Rear cassette

[RecordAceFromNew]

So can anyone advise me on what rear mech to buy?? And will i need to change the chain too???

If I were you I would get a Shimano mtb long cage (SGS) rear mech - which one (except the new Dyna-sys one) depends on your budget and even £8 Tourneys are decent and will work just fine. If the current chain is the right length then every 4 additional teeth will require 2 extra links.

An 8 speed shifter will definitely not index properly with a 9 speed cassette because their cog spacings are vastly different - The Doctor is right that Sheldon was talking about how many cogs will physically fit onto various hubs, not about whether they are interchangeble without other impacts. You can get any 8 speed Shimano cassette or compatibles (such as sram).

Personally I wouldn't change cassette, mech and chain just to get another 3 teeth and a low 11% lower - depending on the hills you can consider up to 34T.

 

[RecordAceFromNew]

I did think of doing that to chris-s, but i would still have to get a new rear mech.

Or would i

front 50/34 rear 11/25 max 33t so if i went to 11/28 would i need to change rear mech???

Whether you need to change the rear mech depends on two things, i) whether the parallelogram is long enough so that the top jockey wheel clears the biggest cog on the cassette, and ii) whether the cage is long enough to take up all the chain slack if and when you are on small both front and back. The latter is indicated by the mech's wrap capacity. The former is indicated by the max cog size spec of the mech - however it is somewhat adjustable by the B screw on the mech, and it is also dependent on the hanger/frame geometry.

For i) you can check how many extra teeth the current mech can clear by measuring the distance between the top pulley and the big cog when you are on the lowest gear - every 2mm is one extra tooth.

 

[jowwy]

This all getting a tad complicated - think i'll stick with the 11-25 and MTFU on the hills.

 

[Manonabike]

So can anyone advise me on what rear mech to buy?? And will i need to change the chain too???

I've done this in the past and I went for the Shimano 105 (long cage) which is what MTB use.

and the cassette is this one