Chain or gears jumping when pedaling hard

[duanelr]

Hey guys,

 

My bike started doing this weird thing lately: when I'm cycling normally, i.e. not exerting massive amounts of force onto the pedals like you would pushing a small gear up a hill, then my gears and shifters work fine. 10 speed deore casette with deore chain , deore derailleur and 1 x narrow wide chainring up front.

 

But when i pedal hard, like up the hill in a small gear, i.e pushing down hard on the pedals, something happens. it feels as if the chain slips for a second, or as if the chain jumps off the casette or something. i'm usually not looking at my drivetrain when this happens. all i know is it causes me to suddenly shift all my weight forward followed by striking my knee on the stem, ouch.

 

any ideas what could be causing this? It's a brand new chain, derailleur and casette combo. as said before it shifts no problem just pedaling normally.

 

my free hub body is fine, rear hub is tight, bb is new... i'm out of things to check...

 

please help,

thanks

[dirtypot]

Old narrow wide on the front?  If so, replace it.  They don't work well when used with a new chain.

[Grease_Monkey]

A buddy of mine had the same issue recently - ended up tearing cartilage in his knee when the chain slipped under hard acceleration. He also had a brand new cassette and chain. It turned out that his chainrings were quite worn, and because of the new chain and cassette the drivetrain did not play well together.

 

He has a 3x9 system, but I guess the same can apply to you - maybe the chainring is worn?

 

The other possible problem is that your shifter cables have stretched slightly (usually happens within first 100km of installation), and that is causing the derailleur to not be aligned nicely with the cassette. Just have a bike shop set your gears for you, or google how to yourself - it is quite easy.

[shaper]

Maybe as dirtypot said

Edited September 19, 2017 by shaper

[mecheng89]

Hey guys,

 

My bike started doing this weird thing lately: when I'm cycling normally, i.e. not exerting massive amounts of force onto the pedals like you would pushing a small gear up a hill, then my gears and shifters work fine. 10 speed deore casette with deore chain , deore derailleur and 1 x narrow wide chainring up front.

 

But when i pedal hard, like up the hill in a small gear, i.e pushing down hard on the pedals, something happens. it feels as if the chain slips for a second, or as if the chain jumps off the casette or something. i'm usually not looking at my drivetrain when this happens. all i know is it causes me to suddenly shift all my weight forward followed by striking my knee on the stem, ouch.

 

any ideas what could be causing this? It's a brand new chain, derailleur and casette combo. as said before it shifts no problem just pedaling normally.

 

my free hub body is fine, rear hub is tight, bb is new... i'm out of things to check...

 

please help,

thanks

Tensioning your derailleur? How old is the chain ring? 

[droo]

If your chain and cassette are both new then either your chainring is worn or there's an issue with your freehub.

[duanelr]

The narrow wide chainring up front is old indeed. Still has life left in it but did not replace it with the other components.

 

Figured the problem was in the back but I'll replace the front and see what happens.

 

Thanks for the advise

[Grease_Monkey]

The narrow wide chainring up front is old indeed. Still has life left in it but did not replace it with the other components.

 

Figured the problem was in the back but I'll replace the front and see what happens.

 

Thanks for the advise

 

 

If the chainring is old then I am 99% sure that's your issue.... Let us know what happens when you have replaced it.

[Sani]

Check the alignment off Your R/D , had the same problem.

[Brakepad]

just to make sure put the chain on the smallest wheel in the back and pedal backwards.

if the chain jumps it might be a stiff chain link or adjustment, alignment of the RD is needed

[porqui]

While you are at it replace the R/D cable and reset the alignment of r/d and set limit screws and may as well check B screw.

[Thor Buttox]

One thing. If you happen to have put a different cassette on, eg, XT to Sunrace, it can be the spacers. Even replacing just the 11 caused issues on mine.

[duanelr]

Issue solved: I was cleaning the bike and noticed that my rear derailleur upper and lower limits were out. I did set them properly before (few months ago) but guess they vibrated loose or something. so re alligned, adjusted, added some removable thread lock and voila, no more skipping