Bicycle Mechanics - Trouble shifting into the large chainring (road bike)

Hi all -- This is my first foray into building a road bike. In comparison, I find building mtbs much easier!

I am running a 2x10 on my road bike. The crank is Tiagra, the FD is 105 and the chain is a 10-speed Dura Ace. After my second ride, I noticed I was having an issue upshifting in the front rings. My partner futzed around with it while I was at work and it was shifting fine. Rode her to school and I cannot shift into the large chainring. Come home, put her on the stand and played with the high limit screw. I also moved the FD up (1 and change mm away from the chainring) as it seemed a wee bit close. Shifts great!!

Today is my group ride and I shifted into the large chainring on my way to the ride. Great, it is working! Unfortunately after that, it was the last time I was able to.

I am just wondering if I need to keep riding in order to stretch the cables properly or if I should be adjusting something that I am missing out on. This just seems kind of strange to me. :o Thanks for any advice.

Cables don't really stretch much at all. Also, if the limit screws are set right in the first place, they shouldn't move. First thing I would check is that the cable clamp screw on the derailleur is not slipping. Then make sure there's not a cable housing ferrule hanging up somewhere or not all the way. Are the cable housings long enough so they don't pull when turning the bars all the way either way? How 'bout the derailleur mount clamp screw, is it tight?

Make sure that you've attached the cable to the cable clamp screw the right way. http://www.hostelshoppe.com/images/tech/fderai13.jpg

If it's not attached like that, the derailleur will be wonky.

I;d give the barrel adjuster a turn to tighten the cable and see what happens. You can easily undo it if that's NOT the problem.

It sounds like the cable is slipping.

The other possibility is that your rear derailler doesn't have enough take-up (a long enough cage) to accomodate the full compliment of ranges you have and/or the chain is too short. (There isn't enough information in the description of the problem to eliminate the possibility.) If you used a "road" derailler with a "mountain bike" (i.e. wide range) casette, it's likely. Here's a test: If you can go to your big ring in front when you're in your smallest rear cogs, but not when you're in the largest rear cogs, you need either a rear derailler with a longer cage, a longer chain or both.

Either that or just don't use those combinations.

Yup, unless you ran pasta for cables, somthing's slipping--cable and/or derailleur clamp.

Try this: remove the cable from the derailleur. Then make sure the derailleur is mounted correctly on the frame (cage is 1-2mm above large chain ring). Tighten the clamp screw onto the frame and then lever the cage (manually) out to the large chain ring position and tighten the clamp screw again (you'll notice that you suddenly might be able to get an extra turn or two!).

Then attach and tighten down your cable (making sure you position it correctly under the washer).

Thank you everyone, I will give it a shot and let you know. I thought since I torqued the clamp screw everything would be perfect!

Make sure that you've attached the cable to the cable clamp screw the right way. http://www.hostelshoppe.com/images/tech/fderai13.jpg

If it's not attached like that, the derailleur will be wonky.

I have been looking for this pix. Thanks. This is the source of many front shifting problems, mine also, and is the simplest of fixes. Went through every possible issue to get the front to work correctly and after I change the cable to match the pix, bingo, fixed no problems.

Good advice from the others above, it really does sound like a slipping cable. Raising the derailleur would remove the slack from the cable but then it sounds as if it slipped again. If it turns out to be a slipping cable consider lowering the derailleur back to where it was.
Another thing to check is to make sure all of the cable is out of the shifter before attaching the cable to the derailleur, flip the small shift lever several times and remove any slack before attaching.

Al