Bicycle Mechanics - New chain, rebuilt rear derailer, and now problems
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05-09-06, 04:18 PM
So I tore apart my rear derailer, an old Shimano Altus, thoroughly cleaned it, lubes with light oil and reassembled it. Works great...
I got a new chain and popped it on.
Now it seems I'm having trouble. The chain movement is not smooth. It's sort of clicking and jumpy, and it might ocasionally skip a tooth. I checked and the links (old vs new) look pretty much the same size. Also both chains have the same number of links. Could it be that the chain will stretch over time to accomopdate the small amount of slack present?
Also, i seem to be having chain alignment issues. With the front derailer all the way 'slack', I still get the chain rubbing the innermost surface (left side when looking sown riding the bike) when on the small chainring. The adjustement screw is all the way out. My hypothesis is that I've got too much tension in tghe shifter cable. (friction shifters). Could this be the case?
05-09-06, 04:23 PM
my recommendation is to conosult someone in that area of mechanics...prehaps go to a bike shop and ask them what to do...i can't help you oujt ...but thats how i solve these kinds of mysteries
05-09-06, 04:27 PM
How old is the cassette? If the cassette is worn the new chain will skip on the most worn cogs.
Did you reassemble the derailleur correctly? The top and bottom pulleys are not interchangable. The top pulley has a bit of sideways float to help align the coga nd chain while the lower pulley doesn't. If you mixed them up, that would hurt the shifting.
Did you shift the shifter all the way to the "most relaxed" position before reattaching the cable?
You didn't put a 1/8" wide (single-speed) chain on instead of a 3/32", did you? That sounds like how one might act......!
05-10-06, 03:43 PM
My bet is that you have a worn cassette. That's common when replacing a well worn chain. Try shifting into the rear cog that you use the least often and see if that one happens to run a little smoother.
When a chain wears, it sctually stretches and changes pitch by a small amount. When that happens gradually, it also wears the cassette cogs to match the new pitch. Now, when you replace the chain, the cassette is the wrong pitch to match the new chain and the chain kind of skips over the tops of the cogs.
05-10-06, 08:43 PM
One other potential cause of this problem could be a stiff link in that new chain. On that rubbing on the inside cage of your FD, you are correct that too much cable tension will give that symptom. Loosen the cable & start over on your FD setup(and follow the manuf. instructions or those at Park Tools, etc.
New chain on old (worn) freewheel/cassette can cause this. If the bike sees a lot of miles--especially offroad, it's not a bad idea to replace the freewheel/cassette at the same time as the chain. Otherwise, you have a new chain on a worn cassette/freewheel and it wont line up--thus the skipping.
I can almost guarantee that's your problem.
You've made two changes to the bike. You rebuilt the derailleur and you installed a new chain. The first thing you need to do is determine which of the two of these causes the problems. I would put the old chain back on the bike and see if you still have the problem. If so, then you know the problem is with the derailleur or its adjustment. If the problem goes away with the old chain, then you likely need a new cassette to go with the new chain.
05-11-06, 10:30 PM
Well went on a longish ride today.
The chain skipped a bit maybe twice during, but generally was shifting crisply, even under heavy load. FD was fixed by loosening the cable a bit.
The bike is 20+ years old but is brand new. Sat around unused for many years. I thoroughly degreased the rear cassette/freewheel/whetever and the teeth look sharp with minimal to nonexistent wear. The reason I replaced the chain in the first place is that I made the mistake of just wiping down once after cleaning and letting it airdry, creating tons of surface rust. Still salvageable, and I will scrape/rub the rust off and relube so I have a spare.
It HAS to be chain stretch. The chain felt smoother and smoother as the ride went on, or maybe the lube was more properly distributed.
The reason I tore down the derailer was that I rode it in the rain,. and the two lil pullies weren't spinning freely anymore. MUCH better now. Still nto a big fan of friction, but it does the job. Truth be told, I'm not a big gear fan. out of 6 in the rear, I use maybe like two or three at most. Maybe its because the spacing isn't large enough for me to tell a real difference from one to another..?
I will ride again when the weather clears and report my findings.
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