I'm looking to do some rides in N. GA and I know that the 12-25 cassette I have isn't small enough for the extended climbing, given my current conditioning level. I know that ideally I would just use what I have and make myself stronger, but I don't want the group I ride with to constantly have to wait for me. I also don't want it to be a miserable experience every time I ride up there.
So I'm wondering how much of a difference going to a 12-27 cassette would make. Would it even be worth changing the cassette for that, or should i look for something even smaller, like a (13-30). Btw, my chainrings are 53-39.

Thanks,
Brian

Almost None. But more importantly, going with a smaller gear is not going to make you go faster...the group will still be waiting.

Give it time, keep riding and get stronger.

If you are still concerned a better option would be to consider a compact or a triple.

I don't think that will help you that much. You can play around with gear ratios here: http://www.sheldonbrown.com/gears/

I think there is a limit to the cassette size you can use, but regardless, the advantage of changing to that gearing probably isn't going to help much in my opinion.

one thing to consider though: If you are mashing your 25 up the hill, you may actually get "faster" on the longer climbs by switching to a 27 since you will be able to spin more and have the legs last longer

On steep hills I noticed a difference between a 25 and 27. I guess it depends on how steep the hill is, and how close you were to stalling. When riding I often find myself clicking one gear higher or lower, usually there's only a one tooth difference, so why a two tooth difference wouldn't be noticeable is beyond me.

On steep hills I noticed a difference between a 25 and 27. I guess it depends on how steep the hill is, and how close you were to stalling. When riding I often find myself clicking one gear higher or lower, usually there's only a one tooth difference, so why a two tooth difference wouldn't be noticeable is beyond me.
Well, going from 25 to 27 is an 8% lower gear. This is slightly less of a difference than going from 12 to 13. So it shouldn't be more noticeable than some of the high gear shifts.

Regardless, 25 to 27 is about a single shift. If you're doing climbs where being able to make one more shift would save your day, then it would be sweet to have the 27. You will be grunting slightly less in the 27 (but may not go any faster - might even go slower). (My problem is that I'm often doing climbs where I'd like to have 2 or 3 more lower shifts available to me.)

You didn't identify your drivetrain, so I'm going to assume Shimano 10-speed. As far as I know, the only 10-speed cassette going into the 30s is the Interlock Racing Design (IRD), like the 11-32 and 11-34 which retails for about $160. You'd also need a long-cage derailleur and lengthen your chain. If you add all that up, you might come out ahead if you go with a mid-level 50-36 or 50-34 compact crankset instead. Some compacts would work well with your existing front derailleur.

If you're still riding 9-speed, you could buy a long-cage derailleur, lengthen your chain and get a much cheaper and widely available 9-speed mountain bike cassette, like an 11-32.

But as said by others, a larger rear cog will not necessarily make you faster. You trade speed for a reduction in effort, so you'd feel better on top of the mountain. Riding at the extreme end of these super-low cassettes, your speed on extremely steep stretches might not be a whole lot more than you could walk.

thanks for the replies. i guess when i said i didn't want the group to have to wait for me, i didn't mean b/c i was going slow, but b/c i couldn't make it up the hill at all.
i ride mtb most of the time, so i'm comfortable with being in a really small gear and spinning my way up a climb. and i'm comfortable mashing for a short period of time. just not for a sustained climb. i just have a feeling that the 25 cog is going to require more mashing than spinning on some of those grades - for me anyway.

thanks for the replies. i guess when i said i didn't want the group to have to wait for me, i didn't mean b/c i was going slow, but b/c i couldn't make it up the hill at all.
i ride mtb most of the time, so i'm comfortable with being in a really small gear and spinning my way up a climb. and i'm comfortable mashing for a short period of time. just not for a sustained climb. i just have a feeling that the 25 cog is going to require more mashing than spinning on some of those grades - for me anyway.

Makes sense. But if you're mashing a 25 on some of those grades, shifting to a 27 isn't going to let you spin. The difference in cadence (at the same power output) is just too small.

But that's not saying a 27 wouldn't help. I used to ride the hills of North Alabama and was always able to make it up to the top in a 39 x 25. But I remember many moments when I would have given my eye teeth for a 27, just to ease the pain for a few seconds. And as sometimerider said, it's a good feeling to have a cog or two in reserve. I for one feel a lot of power-robbing anxiety coming on when I realize that I'm climbing on my last cog.

I went from a 12-25 to a 12-27 and FOR ME it made a WORLD of difference. I dont care about your ratio percent BS here. Im a BIG dude and ANY little thing helps.
I could climb up hills I couldnt on the 12-25 and my legs didnt FRY as fast. I learned to spin more here as well
Enough said

Generally, the 53/39 chainrings are better suited to flat riding with some moderate hill climbs. Compact chainrings such as 50/34 would help climbing steeper hills, but would limit your top speed just a bit on flats, due to difference in chainring sizes.

If you really don't want to sacrifice top speed, then keep your 53/39 chainrings, and just swap out the 12/25 cassette for a 12/27 one.

The best choice for swapping out gear really depends on your level of fitness and the steepness of hills being climbed.

1) If your fitness is not too bad, just swapping out the cassette may be enough for you.

2) If your fitness is so-so, then swapping out the chainrings may be an idea.

3) If your fitness is not the best, then swapping out BOTH the chainrings and cassette may be the best option.

Compact chainrings such as 50/34 would help climbing steeper hills, but would limit your top speed just a bit on flats, due to difference in chainring sizes.

To overcome that limit, all you'd have to do is slightly increase you cadence. To ride 32 mph in a 53 x 12, you need to turn the cranks 90 rpm. To ride 32 mph in a 50 x 12, you need to turn the cranks 96 rpm—a measly 6 rpm more. Of course, if you don't see 32 mph on the flats much, these top speed limit considerations are meaningless.

I went from a 12-25 to a 12-27 and FOR ME it made a WORLD of difference. I dont care about your ratio percent BS here. Im a BIG dude and ANY little thing helps.
I could climb up hills I couldnt on the 12-25 and my legs didnt FRY as fast. I learned to spin more here as well
Enough said

I also swapped from a 12-25 to a 12-27. It was worth it. It allows me to comfortable spin up some steep hills that I couldn't before. On a shimano 10 speed, it is a few minute job if you have the tools.

If you are using 9 speed shimano and you need something bigger, buy an 18 dollar deore der. from nashbar and put an 11-34 on the back. I use 12-27s and there is a difference on the hills from a 25. Often it is the difference between sitting and standing for me.

If you put an 11-34 on the back you can climb just about anything.

Aiyn't no shame in needing a triple. Even with a triple, I still needed 27 in the back, as my bailout gear. It helped a LOT, exchanging that 12-25 for a 12-27. We don't have 'short, moderate' hills around here. They're called the Sange de Cristo (Blood of Christ) Mtns for good reason....I feel like I'm sweatin' blood, pulling some of them.

Sram makes a 11/28 (1070 style cassette) that would work and I believe that that would be a significant differance from a 12/25. I personally am having basicly the same problem and I am going to try this. If that dosent work I will be going to a triple.

Aiyn't no shame in needing a triple. Even with a triple, I still needed 27 in the back, as my bailout gear. It helped a LOT, exchanging that 12-25 for a 12-27. We don't have 'short, moderate' hills around here. They're called the Sange de Cristo (Blood of Christ) Mtns for good reason....I feel like I'm sweatin' blood, pulling some of them.

I think it was during the Tour of Flanders that Paul Sherwen commented on the huge rear cassettes some of the riders were using to get up the hills- they had 25 tooth low gears :) I guess that's why we don't get paid to ride.

Your mileage may vary.

I know several people here have commented that switching from a 12-25 to a 12-27 made a big difference, but for me it was hardly noticeable. I live in the mountains but am a relatively poor climber. I was hoping for more of a difference, but I didn't find it.

I have two rear wheels, one with a 12-25 mounted and one with a 12-27 mounted. My 12-27 wheel broke a few weeks ago and I had to switch back to the 12-25, and I didn't notice any difference.

I'd recommend you go ahead and wear out your 12-25 first, and then buy a 12-27 next.

I think it was during the Tour of Flanders that Paul Sherwen commented on the huge rear cassettes some of the riders were using to get up the hills- they had 25 tooth low gears :) I guess that's why we don't get paid to ride.

Yes it was- I got a kick out of that comment! That race was intense.
I finally traded my triple for a standard double, and am still riding a 11-23 cassette. So far, I have made it up all my usual 'hard' climbs just fine, but I am concerned about trying some of the longer climbs (the ones that will come up after two hours of riding when I am with a fast group and have already spent my energy). As small as the difference may seem on paper, one or two more teeth can be an absolute life saver- I feel it instantly when I shift. I haven't dismounted to make it up a hill since I was a kid, but the thought of it scares the heck out of my ego. I can't decide if I want to rely on harder training or a new cassette to make it up them, but if I had a few more gears, I wouldn't be worried. I'd say go for it; meanwhile, try not to use the bailout gears when you're alone (save them for the group rides).

I just put a SRAM 11/28 on here as well from a shimano 12/27

Are you using Shimano or Sram components? and what chain are you using and how does it shift. THX

Climbing gets much better with those granny gears. I've climbed with my old Bianchi with a 12-24 6 speed changed it to a 14-28, with a 52/38 or 36?...and its leaps and bounds better to ride. Fitness does play a part in climbing, but I have places I ride average over 8% and hit sections of over 20%, being able to pick up cadence in those spots help a lot. Try grinding a 38-24 on a 20% climb is just terrible, worse with old cleats!