UKC

The hills of Sheffield are a bit too much for the current gearing on my CX bike. Its a 9 speed with 50/34 at the the front and I think a 12/26 block at the back. The back mech is Sora with a long cage. Can I just grab an 11/32 block off the shelf from Decathlon and expect it to work OK once fitted?

In reply to TobyA:

Sounds OK. Assuming that the chain isn't worn of course.

In reply to TobyA:

You may need a longer chain but with a new cassette you ought to do that anyway

In reply to TobyA:

It should be ok. Try a 28, doesn't sound much but it will make a massive difference and none of the hills round there are very long. I usually run 34/25 as my lowest but for a recent trip to the Pyrenees I stuck a 29t on the back, felt like mountain bike gears, (up to a point)!

In reply to woolsack:

Cheers - i should have thought about chain length of course!

In reply to TobyA:

Toby,
Besides chain length you will need to consider the capacity of the rear mech (ie. its ability to deal with the range of options). Your cranks provide 50-34=16T and an 11/32 block would provide 32-11=21T. Therefore your rear mech needs a total capacity of 16+21=37T.
Shimano tech docs online will tell you the capacity of your rear mech (and the max size rear cog that it will accommodate.
HTH
N

In reply to TobyA:

I put a 32 on my cross bike for the 3 Peaks. This is with a 34/46 at the front and a mid length LX mech. The Shimano docs said 'not really' and that's about right really - it's a bit noisy in bottom gear. The top jockey wheel is too close to the block. You can do a certain amount by pushing the B tension screw all the way in (or even reversing at and screwing it in from the other side) to give more clearance.

In reply to SteveRi:

Yep, or even get a cheap MTB rear mech e.g. Alivio for £20.
I fitted an 11-32 cassette (8-speed) and Alivio mech to 'er indoor's Tricross so she can winch herself up steep Cornish lanes.
N

In reply to cousin nick:

Nick - thanks for explaining that so clearly! It helps a lot get my head round what I need.

So I dropped in at the bike shop I ride past going into uni and had a nice chat with a guy there. He had a look at the mech on my bike and ummed and ahhed over whether it was an older or newer Sora. He said I could take a chance on an 11-32 cassette and see if it worked and return it if not. So I've just cleaned the bike up and swapped cassettes, but in the lowest gear the chain is basically running between the cassette and the higher jockey wheel on the mech and clicks and clanks a lot. I googled the model number of my mech (found under the mud!) and it seems it is only designed to take up a 27T cog, so it figures that the 32T is too big.

BUT(!) it appears that I can get a new Sora mech that now accommodate up to 32T for 16 quid, which won't break the bank. Can anyone think of any reasons why that shouldn't work?

In reply to TobyA:

hopefully, if it will work with 32T cassette it will also have sufficient total capacity - but check first. The paperwork in the rear mech box will have the details.
N

In reply to TobyA:

Seriously, you won't need more than 30 (ie 34-30). I think that will work ok with your rear mech. It's only the old chaps who need a 32 !!!

In reply to cousin nick:

Shimano now do two versions of the Sora mech with different cages lengths. Total capacity of the longer cage version is 41T, while from your super clear explanation above I know I'll need only 37T. The total capacity of the shorter cage mech is 37t and that will take up to a 32 biggest cog cassette too. Are there any advantages to the longer cage beyond it being able to cope with bigger cogs on the crankset?

In reply to TobyA:

Jaysus does nobody stand up anymore!

In reply to Stig:


These days I am that old chap! I was labouring up the hill in Meersbrook park today (for anyone who knows the area) and some little girl, maybe 10, said "I don't know how you can cycle up this." The irony was she didn't know how close I was to not being able to cycle up there!