I just purchased a brand new Cannondale Synapse Tiagra 6C. I took it on a ten mile ride today, and ran into a problem. If I trim so that the bike shifts down, it is then reluctant to shift up - often it won't unless I coax it with the shifter to complete the shift. If I trim so that bike will shift up, then it won't always shift down. I can't find a happy medium. I've run into this before, but can't remember how to adjust for it. I have forgotten how to resolve this issue. Advice please???

Sounds like classic cable friction. Internal routing? Set the cable tension for just solid upshifting and over move the lever for down shifting. Andy.

Yes, cables are internally routed. For what I paid for this bike, this problem is not acceptable to me. How do I fix it!

I'll speculate this is one of your first bikes of that caliber, so take what I'm saying in that context. Minor shifting issues are normal with all bikes as cables and components settle in, then as they wear down. Minor, tweaking, following a procedure, not random changes are par for the course. You should be able to have the LBS tweak the cable tension, or better yet learn to do it yourself.

First, is it the Front or Rear derailleur that is giving you problems? Next, shifting up is going to a harder faster gear. So that would be larger chainring on the FD, smaller cogs on the RD. Which is it?

Loose cables on the FD will interfere with shifting up into the large chainring.
Overly tight cables on the RD may interfere with shifting into the small cogs.

Agreed that poor shifting is Boy right on a new bike. But do understand that internal routed shift cabling will have greater friction and maintenance needs then classic and straighter outside routing. To a degree this is some of the "cost' of the decision you made when you bought the bike.

Having said that you should take the bike back to the store you bought it from and have them go through the shifting system to make sure that there are no other issues adding their aspect. Like the exposed casings are cut clean, well capped and with nice smooth loops. Like the inner cables have no kinks or distorted sections in them. We add TriFlow to our inner cables as they pass through and around the casings and guides.

Good luck. Andy.

My previous bike was a Fuji Absolute 3.0 with Aliveo shifters. They worked perfectly for the five years I had the bike. The problem is with the rear dérailleur, and break in could be part of the issue, but I am going to pull the cable and apply a light lubricant. I'm also going to inspect for clean housing cuts, snags, kinks, etc. as Andy recommended.

The problem does seem to be worse on the faster gears, so cable tension could be an issue. Any advice on how to adjust the tension would be appreciated. And I really appreciate the feedback. Thanks!

I would have the shop check it out. If you mess with it, you give them an out to deny you warranty service. It could be a simple cable adjustment, or a derailleur hanger tweak, or something could actually be wrong. Don't give them that out.

Fortunately, they are working with me on it, and are OK with me checking and lubricating. The next question is what should I use to lubricate the cable. Seems like I've found articles advising against every lubricant known to man. The LBS isn't all that local, so I need to pick something up at a hardware store. Any suggestions would be appreciated.

You will find barrel adjusters in at least one, possibly 3 places on each cable: at the shifter, in the middle on the frame (where it can be reached while riding) and on the RD itself. Use 1/2 turn increments, then maybe to 1/4 turn increments until shifting meets your expectations.

Oh, I'm familiar with that adjustment. I thought you were talking about something else. Problem is, that adjustment isn't helping. When I get it to shift up, it won't shift down, and vice versa. I'm thinking a friction problem now...

Take it to the shop you bought it from.

If it isn't easily resolved I will, but it is a 50+ mile round trip, and they are OK with me checking into it. Besides, I want to learn about this issue. If it isn't easily resolved, they will get it back.

Well go to a shop where you can buy a new inner cable and something like triflow.

But this is a Brand New Bike - I would expect some minor adjustments, but not replacement of any component. I guess other posts suggesting the existing cable ends, etc. might be the culprit are worth following up on, but for me at least, 25 miles each way is a pretty normal drive. Can you arrange with the LBS to go through the bike and make it work while you are at the shop, and can take it for a test drive?

Damaged or bent components are outside my scope of troubleshooting and I wonder if the FD install is off or the RD hanger is bent or something? Just guessing here.

Considering the time and gas, it's worth looking into myself - besides, I'll learn something. The LBS provides excellent service, and would look into it while I waited, and would let me take a test ride. I just want to make sure it isn't something simple before I go to the time, expense, and trouble of making that drive. I'd hate to get there and it take them about two minutes to fix something I could have easily done myself.

Well so far you've tried a bunch of stuff and have failed so it appears you've reached your limit of know-how, so quit resisting. The lbs will allow you to watch what they do (Rather than living vicariously through a bunch of phantom responders who are shooting in the dark). You need to learn when to give up.

There's lots to check on a bike like yours, including a bent derailleur hanger, clogged cable stops (Carbon fiber blocking stuff), housing kinks, bad endcaps, etc. Let the pros do their job and learn something first hand.

Gruppo, I'm not sure where you got the idea that I'd tried a bunch of stuff. I've asked for suggestions and made educated guesses myself as to what might be wrong, but I have yet to try ANYTHING! I've done everything in my life from replacing engines and transmissions in cars to building and flying my own airplane. I know when to ask for ideas, which might save me time, but I'm not mechanically inept. I fully understand all the things that have to be checked, but often, asking the right question will get you answers that save you a lot of time.

[QUOTE=gruppo;16902295]... living vicariously through a bunch of phantom responders who are shooting in the dark/QUOTE]

I think I should change my name to RoadPhantom Ph.R. - Phantom Responder. Kinda like a cyclist and virtual help kinda guy. I'm really not on the road. Or here. And I'm usually in the dark about things.

This ^. And it sounds like your hanger might be a little off...