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Fact or B.S.?(8 posts)

Fact or B.S.?Trux
Sep 15, 2003 10:04 AM
My LBS tells me it's time to replace the chair on my 2 year old (4,500 miles) bike. They say that I'll also need to replace the gear cluster as the chain and cluster wear together. Won't a new chain work with an old cluster? Is this fact or are they just trying to increase their profit?
the "CHAIR" on your bike........hmmmm?rubendc19
Sep 15, 2003 10:13 AM
Your chain is so old and worn that itOldEdScott
Sep 15, 2003 10:14 AM
likely screwed up your cassette to the point where a new chain won't run well with it. More frequent chain changes make that unnecessary.

But ...

Whether it's more economical to just run both into the ground and replace both as a matter of course (rather than trying to preserve the cassette by spending more on frequent replacement chains) is a matter of some dispute.
Only 2 yrs/4500 miles?MisJG
Sep 15, 2003 11:05 AM
Sounds like B.S. to me. You should be able to get a lot more miles out of the cassette even with a worn chain. I would replace just the chain first and see how everything goes. Maybe go to a different shop for a second opinion. Strange things can happen. FWIW, I have the original cogs on my late '80s Schwinn and they're still going strong. Keep everything clean and lubed and replace the chain when stretched and it's likely you'll never have to replace the cassette.
Depends on conditions.niteschaos
Sep 15, 2003 11:14 AM
I race in pretty rough conditions, so I go through a chain and cassette every 3000 miles. How do I know they are worn out? Because I can tune the rear shifting for only a section of the cogs, not all, and daylight is visible under the chain in some cogs, but not on others. Go to Sheldon Brown's website to see what I'm talking about.
Fact but...biknben
Sep 15, 2003 11:21 AM
Fact: If you allow a chain to wear too much it will begin to wear out the cassette as well. If you regularly check the chain wear and replace it when neccessary you won't have to replace the cassette.

BS: The cassette has to be replaced with each new chain. You could just replace the chain only and see how it goes. You may be able to get away with it. If the chain skips during hard standing efforts than the cassette is toast.

FWIW: Chains and cassettes are very easy for a DIYer to replace. Prices on-line are very cheap for these items. $50 could get you an Ulegra quality chain/cassette combo. Another $30 for the proper tools (that you'll use over and over) and you'll be able to do this all yourself.
re: chain & cog wearFredrico
Sep 15, 2003 11:49 AM
The LBS just might be right.

If you don't change the chain every 2 or 3 thousand miles, it will stretch, and wear down the cogs around 5000 miles, as the bike shop suspects.

So put on a fresh chain. Go out and stomp on the pedals in every cog. If the chain skips on one or two cogs, they've been stretched by the chain, and a new cogset is in order. If the new chain doesn't jump, you're probably good for another 2000 miles.
Facts according to SheldonSpoiler
Sep 15, 2003 3:15 PM
click on this link
and scroll down to the boldface topic "Chain and Sprocket Wear."
The next topic titled, "Measuring Chain Wear." says,

"The standard way to measure chain wear is with a ruler or steel tape measure. This can be done without removing the chain from the bicycle. The normal technique is to measure a one-foot length, placing an inch mark of the ruler exactly in the middle of one rivet, then looking at the corresponding rivet 12 complete links away. On a new, unworn chain, this rivet will also line up exactly with an inch mark. With a worn chain, the rivet will be past the inch mark.
This gives a direct measurement of the wear to the chain, and an indirect measurement of the wear to the sprockets:

If the rivet is less than 1/16" past the mark, all is well.

If the rivet is 1/16" past the mark, you should replace the chain, but the sprockets are probably undamaged.

If the rivet is 1/8" past the mark, you have left it too long, and the sprockets (at least the favorite ones) will be too badly worn. If you replace a chain at the 1/8" point, without replacing the sprockets, it may run OK and not skip, but the worn sprockets will cause the new chain to wear much faster than it should, until it catches up with the wear state of the sprockets.

If the rivet is past the 1/8" mark, a new chain will almost certainly skip on the worn sprockets, especially the smaller ones.