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Gear slipping/Cog teeth slipping

Old 06-05-13, 02:41 PM
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jonny818
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Gear slipping/Cog teeth slipping

I really don't know how to define my question, though I can describe it very well. Alright so on the smallest Cog on my chain ring, whenever I pedal too hard,you can hear and feel that the chain has skipped some teeth on the cog. I shifted down to another crank and the problem persisted. The problem has nothing to do with the shifting at all, as sometimes I can be riding on that gear long enough and when I apply a bit more pressure I can feel it skip various teeth. The chain is quite small for some of the larger gears combined with the larger crank but it fits sort of okay with the small cog and large chain ring. I do believe that the chain is too blame for this, I've looked for a dead link on the chain but I haven't found any. The teeth on this cog appear to be in good condition. The bike had spacers in between the frame hook and the axle of the rim. I took the spacers off because the problem was horrible and this pushed the rim farther away, which actually relieved the skipping. Before I removed the spacers, the bike would skip quite easily, though now it takes quite a bit of pressure. I'll take a picture later on of the rear derailleur and the cogs with the chain in place.
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Old 06-05-13, 02:47 PM
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Start here and learn the proper names for the parts. https://www.parktool.com/blog/repair-help
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Old 06-05-13, 02:59 PM
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Removing that spacer changed the distance between where the rear deraillueur (RD) attachment to the frame and the cogs.

The rear derailleur's high-limit screw may be screwed in too far (or perhaps not far enough), which limits how far away from the bike the RD can physically go. There are two screws next to the each other, one should be labeled H (High).

While in the last gear (smallest rear cog) look from behind and see if the RD's upper pulley (little plastic gear) lines up with the cog. If not, try this:
- If you need to move the RD to the right, unscrew (left) the High-limit (H) screw.
- If you need to move the RD to the left, screw in (right) the F screw.

By the way, make small adjustments, like 1/4 turn at a time. Tip: this screw is easier to turn when the bike's not in the last gear, so: either downshift once or pull a bit of exposed cable, make the adjustment, then check.

I suggest detaching the cable and re-setting up the RD, including the H screw, cable tension/length, and L (Low) limit screw: https://www.parktool.com/blog/repair-...nts-derailleur
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Old 06-05-13, 04:03 PM
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Originally Posted by jonny818 View Post
on the smallest Cog on my chain ring, whenever I pedal too hard,you can hear and feel that the chain has skipped some teeth on the cog. Before I removed the spacers, the bike would skip quite easily, though now it takes quite a bit of pressure. I'll take a picture later on of the rear derailleur and the cogs with the chain in place.
If it skips on the small rear cog under pressure, and especially if it continues with different adjustments, the cause is wear. The small cog commonly is worn on older bikes and those that are ridden a lot in the small cog, which is meant only for high speeds. The chain could well be worn also. Adjustment probably won't help, as you said you can ride OK with lower pressure. You cannot tell the cog or chain is worn by looking at them, unless the wear is severe. Go to Sheldon's page https://sheldonbrown.com/chains.html and look at the Chain and Sprocket (cog) Wear section. There are instructions for measureing chain wear, and if yours is worn very far you can pretty much count on having to replace both chain and freewheel/cassette.
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Old 06-05-13, 07:27 PM
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Originally Posted by davidad View Post
Start here and learn the proper names for the parts. https://www.parktool.com/blog/repair-help
I know the parts, I just don't know how to refer to my problem. To me gears skipping refers to to the gears moving around against their intended way.
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Old 06-05-13, 07:28 PM
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Originally Posted by JiveTurkey View Post
Removing that spacer changed the distance between where the rear deraillueur (RD) attachment to the frame and the cogs.

The rear derailleur's high-limit screw may be screwed in too far (or perhaps not far enough), which limits how far away from the bike the RD can physically go. There are two screws next to the each other, one should be labeled H (High).

While in the last gear (smallest rear cog) look from behind and see if the RD's upper pulley (little plastic gear) lines up with the cog. If not, try this:
- If you need to move the RD to the right, unscrew (left) the High-limit (H) screw.
- If you need to move the RD to the left, screw in (right) the F screw.

By the way, make small adjustments, like 1/4 turn at a time. Tip: this screw is easier to turn when the bike's not in the last gear, so: either downshift once or pull a bit of exposed cable, make the adjustment, then check.

I suggest detaching the cable and re-setting up the RD, including the H screw, cable tension/length, and L (Low) limit screw: https://www.parktool.com/blog/repair-...nts-derailleur
I thought the issue was the derailleur set up. I readjusted the gears and I still have the same problem. Another thing, this only happens on the last cog. All other cogs work fine.
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Old 06-05-13, 09:32 PM
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Just to be sure, you messed with the H-limit screw? Perfect alignment in every cog but the smallest is symptomatic of this.
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Old 06-05-13, 09:42 PM
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Then as I said it's not the derailleur setup, nor the chain primarily. As it happens only on one cog that cog is worn and possibly the chain as well.
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There's no such thing as a routine repair.

Don't tell me what "should" be - either it is, it isn't, or do something about it.

If you think I'm being blunt take it as a compliment - if I thought you were too weak to handle the truth or a strong opinion I would not bother.

Please respect others by taking the time to post clearly so we can answer quickly. All lowercase and multiple typos makes for a hard read. Thanks!
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