14t Chainring skipping...too small?!?

[Galaxyride]

Hi all,

I recently went from an 18t to 14t chainring on my Bosch CX powered Raleigh Kodiak IE. Now the chain is skipping and coming off at the chainring! I tried adjusting the derailleur B screw a bit and it still skips. So next I removed a pin and 2 links then installed a new missing link. Now it skips under a bit more moderate load but it’s still no good. The original chainring is an FSA offset 2.5mm for 148 boost, so I got another identical offset FSA just 4 less teeth. Verified the thickness with a micrometer. One thought was maybe the idler gear design of the bike just doesn’t allow as many teeth to contact the chain...but I’m not sure. I hope not because I really dig the tractor like torque of this gearing for steep climbs. Has anyone experienced something similar?

 

[KenX]

Check for chain stretch, if worn it could have worked with the old sprocket but not with the new......

 

[Doomanic]

I run a 14T on my Performance CX. It does drop the chain occasionally, over very rough ground, but no more than the 15T I ran previously and only if I don't run a chain guard.

 

[KenX]

LynnX dropped from 15 to 14 no issues.......

 

[Galaxyride]

Check for chain stretch, if worn it could have worked with the old sprocket but not with the new......

Forgot to mention....the bike only has 115 miles on it, but I did go ahead and check it with a Pedro’s tool and it’s still less that 0.5%.

 

[Galaxyride]

I run a 14T on my Performance CX. It does drop the chain occasionally, over very rough ground, but no more than the 15T I ran previously and only if I don't run a chain guard.

It has a chainring guard on the outside and additional guard on top of the idler....when it skips/slips it jumps to the inside of the chainring.

 

[Doomanic]

Mine usually jumps to the outside. Only takes a moment to sort, but can ruin a run.

 

[Galaxyride]

Mine usually jumps to the outside. Only takes a moment to sort, but can ruin a run.

I can’t even make it a mile....and the sudden freewheel could be painful if your really pushing.

 

[Doomanic]

Mine only drops the chain when free-wheeling down hill, so not likely to be an issue.

 

[RickBullotta]

Did you remove a couple links from the chain after the switch? You may need to. B-tension is not for compensating for an excessively long chain - it is to set the pulley <-> cassette gap.

 

[Galaxyride]

Did you remove a couple links from the chain after the switch? You may need to. B-tension is not for compensating for an excessively long chain - it is to set the pulley <-> cassette gap.

Yeah as stated in the original post I pull two links...I also have since replaced the derailleur hanger because it had been bent and then straightened prior. And adjusted the B-screw to SRAM specs 14mm from the largest cog. But looks like the smaller chainring is only contacting 5-6 teeth, likely going to try and swap the wife’s 15t just to see if it’s any better.

 

[RickBullotta]

View attachment 20498

Yeah as stated in the original post I pull two links...I also have since replaced the derailleur hanger because it had been bent and then straightened prior. And adjusted the B-screw to SRAM specs 14mm from the largest cog. But looks like the smaller chainring is only contacting 5-6 teeth, likely going to try and swap the wife’s 15t just to see if it’s any better.

Effectively you removed one link. That's really all I was suggesting is whether taking one more out might help. Post a pic of the rear derailleur position when in the largest cog in the back. Also, while not likely, sometimes it's the quick link itself that can cause the skip. Just double check that it's fully clicked into position and that it's not bent.

 

[Galaxyride]

Effectively you removed one link. That's really all I was suggesting is whether taking one more out might help. Post a pic of the rear derailleur position when in the largest cog in the back. Also, while not likely, sometimes it's the quick link itself that can cause the skip. Just double check that it's fully clicked into position and that it's not bent.

I effectively removed two links....perhaps starting with one would have been better. I installed correctly the proper new link listed on KMC’s website....but that doesn’t matter because the front chainring will slip even if applying moderate pedal pressure with the rear brake locked. Not sure that it matters but FSA listed another 14t sprocket that’s black chromoly, but I got the stainless steel version. I appreciate all the input, it’s better to be redundant than miss something basic.

 

[RickBullotta]

I effectively removed two links....perhaps starting with one would have been better. I installed correctly the proper new link listed on KMC’s website....but that doesn’t matter because the front chainring will slip even if applying moderate pedal pressure with the rear brake locked. Not sure that it matters but FSA listed another 14t sprocket that’s black chromoly, but I got the stainless steel version. I appreciate all the input, it’s better to be redundant than miss something basic.

It looks fine at first glance - not too extreme. Is it slipping independent of which cog you have selected on the cassette? Kinda hard to really tell what's up without being hands on.

 

[Galaxyride]

It looks fine at first glance - not too extreme. Is it slipping independent of which cog you have selected on the cassette? Kinda hard to really tell what's up without being hands on.

If I’m in the two larger cogs no problem, I assume due to the reduced load of those ratios.

 

[RickBullotta]

When you pull on the derailleur cage/pulleys does it feel like there is adequate tension to hold the chain? Can you take a pic of the derailleur and chain when in the smallest cog in the rear?

 

[Galaxyride]

When you pull on the derailleur cage/pulleys does it feel like there is adequate tension to hold the chain? Can you take a pic of the derailleur and chain when in the smallest cog in the rear?

Okay....so I borrowed the stock 15t chainring from the wife’s Cube, bought the SRAM guide tool and properly set the B-screw clearance....and VIOLA no more chain slip. I now believe my original hunch was correct, a 14t chainring just does not have enough teeth making contact with the chain due to the illustrious engineering of the drivetrain. The angle from the idler gear down to the chainring is just too steep, much more so than other bikes that share a similar design I’ve noticed. Also the 14t chainring works just fine on my wife’s hardtail Cube. I must say the new found torque and range are very welcome, and combined with the traction from a new Eddy Current rear tire I’m a very happy camper. Dropping down 3 teeth made the bike come alive, I can now climb steep sections in Touring that previously required Turbo or at least Emtb mode and eco is now the default. After all that’s what I got an ebike for climbing and I have found absolutely no negatives. Thank you to all who chimed in hope this helps someone else! Here’s a shot from the pretty side.

 

[RickBullotta]

Okay....so I borrowed the stock 15t chainring from the wife’s Cube, bought the SRAM guide tool and properly set the B-screw clearance....and VIOLA no more chain slip.

Awesome to hear. Now go ride!