Bicycle Mechanics - Front derailleur adjustment

I have a 105 nine speed with a triple in the front. I have a problem with the front derailleur that I can't quite adjust right. If I'm going up hill on a somewhat steep grade on the middle chain ring and the next-to-innermost cassette cog, the chain will often jump down to the smallest chain ring even though I didn't shift it. A related problem is that sometimes when I'm shifting from the big chainring top the middle (on an inner cog in the back), the chain will skip the middle chainring and drop to the small one.

Any ideas what I adjustments I need to rectify this problem?

Thanks.

Rich

It sounds like you just need to use the barrel adjuster to set the cage so that the chain bisects it, when the chain is parallel to the centerline of the bike (center-chainring/middle cog).

The barrel adjuster is usually installed inline on the cable at a stop brazed onto the downtube just below the head tube.

If the adjustment you need seems to be out of range, the cable may be too loose.

Also make sure the derailleur's outer plate is parallel to the chain. Sometimes clamp-on derailleurs get twisted.

RichC

On my 105,after you shift from the small cog to the middle one up front,you can just push the shifter a little bit again and it adjusts if you know what i mean.

Barrel adjuster. Turn it about one turn, then shift all over the place to see how it works. If you still have problems, turn one more and repeat. On yours you need to (in essence) tighten the cable, so one turn out (counterclockwise) at a time until it's all good again.

www.parktool.com has derailer adjustment .Start from the beginning and do it right.

Actually, Pokey, I followed the Park Tool instructions when I replaced my cables. On the whole, I think I did a fairly good job for a first timer. It turned out that the cable needed to be loosened slightly rather than tightened. Did that last night and seemed good on the work stand. It worked well on my ride today. All it needed was one more quarter turn clockwise today. I took my bike out on the hills where I usually had the problem and all was well.

Thank you all for your help.

Rich

I started to ask if it was TP or BP, that would be the difference. Anyway, glad you got it worked out. I gambled to keep it simple and lost ;)

What do TP and BP mean?

Rich

Top pull or bottom pull, the direction the cable comes from. Most road bikes are bottom pull with the cable passing through a guide either below or above the bottom bracket. Some mountain bikes use top pull which keeps the cable routing from being right in the mud.

Thanks, Rainman. Actually, I've decided to follow Pokey's advice and go through the whole process again. But I really don't know how taught the cable should be when I set the pinch bolt. All instructions are vague about it. One source says that it should only be so taught as you can pull it barehanded, but Lennard Zinn says to pull it taught with a pliers.

So how taught do you guys pull the cable after all tension has been relaxed? What's the best way to pull it? Should I get the Park fourth-hand tool?

Thanks again.

Rich

Originally posted by Stinger9oh
One source says that it should only be so taught as you can pull it barehanded, but Lennard Zinn says to pull it taught with a pliers.

So how taught do you guys pull the cable after all tension has been relaxed? What's the best way to pull it? Should I get the Park fourth-hand tool?

Thanks again.

Rich I usually get it by hand.If it is still too slack,then use the cable adjuster.

fourth hand tool?

I just get it hand taught. Also, I usually turn the barrel (or in-line) adjusters all the way in, then out a full turn. That way, if you get it too taught, you still have the full turn back to slacken it some. If you don't turn it the full turn, then you have to unclamp the cable. Not a biggie, but sometimes saves a step!

Cable tension was my bug bear fitting the XO 3spd shifter. I tried hand tight, and I tried pliers, but still the shift was a bit erratic. Eventually, I settled for a slight tug and made the final adjustments on the barrel adjuster. Now it all works fine, but it took a while to suss it out so I think it is specific to each bike to some degree.