High Gears slipping under load

I realise this isn't the best place to ask questions about bikes with gears but from what I know lots of you still have and ride geared bikes.

Anyway my chain hasn't been sitting right on the chainring (front) of my commuter bike. It kinda sits off the teeth a little bit. This slips under load too. I put up with it for as long as I could but on Friday it slipped and I went into a BMW. Low speeds so no damage to car or me thank god. But it could be worse.

So I begrudgingly forked out $35 AUS on a new Shimano Narrow chain (6/7/8 speed model - my bike is a 6). Fitted it just now. Forgot to take out any links so had to undo all my work and remove 3 links which seems to be the same length of my old chain, although I didn't measure. Anyway time for a test ride:

Chain kinda jumps and slips every rotation under load when in high gears (small at rear). When I shift up to lower gears (larger at rear) I don't get this problem as much. Big at front and big at rear gives me no problems at all no matter how much pressure I exert (although I don't use this gearing much for obvious reasons). However small at front and small at rear jumps all over the place.The problem gets less the bigger the cogs I put it in (lower gears). You get the idea.

I realise I should be getting a new cassette and chainrings (maybe even jockey wheels) when I replace the chain but finances mean I can't. Also fitting the new chain has sorted the problem I was having previously. The chain sits fine on the front chainrings and doesn't slip from them. However the jumping and slipping that its now doing appears to be coming from the rear.

I've all but ruled out a stiff link. I'm thinking its an excess of chain and may try taking out a couple more links. Thing is it "looks" right the length its at right now..

I'll have a play with the rear dérailleur adjustment and get back to you. It's gonna have to wait an hour or two though cause I have something to do. In the meantime does anyone agree/disagree/have any suggestions etc...

Cheers

rear dérailleur could be out of line, i find it easier to adjust without the chain on first so you can see the top jockey wheels teeth line up with the cassette, then after the stops are adjusted put it in the middle gear with the chain on and tweak the barrel adjuster so the middle gear is spot on. it does sound like worn rings/cassette though

Fucking bollocks. I can't figure it out.

I lined up the H & L screws of the Rear DR and thats all well. Still jumps.
Adjusted the barrel adjuster a bit and its still jumping.

I figured it may be that the chain was too long (too much slack means the spring arm isn't tense enough and in theory the chain could jump about a bit) so I took out another two links (I can't remove any more links from the chain or it won't go into big cog front and big at back). The B tension screw is pretty tight so its not that.

Fuck knows. Looks like a job for the LBS. Thing is they'll probably just tell me to replace all that shit which is way too expensive for the bike (cost me $75 AUS - I've already spent $25 replacing a spoke and $35 on a new chain).

I should've just got a new bike.

If I didn't have biopace rings I'd just remove the gears and shorten the chain so it's a cheapo single speed.

There were a number of different 6-speed systems with slightly different cog widths, but if the chain's sitting snugly on the larger rings, that's probably not the issue.

As per MrSmith, it sounds like a worn cassette. There are less teeth to hold the chain on the smaller cogs, so any wear and tear will cause more slipping issues. You should be able to get a cassette for not-too-much $.

Might be worth checking the cable for the rear mech as it passes through the guide under the bottom bracket. Spray a bit of GT-85 or something in there to make sure the cable's passing freely - this issue has been known to put shifting out of whack.

Thing is it was working fine before (bar the slipping on the front chainwheels). The rear shifted perfectly. Also the rear cog looks ok and the jumping gets worse the smaller the cogs get

Also the chain "should" be the right one - its an all Ultegra drive train and the chain was sold to me by my LBS (I took it in and said "I need a new chain for this" they took a look at my bike and gave me this one).

Maybe a last ditch bit of fiddling with the indexing barrel on the rear mech would be worth a go. Get the back wheel off the ground, stick it in the smallest cog, start backing off the adjuster till it starts making that "I'm gonna fucking shift, just watch me" ticking noise, and then screw back in quarter or half a turn.

Oh, and get a bit of GT-85 on the innards of your mech, and give it a good wiggle around :)

BringMeMyFix Maybe a last ditch bit of fiddling with the indexing barrel on the rear mech would be worth a go. Get the back wheel off the ground, stick it in the smallest cog, start backing off the adjuster till it starts making that "I'm gonna fucking shift, just watch me" ticking noise, and then screw back in quarter or half a turn.

Oh, and get a bit of GT-85 on the innards of your mech, and give it a good wiggle around :)

Sorry I kinda forgot to mention. It only does the jumping when I'm on the bike and putting more than the most basic amount of force on the pedals. No matter how hard I turn the pedals with my hands it won't jump. So it won't do that "I'm gonna fucking shift, just watch me" thing when I'm adjusting the barrel.

Sounds like previously the chainring was the weakest 'link'. Mismatched chain/cogs now the problem. I'm assuming you can see a bit of 'shark's fin effect' on the teeth of the smallest cogs?

Time to buy a cassette :(

I think I've had the same sort of trouble - a slipping chain with every revolution - on my commuter mountain bike. I even recognise the symptom where the chain just won't jump when the bike's on a workstand, no matter how hard you turn the pedals - this makes you look stupid and paranoid when you're trying to demonstrate the problem to other folk.

Riding in pretty much the same gear all the time, and leaving the bike unloved and uncared for after wet rides home, plays havoc with the cassette. Replacing it solved the problem.

Out of interest, do you tend to ride in just the one gear?

Sounds like you need a new cassette - however shortening the chain may help for a while; remember your new chain shouldn't be the same length as the old one, it should contain the same number of links.

No. Well I suppose one more than the others. But its more like 2-3 more than the others. The teeth seem pretty much ok (I just had a look).

I'll take it into my LBS on Wednesday (I have the day off) and see what they say. They just moved stores and are now really close to me (it'd be quicker to get there than it would be to get to my nearest pub or newsagent) so I've been looking to go in anyway.

If it looks like costing over $50 then I may just convert it to a single speed. But then I'll just end up spending more money on new chainrings (can't use Biopace on single speed) and I'll want to loose the 6 speed to be replaced with a single. That'll be around $50 I'd imagine. Plus the chain I've just paid $35 will be useless.

Fuck I hate bikes some days.

In the meantime I'll be commuting on my $10 "Dutch style" bike. Which is actually an amazing bike for $10 (its worth about $100) and has never let me down. It's just its not as fast or as cool looking as my racer.

Richard Cheese Sounds like you need a new cassette - however shortening the chain may help for a while; remember your new chain shouldn't be the same length as the old one, it should contain the same number of links.

Yeah I know. I'd dumped the old chain in a bucket of fairly liquid though to "clean" it before I put the new one on so couldn't be bothered to pull it out to count the links. I should probably do that tomorrow night when I get chance. It's late here now so all bike mechanics have stopped for the evening.

Thanks for all your help so far guys. I'll keep you posted.

You sure the chain isn't too long? Here's some methods for checking: http://www.parktool.com/repair/readhowto.asp?id=26

tsomething similar happened to me...turned out one of the teeth on the front cog was bent out of shape. i would never have thought of it, but that's what it was.

hippy You sure the chain isn't too long? Here's some methods for checking: http://www.parktool.com/repair/readhowto.asp?id=26

my chain looks pretty much exactly like the perfect set up on that website:

so I can't imagine its that.
There is more to that page you linked though. I'll go through it tonight when I'm not at work.

nimhbus tsomething similar happened to me...turned out one of the teeth on the front cog was bent out of shape. i would never have thought of it, but that's what it was.

Thing is they were fine before and they even 'look' fine now. Also it only really happens in the smaller cogs at the rear. It also happens in big cog front and little cog rear so that should (in theory) mean its not that.

I'm gonna loosen the gears off tonight and completely rest everything (if I'm not too tired from riding my clunker to and from work - it was actually quite a nice relaxed ride this morning. So much more comfortable to ride than my other bikes... but slower.

Again, I appreciate the help guys. Cheers.

Derr hanger been bent at some point after it was working well (installation of new stuff?)
It's usually a chain/cassette incompatibility as others have said though.. http://www.sheldonbrown.com/derailer-adjustment.html#autoshift

A lady in a Saab tried to give me a free lift to work this morning on her bonnet. I politely declined the offer by pulling a great big skid to avoid the bonnet (now blocking the cycle path).

Idiots.

hippy Derr hanger been bent at some point after it was working well (installation of new stuff?)
It's usually a chain/cassette incompatibility as others have said though.. http://www.sheldonbrown.com/derailer-adjustment.html#autoshift

As far as I know nothing has been bashed or bent. The installation was fairly hazard free.
If it is infact a chain/cassette incompatability then its kinda the bike shops fault as I just asked for one and pointed to the bike. They checked it. Thing is they didn't fit it too so I've kinda got no comeback.

Oh well.

tallsam [quote]hippy Derr hanger been bent at some point after it was working well (installation of new stuff?)
It's usually a chain/cassette incompatibility as others have said though.. http://www.sheldonbrown.com/derailer-adjustment.html#autoshift

As far as I know nothing has been bashed or bent. The installation was fairly hazard free.
If it is infact a chain/cassette incompatability then its kinda the bike shops fault as I just asked for one and pointed to the bike. They checked it. Thing is they didn't fit it too so I've kinda got no comeback.

Oh well.[/quote]

Looking at that article its more than likely that I just need a new rear cassette.

I have no idea why I didn't just read Park and Sheldon religiously before I posted this problem.

Shouldn't be too expensive although my LBS will have to fit it as I don't have the tools.

Are you in London? Or Brisbane?
$10 for a freewheel tool and $10 for a chainwhip.

Melbourne.

I've got a chain whip. Don't think I've got the right freewheel tool. I'll check. I'm sure I've not though. Will let you know when I get home.

I'd lend you one but I have two in London and one in Mildura.. not much fscking use am I?!?!
They shouldn't be too expensive and if you have nice LBS they might lend it (unlikely but like I say depends how palsy-walsy you are with LBS).

Can you strip the rear cassette down and re assemble it with the cogs flipped round so you are now driving against the other (un-worn) side of the teeth. Quite a bot of hastle but if you don't want to spend any money it may work.

This will cause more issues as the wear amount of the backs of the teeth are even less than the front, ie. it will be more likely to skip.
"Swap chain and cassette at same time" is roadie/mtber golden rule of driveline repair. That, and "don't fsck up the joining pin on ya chain ya twat" :)

BillB Can you strip the rear cassette down and re assemble it with the cogs flipped round so you are now driving against the other (un-worn) side of the teeth. Quite a bot of hastle but if you don't want to spend any money it may work.

Cassette cogs run on a splined freehub body, the splines (and matching notches on the inside diameter of the cogs/sprockets) will only go on one way, flip them and the splines/notches will not match up.