Cassette options for 105 rear mech

mikey2341

I'm hoping to attempt the Etape and the Fred Whitton this year and wondered what would be the biggest cassette I can get away with. Could I fit a 12-28 or even the sram WiFi cassette??

maddog 2

it depends on which mech you run...

You can run a 11-36 if you want but you'll need a MTB mech.

If you want to retain your existing mech then you need to tell us what model it is (code as well if possible) and what speed you are running (8/9/10 etc).

If you are happy to buy a new mech too, then tell us what shifters you run, and what speed.

jibberjim

Which 105 mech? (the 5700A version will go up to 30 as per spec and probably 32 on all bikes)

11-28 will work for sure.
12-30 will probably work on most bikes.
12-32 may work on some bikes.

If it works will probably depend on things like chainstay length and Q-factors and such like, all you can do is try it.

Shimano 10 speed comes in up to 32, (or indeed 36 even) but yes SRAM 10speed will be compatible.

mikey2341

I think its the 5700 105 (it's on a boardman team if that makes a difference http://www.boardmanbikes.com/road/road_team.html)

I might try the 30, that sounds like it could be the most cost effective option!

Cheers

Gary D

If that is a short cage rear mech (which it looks like from the photo) then according to the Shimano spec sheets, you can go up to a total capacity of 33 Teeth. Allowing for the 16T difference you already have on the front, that leaves 17T. Therefore, an 11-28T or 12-28T cassette would be fine. A 12-30 would take you just outside the capacity, but it could probably be made to work if you got the chain length and indexing adjustment just right. The Shimano specs are a little conservative in my experience.
Otherwise, you would have to change the rear mech for a long cage one where you can then go up to a 39T total difference. However, if you were changing the rear mech, as Maddog said, you would probably be better to fit a MTB mech.
All of the informartion you need is on the Shimano website - once you can figure what all of the numbers mean

Hope that helps.
Gary.

jibberjim

mikey2341 wrote:

I think its the 5700 105 (it's on a boardman team if that makes a difference http://www.boardmanbikes.com/road/road_team.html)

That's a 5700 not a 5700A, so 11-28 may be all that will work.

The A takes it up to 30 see here for 36 quid or so) or a longer cage one which will take it up to 32, again for the same money.

There's no point fitting an MTB mech unless you want a 36, and I really think that's unlikely to be sensible as the jumps will just be silly.

mikey2341

Thanks for this, The cassette isn't too dear from Rose bikes, so I'll look at getting both of them. Cheers for your help

maddog 2

+1

11-28 should be fine. If you need lower then 11-32 and a mech change. Or a 33t chainring.