sorebutt

I am looking to replace my Shimano 105 12-25T, 9 speed cassette with something bigger for more climbing.. what is available in the Shimano line that would give me 27 or larger gear? I wouldn't mind if my fastest gear is 13 or even 14(?)...
Ideally, it would be a simple swap with my old cassette..

thanks in advance...

jeff williams

If for clibing, why not drop teeth off your middle ring? 36-34 or 34-32.
also if its super steep, a bail out gear on your rear cogset.
I've seen them factory grouped but I think you can do it yourself?
I was told by the lbs that it wasn't super smooth shifting and your derailler has to be able to clear.
More the idea of not losing your main drive gearing, just an added-make it or bail cog.
with my upgrades i'm increasing my chainring size and need that big one rear.
Ideas anyway.

Davet

You can get a Shimano 12/27 cassette, or if you need more climbing gearing you can swap out your rear dérailleur for a Shimano MTB rear der and use an 12/32 or 11/34 cassette MTB cassette. If you use the MTB parts, you will also need a longer chain.

I live in eastern Washington at the base of several mountains and the MTB rear dérailleur/cassette combo works very well for me.

1oldRoadie

First question is do your need a larger bottom (power gear) for climbing the big hills....or are you looking for more middle power gears?

The 105 r deraileur can only take a 27 or 28 for a big (power) gear. If you need more go to a triple crank. It is cheaper than trying to buy a new cassette and Rear deraileur.

If you just need a more mid power, https://www.sheldonbrown.com/harris/index.html can sell you single gears to make up almost anything.

As an Originial Old Fat Boy I ride a road triple crank and a modified cassette of: 14-15-16-17-18-19-21-24-27. That gives me 100 gear inches on the top end which gives me 30mph at 100rpm and I will never ride on the flat at 30+mph, ever!

Davet

sorebutt didn't specify whether he had a double or triple, but not everyone wants to give up the cache of a double, so I recommended the MTB der and cassette, Which is about $20 less than a triple crankset and bottom bracket. IMO, the upside to having the MTB gear on the back is that it is very easily changed out to the road dérailleur and cassette with a minimum of fuss.

Then there's the likelihood that sorebutt is a newbie and hasn't got his legs yet.

sorebutt: If are are a new rider, give yourself some time to gain the strength for the climbing you want to do. It will come. Learn to love hills. Find one that you haven't climbed, on every ride, and give it a go. Sooner than you might expect, there will be no unclimbed hill anywhere near you. But I still stand by my original advice.

sorebutt

sorry folks, I do have a triple front (30/42/52T).. and the reason I need a bigger gear in the back it for soem of those really steep hills.
Would I be able to feel the difference between a 12-25 and a 12-27 cassette?

NZLcyclist

Also remember to replace the chain as well. I cannot comment on gearing as I have a 39/53 double. It can be about conditioning too. There is a 3km hill here that woulda killed me when I first started, but the other day I was going up using the 39 and 21,19 and 17T cogs. How long have you been riding?

edit: is this a road bike? loaded tourer? ta.

Brendon

Davet

Now I see the pic of your Giant. Nice bike! There will be only a small difference between a 12/25 and a 12/27, not worth the extra money in my opinion.

Maybe with some training and skill gains, you can tackle the hills. The key to getting up steep hills is tempo, not attacking them, at least at first. Sit and spin up the hills. One way to get better is to do more hills, again and again. It does take time to build the strength and endurance necessary to climb.

I only started riding in 2000. I'm 62 now and I haven't met a hill I didn't like. My climbing training consists of hill repeats; climb a hill and come down, then do it again and again and again. Each ride I try to climb a little faster than the last ride. I have several different road bikes, both are triple. One is equipped with a 12/27 rear cassette, the other is equipped with a MTB rear dérailleur and MTB 12/34 cassette. The last is my 'mountain' bike, the one that I take if there is going to be a lot of steep hills or if I'm riding in the mountains.

The bike is only as good as it's 'engine' which is you. Find a good training schedule, feed yourself properly, and try to do what you can't do. Climb hills, climb more hills and then find a hill that you can't climb and keep trying. It's not easy and doesn't come without effort. You will be surprised how strong you get, quickly. All it takes is practice.

sorebutt

Thanks Dave. I am riding now for a couple of years, but REALLY riding for three months.. I live in California/Bay Area which has amazing routes to bike, and many are involved going up the mountains. I am a heavy man (51 yo), I weigh 210 as a lift weights and the most I could home to lose (in fat) is another 10 lb.


Here is an example of a route I do on weekends, and the steep part of it I believe I can do very soon without resting in the middle. It took me a while to figure out my "tempo", or as I call it the "groove" that I can sustain for the whole climb. However there are very short sections on those switchover turns where the grade is 20% and those take the little spare energy I have and I start falling behind, and have to stop for a minute to recover.

the route

this Pass (Old La Honda Road) is the easiest to climb of all the passes, and I wanted to have a lower gear so I could start climbing the other passes which are much more difficult.
I know that eventually I will be bale to climb all of those, I just wanted to do it sooner..

Gonzo Bob

I agree - The difference between 12-25 and 12-27 is not much. It would lower your low gear by about 8%. If you feel you're close with 12-25, then maybe getting a 12-27 is enough. If not, you need explore other options.

An MTB rear derailer with a 12-32 or 12-34 cassette would be one.

You could also look at getting a smaller inner chain ring. I believe the 105 triple uses a 74mm BCD for the inner ring which can go down to 24T. But Shimano specs the max difference for the 105 triple front derailer at 22 so you can't go all the way down to 24T without also getting a smaller big ring. However, I have successfully run a 24 tooth difference so you could go with 28x42x52. A 26T difference might even work with 26x42x52.

Lastly, although the Shimano road derailers are spec'd at 27T max cog, you can usually get them to run on bigger cogs. I have run mine on 28T and I have heard of folks successfully using a 30T large cog. But I don't know if 12-30 cassettes are available. But what you could try is get a 12-27 9-speed cassette and a loose 30T cog. Take out the 14T cog and spacer and build up a 12-30 by putting the 30T cog and the spacer from the 14T on first.

Davet

The smallest small chainring that should be used would be a 28T. The reason for this is that the front dérailleur can't handle the greater jump (more than 14T difference) from the small ring to the middle ring.

Now thinking about it, a change in the small ring from a 30T to a 28T, along with using a 12/27 cassette might be the difference you need to be able to climb those passes you want.

sorebutt

Thank you all. Good advice all around..
I have decided to leave this bike as it is and just train harder.. And once I have 2 centuries under my belt, I am going to treat myself to a new bike (Right now I'm thinking Serotta).. On this new bike, I will have a triple with a 28t small chainring, and a 12-77 cassette.. And I'll be set..

Davet

You're on the right path; train harder. One thing you will need is endurance, particularly in your lower body. Easy off lower body weight training and go for lower weight and many reps. Pedaling the bike up hills will do the same thing.

If you haven't already discovered it, there is a great forum for Serotta owners and anyone else who is interested: https://www.serotta.com/forum/

Good luck and have fun!