Changing cassette

[Hammerman]

Can anybody help please. I've been cycling for around 6 months now and have already done 3 audaxes, 2x100 and 1x200. My bike is a second-hand Scott AFD. Being based in west Wales I have access to a lot of serious hills and am improving all the time. I'm interested in changing the rear cassette to something more tourer orientated. The largest ring at the moment is 25 and was hoping to change it for a new cassette with something with 33 or 34T. I know the ideal senario is getting a new bike but with a son in uni that is totally out of the question until he finishes gets a good job and buys me van Nicholson . Is it the sort of job I can do myself or should I take it to my LBS. The only jobs I've done so far is adjust gears and brakes and changed a few (rare) punctures . Thanks

[Polar Bear]

Firstly, we need to know what gear spec your bike is including number of sprockets at the rear and the manufacturer.   

If your bike is shimano-equipped and has nine sprockets at the rear you can change the cassette for a mountaainbike 9 speed cassette (typically 11-32 teeth).   However, you will most likely need to change the rear derailleur as it is likely that the one fitted will not cope with the bigger sprockets.   Also, you might need to lengthen the chain which is in essence where you buy a new one.

A number of specialist tools are required to change a cassette and split / join a chain.   A couple of allen keys is more or less all that is required to change a rear mech.

Bike fettling is a very rewarding and slippery slope 

[interzen]

I think that changing a cassette might be a *slightly* cheaper option than buying a new bike

If you have the appropriate tools (chainwhip, cassette lockring tool, large adjustable spanner) then you can easily do it yourself. As ever, Sheldon (RIP) Shows You How: Shimano Cassettes & Freehubs

Bear in mind that you might need to replace the chain as well.

EDIT: an possibly rear mech too, as mentioned ^^^

[marcusjb]

Hi there

You may want to move this into the general knowledge area as you'll get more answers.

The answer is, maybe.

First thing to establish is what rear deraillieur you have?  Depending on the length of the cage on that, depends on what size the largest sprocket on the cassette can be.

33-34T is a very large sprocket and will almost certainly require it to be a mountain bike rear mech with a long cage.  A typical road mech with a 'medium' cage will only go up to 28T at the rear.

So, you may be chagning the cassette and rear-mech - neither of which are a massive job, but the cassette change does require a bit of tooling-up (not hyper-expensive).

Alternativly, it may work out cheaper to change the cassette to one with a 28T sprocket, and look at changing your small chainring up front - what is your chainset at the front and how many teeth does it have on it's rings?

Hope that helps a little!

[frankly frankie]

If you're a reasonably strong/young/fit rider (any 1 will do!) then the 11-28 cassette is a great choice for touring.  If you have more limited ability then the 11-32 is better. 
Personally I always find it a great comfort to have a bottom gear I never use!

[Hammerman]

Thanks for all the replies, it looks like the sort of job I can do myself. The cassette I have at the mo is an 8 speed Sora triple and the smallest ring on the front is a 30T. I think I'll go for the 28T cassette and just carry on with what I'm doing for know. The replies have given me the confidance to have a go. The tools aren't going to cost that much as I have spanners and a chain splitter any way. Watch this space Cheers

[Biggsy]

The 30T chainring can be changed as well for one as small as 24T, though 26T is more practical.  Any make with a 74mm BCD (bolt circle diameter) will fit.

[rafletcher]

And being a triple set-up you'll already have a long arm rear mech, so no need to change that.

[Alouicious]

When the 28T cassette is on, and the guide jockey wheel rattles on the tops of the teeth, replace the mech hanger with a longer one.

When the chain is on the 30T chainring and the 28T sprocket, that's lowest gear.
The smallest sprocket the chain should run to while still on the 30T chainring is 8 teeth less than the 28, so its the 20T sprocket.
Then you move the chain to the middle ring ( 42 ) and a sprocket larger than the 20T to get the next higher gear.
Again, the smallest sprocket the chain should run to while on the 42 ring is 8 teeth less than 20, which is 12.
Then you move the chain to the large chainring ( 52 ) and a larger sprocket than the 12 to get the next higher gear.

8 teeth is 4" of derailleur tension jockey wheel movement. Accomodated by a short arm mech.

Long arm mechs are for 'Alpine' chainsets where the difference in chainring teeth is more than 12, or 6" of chain. eg 42/26 double TA Cyclotourist.

[Ray 6701]

When the 28T cassette is on, and the guide jockey wheel rattles on the tops of the teeth, replace the mech hanger with a longer one.

The mech hanger will be fine it will just need adjusting.