Chain Skipping Under Load

[tiger]

Dear All,

I have a new bike. (http://www.lapierre-bikes.co.uk/node/907)

Everytime I go into either of the smaller front derailleur cogs to go up a hill the chain jumps.

I would take it back to the shop, but we have moved and it is now too far away.

Can anyone help?

[Bill]

About where are you keep the rear dérailleur cogs?

[tiger]

?

Sorry I don't understand

[chainslip]

Mine is doing the same thing. In cog 1 up front and gears 4-7 the chain slips really bad on the trail. It also does it in cog 2 up front and gears 6-8 in the rear. I have put a new rear derailluer (slx), new chain(shimano), new rear cassette 9speed shimano, new hanging bracket, new shifters, the frame has been checked and is straight, the b screw seems adjusted, the hanging bracket has been shaved to allow for more chain rap around the rear gears to try and solve the problem. The the front cogs are sr suntour pff, that is original.

When shifting through the gears it indexes ok, but makes a little noise. It was having problems staying in gear but all the new parts have seemed to help. The bike has 450 miles on it and has not been in a wreck. The bike is a 2012 felt nine sport.

Ideas?

[Bill]

Ok the one thing I did not see is new cables? The only other thing I can think of is , everything compatible? Some combinations are not reliably compatible!

[chainslip]

New cables upgraded to ones that were supposed to have less friction. Everything is shimano but the cranks and front cogs which r suntour? Anyone know about compatability issues with those components?

[tiger]

Got mine fixed, finally.

Although the bike is new I degreased the chain and derailleurs and relubed them. Makes me wonder if the shop had bothered to properly prep the bike before they sold it to me.

Works like a dream now.

[Bill]

@chainslip : Ok I am hoping one of the other guys chimes in and helps out. Some shifters are NOT compatible with deraillers despite what some people lead you to believe. I am not sure which component of yours is not compatible with the other but there has to be one of them. When you said "dearailer (six)" did you mean 6spd derailler? Is the company named six?

@tiger : Glad you got yours fixed. Hopefully can help out chainslip.

[chainslip]

@ Tiger, glad your bike is working well!

@ Bill, sorry it is an SLX derailleur, 9 speed Shimano rear cassette, 9 speed 6mm shimano chain. The shifter is an alivio. The local bike shop ground down the derailleur hanger a little to allow the chain to wrap more around the gears and it helped, the chain was slipping when in 1 up front, so he took 2 links out of it, I will ride it tonight and see how it works. After hours of adjustments, it shifts lighting fast going from 9 to 1 but has problems coming back up the cassette. the chain is slow going into gears 3 and 4 on the rear cassette. It rides on top of the teeth and rattles for couple rotations before fully seating on the gear. Hopefully the shortened chain and slightly re-machined hanger will do the trick. Has anyone else had issues with the Alivio shifter and SLX derailleur combination?

[DaveM]

@chainslip - When you say the chain "slips" are you sure that it is rising up over the top of the teeth in the rear and then re-catching after it jumps a few teeth? If so, yes normally that should be fixed with a new chain and cassette. Was this going on before you changed out all the parts and that didn't fix it, or did it start after you changed the parts.

The chain riding up on top of the teeth when you're shifting sounds like either a stretched chain or an incompatible one. (Any chain it wasn't really a 9 speed chain?)

The shifting problems sound like maybe the derailleur hanger is a little bent or you have a bad piece of cable housing somewhere. If the chain is trying to jump between gears, that could be causing the slipping, but it will have a very different fix.

Chain slip can be a hassle to diagnose because it only happens under load. But I'm not too convinced your shop knows what they're doing. Making a chain shorter to help it stay on the cog is not a proper way to address the problem. It sounds like they can't figure it out and are just trying to jerry rig it to get rid of you. That said, this is all third hand so maybe they found the chain was too long, etc. etc.

[chainslip]

@ DaveM

Thank you for suggestions. The bike shop has tried very hard to work on it and hasn't charged me. He replaced everything at his cost. I rode last night and with the shortened chain and the modified hanging bracket it shifted lighting fast and didn't slip in 11 miles. The chain was shortened because he modified the hanging bracket so the derailleur was farther forward allowing for more wrap around the cog. This caused too much slack in my smallest chain ring which is why it was shortened. Still don't know what caused the issues as all of the measurements were fine. He said in 25 years he had never seen anything like it. If this fix didn't work he was going to flat out replace the bike, which I would rather not do because I really like it over all. Hopefully this is taken care of and I can start participating in a thread about something fun with biking instead of repairs