Gears skip but only in two of them??

[Redders473]

Checked my chain on my trek rail and it needed replacing so i put a new chain on it. But now in 8 and 9th gear the gears skip at first i thought it was the motor but it's only them two gears when I'm putting the power down any ideas ?

 

[RickBullotta]

1) Check for a bent tooth on the cassette
2) Check the B-tension screw/pulley gap

 

[Redders473]

B tension is fine and i will have a look at a
Cassette but pretty sure nothings bent

 

[James_C]

at a suggestion, gears 8/9 are too worn to take a new chain.

suggest putting the old one on until it breaks/slips, then put new cassette/chain on

 

[GMLS]

I had exactly the same problem and spent ages checking and rechecking everything. Cured it by setting the chain gap to just less that the SRAM tool suggested at the sag point. Sounds like you have but also double check hanging bracket hanger

 

[chrismechmaster]

1) Check for a bent tooth on the cassette
2) Check the B-tension screw/pulley gap

Defo bent tooth I would say

I just went out on my Levo it was skipping in one gear couldn’t find anything wrong until closer inspection and found one tooth slightly bend , bent it back and no skipping at all

 

[Gyre]

How badly worn was the old chain? If you still have it, it might be a good idea to take a few measurements and figure out what your percent stretch is.

 

[Redders473]

The chain was .75 in 4 places so needed replacing

 

[Gyre]

The chain was .75 in 4 places so needed replacing

Okay, seems like a worn cassette/chainring isn't terribly likely.

Things to check for:
1) Bent tooth (as others have said)
2) Stiff link in the new chain (should appear in all gears, not just two, but doesn't hurt to eliminate this)
3) Derailleur fine adjustment (barrel adjuster)
4) Bent derailleur hanger

 

[RickBullotta]

Another one that is rare but possible is the front chain guide is misaligned/dragging and creating an exaggerated chainline angle - though that should affect all of the larger cassette cogs.

 

[Mikerb]

All of the a bove are possibilities but I would try your B tension adjustment again as a first step. A new chain can be stiffer ( sideways flex) than your old worn chain and that additional may prevent the chain sitting with full wrap on the bigger cogs. Try extending the B stop gap a little to see if that resolves the issue. Also make sure you have removed all the packing wax chains are often covered in when new........then lube.

 

[Redders473]

After a more detailed look turns out my chain rings bent ever so slightly but it's still only effecting them two gears which seems weird. Anyone tried them hope chain rings for the bosch motor as there the only thing in stock atm

 

[Paul Mac]

It won't be your chainring, it will definitely be a worn cassette.
I've also got a Rail also tried to put in a new chain at .75 and also skipped.
Put the old chain back on and just use it till it doesn't work anymore, you will get 100's of extra miles out of it.
In my experience the old chain wear checker just doesn't work with ebikes.