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View Full Version : B-tension, shifting, chain length issues


Mayhem
04-10-2015, 03:46 PM
On one of my bikes I have the infamous Ultegra 6700. Not known for being the smoothest shifting group ever made. I've always done my own work and have been tuning bikes since Ronnie was president. Never in my life have I had so much trouble tuning as I've had with this group. To keep it short, I tried everything in the book but it always had issues upshifting.

The cables are lubed, H and L adjustment is perfect, everything is good. If I tighten the cable even a hair more then you can start to hear grinding.

The one thing that always stumped me was that with the b tension screw out all the way (I could remove it), the upper jockey wheel was never close enough to the small cog. Neither the hangar nor anything else is bent, it's been like that since new. So one day a light bulb came on and I decided to add one link to the chain. Using the big/big method and an online calculator I was originally at 53 links. Now I was at 54, the jockey wheel moved closer to the cog and the shifting was 1000x better. I would say today it's at 95%, but every ride, unless I give the perfect touch on the shifter, it will misshift going up once every couple of miles, usually from the 16 to the 17. It's worse when I'm in the big ring.

I have 5200 miles on this bike, about 2500 miles ago I ditched the original 11-28 and compact crank to the current 12-25 w/ standard crank. New chain, the shifting was the same.

I want to get it perfect so my question is this: Looking at the pics, do you think I should try adding one more link? Does the chain line look like it could be a hair slacker and does it still look like too much gap between the jockey wheel and the 12T? And with nothing damaged, why do I have this issue with the b tension? It's still unscrewed all the way.

http://i73.photobucket.com/albums/i233/snuffster_2006/011_zpsrncchpyb.jpg

http://i73.photobucket.com/albums/i233/snuffster_2006/020_zpsqceo4quz.jpg

kramnnim
04-10-2015, 04:07 PM
Chain is shorter than it would be if you used the small/small method. (which I always use, as do many other forumites, per a recent thread about chain length)

Mark McM
04-10-2015, 04:40 PM
... and the shorter chain does two things:

1) Extends the cage away from the sprockets (reducing the lateral force trying to move the chain from one sprocket to the next when the derailleur is shifted)

2) Increases the tension in the bottom run of chain (making it harder for the chain to disengage from one sprocket to move to the next).

carpediemracing
04-10-2015, 04:42 PM
The small small method for me would involve seeing where the chain would hang or hit itself in the pulleys, then adding (sorry I should say removing) one pair, i.e. the minimum amount you can add to fix the chain slackness. I would guess that you could add another pair of links and be okay.

For the b-screw thing… I used to remove the b-screw sort of automatically because I'd loosen it all the way and I didn't want to lose it in case I wanted to use it. So I just left it in my toolbox or small parts bowl or whatever. With the current Campy there isn't a b-screw so I just leave it.

It might be that the cable housing is pulling the derailleur away a bit. The spring related to the b-screw is not super strong at the top of its range so it doesn't pull up that last bit very easily. You can experiment by disconnecting the cable housing. Put it in the small-small then move the derailleur to the small cog without moving the wheel, you should have slack to pull the housing out of the stop. Pull the housing from the derailleur so the housing/cable doesn't exert a lot of force on the derailleur. Then see if the derailleur settles in a higher position.

Another cause might be lack of lubrication in the pivots and the pulleys. Any friction in the pivots or even the pulleys will keep the pulleys from going all the way up. The drivetrain looks pristine and excessive cleaning could remove some of the lubricant in the pivots/pulleys. You can check this by back pedaling. If the derailleur moves at all then the pulleys are underlubricated or over sealed or something. If you nudge the derailleur up and it stays up there then you may need to lubricate the pivots on the rear derailleur.

Disclaimer. I have never, ever worked on that model Ultegra so I'm totally talking out my butt. However from a concept point of view that's been my experience wrenching my bike and others' bikes.

Ralph
04-10-2015, 04:46 PM
Chain is shorter than it would be if you used the small/small method. (which I always use, as do many other forumites, per a recent thread about chain length)

I would use more links to begin with than you are using. One can always take them out. To add two more links safely, just use one link plus a quick link.

Mayhem
04-10-2015, 05:04 PM
Okay, I added one link. That's not going to work. It was way too slack. The chain was actually laying on the top of the chainstay when not pedaling and the bottom was sagging. I also forgot to mention that there's @ 7mm of clearance between the jockey wheel and the big cog. Didn't take a pic of that.

ultraman6970
04-10-2015, 05:16 PM
Did you check if the rd hanger is straight??? Ive seen in some bikes that when you tight the quick releases the rd hanger goes out of alignment and that could be one of your problems. Sure the hanger is not lose?

Mayhem
04-10-2015, 05:29 PM
Did you check if the rd hanger is straight??? Ive seen in some bikes that when you tight the quick releases the rd hanger goes out of alignment and that could be one of your problems. Sure the hanger is not lose?

I had the hangar alignment checked at a bike shop a good while back since I didn't have that tool. Of course the mechanic didn't know what was up with the b tension.

carpediemracing
04-10-2015, 05:43 PM
I had the hangar alignment checked at a bike shop a good while back since I didn't have that tool. Of course the mechanic didn't know what was up with the b tension.

Typically the hanger gets bent inward a bit, even if you swear you never put it down on the drive side (like me).

I was going to skip this tip since it's purely subjective and you'd mentioned checking alignment but whenever I have a vague shifting issue I'll stick an allen wrench in the rear derailleur mounting pulley and give the wrench a good twist up. This is going back to bike shop days for me, pretty much every derailleur hanger gets bent inward and I think a little to the back (so the derailleur ends up pointing to the cranks instead of the BB). I can't remember now. I would sight down on the pulleys when the chain was in the small-small (so the pulley cage was as flat as possible) and see if the pulleys lined up with the cranks.

Anyway that's one of those tweak things that work often but is hard to quantify. It's like fine tuning a violin by pushing on the string between the bridge and the tailpiece which holds one end of the strings, or the end of the fingerboard and the pegs which hold the other end of the strings. It works but it's hard to quantify. I do this even now, meaning the derailleur tweak (last played my violin a while ago). Last few bikes I looked at, including a Junior teammate's bike that "wasn't shifting right for a while" had slightly-to-pretty-badly bent hangers. The Junior's bike was pretty bad and all I had to work with was his folding tool kit (worked on it on the side of the course at a Tues Night crit).

regularguy412
04-10-2015, 11:31 PM
My CSI kinda had that problem as it got older. Would be hard to shift accurately when right in the middle of the cog set. I now have a new frame. I suppose that the hanger was ever so slightly bent inward , or possibly twisted (think 'yaw') slightly. Anyway using the SAME rear der on the new frame, the shifting is flawless. The two things I would definitely check are rear hanger alignment AND chain line. It's possible that the front rings are just enough 'out' to made some of the cogs in the rear not want to shift just right.

Mike in AR:beer:

oldpotatoe
04-11-2015, 08:00 AM
On one of my bikes I have the infamous Ultegra 6700. Not known for being the smoothest shifting group ever made. I've always done my own work and have been tuning bikes since Ronnie was president. Never in my life have I had so much trouble tuning as I've had with this group. To keep it short, I tried everything in the book but it always had issues upshifting.

The cables are lubed, H and L adjustment is perfect, everything is good. If I tighten the cable even a hair more then you can start to hear grinding.

The one thing that always stumped me was that with the b tension screw out all the way (I could remove it), the upper jockey wheel was never close enough to the small cog. Neither the hangar nor anything else is bent, it's been like that since new. So one day a light bulb came on and I decided to add one link to the chain. Using the big/big method and an online calculator I was originally at 53 links. Now I was at 54, the jockey wheel moved closer to the cog and the shifting was 1000x better. I would say today it's at 95%, but every ride, unless I give the perfect touch on the shifter, it will misshift going up once every couple of miles, usually from the 16 to the 17. It's worse when I'm in the big ring.

I have 5200 miles on this bike, about 2500 miles ago I ditched the original 11-28 and compact crank to the current 12-25 w/ standard crank. New chain, the shifting was the same.

I want to get it perfect so my question is this: Looking at the pics, do you think I should try adding one more link? Does the chain line look like it could be a hair slacker and does it still look like too much gap between the jockey wheel and the 12T? And with nothing damaged, why do I have this issue with the b tension? It's still unscrewed all the way.

http://i73.photobucket.com/albums/i233/snuffster_2006/011_zpsrncchpyb.jpg

http://i73.photobucket.com/albums/i233/snuffster_2006/020_zpsqceo4quz.jpg

That looks good to me..Might try to route the shifter cables to the back side of the handlebar, if not there already. Seems to make this first gen shifter housing hidden, shift better. Might also try 5mm der housing, 1.1mm der cables and a squirt of light lube in the housing. Seems to make 6700/7900 shift better.

Ken Robb
04-11-2015, 11:36 AM
Could the FSA crank cause a problem?

Cicli
04-11-2015, 11:41 AM
Could the FSA crank cause a problem?

Yes, FSA cranks are a problem but probably not your problem. I loved my 6700 group. Until I got rid of it and put some miles on something else. It was never quite perfect. It was good, but not perfect. Acted almost exactly as you describe.

Mayhem
04-11-2015, 03:35 PM
So after reading some replies I decided to stop assuming the derailleur hanger was good. Eyeballed it from the rear and it did seem slightly bent inward. What I did was unbolt the derailleur, got a spare rear wheel with a threaded axle end and threaded it right into the hanger for a poor man's alignment tool. Perfect fit. Then I measured the distance from the spare wheel to the wheel on the bike at the top and bottom. Sure enough, it was off a hair under 2mm. Fixed it, tuned it up and went for a ride. It did misshift a couple of times so I tightened the barrel adjuster another 1/4 and after that it was trouble free the rest of the way. Upshifts are much faster, no grinding going down or anything. Crossing my fingers and hoping it's good to go now. It it as good as Campy or the 8-9 speed Shimano groups I've had? No, but it's pretty close now.

SPOKE
04-11-2015, 05:33 PM
Be aware that many of the OEM replaceable dérailleur hangers bend pretty easily. They can even bend under shifting loads.
Glad you fixed the issue:banana:

ultraman6970
04-11-2015, 05:48 PM
told'ya!

:p

Mayhem
04-11-2015, 06:05 PM
told'ya!

:p

Well I'm keeping my fingers crossed. With my luck it will start misshifting in the morning. The one single time in my life I take a bike to a shop to get it fixed and they apparently did nothing I guess :(

zzy
04-11-2015, 06:14 PM
Is your chain installed backwards? 5700/6700 chains need to be installed with the logos/branding facing out (yes really).

tristan
04-11-2015, 07:43 PM
Is your chain installed backwards? 5700/6700 chains need to be installed with the logos/branding facing out (yes really).

I was about to type the same thing!!

The chain's orientation will make a big difference to performance.

tristan
04-11-2015, 07:45 PM
Get rid of that Jagwire (?) housing and fit a proper Shimano cable kit (inner and outer) with the PTFE cables that is designed for the 'hidden' shift cables.

regularguy412
04-11-2015, 09:42 PM
Get rid of that Jagwire (?) housing and fit a proper Shimano cable kit (inner and outer) with the PTFE cables that is designed for the 'hidden' shift cables.

This^^ too. I tried jagwire inner cables and found them 'ok' but not so good with once-used housing.

Jagwire for my rain bike, but not for the main ride.

Mike in AR:beer:

Mayhem
04-12-2015, 09:03 AM
Is your chain installed backwards? 5700/6700 chains need to be installed with the logos/branding facing out (yes really).

So after you punked me out (j/k), I flipped the chain over. Went out at sunrise for a ride and just got back in. Over 36 miles it was even better than yesterday, it's 100% now. Every single shift was perfect and the drivetrain was dead quiet, the way I've been trying to get it for the last 5200 freaking miles. This was me the whole time: :D:D:D