rcapilli

I have a Ultegra 10 12/25 on my bike and a Double on my crank. I am looking to climb some big hills in the very near future and wanted to know what my options are for changing gears w/o much trouble. I want to keep my double but looking to change my cassette. I know that I can get a 12/27 cassette and that is suppose to be a better cassette for climbing. Does it make That much difference to that of a 12/25? Also, I spoke to a guy today on the train and he said that I could change to a Mountain Bike Cassette and get a much lower gear for climbing some of the steeper grades. Is that possible? Let me know what you know. Thanks everyone for your help and suggestions.

zvalmart

My understanding is that the Ultegra rear derailer cannot handle a cog larger than 27 (or maybe 28) teeth. I don't think you will be able to run a large MTB cassette (34 teeth) with your derailer. A 27 tooth cog will be a bit lower than your current 25, but it won't make a HUGE difference. I suppose you could go to a compact crank/rings, but that is pretty expensive.

johnny99

25->27 is very small change. If you have 9 speed Ultegra, you can use a MTB cassette (up to 34 teeth) with a MTB rear derailleur. Your shifters will work fine.

sheldonbrown.com has some "touring" cassettes that are more evenly spaced for road riding than a typical MTB cassette (e.g., 13-34 instead of 11-34).

You may also want to look at compact cranksets which will give you a smaller chainring (e.g., 34-50 instead of 39-53).

OC Roadie

I recently faced the same dilema. My bike is set-up with DA 10 speed and I already was running a 12-27 rear cassette. My original plan was to run an 11-34 mountain bike cassette and rear DR. That plan went sour when I realized that mountain bikes aren't up to 10 speed yet (the drive train wouldn't have been compatible). After debating between mounting a triple and compact double, I decided on the compact double 50/34 crankset. Going to a compact double was much cheaper, easier and lighter than going to a triple. This would be my suggestion. I've been told that Santana makes their own tandem cassettes that are 10 speed compatible in 11-34. I was also told by the same guy that they're fairly crappy cassettes, but if you're just going to use on occasion, it might be worth looking into. The last option I'm aware of is getting a Campy 12-29 cassette and praying that it works with your Ultegra set-up, it's a crap shoot, sometimes it works, often times it doesn't. FWIW, I've been very happy with the FSA SLK Compact Crankset, it runs very smoothly and so far I haven't missed any of the gears. Good luck, let us know what you decide on.

viter

It's an 8% difference in the lowest gear. That's not much, but on a steep hill it can make a difference. My argument for 12-27 is that you don't lose anything compared to a 12-25. Only the lowest 2 cogs are different. Here are the steps between gears:

12-25
index teeth step
1 25 8.70%
2 23 9.52%
3 21 10.53%
4 19 11.76%
5 17 13.33%
6 15 7.14%
7 14 7.69%
8 13 8.33%
9 12 -

12-27
index teeth step
1 27 12.50%
2 24 14.29%
3 21 10.53%
4 19 11.76%
5 17 13.33%
6 15 7.14%
7 14 7.69%
8 13 8.33%
9 12 -

The step that will bother you most in both of these cassettes is the 13% from 15 to 17 as it is in the middle of the pattern. As you only use the largest two cogs with the smaller chainring, if you're using these cogs it means you're climbing something steep where having lower gears is more important than close spacing.

bvfrompc

Are we talking Vuelta or even San Fran steep climbs?

If not, can you work your fitness up to the climbs on your 12-25? I live in a mountanous area and I started out heaving and huffin and puffin up the big grades, so I started doing them more often, and after a little while I am able to get up them comfortably on the 25, so I am now huffin and heavin on the 23 or the 21, its so wonderful to see the fitness improve. Weight loss also helps (222 this morning, 252 a year ago.) Don't change your gear, change you! Unless its that crazy steep stuff where the pros use a 27, then get out the triple or the compact! Good luck!

viter

How is the shift between chainrings on that? 50 from 34 is a fair bit bigger change than 53 from 39, so what i mean is how many rear cogs do you need to shift when you shift the front so that you end up in a gear that's not too different from the gear you were previously in?

OC Roadie

Normally I just shift up or down one gear before changing the chainrings, sometimes two. The front shifts are much better than I thought they would be, ignore all the junk about compact specific front DR's, just lower the front DR a bit and adjust the limit screws and it's all god (at least in my case).

ovoleg

If you were looking to get better at climbing, wouldn't it be wise to keep your current setup?

My lowest is 21 and I have to say that it is pretty easy to spin up most terrain unless its a super hill. I guess Im not in great shape for hills(I spin like 65 rpm in 39/21 on steep hills) but with 25, I would guess you should be able to tackle most hills without much trouble? Personally I would never go beyond 25, I rode my friends Bianchi with 12-25 and it was 3 times easier than 21 up most of the hills. I would suggest keeping the cassette and just train a bit more on hills

34? Thats crazy!

Warblade

Last summer I went to see the 05 tour and got to ride up many climbs (Ventoux, Alp d'Heuz, Galibier, up to Courchevel, and many others) But I seemed to do fine on a 52/39 by 12/21.

ovoleg

Yea you have to get used to 39/21. It was pretty bad when I first started but I am getting much better at it. Up really steep and long hills, it does take its toll on you. Being in shape is the deciding factor on which gearing you choose

dekalbSTEEL

sounds like he's looking for a quick fix , may not have enough time for extra training

Warblade

Well I was able to do a little less than a spin up the climbs. Now granted I do race very competetively (went to nationals this year) and am 15.

sydney

Not if it doesn't work for him King Kong...Geezee!! Some folks need a 34 and a 30 granny.

NZLcyclist

I am tackling a 200k event with 2300m of climbing at the end of next month. I am putting on a Shimano Deore LX MTB Deraileur and taking the 11-32 cassette off the MTB.... should make it a bit easier!

Brendon

SpongeDad

I guess it depends on your definition of spin and steep. For me, 65 rpm is mashing. I am pretty uncomfortable outside of 80-100 rpm. I'm riding 39/23 on the harder hills around here, but I had to work hard to get there.

You're right that training with the taller gearing is what develops the power to eventually become better. But it's also true that a little granny gearing never hurt anyone, especially if it helps them get out on the bike more or to try bigger hills.

I'd vote for a 12-27 unless the hill are really long, in which case I might swap out to a compact crank and keep the 12-25.

bbattle

Agreed. When I first got my Orbea, it had a compact crank and Ultegra 12-25. I was killing myself trying to get up Monte Sano. I rushed to the LBS and said I had to have a triple. They priced it out and said they'd do it but why not wait until the cassette needed replacing? In other words, they were saying to get my lard ass in shape first, then come in for an upgrade.

Well, I'm now doing Monte Sano up and down twice and could go for a third time if sheer boredom didn't set in and force me to greener pastures. I climbed Grant mt. twice last Sat. and feel I could conquer Keel Mt. at this point.

I still may make a change but if I do, it'll be to the Ultegra 12-27 cassette and only after I've worn out the 12-25.


Compact cranks are a better deal than going to a triple, IMHO.

crosscut

Also, A cheap method would be to buy the 12-27 and a 130/135mm 38 small plate for the front.

thewalrus

Sheldon Brown's gear calculator results:

23-622 tire and wheel, 175mm cranks

39/25 is 41.0 gear inches
39/27 is 38.0

38/25 is 39.9
38/27 is 37.0

for comparison to a compact crankset, 34/27 is 33.1 gear inches

jazzy_cyclist

I know it's been beaten to death, but this is a good thread, as I've been mulling a compact versus a 12-27 (I have a 12-25 now) for working on climbing next season.

I haven't had a problem getting up hills, but I haven't done that much serious climbing where the hill is a mountain that goes on for a long ways at a considerable grade. I can power up a steep grade for a while, or do moderate grades for a good distance, but haven't done that much of both at the same time.

On the other hand, this is my second season (first full season), and I've made considerable progress. Hills that I had to use a lower gear on last year I can take in a gear that's 2 or 3 cogs higher. If that continues, then I'll believe you guys who climb Alpe D'Huez with a 53/39 and 12-21.

My LBS mentor says that you can climb nearly anything with a 12-27, but he's done Mt Washington a few times, too...

Warblade

Well jazzy keep up the good work, but also realize I have been racing since I was 10, which is the reason I can climb Alpe D'Heuz (which is one hell of a climb for those of you who haven't rode it!) in the 21.

OC Roadie

Some of you saying that you can do any climb on a 21,23 or 25 are right, you can grind through just about anything in those gears if you like spinning at 45-70 rpm and eventually trashing your knees. There's nothing wrong or inferior to wanting more gears. I've been riding the past five years with nothing bigger than a 27 (usually a 23 or 25), recently I put on a compact crankset to help train and prepare for Everest Challenge. I'd like to see some you guys bragging do this ride on your 39/21. It's 206 miles with 29,000' is it okay to ride a 34/27 or should I just train harder? Give the OP a break if he wants more gears, give him advice on his gearing options. I'm sure if he wanted adivce on how to climb in a 39/12, that's what the thread would be about

puddin' legs

Nothing inferior about high gearing. As you get more fit and/or loose weight, you won't be using the top cog or two, then you know it's time for a change. Save the old pie plate for trips with bigger vertical when you'll need it to start the process all over again.

ovoleg

Your right, the lower gears might allow you to try more hills and steeper hills. It's great to have initially but spending extra money might be a problem if your on a budget

I just counted my front rings...OMG . Granted I only stay in the middle ring(only downhill I'll use the large), I was surprised to find that the middle one was 42 and not 39. Since my chain is always on the middle ring, I never counted it but always assumed it was 39 because that seems to be the norm.

I recounted 5 times because I thought I lost track and miscounted, the large ring is 52 and the middle one is 42. What kind of crazy setup is this? Does this mean that originally I had a tripple? My lowest gear is actually 42/21. I totally miscounted the first time around.

Yea 60 is mashing for me too, but some hills if Im doing below 60 that means I am just moving the ring, just to move it, I can barely see straight at that point.

ovoleg

Same here, the longer it is, the more painful it is grinding the 21. Do any current bikes come with anything higher than 27?