Derailleur adjustment with compact crank

I bought a used bike and switched it from a standard crank to a compact crank but I'm having a devil of a time getting the front derailleur properly adjusted. I'm constantly dropping the chain to the outside when I shift from small to large. If I back off the limit I can't get onto the large ring!

Is there an Ultegra level derailleur designed to work with a 50/34 crank?

I love my bike but I was so frustrated today I was ready to throw it into a ditch! :mad: Please help me preserve this love affair!

I'm running a similar set up, and recall that it was a bit fickle to set up. IME, FDs on compacts seem to be more touchy about cable tension, even if the limit screws are correct.

Have you lowered the FD to compensate for the smaller outer ring? What FD are you using now?

Good luck, and don't give up- it will be worth it in the end!

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Originally Posted by Becky

I'm running a similar set up, and recall that it was a bit fickle to set up. IME, FDs on compacts seem to be more touchy about cable tension, even if the limit screws are correct.

Have you lowered the FD to compensate for the smaller outer ring? What FD are you using now?

Good luck, and don't give up- it will be worth it in the end!

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It's currently got an Ultegra FD (not sure of model). Yes, I lowered it when I first made the switch and I monkey with it again when trying to get it better adjusted. It worked flawlessly last weekend; this weekend I was ready to trash it. I can't help but think it would be working better if the curve of the FD were better matched to the curve of the large ring but I can't seem to find something like this.

I'm not sure about Ultegra, but I know Dura Ace can. If DA can, I would presume Ultegra can.
What kind of crankset do you have?
I have a FSA compact on the Axiom with a DA FD, and I was constantly throwing the chain off the crank. The mechanic at the LBS, who spent lots of time adjusting it, attributes it to USER ERROR! :eek::rolleyes: Yes, you MUST be very careful about where your chain is on the cassette (mid cassette is best) and not heave the shifter too much. Just a soft touch. It took me a while to learn the technique. I am really good with the user error problems!
That said...
My ID8 has a Shimano Ultegra compact crankset and Shimano FD (also DA) and I have had no trouble whatsoever with throwing the chain.

Last week I was able to shift it without thinking about it; today I had to be so careful my shifts were taking forever!

I want to race on this bike in just a few weeks and I want to feel confident that when I shift I won't end up on the side of the road fixing my chain! :(

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Originally Posted by MDHillSlug

I want to race on this bike in just a few weeks and I want to feel confident that when I shift I won't end up on the side of the road fixing my chain! :(

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Do you have time next weekend to do some HoCo hills with me? We can run it through its paces and see what's up....

Anyone have experience with the FSA Gossamer FD? It says it's specifically designed for compact cranks.

I've got ultegra shifters, front derailleur, & am running a 50-34 crank without a problem. It did ocassionally go off the inner chainring when i first got it, told the bf to tweak it, he spent about 5 mins, and it's been fine ever since.... I can force it off if I'm dumb and don't realize that I'm in the big chain ring and I keep trying to shift into it (I dunno why, but I did that the other day)

Bf's also got the same set up on one of his bikes (ultegra and compact cranks), so it can be done and it didn't seem particularly difficult to do.


What cranks are you using? I know in some of the crank reviews I've been reading (fsa gossamers), people have claimed that buying shimano compact cranks completely solved any problems they had with tuning the compact or the chain going off the cranks...

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Originally Posted by Catriona

I've got ultegra shifters, front derailleur, & am running a 50-34 crank without a problem. It did ocassionally go off the inner chainring when i first got it, told the bf to tweak it, he spent about 5 mins, and it's been fine ever since.... I can force it off if I'm dumb and don't realize that I'm in the big chain ring and I keep trying to shift into it (I dunno why, but I did that the other day)

Bf's also got the same set up on one of his bikes (ultegra and compact cranks), so it can be done and it didn't seem particularly difficult to do.


What cranks are you using? I know in some of the crank reviews I've been reading (fsa gossamers), people have claimed that buying shimano compact cranks completely solved any problems they had with tuning the compact or the chain going off the cranks...

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Not Gossamers, FSA Pro cranks. I'd rather change the FD than the cranks if it would help. I'm thinking seriously about the FSA Gossamer FD.

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Originally Posted by Catriona

I know in some of the crank reviews I've been reading (fsa gossamers), people have claimed that buying shimano compact cranks completely solved any problems they had with tuning the compact or the chain going off the cranks...

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That was my experience.
FSA (SLK) crank + Shimano FD = chain off the crank upon shifting (okay..not CONSTANTLY...but often).
Shimano crank + Shimano FD = no shifting issues.
Cannot speak to FSA crank + FSA FD.

Front derailleurs specifically designed to work with compact cranks are usually put into use to help prevent dropping the chain to the inside of the small ring due to the big differential between c-ring sizes...not the issue you are having. I would recommend checking the angle of the cage over the big chainring, and make sure it is exactly parallel, also that the FD sits only about 1mm above the chainring teeth (i.e., as close as possible).
I run an FSA compact crank with Ultegra FD and have zero problems.

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Originally Posted by 7rider

That was my experience.
FSA (SLK) crank + Shimano FD = chain off the crank upon shifting (okay..not CONSTANTLY...but often).
Shimano crank + Shimano FD = no shifting issues.
Cannot speak to FSA crank + FSA FD.

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I'm using an FSA crank with ultegra front derailleur. The chain mostly doesn't go off the crank, but it does happen occasionally.

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Originally Posted by lunacycles

Front derailleurs specifically designed to work with compact cranks are usually put into use to help prevent dropping the chain to the inside of the small ring due to the big differential between c-ring sizes...not the issue you are having. I would recommend checking the angle of the cage over the big chainring, and make sure it is exactly parallel, also that the FD sits only about 1mm above the chainring teeth (i.e., as close as possible).
I run an FSA compact crank with Ultegra FD and have zero problems.

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Margo, thanks for the insight.

Because the curve of the FD doesn't match the curve of the 50T ring the spacing between FD and crank varies at all points. I know I can't lower it any more or the chain can't get onto the big ring.

With a braze-on FD how much adjustment do I have for parallel? Should I give this another try on my own or drop it off at the LBS and hope they can work some magic? Why did it work perfectly last week but fail me yesterday?

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With a braze-on FD how much adjustment do I have for parallel?

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You should have some. Often the derailleur and the braze on fall in love in a certain position, but if you hold the derailleur firmly in the alternative, more ideal position, it should move a bit for you. Definitely try it again...what have you got to lose? Derailleur adjustment stuff tends to be finicky more often than not, and so often requires patience and at least a few tries til you find the sweet spot. Good luck.

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Originally Posted by lunacycles

You should have some. Often the derailleur and the braze on fall in love in a certain position, but if you hold the derailleur firmly in the alternative, more ideal position, it should move a bit for you. Definitely try it again...what have you got to lose? Derailleur adjustment stuff tends to be finicky more often than not, and so often requires patience and at least a few tries til you find the sweet spot. Good luck.

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I had the bike in my car so I could take it by the LBS; the alignment looks good to me.

Anyway, I swung over to the LBS after work. The wonderful mechanics there took a look at it right away, made some adjustments on the spot, and returned the bike to me. Hopefully this will work.

When I wheeled the bike into the store one of the staff said "Wow, what is that? I've never seen a bike like that!" This really made me smile :) :cool:

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Originally Posted by MDHillSlug

I had the bike in my car so I could take it by the LBS; the alignment looks good to me.

Anyway, I swung over to the LBS after work. The wonderful mechanics there took a look at it right away, made some adjustments on the spot, and returned the bike to me. Hopefully this will work.

When I wheeled the bike into the store one of the staff said "Wow, what is that? I've never seen a bike like that!" This really made me smile :) :cool:

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Is this your tri bike you're fiddling with? Did you take it to Proteus or somewhere else?

Yes, the tri bike. I took it to City Bikes since they are the most convenient for me.

If you still have problems, bring it to me. I've used 105, Ultegra, and DA front derailleurs on FSA and DA cranks. The 105 or ultegra setup on the FSA cranks with a clamp-on FD was the most finicky. The DA/DA braze-on match is amazingly awesome. But, if it's an alignment issue, I will be able to fix it. I usually have to totally re-do the FD on the FSA bike after the shop messes with it. So, I learned how to do it pretty well. If the cage needs to be moved, it can be a pain. You don't have as much range with a braze-on, but it can be moved a little bit.

However, I'm thinking that since this is your tri bike with non-indexed shifting in the front, some of it is going to be user error. Maybe you aren't used to the throw of the lever yet. Some compacts are a little more finicky about what rear cog you're in when you shift (are you any more successful shifting from the smaller end of the cassette?). Even so, it should be relatively rare to get the chain to go off to the outside if the FD is adjusted right. It's a lot more common to have drop to the inside with a compact.

You might try re-setting the limit and then tightening the cable tension if it gets a little sluggish. Adjust the FD upper limit screw a TINY bit at a time, and while you're in the little ring.

Lots of great advice here! Working with a compact crank does take a bit more time, but I'm sure that your LBS will get it right. Have fun with the new crank!!!:D

Instead of doing my Wednesday bike commute I took the tri bike out for a test ride this morning. The good news: no dropped chains! :) The bad news: I sometimes had trouble getting the chain to go onto the large ring and if I was on the large ring and using the two smallest cogs I had FD chain rub and couldn't trim out to stop it. :( Obviously I need to move the limit out a tiny bit. Do you think I should do this right away or wait until after my next ride on Saturday? And the stupid question so I can get it right the first time: to move the cage out do I loosen or tighten the limit screw?

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Originally Posted by MDHillSlug

Instead of doing my Wednesday bike commute I took the tri bike out for a test ride this morning. The good news: no dropped chains! :) The bad news: I sometimes had trouble getting the chain to go onto the large ring and if I was on the large ring and using the two smallest cogs I had FD chain rub and couldn't trim out to stop it. :( Obviously I need to move the limit out a tiny bit. Do you think I should do this right away or wait until after my next ride on Saturday? And the stupid question so I can get it right the first time: to move the cage out do I loosen or tighten the limit screw?

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Don't touch the limt screw (except maybe a tiny bit looser to improve shifting to the big ring)! One of the limitations of a compact is that, when you're cross-chained small to small, the chain will drag across the teeth of the large ring. Just don't cross-chain and you'll be fine :)

I can get to about the third cog from the bottom (14T) with the help of the trim before my chain drags on the large ring. I try to shift to the large ring sooner (15T or 17T), depending on cadence and terrain, but the best laid plans....

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Originally Posted by Becky

Don't touch the limt screw (except maybe a tiny bit looser to improve shifting to the big ring)! One of the limitations of a compact is that, when you're cross-chained small to small, the chain will drag across the teeth of the large ring. Just don't cross-chain and you'll be fine :)

I can get to about the third cog from the bottom (14T) with the help of the trim before my chain drags on the large ring. I try to shift to the large ring sooner (15T or 17T), depending on cadence and terrain, but the best laid plans....

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No, I was big/small, not crosschained.

BTW, when I was at the LBS the wrench told me that my chain was a bit too short because he couldn't get it to go big/big. I pointed out that I shouldn't ever be big/big!

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Originally Posted by MDHillSlug

No, I was big/small, not crosschained.

BTW, when I was at the LBS the wrench told me that my chain was a bit too short because he couldn't get it to go big/big. I pointed out that I shouldn't ever be big/big!

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Gosh, I'm sorry! I'm not reading very closely again- my fault! :o:(

In that case, I'd loosen the high limit screw the tiniest amount (quarter turn or so), and try again. You're almost there, and soon it will be perfect!

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BTW, when I was at the LBS the wrench told me that my chain was a bit too short because he couldn't get it to go big/big. I pointed out that I shouldn't ever be big/big!

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Yes, but you want your bike to be able to do this, should you be in one of your less clear/ more tired moments and accidentally make that shift. If the chain is too short and you accidentally shift "big-big" while riding, it can literally rip the derailleur off the frame, potentially destroying your frame, at a minimum destroying the derailleur. A longer chain also just shifts better.

You shouldn't be using trim at all to avoid rubbing in large ring/small cog combos. The cable should be pulled all the way tight (shifting completely). Trim when in the large ring will help you avoid rubbing the inner part of the cage in the larger cogs.

I would NOT mess with the limit at this point. You are getting rub in the smallest 2 cogs. This indicates that you've probably still got an alignment issue. Can you see where relative to the tail of the cage the rubbing is occurring? When you are standing near the rear of the saddle on the right side, facing forward, and when the bike is in the big ring/small cog, you should be able to look down and see that the chain is centered over the tail of the cage. If it's too far in or too far out, then you will have excessive chain rub despite properly set limits.

Also before you mess with the limit screws, check your cable tension. You are having symptoms of slow shifting and too much chain rub. That could be a limit issue, but I'd be hesitant to go there first given the bike's propensity to throw the chain off the outside. Try testing cable tension first. Hand shift by pulling the cable. Does the rubbing stop when you are pulling on it? If so, then maybe you just don't have the cable tight enough such that when you've got the lever pulled all the way, you aren't getting full movement of the cage (but you can get the additional necessary tension by pulling with your hand).

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Originally Posted by lunacycles

Yes, but you want your bike to be able to do this, should you be in one of your less clear/ more tired moments and accidentally make that shift. If the chain is too short and you accidentally shift "big-big" while riding, it can literally rip the derailleur off the frame, potentially destroying your frame, at a minimum destroying the derailleur. A longer chain also just shifts better.

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This is true, but it is easy to have too long of a chain on a compact if the chainstays are relatively short. That's because when in the small/large combo, you don't have enough chain tension to pull the RD away from the sprockets. With some setups, tightening the Bscrew to its max won't fix that. So, to avoid that, the chain will be a tad short and noisy. But, it shouldn't be shortened so much that the RD is being pulled sharply forward when in the big/big. You still need enough chain wrap to reach this gear and sustain a bit of an S shape in the RD, even if it's noisy.

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Originally Posted by aicabsolut

This is true, but it is easy to have too long of a chain on a compact if the chainstays are relatively short.

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If your rear derailleur hanger is designed and aligned correctly for the gears and components you are using (e.g., "road") you shouldn't have the rear derailleur guide pulley bumping up against any cog with the b-tension screw adjusted correctly...just hasn't been my experience. Even if this were to be the case, I'd rather live with a little chain noise in the small/large combo than risk ripping my rear derailleur/derailleur hanger off due to a too short chain...

I determine chain length by "dummying it up" in the small/small combo, and ensuring the chain is just short enough that there is no chain rub against the bottom part of the rear derailleur cage in this combo. I then shift through all gears to ensure it can handle them, keeping in mind stated derailleur capacities as stated by the manufacturer. This has never failed me.

And I am trying to understand: what does chainstay length have to do with it? Thanks.

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Originally Posted by aicabsolut

You shouldn't be using trim at all to avoid rubbing in large ring/small cog combos. The cable should be pulled all the way tight (shifting completely). Trim when in the large ring will help you avoid rubbing the inner part of the cage in the larger cogs.

I would NOT mess with the limit at this point. You are getting rub in the smallest 2 cogs. This indicates that you've probably still got an alignment issue. Can you see where relative to the tail of the cage the rubbing is occurring? When you are standing near the rear of the saddle on the right side, facing forward, and when the bike is in the big ring/small cog, you should be able to look down and see that the chain is centered over the tail of the cage. If it's too far in or too far out, then you will have excessive chain rub despite properly set limits.

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I think the alignment is OK, but I'm not completely sure.

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Also before you mess with the limit screws, check your cable tension. You are having symptoms of slow shifting and too much chain rub. That could be a limit issue, but I'd be hesitant to go there first given the bike's propensity to throw the chain off the outside. Try testing cable tension first. Hand shift by pulling the cable. Does the rubbing stop when you are pulling on it? If so, then maybe you just don't have the cable tight enough such that when you've got the lever pulled all the way, you aren't getting full movement of the cage (but you can get the additional necessary tension by pulling with your hand).

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Just checked, I can't make it go any further by hand.

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Originally Posted by lunacycles

If your rear derailleur hanger is designed and aligned correctly for the gears and components you are using (e.g., "road") you shouldn't have the rear derailleur guide pulley bumping up against any cog with the b-tension screw adjusted correctly...just hasn't been my experience. Even if this were to be the case, I'd rather live with a little chain noise in the small/large combo than risk ripping my rear derailleur/derailleur hanger off due to a too short chain...

I determine chain length by "dummying it up" in the small/small combo, and ensuring the chain is just short enough that there is no chain rub against the bottom part of the rear derailleur cage in this combo. I then shift through all gears to ensure it can handle them, keeping in mind stated derailleur capacities as stated by the manufacturer. This has never failed me.

And I am trying to understand: what does chainstay length have to do with it? Thanks.

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Chain wrap length has to do with the size of the large ring, the size of the large cog, and the length of the chainstay. It needs to be long enough to reach from the large ring to the large cog (along the length of the chainstay) without pulling the rear derailleur too far forward.

I can tell you that with a 34T inner ring, a 25T large cog and a smaller, compact race geometry rear triangle, that being one link too long will cause the rear derailleur pulleys to rub the rear cog when in that combo even with the B-screw tightened all the way (how my newest bike was built). There's nothing wrong with the derailleur hangar. I don't have this problem on a bike with longer chainstays or a bike with a 36T inner ring. With a compact, you still need a lot of chain wrap to get into the larger cogs while in the big ring, but then there's even more chain slack when in a 34T ring compared to standard cranksets. Of course being one link too long also causes a little bit of rub on the bottom part of the pulleys sometimes, but this isn't a problem functionally. Not like having the derailleur body bumping against the cog. I used a chain length calculator and verified that the chain was one link too long. Removing it still requires the B screw to be all the way tight, but there's no more bumping. There is more noise in the big/big combo, and I'm sure there's rougher tension on the chain when in the big ring by looking at the RD pulley angles, but it was necessary.


MDHillSlug, I guess you can try loosening the H limit now some, but do it slowly. Like 1/8 of a turn at a time, then re-check the shifting. You might want to put up with a little bit of rubbing if you don't use the small cog a lot, if that helps you keep the chain on.

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Originally Posted by aicabsolut

Chain wrap length has to do with the size of the large ring, the size of the large cog, and the length of the chainstay. It needs to be long enough to reach from the large ring to the large cog (along the length of the chainstay) without pulling the rear derailleur too far forward.

I can tell you that with a 34T inner ring, a 25T large cog and a smaller, compact race geometry rear triangle, that being one link too long will cause the rear derailleur pulleys to rub the rear cog when in that combo even with the B-screw tightened all the way (how my newest bike was built). There's nothing wrong with the derailleur hangar. I don't have this problem on a bike with longer chainstays or a bike with a 36T inner ring. With a compact, you still need a lot of chain wrap to get into the larger cogs while in the big ring, but then there's even more chain slack when in a 34T ring compared to standard cranksets. Of course being one link too long also causes a little bit of rub on the bottom part of the pulleys sometimes, but this isn't a problem functionally. Not like having the derailleur body bumping against the cog. I used a chain length calculator and verified that the chain was one link too long. Removing it still requires the B screw to be all the way tight, but there's no more bumping. There is more noise in the big/big combo, and I'm sure there's rougher tension on the chain when in the big ring by looking at the RD pulley angles, but it was necessary.

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Howdy aicabsolut, thanks for your reply and for the opportunity to respond again.
Over 20 years of wrenching I have experienced my share of b tension screw problems (i.e., derailleur guide pulley bumps against largest rear cog in small/large combos), but in my experience I haven't found that removing a chain link is the best answer, particularly if it creates a situation in which the chain is potentially too short and can potentially cause permanent damage to the components or frame. I hear you had this problem on your current bike and you solved it by removing a link. That's impressive troubleshooting. But to say this is a general tendency on bikes with short chainstays and a compact crank is a bit misleading/generalizing, imo, particularly in recommending that one should consider running a chain that may be too short in an effort to solve it (per your post previous to this one). Given the bikes I set up (frequently with the drivetrain set up you describe) I personally believe your situation is more the exception than the rule.

As a manufacturer, I believe what is the more likely culprit in your case is that your derailleur hanger is either not correctly aligned in the fore/aft sense or your hanger is too short for your app. That is: the threaded portion of the hanger needs to be the correct distance behind the dropout or shifting issues like this can arise. And/or, if the vertical distance between the dropout and derailleur mounting hole is not long enough, you can have the problem of the derailleur pulley being too close to the cog when running a larger rear cog, regardless of b-tension screw adjustment (and one reason I tend to put longer derailleur hangers on the majority of my frames). A lot of road frames come with short hangers, and maybe the one on your frame just isn't designed for a 34/28 (although that would seem odd given the current road offerings). Anyway, big old thread drift putting readers to sleep is going on here, but I did want to clarify my explanation a bit.

Ok, I understand what you mean. I used several gear calculators (math works a bit better for me to understand things), like the one you can find on the ParkTools site, and they all told me that my chain was put on one link too long. Taking it to the shop, the guys weren't crazy about removing the link, but it still seems safe in terms of not pulling the RD pulleys too taught. It's still not ideal such that I don't think I can run larger than a 25T cog on the rear with this bike. They said I just didn't luck out with the components I chose on this frame.

Anyway, I just wanted to point out that there can be some problems caused by erring on the side of a chain that is too long. Yes, it is can be catastrophic to have a chain that is definitely too short. I guess I am just advocating making sure the chain is properly sized for the individual setup.

After Wednesday I backed out the limit screw a quarter turn; seems to be just enough to do the trick. It was all good today! :D

Thanks for all your help!

Having just converted a triple to a compact crank on one of my 5 bikes, I have learned a lot.

I needed a 165 mm 9-speed crank for my short legs. The only model available was the Shimano Sora. I liked it -- much lighter than the Truvative triple.

FSA 9-speed compact cranks only come in 170mm lengths which would cause me too much toe overlap with the front wheel.

The compact crank works with a double front derailleur and triple rear derailleur. I replaced a Shimano Tiagra triple front derailleur with a Shimano 105 double front derailleur.

The compact crank must mate with its bottom bracket. I replaced a generic Truvativ triple bottom bracket with a Shimano hollowtech.

The Shimano 105 triple rear derailleur works perfectly!

Depending upon the other components -- 10 speed or 9-speed rear cassettes and shifters, the compact crank doesn't need Ultegra level, especially if the rest of the compenents in the drive train are less than Ultegra-level in quality.

Why are you using a long cage rear derailleur?

maybe 'cause she had it from the triple that she was converting to a double?

My FD has been well behaved on my last two rides but yesterday the RD decided that it wanted to skip past one of the cogs towards the middle of the set. Everything else seemed OK. What would cause this all of a sudden and what do I do to fix it?

Did it do it repeatedly?

Sometimes, we just get the "throw" wrong of the lever. Other than excessive wear to the cassette or chain, that's a fairly good guess when you have skipping problems on one cog and towards the middle. Did it matter which side you were shifting from? (Did it skip only when shifting easier or harder into that cog?)

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Originally Posted by aicabsolut

Did it do it repeatedly?

Sometimes, we just get the "throw" wrong of the lever. Other than excessive wear to the cassette or chain, that's a fairly good guess when you have skipping problems on one cog and towards the middle. Did it matter which side you were shifting from? (Did it skip only when shifting easier or harder into that cog?)

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Yes, repeatedly. Yes, in both directions. The chain, cogs, and cranks are all new, with less than 250 miles on them.

Only in the middle on one cog? You might want to check that the cassette is still on there tightly.

Hmm... the only time I had a similar experience it turned out (weirdly) that the rear cable was installed too tightly. I thought maybe tightening it would help because it was pretty new, so when that didn't work, I loosened it and the problem was solved. I'm not sure that's typical, though.