I was out for a 30 mile after work ride last night when at around 22 miles in my rear derailleur starts acting up. I no longer can shift up to my two largest rear cogs (21t and 20t I think). No matter how hard I pull up on the shift lever it just won’t budge. I have not looked at all at the bike since I parked it last night (had to spend some time with the fam). Just wondering if anyone has any idea what may cause a derailleur that was working normally to act up like this. The only thing I can think of is the high limit set screw somehow got adjusted. But how that happened while riding is beyond me. Maybe a rock stuck in the mechanism?
Check your chain line to make sure the chain is on the derailuer pulleys. I had that happen once, and all that had happened was the chain somehow wasn’t going on one of the pulleys.
Was it recently re tensioned or recabled? Might have had some cable slip on the RD or perhaps it got caught up on something during a recabling and you got a bunch of slack you didn’t need all of a sudden.
Nope same cables for about 700-1000 miles now so that is not it. The cabel is is taunt all the way through, as a matter of fact I’d say shifting felt a bit stiff.
Hmm, Did you try to manually shift (pulling on the cable directly)? Not that it will stay there, but at least that takes the RD out of the equation.
Obiviously if you have too much internal routing going on you cannot do this.
No but I will try, it’s on a Cervelo P3 so there is a good deal of internal routing
.
If you are using standard cable housing (not nokon), the housing can fail. This usually happens as a result of nicking the plastic off, exposing some of the steel cable, which then rusts. Most often, the housing will just “explode” all of the sudden during a shift, and you can no longer shift at all. However, once or twice I have had a housing just develop a small split. During that period, you get what you are describing; suddenly a little more slack.
So check the housing for integrity. My first bet would be that the cable simply slipped as a result of the retaining screw losening, so just check and see if the screw that retains the cable is tight.
Paul
Thanks Paul- that makes sense- I’ll look into it tonight.