Any thoughts on why my chain's jumping on the smallest cogs?
Discussion
Evening all,
I'm bloody hopeless at adjusting gears, so looking for some real muppet level advice here!
I don't generally use the smallest couple of sprockets on my commute, but have just discovered that when I do, the chain is jumping a lot.
It's not jumping to a different cog, just not sitting correctly on the cog I've chosen.
Bike is a Boardman CX Pro. The rear mech is a Sram Force. The rear cassette has around 1,200 miles on it. The rear mech, hanger & chain were replaced around 120 miles ago after I managed to bugger up the old ones in a crash.
The bike hasn't taken any sort of knock since the old kit was replaced, and as far as I'm aware, it could well have been misbehaving since the LBS fitted the new kit. I have no memory of the accident in which I knocked the rear mech and bent the hanger originally, although obviously it couldn't have been in both the two smallest sprockets at once!
The chain and rear mech actually got busted when I went into first gear going up a hill and pulled the mech into the spokes, so definitely couldn't have caused any damage to the smaller sprockets at that point.
Any thoughts?
I'm bloody hopeless at adjusting gears, so looking for some real muppet level advice here!
I don't generally use the smallest couple of sprockets on my commute, but have just discovered that when I do, the chain is jumping a lot.
It's not jumping to a different cog, just not sitting correctly on the cog I've chosen.Bike is a Boardman CX Pro. The rear mech is a Sram Force. The rear cassette has around 1,200 miles on it. The rear mech, hanger & chain were replaced around 120 miles ago after I managed to bugger up the old ones in a crash.
The bike hasn't taken any sort of knock since the old kit was replaced, and as far as I'm aware, it could well have been misbehaving since the LBS fitted the new kit. I have no memory of the accident in which I knocked the rear mech and bent the hanger originally, although obviously it couldn't have been in both the two smallest sprockets at once!
The chain and rear mech actually got busted when I went into first gear going up a hill and pulled the mech into the spokes, so definitely couldn't have caused any damage to the smaller sprockets at that point.Any thoughts?
Kermit power said:
Evening all,
I'm bloody hopeless at adjusting gears, so looking for some real muppet level advice here!
I don't generally use the smallest couple of sprockets on my commute, but have just discovered that when I do, the chain is jumping a lot. It's not jumping to a different cog, just not sitting correctly on the cog I've chosen.
Bike is a Boardman CX Pro. The rear mech is a Sram Force. The rear cassette has around 1,200 miles on it. The rear mech, hanger & chain were replaced around 120 miles ago after I managed to bugger up the old ones in a crash.
The bike hasn't taken any sort of knock since the old kit was replaced, and as far as I'm aware, it could well have been misbehaving since the LBS fitted the new kit. I have no memory of the accident in which I knocked the rear mech and bent the hanger originally, although obviously it couldn't have been in both the two smallest sprockets at once! The chain and rear mech actually got busted when I went into first gear going up a hill and pulled the mech into the spokes, so definitely couldn't have caused any damage to the smaller sprockets at that point.
Any thoughts?
Could be a stiff link where the chain was put on, but I'd expect it to jump in other gears as well.I'm bloody hopeless at adjusting gears, so looking for some real muppet level advice here!
I don't generally use the smallest couple of sprockets on my commute, but have just discovered that when I do, the chain is jumping a lot.
It's not jumping to a different cog, just not sitting correctly on the cog I've chosen.Bike is a Boardman CX Pro. The rear mech is a Sram Force. The rear cassette has around 1,200 miles on it. The rear mech, hanger & chain were replaced around 120 miles ago after I managed to bugger up the old ones in a crash.
The bike hasn't taken any sort of knock since the old kit was replaced, and as far as I'm aware, it could well have been misbehaving since the LBS fitted the new kit. I have no memory of the accident in which I knocked the rear mech and bent the hanger originally, although obviously it couldn't have been in both the two smallest sprockets at once!
The chain and rear mech actually got busted when I went into first gear going up a hill and pulled the mech into the spokes, so definitely couldn't have caused any damage to the smaller sprockets at that point.Any thoughts?
Trying to upshot or jumping where it is?
Mum ping where it is, the smallest cog if most easily effected by dirt - give it a clean. Also most effected by ware is you chain 120 new as well?
Up shifting, simple to adjust. Put the shifter to that position check cable isn't preventing movement of the mech, move the H screw to see of it is one way will move the mech in as if shifting to a lower gear the other way is the stop position to stop the chain falling off the last cog. You want the stop so the chain can't fall off and runs the chain all in line. Then tighten the cable with the barrel to take up slack and doesn't move. Now shift once to a lower gear it should shift, if not tighten cable until it does - job done, all the other indexing should be correct.
Mum ping where it is, the smallest cog if most easily effected by dirt - give it a clean. Also most effected by ware is you chain 120 new as well?
Up shifting, simple to adjust. Put the shifter to that position check cable isn't preventing movement of the mech, move the H screw to see of it is one way will move the mech in as if shifting to a lower gear the other way is the stop position to stop the chain falling off the last cog. You want the stop so the chain can't fall off and runs the chain all in line. Then tighten the cable with the barrel to take up slack and doesn't move. Now shift once to a lower gear it should shift, if not tighten cable until it does - job done, all the other indexing should be correct.
Herman Toothrot said:
Trying to upshot or jumping where it is?
Mum ping where it is, the smallest cog if most easily effected by dirt - give it a clean. Also most effected by ware is you chain 120 new as well?
Up shifting, simple to adjust. Put the shifter to that position check cable isn't preventing movement of the mech, move the H screw to see of it is one way will move the mech in as if shifting to a lower gear the other way is the stop position to stop the chain falling off the last cog. You want the stop so the chain can't fall off and runs the chain all in line. Then tighten the cable with the barrel to take up slack and doesn't move. Now shift once to a lower gear it should shift, if not tighten cable until it does - job done, all the other indexing should be correct.
It's jumping in place, not to another gear. Chain is also new, yes. Neither the cassette nor the chain are spotless, but they're not particularly dirty either.Mum ping where it is, the smallest cog if most easily effected by dirt - give it a clean. Also most effected by ware is you chain 120 new as well?
Up shifting, simple to adjust. Put the shifter to that position check cable isn't preventing movement of the mech, move the H screw to see of it is one way will move the mech in as if shifting to a lower gear the other way is the stop position to stop the chain falling off the last cog. You want the stop so the chain can't fall off and runs the chain all in line. Then tighten the cable with the barrel to take up slack and doesn't move. Now shift once to a lower gear it should shift, if not tighten cable until it does - job done, all the other indexing should be correct.
I would say its one of two things,
1. The chain has one or more stiff links. If you grasp the chain and bend it from side to side this will bed in the links.
2. More likely cause IMO is different rates of wear on the cassette and chain (120 miles v 1200 miles). Because the chain is under greater tension on the larger sprockets, it will only jump on the smaller ones under less tension. Cleaning the cassette and chain will only exacerbate the problem.
The only proper remedy would be to replace the cassette and chain.......
1. The chain has one or more stiff links. If you grasp the chain and bend it from side to side this will bed in the links.
2. More likely cause IMO is different rates of wear on the cassette and chain (120 miles v 1200 miles). Because the chain is under greater tension on the larger sprockets, it will only jump on the smaller ones under less tension. Cleaning the cassette and chain will only exacerbate the problem.
The only proper remedy would be to replace the cassette and chain.......
Newer chain on older cassette is the obvious answer but I would guess its also the barrel adjuster, where the cable goes into the mech. Adjusting this determines how far the mech moves between shifts like the limit screws. It will inevitably move as you handle the bike, was it , ride it etc so when you shift cogs, instead of shifting 1 cog at a time, you are essentially shifting 1.1 cogs if its out of sync.
As you describe the problem, this wont make much difference at the top of the cassette in your case as the problem is at the bottom thus by the time you reach the smallest sprockets, all those extra ".1s" accumulate and each shift is more like 1.5 or something thus it wont stay in gear... hopefully thats made some sort of sense....
As you describe the problem, this wont make much difference at the top of the cassette in your case as the problem is at the bottom thus by the time you reach the smallest sprockets, all those extra ".1s" accumulate and each shift is more like 1.5 or something thus it wont stay in gear... hopefully thats made some sort of sense....
Sounds very much like the chain has been installed incorrectly and is too long. It's easy to mess up chain installation......search t'internet for chain installation videos, there are loads. Thankfully chains are also very easy to install correctly, once you know how to do it of course. Feel free to post up pic....
Lighterfuel said:
Sounds very much like the chain has been installed incorrectly and is too long. It's easy to mess up chain installation......search t'internet for chain installation videos, there are loads. Thankfully chains are also very easy to install correctly, once you know how to do it of course. Feel free to post up pic....
I'll put a pic up tomorrow if I've not sorted it, but I doubt the chain is the wrong length. My LBS fitted it, and given the number of very nice bikes they deal with, I can't imagine that their mechanics would get something that basic wrong?I've just double-checked my mileage logs on Strava. I got my numbers mixed up! 
The rear cassette was about 600 miles old when the chain was changed. Since then, I've done around 400 miles. This was pretty much all commuting, so little or no use of the smallest two cogs.
600 miles surely isn't enough to get inconsistent wear, is it?
The rear cassette was about 600 miles old when the chain was changed. Since then, I've done around 400 miles. This was pretty much all commuting, so little or no use of the smallest two cogs.
600 miles surely isn't enough to get inconsistent wear, is it?
IMHO, no.. but personally I think the case for changing cassettes is overblown by bike shops, and then repeated as perceived wisdom 
Difficult to say without seeing, but i'd be looking for setup problems: cable tension, stops, bent mech hanger, b-screw adjustment (how far is the mech floating clear of the sprockets at each end) - and ensuring if it's a directional chain that it is the correct way round.
Difficult to say without seeing, but i'd be looking for setup problems: cable tension, stops, bent mech hanger, b-screw adjustment (how far is the mech floating clear of the sprockets at each end) - and ensuring if it's a directional chain that it is the correct way round.
av185 said:
More likely cause IMO is different rates of wear on the cassette and chain (120 miles v 1200 miles).
It sounds like the problem is resolved, but I'd be pretty peeved if a (road) cassette had enough wear for it to be a problem after only 1200 miles, especially if it were on the barely used sprockets.Gassing Station | Pedal Powered | Top of Page | What's New | My Stuff