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Old 07-07-03, 05:39 PM   #1
Spire
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Chain slip on front chainring????

I recently replaced the chain on my mountain bike and as a result I was getting some intense slipping. I then replaced the cassette and the slippage significantly reduced. However it is not eliminated, it still happens every once in a while. Is it possible for the chain to slip on the front chainrings? Is this probably? Should I replace them? What sort of price range do they cost?
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Old 07-07-03, 06:09 PM   #2
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Which ring is it slipping? Granny or big one? Usualy its because the front derraileur isnt adjusted properly. You have to use the limit screws to prevent the derraileur from moving too far to the left or right. go to www.parktool.com, they have a good writeup on adjusting derraileurs
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Old 07-07-03, 06:54 PM   #3
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It not falling off. It is slipping on the chainring (or at least I assume it is because the chain and casette are both brand new) The chain is slipping on the cogs. The derailler is adjusted correctly.

What I mean by slips is when I exert a certain force on the pedals, my foot suddenly goes round because the resistance temporarily goes away and I hear a crunching sound.
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Old 07-07-03, 07:21 PM   #4
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wow...same exact thing is happening with me, same EXACT thing, new chain, new cassette and slipping on the chainrings when i crank hard out of starts usually. what i have diagnosed is that its the cassette not being tightened fully. wheneven it happens to me, my cassette seems to be loose. i tighten it, and the problem goes away, but when it reloosens [i never tighten the cassette down hard cause i dont have a chainwhip and its a pain to get off if its tight], the problem starts again. just now before i read this post i tightened the cassete really tight so itwont loosen again. we will see if this got the problem to stop on my ride tommorow.
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Old 07-07-03, 10:27 PM   #5
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Mabe the splines on the cassette body (not sure if thats right, cant think of what I want to say) are worn enough that the cassette cant hold itself on properly.
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Old 07-07-03, 10:34 PM   #6
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Had a problem like that, I would wait for a bit. See if it settles in.


OR

Is the chain trimmed to the correct length?
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Old 07-08-03, 03:15 AM   #7
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i have had this problem before...

if i remember right it was my middle chainring. if the small chianring is worn the result is usually chainsuck, but for the middle and big rings you usually get slippage when they are worn. it's a super loud obnoxious cracking noise (and i often hit my knee on the handlebar since there is no counter-pressure - ouch!).

if the slippage is bad, then replace now before you damage your chain. if it's not really bad you could wait as danka24 suggested and it might settle out.

i agree that a loose chain will contribute to the problem. check that you have the right length and not too moch slack.

if you need to replace there are 2 options:
1) buy a single chainring(s) and replace it - you have to pull the crank which is not hard but you need a $15 crank puller - and a single ring costs like $10-40 depending on what you buy (crap, LX, XT, steel/aluminum/titanium)
2) buy a whole new crank (both left and right cranks plus the 2 chainrings) which can often be cheaper than replacing 2 rings - maybe $50-$200 depending on Doere, LX, XT, XTR or non-Shimano - and then you have allnew stuff.

i had slippage on my commuter middle ring recently and bought a whole new Doere crank for about $65 i think and changed it myself. on my full suspension i replaced the middle ring (slippage) and the small ring (chainsuck).
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Old 07-08-03, 05:09 AM   #8
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I think I may have figured it out.

The chain was the right length for the old cassette (round the large cog in the front and around the large cog in the rear without going through the deraillers + 1 extra link). What I had forgotten to take into account is that when I changed the cassette, I switched the 14-32 for a 14-28. That could conceivably mean that there are 2 extra links on the chain. Does this make sense, could it be responsible?
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Old 07-08-03, 03:50 PM   #9
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Hmmm I had the front middle chainring worn out, wasnt noticable to the eye, or I should say to my eye, but I changed it, and voila!!
There it is, all fixed Senoir.

I think you have to clean all the grungh so the ring is all shinny like, then you can tell if them teeth is worn!

or a stiff link?
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Old 07-09-03, 04:13 AM   #10
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I checked for still links, I couldn't find one.

The chain only seems to slip once in a while. Can I be sure that it is the chainrings becasue I replaced the chain and cassette. Is it possible there is something else causing it?
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Old 07-09-03, 04:22 AM   #11
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Spire, if the chain is not way loose and the deraileurs seem in order and the chain and cassette are new... seems like the front chainrings are the next spot.

which one(s) are slipping? if everything works fine in the small chainring and it slips badly in the middle and maybe a little in the big (or not at all) -- i'd say it's almost definitely the chainrings. or if you get chain-suck in the little and slippage in the middle and/or big i'd again say you need new rings. as a rough guide, i use 1 cassette for every little ring (i climb a LOT), 2 cassettes for every middle, and maybe 3-4 cassettes for every big ring unless i break teeth on rocks which has more to do with riding conditons than miles/wear.

so:
1) compare the slippage in different rings
2) visually look at the chain as it goes around a ring. when it is badly worn it can be clear to the eye that the chain only matches half of the contact area and the rest you may actually be able to see space or easily lift the chain away from the ring. my middle was worn like this and i could visually see and feel with the hand that the new chian did not match the old chainring.

sounds like your choice is between replacing one or two chainrings or a new crank/rings set. but figure out which rings are worn.
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Old 07-10-03, 12:25 AM   #12
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Look at your chainring teeth, if they are shaped at all like shark-fins, your chainring probably needs to be replaced. I've seen slippage from worn CR teeth many times

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