Changing Cassette - copule of questions

[Tomba]

I've got a 12-26 Sram PG950 at the moment and thinking of changing to a 11-32 to make hills a bit easier. I know I could get fitter but i'd like the 32 as a bail out on the really steep hills.

My derailleur is a Tiagra 4500 9 speed. I think its the GS model although not sure, dont see any markings, just comparing it to the two pics on Shimano website. Does anyone know where the markings would be? If it helps the bike is a Cannondale Synapse Tiagra 2011.

I think but not sure, that if it is the GS am I right thinking it can take the 11-32 but the SS wont?

So if it is a GS version. How easy is it to change a cassette?

And would this tool do the job?

From some digging around on the web it appears I would also need a longer chain?

 

[HLaB]

I've no idea about the length of the derailleur but SS and GS rings a bell from when I last looked. Providing you have a long cage (I think SS is short cage and hasn't the capacity) its a straight forward swap but you'll also need a chain whip, the linked to lockring tool and a large spanner (I forget the size I use an adjustable) and you are right you'll need a longer chain, I wrap my chain round the big cog and ring (but not through the rear derailleur) and allowing for an inner and outer link overlap is the ideal length. Google around and you'll find plenty of videos on line. Your cassette might be a bit stiff its the first time you've had it off (ooer), I usually just go away, come back and try again, etc that usually works for me but other say about larger spanners etc.

 

[Tomba]

Thanks HLaB. I knew about the chain whip tool, just forgot to add it in.

I've now watched a youtube vid of a guy changing one and it looks within my limited capabilities.

I just need to find out if my derailleur is compatible and to determine the chain length.

Or I could go to the LBS and get them to do it. But my thinking was to keep the 12-26 and chain and when i'm fitter I could swap them back myself.

 

[the_mikey]

I have a similar set up, I have a 11-32 cassette, but I swapped the derailleur from a tiagra derailleur to a shimano XT deore derailleur (a MTB derailleur), this is because the tiagra derailleur cannot work with anything more than 26T on the cassette, and you also will need a long cage to take up the slack in the chain, it's a massive difference between (50T+32T) maximum and (34T+11T) minimum. You will also need a new chain, as a longer chain length will be required.

 

[bobones]

You'll only have the GS if you've got a triple. Both 4500 GS and SS have 27T max in any case. In practical terms a 28 will work, a 30 might if top jockey clears cassette, but a 32 is stretching it. The 4600 RD officially supports 30T though, which means a 32 might work. Otherwise get a mountain bike RD.

 

[youngoldbloke]

Quote from an earlier posting Put a new 12-32 cassette (7 speed) on my Peugeot 525 - now winter bike - it shouldn't work with the Shimano short cage mech, but popped the wheel back in and turned the cranks, moved through the gears. Smooth as silk. No adjustments required, didn't have to increase chain length either. Moral seems to be - try it and see!
I had previously fitted a 12-28 with 48/38 chainrings, replacing the original 13-26 (with 52/42). I think at that point I increased the original chain length by 1 link. The rear changer - now almost 20 years old - is an Exage 500.

 

[RecordAceFromNew]

You don't really need to check the mech model code, knowing that is not going to give you certainty anyway given 32T is beyond spec for whichever Shimano road model.

All you need to do is to see whether your mech can be pushed to accommodate a 32T is to see whether it can deliver 12mm of clearance between the existing 26T sprocket and the top jockey wheel (sprocket radius increases by 2mm for every T). You likely have to adjust the B screw to achieve that, see this. The other thing that will come into question is wrap range, which is dependent on what else you have.

 

[Tomba]

Thanks for the replies

Might just go ask my LBS to do the job. Knowing me i'll cock it up now that its not a simple swap of cassette and chain