55/Rad

Setup: Cervelo P3C with DA barends, ders, cassette and chain. Less than a year old, less than 500 miles total. Friend brings me the bike and asks me to tune it up.

I find after doing the basics that the shifts are hesitating in the middle range - in both chain rings. After an hour of adjustments to no avail, I take the bike to the shop to have them check the rear der hanger alignment. It is apparently lined up correct. Mechanic measures chain and says it's close to being worn and this may be the problem. Cassette looks and should be fine given the mileage. Cables are new and moving freely in the housing.

Owner says the hesitation has been there from day one...this bike is too expensive and still too new for it not to be perfect...

Other than switching out a chain - which I will do - any ideas or thoughts?

Thanks.

55/Rad

desertdork

For clarity, does it hesitate on both upshifts and downshifts?

55/Rad

Yes...

I might add that the original setup had the DA barend shifters, which were recently replaced with the Zipp Vuka R2C shifters, along with new cables and housing. Different shifters, same problem.

San Rensho 

Brands of housing/cable make a difference. I had changed to a Bontrager set and the shifting was awful. Went back to generic and the shifting got much better.

Could also be the rear der is worn. Pivots eventually wear making for sloppy movement. Check by twisting the der and checking for play.

By the way, when I had the shifting probles, I checked the chain and it was near the wear limit so I changed it. Made no difference in shifting, but it can't hurt to change it.

Kimmo 

NFI what the problem is, but it's obviously pretty obscure and subtle.

IMO >8spd groups don't use enough cable pull per shift, given all the hassles I've seen...

All I can recommend is finding a way to increase the tension of the RD's return spring (the one that pulls the cable).

LarDasse74

Who is the manufacturer of the cassette?

55/Rad

Ultegra 6600 cassette. Not the DA I mentioned in the OP.

Update...

I had the derailleur hanger examined for alignment and it was fine. It appears the chain is more worn than I anticipated, so tested a couple (used) ones I had laying around. Seemed to improve the shifting a hair but I still get a hesitation in the middle. Might need a brand new one but I don't want to spend the money unless absolutely sure.

Next up...I'm going to switch out the cassette to see if that helps. Then, if not, the rear derailleur.

55/Rad

Burton

Personally I`m surprised the chain is already shot with that little milage on the machine but that alone shouldn`t cause an issue anyway.

You`ve already swapped out the shifters I believe and the front derailleur isn`t apparently an issue so if the cable runs are good, that only leaves the cassette and the rear derailleur.

Yeah - if nothings visibly stuck between any cassette cogs, I`d suggest just swapping out the rear derailleur. If its always been like this and it does turn out to be the derailleur - should have been a warranty claim a long time ago.

55/Rad

Turns out I under estimated the actual mileage. Owner states it is closer to 2000 miles, which explains the wear in the chain. He also claimed the hesitation has always been there. I changed out the rear cable and housing for a second time and swapped out the cassette. 2 actually, with no improvement. Next up...the rear derailleur.

I'll add that the system is working fine, just not close enough to perfect that I feel it should be. The front is perfect...it's the dang rear that's driving me crazy.

Thanks again for your help...

55/Rad

ericm979

Check the cable routing.

55/Rad

Done. And redone. Cables are internally routed through the down tube. No problems there.

well biked

Not to second-guess (but I am, I suppose), but first you say the derailleur hanger alignment is "apparently lined up correctly" and then you say it's been "examined." My question is this: has a competent mechanic checked the derailleur hanger alignment with a derailleur hanger alignment gauge? If not, it needs to be done, and any misalignment corrected with the gauge. Rear shifting that is off in both directions is a common symptom of a misaligned derailleur hanger (and it sounds like you already know this). Ten speed drivetrains are very picky about derailleur hanger alignment.

55/Rad

Sorry for the confusion. Rder hanger alignment has been checked with a gauge by a very competent mechanic. Apparently, it is straight. I just didn't see the test in-person but I do trust this mechanic.

well biked

No problem, I just wanted to make sure the hanger had been checked with a gauge instead of someone just eyeballing it and saying it looks okay. Modern drivetrains are too picky for that, and my first guess when one is off in both directions is that the hanger is out of alignment. Sounds like you're covering all the possibilities. Good luck in getting it sorted out.

joejack951

Have you lubed the cable where it enters and exits the down tube? I troubleshot a similar problem at the front derailler on a friend's Tarmac and a little lube solved it.

55/Rad

Okay...after several hours and a lot of changing parts and setup, I finally figured it out.

Bike definitely needs a new chain but what was causing the problem was the cable itself. The Zipp R2C shifters came with a set and I naturally tried those first. Somewhere along the way, I figured there might be a problem and switched the rder cable out for a new standard cable. No change.

After changing out the cassette and derailleur with no improvement, I went back to the cable. It is internally routed and though it seemed OK, there certainly was some friction. I switched out the cable and put a teflon coated one in. But this time, I ran a sleeve on the cable on the inside of the downtube, hoping to alleviate any friction that may have been caused by the 2 derailleur cables crossing each other in the down tube or the cable pressing against the tubing. I couldn't see if they actually were/are, but I figured what the hey.

System works great. It seems finicky as hell but its working well.

Thanks again for all the advice and help.

55/Rad