I know this is probably covered somewhere in one of the posts. i’ve looked a bit but havent found exactly what i’m looking for so here goes…
I replaced my cables this past weekend. I sent my limits (first using small crank in front and large cog in back, then large crank in front and small cog in back). Both were done without any cable tension. The limits look good. When i reattached my cable (done with the chain on the small crank up front) everything looks ok…except that even though everything limit wise was fine i’m getting chain rub in my lowest gear setting (large crank up front / small cog in back). I also noticed that even though i switches between cranks just fine, my left shifter doesn’t click all the whey into position when i shift to the large crank (it’s frictional isnt it? does it even have to?)
so this leads me to believe it’s a cable tension issue and that i put too much tension on it when it set it. The cable it setting an artificial limit for travel when it shifts to the large crank (i can visually see that ihave not hit my limit on the derailleur)…Does this sound correct to you guys? If so…how much tension should be on it? when you’re setting it do you just simply (and lightly) take the slack out? or do you really pull up and take the slack out?
It’s very hard to get your chain not to rub when cross chained all the way like that, especially on a TT/Tri bike because they typically have very short chain stays increasing the angle. You should be able to get it to run 1 cog lower/higher without rubbing though. Here’s a thread where I gave some tips on RD tuning.
In regards to your shifter not clicking all the way, if you get clicks it’s indexed shifting, if no clicks it’s friction. If you have clicks but can’t get it click the last time, then it’s likely an outer/high limit screw issue preventing your derailleur from moving it’s full length therefore preventing your shifter from going. If the shifter will click but the derailleur doesn’t stay it’s a cable tension issue (too loose).
One final thing, you can adjust your outer/high limit screw with the cable attached. It’s really the lower limit screw that needs to be set before the cable is attached. You can adjust it after but it’ll affect your cable tension but if you have inline adjusters that’s easy enough to fix.
Greg, i’m not getting rubbing during a cross chain… the only place i’m getting rubbing is when i’m in big crank up front and my smallest cog on the cassette (in my case my 50 up front and my 12t in back).
I believe my RD is set up fine. I’ve adjusted the barrel adjuster and have no issues shifting up/down in any arrangement.
Aside from the chain rub, i think my FD is set up in a workable (though not 100% perfect fashion). I just want to get rid of the chain rub in the instance i mentioned above.
If i’m correct, with my FD limits set correctly, i just now need to play with cable tension on the FD?
I’m going to assume it’s rubbing on the outside of the cage.
With the bike in a stand, pedal and try to move der over with shifter. If that makes the sound/rubbing go away, tighten your cable tension. If it doesn’t adjust your limit screw so the der can shift out further.
Ok greg thanks for the advice. Yes it is rubbing on the outside of the cage. I’ll have to try that when i get home from work later tonite. What i did notice yesterday was that i wasn’t hitting my limit for der travel to the outside. I could still see space for movement where the der touches the limit screw which lead me to believe i had either to much or too little cable tension… i just wasn’t sure which one! Sounds like from your advice i may need more cable tension…
in any case i’ll go back and double check the limits and then play with the cable tension to see if i can fine tune it. I appreciate the advice.
With all due respect, take it to a shop and observe them set it up (if they will let you). You are over your head.
I’d disagree. This is one of the simplest DIY tasks a cyclist can do and if you are going to fix your own bikes you have to start somewhere. Just think how much quieter group rides would be if everyone knew how to adjust their own derailleurs
Assuming the the height (small as possible gap between outer cage and big ring) and orientation (absolutely parallel to rings) of the FD is correct, this is pretty easy to fix.
Shift into small chainring, largest rear cog. Undo the cable binder bolt.
Adjust the low range limit screw with the cable completely unattached so that the inner side of the FD cage just barely doesn’t rub. You want it really close.
Grab the cable with a pair of pliers in your right hand, pull firmly and re-bind the cable with your left hand. Ensure that there’s no slack in the cable prior to tightening. You want the cable to be under a bit of tension in the small ring, but not so much that it holds the FD off of the low limit screw. This is easier to do if you have a barrel adjuster for the FD cable, but not that hard to get right if you don’t.
Shift into the large chainring and set the high limit screw.
Ivan…with all due respect i did originally take it to a shop to have it re-cabled. $$$$ later and a result i’m not 100% happy with (limits weren’t set correct, chain rub, poor routing of the cables - they almost touched my knees!, the front der set screw wasn’t tight enough and it pulled out and pulled the crimp off!). Yes i could take it back but now i’d rather learn it for myself. I’ve researched the resources (Zinn, park tool online, etc) and spoken with a friend who used to own a bike shop so i’m not approaching this willy nilly.
While i may not be a bike pro i’m not a technically inept fool. I’ve got graduate level degrees in aerospace and mechanical engineering. If i can design parts for smart bombs i think i can learn to tune a derailleur. So please forgive me if i’m trying to learn a new skill so i don’t have to pay a bike shop some crazy fee the next time or god forbid i’m away at a race and something happens… i’d like to know how to fix my bike.
Greg / Hiro, thanks for the advice. much appreciated. I wish my P2 had an inline adjuster for the Front der! that would make life a bit easier as setting up the rear der was a snap.
Ivan…with all due respect i did originally take it to a shop to have it re-cabled. $$$$ later and a result i’m not 100% happy with (limits weren’t set correct, chain rub, poor routing of the cables - they almost touched my knees!, the front der set screw wasn’t tight enough and it pulled out and pulled the crimp off!). Yes i could take it back but now i’d rather learn it for myself. I’ve researched the resources (Zinn, park tool online, etc) and spoken with a friend who used to own a bike shop so i’m not approaching this willy nilly.
While i may not be a bike pro i’m not a technically inept fool. I’ve got graduate level degrees in aerospace and mechanical engineering. If i can design parts for smart bombs i think i can learn to tune a derailleur. So please forgive me if i’m trying to learn a new skill so i don’t have to pay a bike shop some crazy fee the next time or god forbid i’m away at a race and something happens… i’d like to know how to fix my bike.
I am an engineer also and it always amazes me when I can’t figure out the simple stuff on my bike. It really is simple but it just takes a lot of time to figure everything out, but when you it is super simple.
I think you hit the nail on the head the first time. You put too much tension on the cable. I don’t agree with the other poster who said to pull it tight with pliers. Just do it with your fingers. Take the slack out of it and make it taught, but not tight. Once you’ve tightened the clamp bolt, you should be able to wiggle the cable some. It shouldn’t be loose, but it shouldn’t be super tight, either.
When the cable is too tight, it makes shifting to the big ring difficult and/or incomplete (so that it won’t “click” into place and will often fall back to the small ring). I can see how an over-tight cable could also keep the derailleur from resting completely against the lower stop.
Not a hard fix at all … even for an inexperienced, mechanically challenged rookie engineer such as yourself.
You can install an inline barrel adjuster if necessary. Undo the inner cable, pull it out, measure the amount of housing to remove to make room for the adjuster (leave a bit of housing on both sides), cut, file and reinstall everything. I’ve found this to be a bit of a pain in the ass as most inline adjusters either slip or are too hard to turn once under tension. I’ve yet to find a good, durable inline adjuster. Also, measuring, carefully cutting and filing all of that housing takes time. Because you can live without an inline adjuster for the FD, I typically recable without one for the FD for these reasons.
Bobby… thanks! I figured it couldn’t be rocket science to fix the darn thing correctly. Though maybe my wife is right…she always tells me i’m the dumbest smart guy she knows! let’s hope not.
this is why i love the ST forums… always a good place to share information and maybe learn something new.
Forgive me. It seemed an insurmountable problem to describe the intricies of fd alignment, cable tensioning and all the sublties that go with fd adjustment so that it shifts clean, quick and doesn’t rub in an internet forum. Best of luck.
Jeff, when you said P2, it woke me up. For about a year, I had a problem like you described. Took it to many shops and they could make it not rub, but it would throw the chain, not shift etc. Being an engineer too, I couldn’t stand it not working or knowing why. It worked fine for over a year. then one day I discovered that the cage was not running parallel to the chain when in the big/small combination where it rubbed. The P2 I have had a frame mount for the FD that is round and I run a SRAM FD. I loosened it up, rotated it till the cage was running parallel to the chain, tightened it back up, rest limits, and cable tension and no more issues!!! Somehow in a rough shift up front, the FD had slipped on the FD mount and was not aligned properly. More than a few shop wrenches missed this. Hope this helps.
