (both front and rear) will stretch over time and affect your shifting, but you can compensate for that using the barrel adjusters near the end of the cables -- not by messing with the set screws.
Just wanted to clarify what the LBS told you, though. There are gear combinations that were never designed to work: when the chain is on the smallest front chainring (which gives low gear ratios), you shouldn't use a very small rear cog (high gear ratio.) Same for largest chainring (high gear ratio) and a large cog (low gear ratio). Even if they don't happen to rub the front derailleur cage, these combinations put a lot of sideways tension on the chain and on the gear teeth, and wear the parts out sooner.
If you examine the chain from above in one of these "bad" gear combos, you can see that it's canted diagonally, rather than running parallel to the plane of the bike. And you're not losing anything by giving up these extreme combinations; they duplicate gear ratios you could achieve by using the middle chainring (assuming you've got a triple) and shifting two or three cogs toward the middle on the rear.
Now, if the problem was that you could NEVER get the chain to run smoothly on the smallest two cogs -- regardless of which chainring you were on -- then it definitely needed fixing. In particular, when you're on the largest chainring, the smallest rear cogs should run very smoothly. That's why the small cogs are there in the first place.
If the LBS folks seemed to tell you it's normal for certain cogs never to run smoothly, then they may have misunderstood the problem, and thought you were talking about small front/small rear combinations. If they really meant that you shouldn't expect the small cogs to work, even in combination with the large chainring -- or if the reason they misunderstood was that they weren't listening to you -- then you may need a new LBS. I'd give them the benefit of the doubt, unless this is part of a pattern of suspect advice.
Sounds like your adjustments came out all right -- if you're satisfied with the way the gears shift now, and the chain never falls off the front chainrings, then declare victory and leave the set screws where they are. Once the set screws are adjusted the way you want them, you'll rarely need to touch them again. The derailleur cables (both front and rear) will stretch over time and affect your shifting, but you can compensate for that using the barrel adjusters near the end of the cables -- not by messing with the set screws.
Just wanted to clarify what the LBS told you, though. There are gear combinations that were never designed to work: when the chain is on the smallest front chainring (which gives low gear ratios), you shouldn't use a very small rear cog (high gear ratio.) Same for largest chainring (high gear ratio) and a large cog (low gear ratio). Even if they don't happen to rub the front derailleur cage, these combinations put a lot of sideways tension on the chain and on the gear teeth, and wear the parts out sooner.
If you examine the chain from above in one of these "bad" gear combos, you can see that it's canted diagonally, rather than running parallel to the plane of the bike. And you're not losing anything by giving up these extreme combinations; they duplicate gear ratios you could achieve by using the middle chainring (assuming you've got a triple) and shifting two or three cogs toward the middle on the rear.
Now, if the problem was that you could NEVER get the chain to run smoothly on the smallest two cogs -- regardless of which chainring you were on -- then it definitely needed fixing. In particular, when you're on the largest chainring, the smallest rear cogs should run very smoothly. That's why the small cogs are there in the first place.
If the LBS folks seemed to tell you it's normal for certain cogs never to run smoothly, then they may have misunderstood the problem, and thought you were talking about small front/small rear combinations. If they really meant that you shouldn't expect the small cogs to work, even in combination with the large chainring -- or if the reason they misunderstood was that they weren't listening to you -- then you may need a new LBS. I'd give them the benefit of the doubt, unless this is part of a pattern of suspect advice.
08-28-05, 04:56 AM
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Originally Posted by Paul Graham
Hi Fretman -
Sounds like your adjustments came out all right -- if you're satisfied with the way the gears shift now, and the chain never falls off the front chainrings, then declare victory and leave the set screws where they are. Once the set screws are adjusted the way you want them, you'll rarely need to touch them again. The derailleur cables (both front and rear) will stretch over time and affect your shifting, but you can compensate for that using the barrel adjusters near the end of the cables -- not by messing with the set screws.
Just wanted to clarify what the LBS told you, though. There are gear combinations that were never designed to work: when the chain is on the smallest front chainring (which gives low gear ratios), you shouldn't use a very small rear cog (high gear ratio.) Same for largest chainring (high gear ratio) and a large cog (low gear ratio). Even if they don't happen to rub the front derailleur cage, these combinations put a lot of sideways tension on the chain and on the gear teeth, and wear the parts out sooner.
If you examine the chain from above in one of these "bad" gear combos, you can see that it's canted diagonally, rather than running parallel to the plane of the bike. And you're not losing anything by giving up these extreme combinations; they duplicate gear ratios you could achieve by using the middle chainring (assuming you've got a triple) and shifting two or three cogs toward the middle on the rear.
Now, if the problem was that you could NEVER get the chain to run smoothly on the smallest two cogs -- regardless of which chainring you were on -- then it definitely needed fixing. In particular, when you're on the largest chainring, the smallest rear cogs should run very smoothly. That's why the small cogs are there in the first place.
If the LBS folks seemed to tell you it's normal for certain cogs never to run smoothly, then they may have misunderstood the problem, and thought you were talking about small front/small rear combinations. If they really meant that you shouldn't expect the small cogs to work, even in combination with the large chainring -- or if the reason they misunderstood was that they weren't listening to you -- then you may need a new LBS. I'd give them the benefit of the doubt, unless this is part of a pattern of suspect advice.
Sounds like your adjustments came out all right -- if you're satisfied with the way the gears shift now, and the chain never falls off the front chainrings, then declare victory and leave the set screws where they are. Once the set screws are adjusted the way you want them, you'll rarely need to touch them again. The derailleur cables (both front and rear) will stretch over time and affect your shifting, but you can compensate for that using the barrel adjusters near the end of the cables -- not by messing with the set screws.
Just wanted to clarify what the LBS told you, though. There are gear combinations that were never designed to work: when the chain is on the smallest front chainring (which gives low gear ratios), you shouldn't use a very small rear cog (high gear ratio.) Same for largest chainring (high gear ratio) and a large cog (low gear ratio). Even if they don't happen to rub the front derailleur cage, these combinations put a lot of sideways tension on the chain and on the gear teeth, and wear the parts out sooner.
If you examine the chain from above in one of these "bad" gear combos, you can see that it's canted diagonally, rather than running parallel to the plane of the bike. And you're not losing anything by giving up these extreme combinations; they duplicate gear ratios you could achieve by using the middle chainring (assuming you've got a triple) and shifting two or three cogs toward the middle on the rear.
Now, if the problem was that you could NEVER get the chain to run smoothly on the smallest two cogs -- regardless of which chainring you were on -- then it definitely needed fixing. In particular, when you're on the largest chainring, the smallest rear cogs should run very smoothly. That's why the small cogs are there in the first place.
If the LBS folks seemed to tell you it's normal for certain cogs never to run smoothly, then they may have misunderstood the problem, and thought you were talking about small front/small rear combinations. If they really meant that you shouldn't expect the small cogs to work, even in combination with the large chainring -- or if the reason they misunderstood was that they weren't listening to you -- then you may need a new LBS. I'd give them the benefit of the doubt, unless this is part of a pattern of suspect advice.
08-28-05, 01:43 PM
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You thought right. Glad you got it working now.
If you notice the problem again, try changing the cable tension with the barrel adjustor before you mess with the set screws again...since the problem started a month after you got a new bike, it could well be that the cable had stretched and you just needed to increase its tension. Then again, maybe the set screws had never been adjusted right, and you did exactly what was needed.
If you notice the problem again, try changing the cable tension with the barrel adjustor before you mess with the set screws again...since the problem started a month after you got a new bike, it could well be that the cable had stretched and you just needed to increase its tension. Then again, maybe the set screws had never been adjusted right, and you did exactly what was needed.
Last edited by Paul Graham; 08-28-05 at 01:50 PM.
