Bicycle Mechanics - Dearilleur Adjustment
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08-25-07, 01:44 PM
I have a Campy mirage triple 32-42-52 with a 12-25 rear cassette. Two things are going on right now and I am wondering if they are both the result of the same adjustment being needed. In all three front positions the rear will not move to the lowest ring. The shifter clicks but the chain does not move. I am also barely able to get the front derailleur to access the smallest crank. I have to work the indexing back and forth before it finally moves off the middle crank. Could these two conditions be related to the same adjustment and what would that adjustment be? Looking for some input as I am new to these types of adjustments, but I am wanting to learn. Thanks!
08-25-07, 01:48 PM
Off the top of my head, it sounds like the limit screws need to be backed out SLIGHTLY.
08-25-07, 01:53 PM
Did it ever work right?
I'm inclined to disagree with the previous poster. Once correctly set limit screws seldom need readjustment. The first thing that I would look at is the rear derailleur hanger alignment. Those things are easily bent inward. When that happens, the upper pulley gets cocked goofy and it won't access the biggest rear cog.
08-25-07, 02:09 PM
How do I check the alignment? It was working properly. I just bought the bike and it was working when I test rode it. From what I have read, it does seem as thought the set limit screws should not be messed with if it was working previously. I looked at it and the alignment appears to be ok. But just looking at it, I suppose it could be slightly off and I wouldn't see it. Is that possible? Is there a more formal way for me to check the alignment, perhaps using a level. We are talking about the alignment of the tension pulley and the guide pulley, right?
08-25-07, 03:05 PM
A little more information. On the front derailleur, the chain will access the small crank about 50% of the time without manipulating the indexing. It just seems like the guide needs to be moving a little bit further to the left. On the rear derailleur, if I ride for a short distance (50 yds or less) with the bike in high gear, the chain does eventually move to the smallest ring. When I look at the alignment, if anything it looks like the lower pulley is maybe just slightly outside the middle pulley, but just barely if at all. Does this sound like alignment or cable adjustment or screw adjustment? If the chain does eventually make it down to the lowest ring, would that eliminate alignment from being an issue?
08-25-07, 04:25 PM
If it shifts properly in the other gears (proper indexing), and you haven't crashed, I too would suspect the limit adjustments. It's easy enough to check and return to the original position if that's not it.
08-25-07, 05:40 PM
How do I check the alignment?
Shift into a geat that will make the derailleur arm point straight down. Then prop your bike against something so that you can look at it from the back. If the derailleur arm is pointing toward the wheel even the slightest bit, it's bent.
On bikes with 7-speed cassettes and fewer you can probably bend it back adequately just by eyeball. The more cogs you have on the rear, the picker they become about derailleur hanger alignment. In that case I'd suggest using a hanger alignment tool or taking it to a shop.
08-25-07, 06:38 PM
I'm going to invest in some tools, including the hanger alignment tool and evaluate the alignment. I accessed some Internet sites which suggested the same thing you did Retro Grouch. Put the front on the middle crank, the rear on a middle cog, and eyeball the alignment from the rear. By sight, it is definitely not pointing toward the wheel at all. However, since I just bought the bike, I am going to check it out more thoroughly. This bike has been ridden very little the last 4 years. I don't think I am going to mess with the limit screws at all, but there are tension and other screw adjustments that can be tried. Thanks for all your input and I appreciate any further ideas any of you might have!
08-25-07, 06:43 PM
The front derailluer on the campy group requires a different setup than the Shimano regarding the parallel setup. Make sure that is right and that the clearance of the outer cage to the large CR is with in the1 to 2mm range. See Sheldon Brown for the proper setup.
08-25-07, 08:00 PM
Thanks for all your input and I appreciate any further ideas any of you might have!
Another common problem is that short section of cable housing that's adjacent to the rear derailleur. That always has a pretty good bend in it. If it's a little too short the bend is even tighter. I think that it wears on the inside, binds the shift cable so it won't allow the chain to pick up the smallest cog.
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