Swap Sora 12-25 for 11-30. Possible? If so, simple?

garynevstasche · April 2012

Recently purchased a Defy 3 2012. Clocking up some very enjoyable miles on it, but getting the feeling that when it comes to steep climbs it might be a bit high geared.

It has a 50-34 compact with a 12-25 cassette (all Sora), and I was wondering if it would be a). Possible and b). Reasonably straightforward to swap the 12-25 for the Sora 11-30. I'm assuming (perhaps incorrectly) that some adjustment to the derailleurs and chain would be required.

Also wondering whether it would be worth buying a separate rear wheel specifically for the cassette, or just replace the casette on my current wheel.

Any advice gratefully received.

canty91 · April 2012

Hi, assuming the cassette has the same number of gears it should be ok.
You may have to adjust the rear mech but not necessarily, give it a try without adjusting it, but you'll probably just have to adjust the B-screw so that the upper pulley doesn't touch the innermost cog on the cassette.
You will need a chain whip and the correct cassette lock ring tool, but other than that just a wrench.
All the best
Chris

rolf_f · April 2012

Probably not. Might depend a bit on the model but this is from the Wiggle spec of a current Sora mech

31 tooth total capacity, rear sprocket size range 11-27T

So, 11-30 is a range of 19 so you've only got 12 teeth left for the front to reach 31. If you are running a compact front, you'll have 50-34 which is 16. If standard, probably 53 -39 which is 14.

And the cassette limit only goes up to 27 teeth (but maybe 28 at a push).

You could get a medium cage Sora mech which gives 37 tooth total capacity which is covered by your proposed cassette but unfortunately the cassette capacity is still only 11-27 on the medium cage mech.

To put it more simply, you need an MTB rear mech. That said, I'd get a 12-27 cassette and just work on the hill climbing (I get the feeling you might be worrying too much about your gearing - just get up some hills and then decide!). You wouldn't need a separate wheel - just swap the cassette and put on a slightly longer chain when you need it.

FSR_XC · April 2012

garynevstasche wrote:

Any advice gratefully received.

Keep working on the hills.

As Rolf F says a 12-27 might be worth it, but give it a few months of building the leg muscles and you'll wonder what you were worried about.

CRAIGO5000 · April 2012

There is a huge downside too in that you'll not find the correct cadence on the relative flats with a cassette with too much range. It'll feel a right pain on the country roads with +/- 1-2% sweeping gradients where a close ratio cassette comes into it's own. You'd probably find you'd then over and under spin.

It's up to you but as you're already on a compact crank set-up, I'd advise to hit the bike more and the hills and get stronger with your current cassette as 12-25 is a decent range cassette and great for hills when matched with a 34T crank imo.

garynevstasche · April 2012

Thanks for all the responses guys.

I think I'll keep hitting the hills as suggested.

On reflection I'm probably over-worrying about the gearing, I've been hearing a lot about needing to get nearer 1:1 or I'll struggle on the steeper stuff, but you've helped put my mind at rest.

garynevstasche · April 2012

As a parting thought, given that the 11-30 wouldn't be possible (and by the sounds of it may not be particularly suitable even if it was possible), would a potential solution (should my attempts on hills fail spectacularly) be to get the Sora Triple (50/39/30). I'm assuming (again, perhaps incorrectly, that as my shifters are all Sora they will be compatible with a triple (tell me if I'm wrong though), would my cassette (11-25) be compatible?

EDIT: Ignore the above, just done the sums on the ratios, and even if it did work (which I'm not convinced it will, I'm sure derailleurs would need to be changed) a 30/25 is 1.2 and a 34/27 is just under 1.26. Not sure all the effort above just changing the cassette would be worth it.

ineedalager · April 2012

What you should do if you are still struggling on the hills is get a long cage MTB Shimano Deore rear mech and an 11-32 cassette this will give you 1.06. it's an easy swap if you have a chain whip and cassette tool.

What cage does your shimano mech have now as I have Sora on my Spesh Allez and it's a medium cage it will easily do an 11-28 and I have an 11-32 on there and it runs fine. The specs say max is 26 for my mech but the bike shop fitted a 28 and said I could get away with that. I was experimenting with my other bike and found the sora medium cage mech and 11-32 worked fine.

Your best bet if you don't have the tools in to go to your LBS where you bought your bike will be best and ask them what you can fit and what it will cost they don't charge an arm and a leg as it's a quick 15 minute job to change them.

Don't take too much notice about the ratio post and gaps between gears as a begginner it will mean very little to you what you are concerned about is having some better gears for the hills.

ptr_ · April 2012

Climb more hills.

If in 6 months you decide you need more gearing then switch to a 12-27 but I doubt you'll need it, 34/25 is enough to get up almost anything in the UK.

John.T · April 2012

If you are getting a new cassette I would recommend a 12/27. It is the same as the 12/25 except for the 2 biggest sprockets. You would only use these on the 34 ring so it just gives you lower gears at the bottom end of the range. The difference between a 25 and a 27 is quite noticeable. I have never considered using a 12/25 as the 21,23,25 gaps are too small at this end of the cassette. You can run 12/27 with your current Sora set-up with no problem. Correct chain length is important as you are close to the rear mech's limits. Just go as long as possible while still taking up tension on the 34/12 and it will be fine.

Swap Sora 12-25 for 11-30. Possible? If so, simple?

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