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PostPosted: Sun Nov 13, 2011 10:49 pm 
Retro Guru
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Location: Hampshire
Hi.
My bike came with a sram pg950 cassette which has been on there for about the last 4-5000 miles. My gears recently started mis-behaving ....it was if the chain was jumping up (but not like the occasional tick or jumping when you have badly adjusted mech or shifters). I thought the chain maybe worn, and when I checked with a wear indicator it was past 0.75 wear. I laid it next to a spare chain I have and could see a visible difference so stuck the new spare on (sram pc971). This seems to have made the gears worse. The changes between gears seem ok for the most part, but in at least 3 different sprockets the chain seems to jump. I think my casette is worn but would like a second opinion. Does this sound right ??

I am not sure what to look out for to identify cassette wear. The very tops of the cassette teeth don't look too bad. The gaps between the teeth however don't like quite even as if one edge is a bit more worn than the other.

If I get a replacement, what should I go for ? I wouldn't mind going a rung up the ladder in terms of spec and 9-speed cassette prices are good at the moment. I was thinking about sram pg990, mainly because its sram, its light and the alloy spider will hopefully work well when I get a new Hope rear wheel at Christmas (currently have a worn Deore hub). I've heard that Hope's alloy casette body can get damaged by some cassette designs, so think the alloy spider may help. What do others think ?


Last edited by raymondluxuryyacht on Thu Nov 17, 2011 12:41 am, edited 1 time in total.

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PostPosted: Sun Nov 13, 2011 10:52 pm 
National & North West AEC
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Sounds like a worn cassette. Might be worth posting up a picture for us to have a look at.


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PostPosted: Sun Nov 13, 2011 10:54 pm 
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Joined: Mon Sep 12, 2011 5:03 pm
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Chains and cassettes wear together - stick a new chain on an old cassette and the pitch is different, so will slip even more. Those inidcators are not always very accurate mind, the old chain was probably even worse.

4-5000 miles is good going, I'd replace it as everything indicates is worn too far now.

The 950 is a good cassette, the ones above are lighter, but don't last any longer. I have one on ebay right now:

http://www.ebay.co.uk/itm/150698223341? ... 1555.l2649


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PostPosted: Sun Nov 13, 2011 10:56 pm 
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I think the alloy spider is a wise idea for your proposed Hope freehub, but aren't the smallest cogs all-steel and fit directly onto the freehub? I wish cassette manufacturers would supply just the smallest 2 or 3 cogs though :( they always wear faster as they spin 2-3 times faster than middle and largest cogs.


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PostPosted: Sun Nov 13, 2011 11:00 pm 
Gold Trader / rb Rider / Special
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If a chain is past 0.75 you can often get away with changing just the chain but not always.

Depends at which point between 0.75 and 1.0 your chain sits. The nearer to 1.0 the more likely the cassette will need replacing. Its good practice to replace your chain before 0.75 to prolong life of cassette.

A really worn cassette will start to look like sharkfins. Can be tricky to spot though.


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PostPosted: Sun Nov 13, 2011 11:07 pm 
Retro Guru
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Thanks all. I am sure you are right about the bottom sprockets dr. I'd rather not buy shimano as they don't seem to wear well, so it looks like the pg990 or another pg950 are best options. The pg970 seems a bit odd as its got a spider just for the largest two sprockets and I am not convinced by this "halfway house" between the other two models.

If I get time I may try to take a pic of the cassette, though its hard with my little lad around ! He seems to want to "help" with whatever I'm doing ;-)


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PostPosted: Sun Nov 13, 2011 11:46 pm 
King of the DuckBoard
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raymondluxuryyacht wrote:

If I get a replacement, what should I go for ? I wouldn't mind going a rung up the ladder in terms of spec and 9-speed cassette prices are good at the moment. I was thinking about sram pg990, mainly because its sram, its light and the alloy spider will hopefully work well when I get a new Hope rear wheel at Christmas (currently have a worn Deore hub). I've heard that Hope's alloy casette body can get damaged by some cassette designs, so think the alloy spider may help. What do others think ?


Buy a 'Recon' alloy 9 speed 155 grams 8)


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PostPosted: Mon Nov 14, 2011 10:14 am 
retrobike rider
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hedgehog wrote:
Chains and cassettes wear together - stick a new chain on an old cassette and the pitch is different, so will slip even more. Those inidcators are not always very accurate mind, the old chain was probably even worse.

4-5000 miles is good going, I'd replace it as everything indicates is worn too far now.


Yep new cassette = new chain too I'm afraid!


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PostPosted: Mon Nov 14, 2011 10:17 am 
Gold Trader
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I've heard several say that to prolong a new cassette's life you should buy three new chains for it


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PostPosted: Mon Nov 14, 2011 12:09 pm 
Gold Trader / rb Rider / Special
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Dead rats - thats about right. Isnt it something like 3000miles per chain?

Also, your chainrings may be worn.


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