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Old 02-19-09, 03:41 PM   #1
dsimon
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Compact Double 10 Speed Question

I've got around 120 miles on my new bike, Jamis Nova, with a 50x34 up front (FSA Gossamer Compact), with 105 brifters, rear derailleur, front derailleur, and 12x25 10 sp. cassette.

My issue is this: I know that when I am in the big chain ring up front, I cannot (or should not) use the big chain ring on the back. I am unable, however, to use even the 3rd or 4th largest chain rings on the back. When I try to shift to these chainrings, the chain is constantly slipping, so much so that I have a hard time pedaling up any sort of a decent hill at all. Yes, I know, HTFU, sure. Doesn't help me now.

I took the bike back to the shop and had them realign the RD, but I have been having the same issues, and its really frustrating. Is this just what I should expect using a compact double? From the big chain ring, which rings should I be able to use in the back? How about from the small chainring?

Thank you in advance.

-Dan
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Old 02-19-09, 03:44 PM   #2
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Nope. Something else is wrong.

You should be able to shift into all the gears. The reason for not using them has nothing to do with the derailleur's ability to do it.
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Old 02-19-09, 03:49 PM   #3
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You should be able to use all of your gears. It is not ideal to use all of your gears. You may get some sounds in some gears due to less than optimal chain angles, but you should be able to shift into all of your gears and function.

There definitely seems to be an issue with your bike.
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Old 02-19-09, 03:54 PM   #4
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Alright thanks a lot. I will take it back down and have them go over it again.
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Old 02-19-09, 03:58 PM   #5
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chain is too short? or routed incorrectly through the derailleur pulleys?
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Old 02-19-09, 04:18 PM   #6
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I don't think the chain is routed incorrectly... how would I know if it was too short?
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Old 02-19-09, 04:32 PM   #7
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Quote:
Originally Posted by dsimon View Post
I don't think the chain is routed incorrectly... how would I know if it was too short?
What does your derailer look like when you go to the small small combination? That is, in what direction is the derailer pointing?
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Old 02-19-09, 04:34 PM   #8
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Was it okay when you first got it and this happened recently?
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Old 02-19-09, 04:41 PM   #9
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No, it has been dicey since I got it. I went on a couple of flat rides and didn't really notice, but twice in the past two weeks I have ridden to work. The route includes a couple of hills, where I've really been noticing. As I said, I took it in and the tech realigned it, but the issues have persisted. I will check which direction it is pointing later tonight when I am at home.

I was kicking myself over getting a compact double without really trying one out, but then it doesnt make sense that these would be popular if they were so frustrating.

To provide further insight- I can shift the chain all the way to the big ring in the rear, but it never settles in, even on the 3rd or 4th biggest. It is just skipping with every downstroke.
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Old 02-19-09, 05:11 PM   #10
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I doubt it's the fault of the compact double. I have a compact double with a 10-speed rear cluster, and it works fine under load in any gear pair. It sounds like something is flexing, and putting your derailleur out of alignment- so much so that it's catching another gear momentarily. Maybe tighten your rear skewer more? Tighten the rear shift cable a tiny bit to center it more over the cogs when in the big chainring? 10-speed Shimano drivetrains are a little finicky, IMO. Adjust the b-screw so the guide pulley is just barely off the 25 cog when in 50/25 gear? Make sure the chain length is right?
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Old 02-19-09, 05:22 PM   #11
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Front deraiuler is out of adjustment

Your left shifter should have 3 clicks, the middle one is claaed the 'Trim' . My bet is that you need to adjust the cable tension. Shift to the innermost position. Loosen the cable clamp bolt at the front der. Now just pull it taunt and lock it back down. You should now have 3 positions on the shifter. 1. small chainring 2. big chainring with big gears in the back 3. big chainring with small gears in the back.
Most of the tim with my Dura-Ace it shifts from 1 to 3 , then a small tap will bring it back to 2.
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Old 02-19-09, 06:19 PM   #12
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Quote:
Originally Posted by dsimon View Post
I don't think the chain is routed incorrectly... how would I know if it was too short?
With chain on biggest cog in the rear, the chain should still have noticeable bend as it goes through the pulleys. If, as you get the chain to bigger pulleys, the cage is pulled so far toward horizontal that the chain passes through the pulleys almost straight, then its too short. See pictures http://www.parktool.com/repair/readhowto.asp?id=26.

After reading the other posts, however, I beginning to suspect cable tension or limit screw issues; although the shop should have figured that out in about two seconds.

Try This:

1. Shift chain to smallest ring., disconnect cable.
2. Push derailleur with your hand toward the wheel, it should slide easily all the way over until pulleys line up with big cog. If it hits a stop before getting all the way over, the low gear limit screw is too tight and needs to be loosened so loosen screw until you can move the moves all the way over and cage lines up under the big cog.
3. Reconnect cable, pulling it taught with just your fingers; tighten anchor bolt.
4. Shift the gears one at a time, adjusting cable tension any time there is any hesitation moving one cog to the next (increase tension to adjust for hesitation moving from small to big); decrease tension to adjust for hesitation moving from big to small.
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Old 02-19-09, 10:52 PM   #13
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My left shifter does have 3 clicks. The shop got that part set up and the tech showed me... that I did not know about.

DOS- Thank you, I will give that a look and report back.
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Old 02-20-09, 02:06 AM   #14
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You might want to "eyeball" the chain line.
Put it on the small ring and 5th gear or the large ring and 6th gear.
Walk around to the back of the bike and "sight" down the chain. It should be near perfectly straight between the ring & cog, compared to the relatively severe angle if it were on one of the end cogs.

BTW-
Rings are the front with the cranks.
Cogs are on the cassette.
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