Replacing Chain and Cassette on a Giant Defy

[chrisb1357]

Hi all,

Well I always like to give stuff ago myself and enjoying learning how to maintain my two bikes so hear go's.

I have had my Giant Defy 4 for a year now and coming up to only 1,500 miles since new. A few months back a local bike shop checked my chain stretch and suggested it would need changing around spring this year so I have now decided to think about giving it a go with changing the chain and cassette myself which would be a first for me (Only ever changed gear cables and re-index my gears before as still learning).

I first need to get myself a chain stretch checking tool which only cost a few quid to check myself to see how far the chain has stretched as I have read that if its at 0.5% stretch then its a good idea to think about changing them as a pair.

Currently on the bike I have a SRAM PG 850 11-32 Cassette and a KMC Z7 Chain

Would I be best to change like for like as in same SRAM cassette and a better KMC chain like the KMC X8 Ept 8 Speed Chain and also add a quick link into the chain as well which I don't have at the minute.

I would also need to purchase my own chain whip tool and lockring removal tool and chain splitter that I do not currently have but they will come in use later on.

Thanks

 

[rusty bearing]

If your chain is only 50% (your 0.5) then no need to change at that point. Up to 75% you can often change the chain only but that's not hard and fast rule as the cassette may have lived through the life of several chains and be completely worn out.
Past 75% yes change both. You can do like for like but you don't have to, if a similar Shimano cassette was on offer you could use that instead. Quick link? KMC usually include on in the packet with the chain.

 

[Spiderweb]

If your bike has only covered 1500 miles from new then the chain may need replacing but the cassette will be fine.
Roughly speaking you should be able to get through 3 chains to one cassette.

 

[gbb]

If your bike has only covered 1500 miles from new then the chain may need replacing but the cassette will be fine.
Roughly speaking you should be able to get through 3 chains to one cassette.

I'd agree. while the general rule is one cassette to three chains, leaving a chain too late can of course compromise the cassette but....if budget is tight or you like to get the most for your money, I'd just change the chain and see how it feels, the cassette may well be fine.

 

[raleighnut]

And if you're really tight you can store the old chains in a jam-jar full of oil then at the point where a new chain won't run due to wear on the sprockets then a part worn one will DAMHIKT.

 

[chrisb1357]

Thanks for the advice,

I was not aware that you can usually go though 3 chains to one cassette and its not something the bike shops tell you so good to also know this.

May I ask how you can tell a cassette is worn and when that needs changing?? Would slipping and jumping chain i.e moving up and down sprockets on its own by a cause of a worn cassette (By the way mine is not doing this at the minute). Same for the front cranks as well how can I tell.

Going to order a chain stretch tool and check for myself to see how far its gone before I order anything or can just order chain to keep ready. I have looked after my bike well over the last year so if its no more than 75% then its ok to continue with same cassette but change the chain soon just before it hits this level of stretch. If over change both

Need to order myself a chain splitter tool as well for home and when on the bike. Is it advised to keep a spare pair of quick links if my chain ever snaps when out on the road to get me home?. its not something I have at present when on long rides but others I know do carry such things with them.

Many Thanks

 

[al-fresco]

I've never actually worked out what a worn cassette is actually doing - because the chain only skips or jumps under load, not on a workstand so I've never actually been able to see it happening. Generally, if the skipping/jumping tends to occur on hills, especially when I'm out of the saddle, I put it down to a worn cassette. Put a new cassette on and the problem goes away. As others have noted the skipping/jumping often shows up (or gets much worse) when you put a new chain on an old cassette.

If your chain breaks, assuming you haven't forced the pedals and ripped your rear mech off, a spare powerlink will have you on your way in no time so I always carry them.

 

[mmmmartin]

It might pay you to join a local club, you might find people there who already not only own this toolkit but know how to use it. Sheldon Brown's website is a mine of information, as is the Park Tool one. As a rule of thumb, the lengthening of the chain (caused by the wear on the bits where the links join not the actual stretching of the metal) is what wears the cassette in the wrong places so if you keep replacing the chain it'll take a long time for the cassette to wear.
And yes, a few quid on a magic link that weighs 3 grams will get you on the road again within minutes. Not only that, but it'll get your riding companion back on the road so your ride isn't ruined waiting around for help.

 

[rusty bearing]

Thanks for the advice,

I was not aware that you can usually go though 3 chains to one cassette and its not something the bike shops tell you so good to also know this.

May I ask how you can tell a cassette is worn and when that needs changing?? Would slipping and jumping chain i.e moving up and down sprockets on its own by a cause of a worn cassette (By the way mine is not doing this at the minute). Same for the front cranks as well how can I tell.

It,s difficult to visually determine the state of a cassette and when it needs changing. Physical clues like gear changes being be horrible , noisy and sometimes feeling like a short loss of drive are a giveaway though. Often manifests in particular cogs as people tend to favour certain gear ratios over others. I get the bit about three chains per cassette, this is ok for a home mechanic as if it don't work it don't work. When you get paid to fix bikes customers want them right so I err on the more conservative side.
On the chainset it's easier to tell, the teeth get visibly sharp and pointy

 

[Yellow Saddle]

It,s difficult to visually determine the state of a cassette and when it needs changing. Physical clues like gear changes being be horrible , noisy and sometimes feeling like a short loss of drive are a giveaway though. Often manifests in particular cogs as people tend to favour certain gear ratios over others. I get the bit about three chains per cassette, this is ok for a home mechanic as if it don't work it don't work. When you get paid to fix bikes customers want them right so I err on the more conservative side.
On the chainset it's easier to tell, the teeth get visibly sharp and pointy

Some of the clues you mention are a-symptomatic of chain wear. A worn chain does not influence shifting. Not at all. Nor does it make a different noise from a new chain, given the same lubrication and cleanliness on both.
When you get paid to fix customer bikes, erring on the conservative only benefits your till.

It is easy to diagnose whether a cassette is worn or not. Further, if it is not completely worn - say on its second chain only - then the next chain will not skate over the worn sprockets before that chain is worn out. Only the next chain will skate. In other words, there is no benefit to err on the conservative side, especially since the biggest risk for chain break is poor installation. Your installation itself introduces a risk that wasn't there with the old chain. This subtlety of chain wear is widely misunderstood.

 

[Dogtrousers]

It is easy to diagnose whether a cassette is worn or not.

How?

I only ask because my bike is coming up for a new chain, cassette (and possibly chainrings) in the next couple of months probably. I'll probably be replacing the cassette anyway as it's on its fourth chain already. But it'd be good like to know how to inspect it.

 

[Yellow Saddle]

How?

I only ask because my bike is coming up for a new chain, cassette (and possibly chainrings) in the next couple of months probably. I'll probably be replacing the cassette anyway as it's on its fourth chain already. But it'd be good like to know how to inspect it.

You can't inspect it, only diagnose it by testing.
Fit the new chain and then find a nice steep hill and pedal as hard as you can in each gear. If you know yourself and your bike well, just test in your most-frequently used gears. If it doesn't skate under those conditions, it will not skate until you fit the next (or subsequent) chain. It will not start to skate halfway through the new chain's life, so no need to err on the side of conservatism.

 

[rusty bearing]

Some of the clues you mention are a-symptomatic of chain wear. A worn chain does not influence shifting. Not at all. Nor does it make a different noise from a new chain, given the same lubrication and cleanliness on both.
When you get paid to fix customer bikes, erring on the conservative only benefits your till.

I was referring to the effect you get from putting a new chain on an old worn cassette. We are not trying to 'benefit our till' as you put it but give our customers the best service and advice we can. You may take a different view but that is of course your prerogative............