Aug 19, 2002 3:44 AM
|I just had a new chain installed by LBS and it seems like it is too long. It rattles in the smaller cogs when on the small chain ring and occasionally skips. I hesitate to take it back because I have to re-tune the bike every time they tune it. How do I know if its too long? count the links?|
|Hard to mess up.||RickC5|
Aug 19, 2002 6:32 AM
|Since your LBS installed the chain, I assume the old chain was still on the bike when you brought it to them. All they needed to do was 1) remove the old chain, 2) lay the new chain next to the old chain on the floor to determine the length, 3) remove the excess links from the new chain, 4) clean & install the new chain & lube it. Not too difficult.
Given you are experiencing problems, something's wrong (DOH!). I understand your hesitation, but you really should take it back to that shop and demand some satisfaction. They didn't give you what you paid for, plain & simple.
Then, find a new LBS.
|re: New Chain||clintb|
Aug 19, 2002 7:31 AM
|Generally a too long chain does not skip. It will have too much slack on the lower run and the derailleur won't be able to take up the slack when in smaller ring/cogs.
Think of it this way. When you're pedaling, the top run is under tension from the front rings and that tension is pulling the chain onto the rear cogs. The derailleur, as set by the "b" limiter, is pushing the chain up to the bottom of the cogs and makes it more of a circular contact area between the chain and cogs. Both of these considerations together make it difficult for the chain to skip in an unworn system.
How many miles do your cogs have on them?
Did they replace the chain with the exact part? Making sure that if you have 9spd, they didn't put an 8spd chain on.
There is actually a formula for figuring out chain length. A fairly long one, but useful if you're interested. Shimano, on the other hand, has a simplistic method for chain length. With the chain on the big ring (front) and small cog (rear), the rear derailleur guide pulleys should be 90 degrees to the ground. Basically draw a line through them to the ground and it should be straight up and down.
Hope this helps.
|Sounds like a worn cassette (nm)||Kerry|
Aug 19, 2002 5:51 PM
|Sounds like a worn cassette (nm)||elcameron|
Aug 19, 2002 8:24 PM
|The cassette was replaced with the chain. Thanks for the re. Could the small chainring be worn out? Only 5000 or so miles on the bike.|
|Sounds like a worn cassette (nm)||clintb|
Aug 20, 2002 5:22 AM
|Ok, do the simple Shimano method of checking chain length.
1. Shift chain into small cog and large chainring.
2. Put bike on level surface.
3. Draw an imaginary line through the guide pulleys to the ground.
4. If the line deviates from 90 degrees you have either too short or too long of a chain.
Too long a chain will be characterized by the bottom pulley pointing to the rear. Too short and the bottom pulley will point to the front.
I'll ask again. Was the chain replaced with the EXACT same model? If not, then what?
|Sounds like a worn cassette (nm)||clintb|
Aug 20, 2002 11:09 AM
|Didn't see the part about 5000 mi on bike. I would have a hard time believing that either chainring would wear within 5k miles. If you put it through absolute hell though, that's another story.|
Aug 20, 2002 6:04 AM
|Could it be as simple as not enough shift cable tension? That would fit your symptoms.
Aug 21, 2002 7:37 PM
|Right on the money!! All that was needed was just a little tension adjustment. I have not done much bike repair; very nice to find a solution that doesn't cost anything. Thanks|
Aug 20, 2002 11:50 AM
|"Rattles in the smaller cogs when on the small chain ring." Slapping on the chain stay I assume? Sure sounds like it might be a little too long to me. My way to figure chain length is to wrap the chain around the big ring and biggest cog, bypassing the derailleur, and add one inch. That gives you the shortest possible chain that will cover the big/big combination which is what you want.
Couple of questions: How did the bike work before you had the chain and cassette replaced? What made you think that you needed a new chain and cassette? There are a number of possibilities but it's usually prudent to check out the simple stuff first. Before we go too far astray I'd check the chain length and maybe fiddle with the derailleur cable tension a little.