# Front Derailleur Rub in highest gears. Help



## arkitect (Apr 25, 2011)

Hey guys, I have a problem that I can't seem to resolve. I have a new 2011 Cervelo R3 and I love the bike. I have Dura Ace components and the bike came with Rotor cranks. 

Here is the problem: I have dropped the chain off the big chainring about 6 times during the first 500 miles of riding, so to prevent that from happening any more, I have adjusted the limit screw on the front derailleur about 1/4 turn. However, by doing this, I now get severe chain rub in the highest 2 gears/cogs on the cassette. How do I fix this? Shimano has stated that the Dura Ace 7900 derailleur could allow shifting across the entire cassette without trimming (i find that hard to believe, but that seems to imply an installation problem on my bike.....)

By the way, it would seem to me that the front derailleur cage should be angled slightly (toe-in) so it would be more parallel to the chain in the highest gear. However, all guides that I have seen say to align the cage parallel with the chainrings

Thanks!!


----------



## Kontact (Apr 1, 2011)

Take the bike back to the shop and have them fix it. You paid for correct assembly.


----------



## JCavilia (Sep 12, 2005)

Did you try any cable adjustment before you messed with the limit screw? Try putting the limit screw back to where it was, so there's (barely) no rub in the highest gear, then turn in the adjuster a little, so the derailleur doesn't move quite as far with that last click. With some tinkering with both adjustments you might be able to find a balance point that works.

How does the chainline look? When you sight down between the two chainrings, does it line up about with the middle of the cassette? If the crankset seems too far inboard you might have a compatibility issue with the bottom bracket.

The usual recommendation for front der adjustment is parallel. The angle you suggest would probably cause rubbing in the low gears.


----------



## arkitect (Apr 25, 2011)

JCavilia said:


> Did you try any cable adjustment before you messed with the limit screw? Try putting the limit screw back to where it was, so there's (barely) no rub in the highest gear, then turn in the adjuster a little, so the derailleur doesn't move quite as far with that last click. With some tinkering with both adjustments you might be able to find a balance point that works.
> 
> --- No I did not. Essentially, prior to adjusting the limit screw, I was still getting derailleur rub (severe) in my highest cog. Since I adjusted the limit, I now get it in the highest 2 cogs.
> 
> ...


---That makes sense. I was hoping to be able to fix this on my own but I may need to make a trip to the shop where I bought it.


----------



## Camilo (Jun 23, 2007)

I'd call ahead and ask them if you can bring it in and they'll fix it while you wait, and let you watch them so you learn how to tweak it.

Does this shifter (not derailleur, shifter) have trim?


----------



## Kontact (Apr 1, 2011)

The basic problem with Arkitect's question, and similar ones, is that it starts with a misunderstanding of how derailleur adjustments work and goes from there.

The real question is "How do I set up a front derailleur?" If you don't know the answer to this question, no amount of advice on troubleshooting will help.

The chain didn't fall off due to a limit screw. Of the five adjustments that can be performed on a front derailleur, 3 of them may have caused the problem - if it is an adjustment problem and not something else, like a bent chainring tooth.

That is why I advise getting the bike back to the shop. Messing with derailleurs is a great way to screw up your paint, frame or wheels - if you don't understand the basics. And you're never going to understand the basics if you don't read a book or manual, or at least start with a properly working system.

Get the bike fixed by someone in the know - they know what to look for. THEN learn how to do it yourself.


----------



## arkitect (Apr 25, 2011)

Kontact said:


> The basic problem with Arkitect's question, and similar ones, is that it starts with a misunderstanding of how derailleur adjustments work and goes from there.
> 
> The real question is "How do I set up a front derailleur?" If you don't know the answer to this question, no amount of advice on troubleshooting will help.
> 
> ...


Kontact, thanks for your input. I posted on this forum to get assistance from others so I did not have to take it to the shop and try to watch them. I am not a newbie and have built up 2 bikes from frame in the past but I have never had this adjustment issue to deal with so was looking for input from others. Just trying to eliminate possible causes for this to occur. 

I have extensively reviewed Shimano's derailleur installation instructions, the derailleur is installed exactly to their specs. Shimano states, "If the chain falls to the crank side, tighten the adjustment screw clockwise 1/4 turn." I did this.

Their installation document also states, "To improve gear shifting performance, the SIS adjustment method for the FD-7900 front derailleur is slightly different from previous derailleurs. In addition,the trimming mechanism has also been abolished in order to improve shifting performance."

I will stop by the shop and have them troubleshoot for me


----------



## Kontact (Apr 1, 2011)

arkitect said:


> Kontact, thanks for your input. I posted on this forum to get assistance from others so I did not have to take it to the shop and try to watch them. I am not a newbie and have built up 2 bikes from frame in the past but I have never had this adjustment issue to deal with so was looking for input from others. Just trying to eliminate possible causes for this to occur.
> 
> I have extensively reviewed Shimano's derailleur installation instructions, the derailleur is installed exactly to their specs. Shimano states, "If the chain falls to the crank side, tighten the adjustment screw clockwise 1/4 turn." I did this.
> 
> ...


Terrific! It sounds like you are doing the right things.

The reason I pushed you toward the shop is that I've been seeing a lot of front shifting issues lately that aren't a result of derailleur set up. Some are frame problems, some a crank problems. Diagnosing them is a pain, and making sure the LBS knows about them from the get go will insure your problem is dealt with as a bike problem, not a customer problem.


----------



## nhluhr (Sep 9, 2010)

arkitect said:


> Shimano has stated that the Dura Ace 7900 derailleur could allow shifting across the entire cassette without trimming (i find that hard to believe, but that seems to imply an installation problem on my bike.....)


They only make that claim if you're using full dura-ace. your bike has an FSA crank. It's not a full system and the integration is not going to be as perfect. That said, it's the adjustment not the parts that are causing your problem.

Also, just making a full 1/4 turn adjustment is a little bit... granular. Sometimes the correct adjustment is much less than a 1/4 turn away.


----------



## arkitect (Apr 25, 2011)

*Update*

Well everyone, i am back from the bike shop I bought my Cervelo at and they spent about 30 minutes adjusting my FD to try and eliminate the chain rub. Bottom line, they checked the FD alignment, it was fine. They then adjusted the FD some more and although the rub was better, it was not completely eliminated. A second mechanic took a look at it and adjusted things as much as he could but told me that if he tried to adjust it out any further, I would drop the chain over the big ring. 

The FD has a gap between it and the chain when stationary but when riding, it still rubs slightly while pedaling. (It seems to happen when the pedal is at about the 3 o'clock position.) The shop felt that the problem is caused by the chainring on the ROTOR cranks (standard ring) flexing while pedaling ( I do weigh 195 pounds). They were going to contact their Cervelo rep for other ideas but I would think that an amateur, recreational rider should not be able to flex a chainring as much as a pro would so not sure what to do. Maybe the Aero chain rings by ROTOR would be a bit stiffer? Thoughts?


----------



## arkitect (Apr 25, 2011)

UPDATE:
Still having a problem. I contacted Cervelo to see if they thought this performance was normal and they said no and that I should give the shop a chance to correct it. I spoke with the shop owner who agreed that this should not be happening and to take it in and he would have his best mechanic look at it. So, yesterday I took it in. He looked at the derailleur, did some adjustments and had me take it out. I came back in..........same issue. He then hopped on the bike and came right back. He said that he was also able to make it rub and he weighs 150. He didn't even have to stand up to make it happen.

He spent 2 hours looking at it, taking off the cranks, switching out rings, switching out the spider arm but to no avail. He was very, very frustrated as he could not pin point the problem and could not understand why it was still happening, everything looks perfect. He said the ROTOR rings initially ( a year ago) had flex in them and Thor refused to ride them. They were redesigned and are stiffer so they are not the issue.

There is a big gap between the chain and FD when on the stand. You take it out, and it rubs. The shop is great, and are doing everything they can to fix it. I had to leave it there but when I was heading out the door, they were in the process of changing the cranks out with a Dura Ace set. If this takes care of it, the cranks are the cause. If it does NOT, maybe it is a crack in the frame?? 

THey have not heard of this ever happening before and it is a mystery at this point.


----------



## arkitect (Apr 25, 2011)

*Problem solved*

For anyone who cares, I FINALLY got my derailleur rub problem solved, and it was something unexpected. Cervelo sent my LBS a new ROTOR crankset as they insisted that their frame was not flexing, causing the rub, it had to be the cranks. Well, they were right. The cranks sent with the bike had a flaw of some kind, causing them to flex somehow and rub the FD. The LBS put on the new cranks and I took it out for a 2 hour ride up a canyon climb and I could not get the chain to rub at all.

Oh yeah, feeling happy now! The shop, and Cervelo, had never heard of this problem before and were stumped. I am lucky to have a great mechanic who was passionate about figuring out the problem, he even stayed late the night I dropped off the bike, just to see if the new cranks were the solution!


----------



## kreyszig (May 2, 2006)

arkitect said:


> For anyone who cares, I FINALLY got my derailleur rub problem solved, and it was something unexpected. Cervelo sent my LBS a new ROTOR crankset as they insisted that their frame was not flexing, causing the rub, it had to be the cranks. Well, they were right. The cranks sent with the bike had a flaw of some kind, causing them to flex somehow and rub the FD. The LBS put on the new cranks and I took it out for a 2 hour ride up a canyon climb and I could not get the chain to rub at all.
> 
> Oh yeah, feeling happy now! The shop, and Cervelo, had never heard of this problem before and were stumped. I am lucky to have a great mechanic who was passionate about figuring out the problem, he even stayed late the night I dropped off the bike, just to see if the new cranks were the solution!


I just read the whole thread. I am glad your problem is fixed! Hopefully it was a unique case and not an indicator of the Rotor quality control...


----------



## Kontact (Apr 1, 2011)

Glad to hear they solved the problem. Rotor cranks are weird and sometimes hard to deal with.


----------



## rgordin (Oct 22, 2010)

Good to have a shop that will doggedly work at a problem like that. Many a shop would have told you that the rub won't hurt anything and/or that it was within tolerance. Kudos to the shop and Cervelo.


----------



## Shinjukan (Aug 22, 2011)

*Similar Issue*

Sorry guys if I use this thread to post my front derailleur question. I just signed up to this wonderful forum a few days ago and learned that I can't create my own thread if I've done less than 5 posts. Since the OPs issue has been resolved I thought of following it up with mine.

Attached is a pic of my front derailleur and crankset. I've read and viewed in more than a dozen sites that the distance between the outer cage plate and the biggest chainring teeth should be about 1-3mm. I bought my bike last July and I've noticed that when I'm on the big ring/small cog combo, the chain rubs on the outer cage plate (referred to by the yellow circle) no matter what adjustment I make--trimming or re-shifting the front shifter, or high-limit screw. I measured the gap and it's more like 5mm. So with this, I am beginning to think that the height of my front derailleur is perhaps the culprit to the chainrub issue. What do you guys think? Should I go ahead and lower it by myself and should that do the trick? Other than this issue, the shifters and gears work wonderfully well that's why I'm hesitant to do it and risk messing things up further. The shop where I bought it is 30 miles away from me and I just don't want to travel the distance only to be told that it's how it should be.

Thanks.


----------



## nhluhr (Sep 9, 2010)

So you are saying you're in the HARDEST (highest) gear; big chainring and small cog, correct?

I do believe that your derailleur appears to be a couple mm high but that won't affect rubbing in this situation.

First of all, to eliminate this rub, you'll need to tighten the cable a hair on the barrel adjuster, maybe 1/4 to 1/2 turn if the rub is minor. If the H limit screw is preventing it from moving, back that screw out in tiny increments. With that said, it could be that your derailleur is slightly angled (rotated about the seat tube) which would throw off the adjustment. So before you start adjusting tension and limits, ensure that the cage is perfectly parallel to the chainrings. Use a straight edge like a ruler to help visualize it.

You can refer to this link for more info:
Park Tool Co. » ParkTool Blog » Front Derailleur Adjustments


----------



## frdfandc (Nov 27, 2007)

Shin, your derailleur is too high. You should start over from the beginning for setting up the FD.

Here is what I do on the bikes I service and build.

Shift the cassette to the smallest chain ring. With the derailleur over the smallest chain ring, set derailleur height adjustment above the large chain ring there. The space between the cage and the biggest tooth on the large chain ring should be 1-2mm. 

Adjust cable tension as needed to allow proper shifting. 

Park Tool does it differently.

Park Tool Co. » ParkTool Blog » Front Derailleur Adjustments


----------



## Shinjukan (Aug 22, 2011)

Thanks, frdfandc. Based on the ton of information including pictures and videos I've seen, I'm suspecting that my FD has been set up a few millimeters higher than normal by the LBS where I purchased my bike. And correct me if I'm wrong but based on the picture I posted earlier in which I encircled in yellow the part of the FD which I've seen that the chain is still rubbing while I'm on the big ring/small cog combination, do you think by lowering the height of the FD solve that? I'm already tempted many times in the past to muster enough courage and do it, but I'm afraid that if I ended messing up with it I would be missing a couple of our rides with my buddies. It shifts fine and works flawlessly, it's just that when I get to the 2 smallest cogs on the rear and the big chainring up front I get that droning rubbing sound by the chain on the FD cage plate. That's why I'm hesitant to tinker with it now.

Thanks for all your inputs.


----------



## Erion929 (Jun 10, 2010)

Shinjukan said:


> I'm already tempted many times in the past to muster enough courage and do it, but I'm afraid that if I ended messing up with it I would be missing a couple of our rides with my buddies. It shifts fine and works flawlessly, it's just that when I get to the 2 smallest cogs on the rear and the big chainring up front I get that droning rubbing sound by the chain on the FD cage plate. That's why I'm hesitant to tinker with it now.
> 
> Thanks for all your inputs.




You sound like me....hate to tinker with derailleur adjustments cuz I'd likely make it worse and get in so deep I lose riding time.

What I do in those cases is RIDE the 30 miles to your "local" shop and pay the $10 for a front der adjustment....much easier to get it right. And you would've been done with it now. Plus you still get a 60-mile ride in 


**


----------

