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-   -   Cassette/Chain Replacement questions (https://www.bikeforums.net/bicycle-mechanics/186411-cassette-chain-replacement-questions.html)

killingtime 04-07-06 07:05 AM

Cassette/Chain Replacement questions
 
My LBS says it's time for a new chain and cassette after 2,000+ miles on my 2005 Cannondale R700. Being still somewhat of a newbie I have some questions about replacing them.

The bike came with a SRAM 950, 9-speed, 12-26 cassette and Shimano CN-HG53 chain. I didn't realize there was such a mix with a bike that has a Shimano 105 front derailleur and Ultegra rear. Is that common?

Any recommendations on replacing the cassette and chain?

juicemouse 04-07-06 07:38 AM

Yes, it's common and it's totally acceptable. 9-speed is 9-speed. Bike manufacturers spec the parts they think they can make the most money on.

In terms of suggestions, I highly recommend a new SRAM 9-speed chain. They shift at least as well as a Shimano, and they have a cool little link that allows you to disconnect and reconnect the chain by hand without any tools. This is useful for giving the chain a thorough cleaning, which will prolong the life of both the chain and the cassette. You'll still need a chain tool to shorten the chain to length the first time you install it. I have no experience with 9-speed Shimano-compatible cassettes, but my 8-speed SRAM cassette shifts just as well as the Shimano it replaced, and was much less expensive.

San Rensho 04-07-06 07:41 AM

First, measure the chain to make sure you need a new chain. If you are changing it while it is still within the wear limit, then you shouldn't need a new cassette.

You can get a chain stretch guage at most LBSs. Check your (cheap)chain often and replace well within the wear limit and your (expensive) cassette will last a long time.

twilkins9076 04-07-06 08:38 AM


Originally Posted by San Rensho
Check your (cheap)chain often and replace well within the wear limit and your (expensive) cassette will last a long time.

Ditto this thought...and add that you can extend the life of your chains and cassettes by keeping them clean and well lubricated.

capwater 04-07-06 09:07 AM

Unless your chain is really trashed (ie; way beyond the wear limits), you shouldn't need a new cassette with every chain replacement. That's the whole point of changing your chain at the proper interval. 2k on a cassette isn't that many miles. In fact mileage alone isn't a very good indicator of wear, park tool chain checker is pretty accurate. PowerLinks on SRAM chains are a great invention. I suspect your LBS is not trying to screw you, but rather sell you two things (one you need and another that can't hurt).

FYI; I just replaced a chain after about 6k miles of hard training and a fair number of races. Cassette is still running smoothly.

grolby 04-07-06 09:08 AM


Originally Posted by San Rensho
You can get a chain stretch guage at most LBSs. Check your (cheap)chain often and replace well within the wear limit and your (expensive) cassette will last a long time.

An ordinary ruler works just as well as a chain stretch guage. A new chain will measure at exactly 12 inches for 12 links, measuring between the centers of the link pins. As the chain wears, this distance will elongate slightly. When you get a center to center measurement of 12 1/8", it's time to replace the chain. If it reaches 12 1/4", it's REALLY time to replace the chain, and probably your cassette as well.

filly 04-07-06 09:59 AM

1/8" is too much
 
replace at 1/16"

mycoatl 04-07-06 11:34 AM


Originally Posted by San Rensho
Check your (cheap)chain often and replace well within the wear limit and your (expensive) cassette will last a long time.

I realize that some cassettes are quite spendy, and why replace 2 things when you can replace only 1. However, a SRAM 970 9 sp cassette is $35 at Nashbar and a SRAM 970 9 sp chain is $31. I think the expensive cassette/cheap chain thing doesn't hold true for a lot of us. Good chains aren't cheap, and decent cassettes don't have to be expensive.

Still good advice though--a cassette should last longer than a chain.

operator 04-07-06 12:54 PM

You're forgetting that if the chain and cassette are both worn enough that you have to replace both, be prepared to replace the chainrings as well.

That WILL cost. $31 vs $31 + $35. I think that's a no brianer, especially seeing as how cassette/chain wearing will cause skipping.

HillRider 04-07-06 04:50 PM


Originally Posted by operator
You're forgetting that if the chain and cassette are both worn enough that you have to replace both, be prepared to replace the chainrings as well.

Wrong. Chainrings way outlast both chains and cassettes. I replace chains and cassettes annually (about 6000 miles) but chainrings always last 25,000 miles or more.

Chainrings have more teeth than cogs so they share the load over more area and, since the chain is applied to the chainrings under load, worn chainrings are much more tolerant of a new chain than cogs.

If you need to replace the chain and cassette at 2000 miles you either: 1) are an extremely strong rider, 2) dreadfully neglect to clean and lube the chain, or 3) have an unethical LBS.

Old Hammer Boy 04-07-06 08:38 PM


Originally Posted by HillRider
Wrong.
If you need to replace the chain and cassette at 2000 miles you either: 1) are an extremely strong rider, 2) dreadfully neglect to clean and lube the chain, or 3) have an unethical LBS.

+1 on this. My wife has an HG53 on her Trek 2100, and has over 5,000 miles on the chain. I lube and clean it often. It's still well below 1/16" of stretch, the cassette and rings are in great shape, and it shifts like it did the day she bought it home. 2K miles is sure not very much, but like HR says, if you haven't taken care of it, and/or ride in dirty or wet conditions often, it's possible. I'd sure measure it before I turned over my hard-earned money. It's not rocket science.

TallRider 04-08-06 06:40 AM

Just to know which direction the causality works here:
  • a worn chain will cause cassette and chainrings to wear out
  • worn cassette or chainrings will not cause the chain to wear out
There are good mechanical reasons for this, and I can go into them if desired.

This is important becuase you need to be careful to replace your chain once it gets worn. However, you have no need to replace cassette or chainring, unless a new chain skips on them. More likely a problem with cassette than with chainrings.

So, get your new chain, ride it, and if the chain skips, jumps or hops (or crackles or pops) when pedaling hard in certain cogs, you know that those cogs are worn and you should replace the cassette (or just those cogs, which are probably the ones you use most frequently, if you're able to replace individual cogs).

sngltrackdufus 04-08-06 06:59 AM


Originally Posted by mycoatl
I realize that some cassettes are quite spendy, and why replace 2 things when you can replace only 1. However, a SRAM 970 9 sp cassette is $35 at Nashbar and a SRAM 970 9 sp chain is $31. I think the expensive cassette/cheap chain thing doesn't hold true for a lot of us. Good chains aren't cheap, and decent cassettes don't have to be expensive.

Still good advice though--a cassette should last longer than a chain.

http://www.blueskycycling.com/produc...-Combo-Kit.htm :)

killingtime 04-08-06 08:29 AM

Thanks for all the advice so far. I appreciate it.

Alright, here's the update. I measured the chain this morning using a tape measure. My center-to-center measurement is ever so slightly between 12 1/16" and 12 1/8", so it looks like the LBS was correct, right? Time to swap the chain? I have found my LBS has been very good to me and has not tried to sell me things I don't need!

As to mileage, I added it up. I have 2144.5 miles on this chain. I read on one bicycle maintenance site that they have seen chains require replacement after only 1500 miles while some last up to 20,000!

As for reasons for the chain stretch so soon, I would love to believe I am an extremely strong rider but I doubt it!

I clean and lube the chain often, however, one thing I recently learned was that I was not getting all of the old lube off before adding more and I was accumulating dirt and gunk on the chain and cogs (my bad!) But I would not say the situation ever got horrible. It just seemed that the chain and cassette were not as shiny as they could be. Could that be enough to cause premature wear?

Big R 04-08-06 10:59 AM

I wouldn't worry too much about premature wear...If you got 2000+ miles out of a chain, then even $30 on a replacement should be money well spent!!

operator 04-08-06 12:45 PM


Originally Posted by HillRider
Wrong. Chainrings way outlast both chains and cassettes. I replace chains and cassettes annually (about 6000 miles) but chainrings always last 25,000 miles or more.

Chainrings have more teeth than cogs so they share the load over more area and, since the chain is applied to the chainrings under load, worn chainrings are much more tolerant of a new chain than cogs.

If you need to replace the chain and cassette at 2000 miles you either: 1) are an extremely strong rider, 2) dreadfully neglect to clean and lube the chain, or 3) have an unethical LBS.

Wrong. Just becuase it doesn't happen to you does not mean it won't happen. How exactly are you generalizing this for every single rider and for every single gear/chain/cassette combo out there in their riding condition?

I never said you have to replace the chain and cassette at 2000 miles (you came up with that arbritrary number). Nor did I say you have to replace all three together as soon as the chain was worn. My point was if you let the chain wear out, it WILL accelerate the wear on the cassette and the chainring.

So please tell me how you can guarantee that won't start destroying your chainrings and cassette when your chain becomes worn. I'd dearly love to know.

TallRider 04-08-06 03:12 PM

Chainrings will get destroyed by a worn chain, especially aluminum chainrings. However, they don't get destroyed as quickly as rear sprockets. HillRider's main point was that if the chain is worn at just 2000 miles, it's highly, highly unlikely that the chainrings need to be replaced. Also, chainrings with wear at a similar level to worn sprockets pose less of a problem for the chain to skip, so even if chainring teeth wore down at the same rate as sprocket teeth, you wouldn't need to replace them as frequently.

HillRider didn't come up with the "artibrary" number of 2000 miles; the OP mentions this. So he's responding in context of the thread.

So chill. And maybe dial zero. And, rest assured that worn chains will accelerate chainring wear, as you note. Here's my brother's granny ring, after 10,000 miles without changing his chain or giving it much maintenance.
http://www.unc.edu/~cupery/pics/bike...worn_teeth.jpg

HillRider 04-08-06 03:56 PM


Originally Posted by operator
Wrong. Just becuase it doesn't happen to you does not mean it won't happen. How exactly are you generalizing this for every single rider and for every single gear/chain/cassette combo out there in their riding condition?

I never said you have to replace the chain and cassette at 2000 miles (you came up with that arbritrary number). Nor did I say you have to replace all three together as soon as the chain was worn. My point was if you let the chain wear out, it WILL accelerate the wear on the cassette and the chainring.

So please tell me how you can guarantee that won't start destroying your chainrings and cassette when your chain becomes worn. I'd dearly love to know. Next time you want to be an ass, start by reading the post before attacking it.

Well, Tim has defended my points quite adequately so there isn't much more to add.

I read the original post quite well ,thank you and as noted, I said that chainrings don't have to be replaced nearly as often as cogs and chains and they are less influenced by chain wear than cogs are. Also, as noted, the 2000 mile figure came from the original post, not from me.

Tim's illustration of a badly worn chainring shows it can happen in moderate distances if subject to complete drivetrain neglect but it still took a lot of miles to do that amount of damage.

RockyMtnMerlin 04-08-06 04:39 PM


Originally Posted by HillRider
If you need to replace the chain and cassette at 2000 miles you either: 1) are an extremely strong rider, 2) dreadfully neglect to clean and lube the chain, or 3) have an unethical LBS.

+2

stevkato 08-04-06 04:27 PM

So, I'm very curious - what did you end up doing? I have the same bike (with the same components!) and my chain is in need of replacement. Did you go with the SRAM chain? What were your results?

killingtime 08-19-06 04:12 AM

For the chain, I got the SRAM PC-970 9-speed chain with the removable "PowerLink." It makes big difference to be able to remove the chain to clean.

As for the cassette, I went with the SRAM PG970 12-26 9-speed cassette.

Replacement worked out great and new components look great on the bike!


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