damn two smallest sprockets slipping

penguinonabike

i changed my chain recently.. i had advice form my LBS and they looked at my chainrings front and sprockets rear.. said no wear so no need to replace them unless i get problems after replacing the chain..

i did the chain and hey presto on the stand after it shifted lovely all gears going in no adjustment needed... cool i thought..

went out for a short ride round the estate to test under strain.. no skipping nothing..

now .. here is the problem...

it is mad that all chainrings, and sprockets engage and no problems happened

it was like that for a month or so..

now i get kinda slipping when i am in the biggest chainring at front and smallest two sprockets at rear,, but.... not all the time.. and it only happens when i am going for speed downhill and pushing bike to limits.. and it just kinda jumps for a split second and then its ok..

i have on the rear a 6 speed all in one sprocket set and the two rings themselves are loose ones added on to this to make it 8 speed...

should i replace those on their own or would it need all 8 doing together... the others dont do it at all..

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Wide load!!

DIRTBLASTER

I'm not sure but I had few thoughts.

Thought 1: Rear Derailleur is it adjusted correctly.
Thought 2: How often do you use the other gears that seem to work fine still like I said I'm not sure but if you're using them just as much as the ones that went bad do you think their is chance that they will also fail soon?

Hope my thoughts help. Good Luck.

penguinonabike

those had gone thru me grey matter lol..

1. yes perfectly indexed gears all fall into place perfect.. derralieur lined up perfect too so not that one..

2. I use them more than the two that slip way more so they should have been first to go me thinks ... i may just soon replace all the rear ones and put on a new chain that will solve it as front rings have no wear.. thing is the rear ones have no wear either...

weird..

thanks for the answer tho.. still baffled..

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Wide load!!

dabac

There's always a certain risk when you only replace some parts of the drivetrain, and when it comes to sprockets the smallest usually wears out first due to least amount of teeth engaging. It might very well be that yours are simply too worn to play nice with the new chain. Advice would then be to get them replaced before they've stretched the new chain.

moparchris

yeah nobody seems to realise that chains wear and "stretch" which is just the pins wearing and distance between the rollers getting bigger, once the distance between the rollers gets bigger it starts to wear the cassette and c/rings to the distance between the rollers that the chain has and then if you put a new chain on it wont mesh propperly with the worn cogs and worst case it will slip under load but otherwise it will cause the chain to wear quicker than usual because its putting more force on it where otherwise the rollers would be resting on the edge of the teeth on the cog and more evenly distributing the load. so if you check and replace your chain regularly the cassette and chainrings should last ages

and if your gettting slipping its probly best to replace the whole cassette and possibly even the chainrings

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GT Ruckus SS
2006 Giant Trance 1
Giant TCR Euro

jackkkk1

I had a similar thing and it had me confused for a while as I dont use the 8th and 9th spocket that much, only down hills so how could I have worn them out?

on some cassettes the spacers between the 8th and 9th sprockets are plastic

I had overtightened the cassette lock ring, thus squeezing the plastic spacer thus decreasing the space between the spockets, the chain hasn't got enough width and therefore rides up on the sprocket next door.

It only seemed to ride up under load, dont know why.

I loosened the cassette lock ring just a bit and all worked fine.

hope this helps

tyler_derden

Is the chain the same length as the original?

If it is not, it may be pulling the top derailleur pulley further from the cogs resulting in some misbehavior. You might be able to fix it with a "B-screw" adjustment on the derailleur or by adding a cuple links to the chain.

TD

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"When I was a child, I spake as a child, I understood as a child, I thought as a child: but when I became a man, I put away childish things."