New cassette - from 12-25 to 11-32 (9 speed)

Fian

I have a 30/42?/50 triple chainring with a 9 speed 12-25 cassette on the back. I am heavy - roughly 90kg (excluding bike) so heading up the dublin mountains at 30/25 I am certainly not spinning out! I can manage it though.

However I hired a compact bike when on holiday in Gran Canaria a month ago or so. Much steeper climbs but I flew up them (relatively speaking!) didn't even need to drop into the granny gear.

My existing cassette is 12-25 cogs, I am guessing the cassette on the hire bike was 11-34. So I guess in the lowest gear the ratio was 34/34, which is a lighter ration than the 30/25 my existing triple will give me.

Is it possible for me to just change my existing cassette to a 9 speed 11-32 cassette? I have Tiagra front and rear derailleurs.

Do I need to do anything other than change the cassette? Should I get a new chain while I am at it? Can I be confident the existing derailleurs will just work with a new cassette - I can't think of any reason why they wouldn't, I assume the horizontal distance between teh cogs is identical and that the derailleur should clear the larger 32t cog?

Seems to me I would get a lower climbing gear, enabling me to spin a bit better rather than the mashing I am currently employing (especially climbing up past lough Bray!) and as a bonus I would also get a faster top gear.

However I am new to all this so if I am missing out on an obvious pitfall I would be very grateful if someone could point it out to me.

Of course the ideal solution is actually to go and buy a new bike, with a carbon frame, di2 shifting and hydraulic disk brakes, but in the absence of unlimited funds I guess the cassette change would probably make a big difference for the money involved?

mcgratheoin

Fian wrote: »

Seems to me I would get a lower climbing gear, enabling me to spin a bit better rather than the mashing I am currently employing (especially climbing up past lough Bray!) and as a bonus I would also get a faster top gear.

Not sure how you worked this out - if you go from a 12 to an 11 smallest cog your top gear will be "slower" as you term it. Also, what do you mean when you refer to the "granny gear" on a compact? Were you climbing in the big ring the whole time or do you mean that you hadn't exhausted every cog on the cassette. It's unlikely that the compact bike you hired had a 34 cassette, it probably was a 32 largest cog, so an 11-27 will get you close and an 11-30 will be easier on your own bike. Also be wary of getting a very gappy cassette - particularly with a 9 speed. I'm not sure that putting a 30x32 on your bike is really where you need to be going either, that's less than one wheel revolution for every turn of the pedals. Be aware as well that if you're riding a clunker with poor wheels and a grinding bottom bracket, a newer, lighter bike with better wheels will add a significant amount to your performance. I recently upgraded my bike significantly and for the same effort I'm going about 10% faster over flat and undulating spins.

On your original question, in principle yes you can just swap out the cassettes, however a larger cassette may require a longer chain, in which case a larger derailleur may be necessary to maintain tension when your chain is spanning two of your smaller gears.

quozl

Going from a 12 to an 11 smallest would result in a faster top gear, as the OP thinks. Smaller at the back, larger at the front means faster speed per pedal revolution. Larger back, smaller front means the opposite.

I'd agree that it probably was a 32 on the hire bike - that's SRAMs wi-fli range. I haven't seen any road bikes with 34 rear cassettes though I'm sure that some people do it.

You would need a longer chain if you put on a 32 or 34. As if you change into the big front ring, big sprocket combo, you would be using a 50+34 rather than a 50+25 so would need 4 or 5 more links length of chain. Of course you shouldn't be in that combo but more sensible combos would still need some extra links unless your current chain is incorrectly long.

I think that mcgratheoin is probably right about 30/34 being too low for you. That's quite a big difference from the likely 34/32 you had on your hire bike and you didn't even use the lowest gear on that. Even a 28 would be a fair difference from the 25. Or a 30 would be slightly lower that the hire bike if our guesses are correct that it was a 32 rear sprocket. I'm just saying this because you have a triple which already has quite a small front chain-ring.

Fian

Thanks for your help!

I was in the small ring on the front on the hire bike, by not using the "granny gear" I just meant that I had not needed to go all the way down to the lowest gears available (small front ring and biggest back cog).

I will have a faster gear in top gear (for flat/descents) if move to an 11 (50/11 being faster than 50/12), and moving from a 25 big cog on the cassette to 28/30/32 I will have a lower/easier climbing gear (30/30 being easier to spin than 30/25). So i guess a bigger range, albeit a bit more "gappy" as you point out, but that will be offset by having three options on the front rings I guess?

I could well be completely wrong about the ratios on the bike I hired, but they certainly felt like the gears went to lower ones than the 30/25 I can go to on my existing bike. It was a CAD 10 with 105 compact gearing, but i never counted the cogs!

I guess my existing bike is not a clunker, though it is not as good as I would like it to be (I guess that's pretty much a universal truth!) My existing is a ridley eos 1008A. I can't generate a link because I am a relatively new poster but if you put in www and html at the beginning and end of that text below you will see one.

slanecycles.com/ridley-eos-el-1008a-bike-tiagra-whiteblue-2011-p-18784.

Thanks in particular for the advice on the range of the cassette, maybe an 11-32 is too low, I might try this one:

SHIMANO CS-HG50 9-speed cassette 11-30 (11-12-14-16-18-20-23-26-30)

I know that 30/30 would be a very low gearing but tbh that is exactly what I want, I don't mind having one gear that is lower than I really need for the really steep bits. And the 30/36 I would have would be slightly easier than my existing granny gear of 30/25.

cdaly_

I run a 13-32 9-sp cassette with the same triple. It works nicely with the medium cage rear mech (which is what you'll already have with a triple) so no problem there.

I very happily use the 30x32 granny gear when climbing 'cos I cannot be arsed pushing harder. That said, I have the bike loaded up with a load of crap so I'm lugging around 110kg total weight around...

Fian

Hmm,

Just looked up cad 10 compact, it seems the gearing on the hire bike was 12-27 and on the front 50/34.

So that means lowest gear I had was 34/27 versus my existing 30/25. Which is a heavier lowest gear than my existing one!

Maybe it was the better quality wheels or other components that made it feel easier, maybe the lighter frame or maybe it was just the sunshine and the general wellbeing that comes from being on a holiday!

Anyway I am very glad I posted on here before I bought because your responses prompted me to research it a bit better. I will still probably look to change the cassette, but I guess an 11-28 is probably more sensible than the 11-32 I was originally thinking of.

thanks both of you for your help.

Would i have trouble if i got an 11-28 Shimano HG80 cassette? That is described as a MTB cassette it seems. Would that work on my road bike?

Cee-Jay-Cee

Ive a Ridley Conpact with 9spd Tiagra and I fitted a 30/12 cassette and I'd only use the 30 on the steepest of mountain climbs, regular hills are manageable on the 25 or lower. A 30/30 should allow you climb walls, I couldn't see you needing anything bigger than it.