On Thursday, May 28, 2026 at 2:22:21 PM UTC-5 Tim wrote:

Hi Ted. The first time it jammed it was the already stretched out chain I 
put back on without checking it. 


Well, so much for that hypothesis!
 

So with Ultegra brifters, a 105 RD and the new 105 FD, is there some other 
reason that this problem could have occurred? I'm fine replacing the 
chainrings but now worried the problem could persist. 


Did you also add the brifters when you added the front derailer? I have 
limited experience with Shimano brifters, but my memory is they do kind of 
a 2-step, where the front derailer does an initial small movement as you 
start pushing the lever, then the full movement. Wild speculation on my 
part, but that bit of hesitation could be letting the chain get between the 
rings. 

Also, another basic question - did you try easing the FD inner limit screw 
a bit, so the cage is closer to the frame on the small ring?

There's another possibility that occurred to me, that could fit with the 
LBS's rude dismissal of 3-bolt chainrings. If somehow the chain got into 
the gap and was forced down hard enough, it could theoretically bend the 
outer ring away from the inner ring. I expect that would be immediately 
visible as runout, i.e. side-to-side wobbling of the teeth as you spin the 
crank. Does the jamming always occur in the same place on the chainrings? 

Barring something like that, I would be surprised if replacing the 
chainrings solved the problem, unless somehow you've managed to wear the 
inner surface of the outer ring a bunch. I've ridden RH chainrings a pretty 
large amount of miles and haven't seen any wear like that.
 
Ted Durant
Milwaukee, WI USA

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