Chain slipping over sprockets
Discussion
Hiya,
I have just done a major refurb of my mountain bike (GT Tempest aprox 2002 vintage), and have replaced the whole of the drivetrain, which was originally Shimano Deore, and is now completely Shimano Deore still, apart from SRAM chain and cassette (same number of teeth), but apparently it's completely compatible.
I've got it all indexed and shifting beautifully, but if I am running on the middle chainring and one of the middle rear sprockets, the chain can jump off the rear sprocket and slips for half a crank rotation under very heavy pedalling. It's extremely erratic, and as such, identifying exactly what is happening is hard. It only does it when I least want it to (ouch..as nuts hit the bars!)
Any idea what could be wrong? I'm thinking the chain could be too long, but I can't really tell if the derailer should be extended or relaxed in those middle gears.
Hmmm.
Also, anyone have a guide as to how to get tyres to seat on the rims properly? I have taken the bloody things off about 10 times now. I'm obviously doing something wrong.
I have just done a major refurb of my mountain bike (GT Tempest aprox 2002 vintage), and have replaced the whole of the drivetrain, which was originally Shimano Deore, and is now completely Shimano Deore still, apart from SRAM chain and cassette (same number of teeth), but apparently it's completely compatible.
I've got it all indexed and shifting beautifully, but if I am running on the middle chainring and one of the middle rear sprockets, the chain can jump off the rear sprocket and slips for half a crank rotation under very heavy pedalling. It's extremely erratic, and as such, identifying exactly what is happening is hard. It only does it when I least want it to (ouch..as nuts hit the bars!)
Any idea what could be wrong? I'm thinking the chain could be too long, but I can't really tell if the derailer should be extended or relaxed in those middle gears.
Hmmm.
Also, anyone have a guide as to how to get tyres to seat on the rims properly? I have taken the bloody things off about 10 times now. I'm obviously doing something wrong.
If you think the chain is to long the best way to check is to put it on the largest chain ring at the front and the largest gear on the rear cassette. The derailleur should be pull all the way forward. If this is not the case then your chain may well be to long.
As for the tyre not seating properly while this may not be the right method the only way I've found to get around this is to over inflate the tyre to seat it, and then once it is seated to reduce the air pressure to what you want.
As for the tyre not seating properly while this may not be the right method the only way I've found to get around this is to over inflate the tyre to seat it, and then once it is seated to reduce the air pressure to what you want.
Mr Gear said:
Ok, cheers for that both of you. Sounds like a common-sense method for checking chain tension. After all, there is no reason the chain should ever need to be longer than both big sprockets.
I don't think it's a stiff link, because the chain is brand new, but I'll check that too.
The stiff link is unlikely because it would be jumping on all sprockets. If there is one it's likely to be the one where you joined the chain.I don't think it's a stiff link, because the chain is brand new, but I'll check that too.
The derailleur should be fully stretched when on big ring-big sprocket.
BOR said:
Re seating the tyres: I "bounce and rotate" the wheel as I'm inflating it.
I've now actually bought some mounting lubricant (OooooooOooooh ! ) to make it easier for the tyres to centre themselves during fitting.
Do you do the bounce at very low PSI? Or whack the pressure right up and then bounce? Riding on over-inflated tyres has not made them pop into place yet. I have even WD-40'd the rims to help lube them into place, but to no avail.I've now actually bought some mounting lubricant (OooooooOooooh ! ) to make it easier for the tyres to centre themselves during fitting.
BOR said:
I bounce them all the time, from low pressure through medium then high. They do eventually pop into place.
the problem I had, was that the tyres weren't centering on the rim before they popped, which gave the appearance of a warped wheel.
Sounds like my problem exactly. The rim is pretty straight, but the tyre is all over the place. the problem I had, was that the tyres weren't centering on the rim before they popped, which gave the appearance of a warped wheel.
the slipping issue may be due to the drellular (spelling!) spring being shot. how old is the drellular? it may be worth changing this.
Suggesting this as I had exactly the same issue, went through all the obvious checks but everything was ok.
btw, I could get the chain to slip when putting pressure on the pedels when riding off a curb.
Suggesting this as I had exactly the same issue, went through all the obvious checks but everything was ok.
btw, I could get the chain to slip when putting pressure on the pedels when riding off a curb.
scooters said:
the slipping issue may be due to the drellular (spelling!) spring being shot. how old is the drellular? it may be worth changing this.
Suggesting this as I had exactly the same issue, went through all the obvious checks but everything was ok.
btw, I could get the chain to slip when putting pressure on the pedels when riding off a curb.
The mechanism is brand new, straight out the box. I believe it IS chain tension issues, but they are not caused by the spring being bad, more likely too long a chain or improper adjustment of the derailleur. I haven't had time to fix it yet, but cheers for the extra input.Suggesting this as I had exactly the same issue, went through all the obvious checks but everything was ok.
btw, I could get the chain to slip when putting pressure on the pedels when riding off a curb.
Re the chain - crank up the spring tension on the derailleur and see if that helps: otherwise it does sound like a stiff link.
I had to get a new tyre for my daughter's bike at the weekend; just an el-cheapo fron Halfords. It had clearly been hanging on the rack in the shop for yonks and as a result the bead was distorted: around six or eight inches of the circumference wouldn't sit up on the rim, but stayed down in the well.
No amount of heaving on it would sort it out, so I smeared washing-up liquid all the way round the rim, blew it up to 80psi and left it; after five or ten minutes it popped into position and has stayed there with the pressure back down where it should be.
It'd be very had work to do without a track pump, though.
I had to get a new tyre for my daughter's bike at the weekend; just an el-cheapo fron Halfords. It had clearly been hanging on the rack in the shop for yonks and as a result the bead was distorted: around six or eight inches of the circumference wouldn't sit up on the rim, but stayed down in the well.
No amount of heaving on it would sort it out, so I smeared washing-up liquid all the way round the rim, blew it up to 80psi and left it; after five or ten minutes it popped into position and has stayed there with the pressure back down where it should be.
It'd be very had work to do without a track pump, though.
Mr Gear, if you replaced gear cables as part of your refurb bear in mind these will stretch as they bed in, and may require you to re-adjust the indexing, as to the slipping, does it happen on all three front chainrings, or only one? Did you increase the number of speeds when updating the drive train, say 7 rear sprockets to 8?
HDM said:
Mr Gear, if you replaced gear cables as part of your refurb bear in mind these will stretch as they bed in, and may require you to re-adjust the indexing, as to the slipping, does it happen on all three front chainrings, or only one?
It only slips when running on the smallest chainring, which I think shows that it is a symptom of slackness in the chain. HDM said:
Did you increase the number of speeds when updating the drive train, say 7 rear sprockets to 8?
Nope, exactly the same sprockets, exactly the same number of teeth.Shamefully, I still haven't got round to having a tinker yet. Been busy with work and riding my roadbike for the time being.
You keep mentioning the new chain, but then say you are unsure if it's too long. This makes me wonder if you have simply fitted a new chain without shortening it first ?
Whenever I fit a new chain, I have always had to remove a few links to get the correct length. A simple test would be to compare the length of the old chain to the new one, but if you've thrown the old one away, then you'll have to check the derailleur position big ring-big ring and small ring - small ring.
If the derailleur spring has weakened with age, one solution could be to remove one link too many from the chain. You will no longer be able to select big ring- big ring, but you wouldn't normally run like that anyway.
Whenever I fit a new chain, I have always had to remove a few links to get the correct length. A simple test would be to compare the length of the old chain to the new one, but if you've thrown the old one away, then you'll have to check the derailleur position big ring-big ring and small ring - small ring.
If the derailleur spring has weakened with age, one solution could be to remove one link too many from the chain. You will no longer be able to select big ring- big ring, but you wouldn't normally run like that anyway.
BOR said:
You keep mentioning the new chain, but then say you are unsure if it's too long. This makes me wonder if you have simply fitted a new chain without shortening it first ?
Whenever I fit a new chain, I have always had to remove a few links to get the correct length. A simple test would be to compare the length of the old chain to the new one, but if you've thrown the old one away, then you'll have to check the derailleur position big ring-big ring and small ring - small ring.
If the derailleur spring has weakened with age, one solution could be to remove one link too many from the chain. You will no longer be able to select big ring- big ring, but you wouldn't normally run like that anyway.
You are absolutely right, this was the textbook mistake I made. I asked the shop to give me replacements for the parts the bike was currently fitted with, so I assumed (probably wrongly) that the chain would go straight on. I don't know if it was the same length as the old one, and I suspect it is longer.Whenever I fit a new chain, I have always had to remove a few links to get the correct length. A simple test would be to compare the length of the old chain to the new one, but if you've thrown the old one away, then you'll have to check the derailleur position big ring-big ring and small ring - small ring.
If the derailleur spring has weakened with age, one solution could be to remove one link too many from the chain. You will no longer be able to select big ring- big ring, but you wouldn't normally run like that anyway.
In case anyone cares, I have now solved this problem!
The chain was NOT slipping over the rear sprockets, it was actually slipping over the front chainring. The middle one was worn out and with everything else being new, it became the weak link on the drivetrain.
So I have now shortened the chain slightly and changed the cranks and chainrings, and now the bike feels better than new! It has cost over £200 on a bike that wasn't worth that much (effectively written-off by worn out parts), but I think it was the right thing to do, as I love the bike and it has a great quality frame and wheels that deserve decent components that it now has.
The chain was NOT slipping over the rear sprockets, it was actually slipping over the front chainring. The middle one was worn out and with everything else being new, it became the weak link on the drivetrain.
So I have now shortened the chain slightly and changed the cranks and chainrings, and now the bike feels better than new! It has cost over £200 on a bike that wasn't worth that much (effectively written-off by worn out parts), but I think it was the right thing to do, as I love the bike and it has a great quality frame and wheels that deserve decent components that it now has.
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