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PostPosted: Thu Dec 30, 2010 1:48 pm 
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Posts: 29
Hello,

I'm hoping this is a good place to post this question!

I've ordered a new bike with a Campy groupset. It's a standard compact (50/34) & 12/27T rear. My previous bike had 50/34 & 12/28T

However, I have the option of a 12/29T cassette to go with 54/39 rings instead of 12/27T. I plan to do a few races in 2011 & the Pyrenees (Col Du Tourmalet) . Should I opt for 12/29T? How difficult is 12/27T, particularly in the Pyrenees?

I ride a lot of 15% plus (22% max) gradient hills. I'm pretty fit and weigh 74kg.

Please can you advise?

Thank you


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PostPosted: Thu Dec 30, 2010 4:13 pm 
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Posts: 2527
No one can advise you on the proper gearing, but with the compact, you may find the 50/12 top gearing is lacking, since it's about the same as a 53/13.

If you'll be riding a lot of grades of 15% or more, the 34/29 might be a wise choice. It depends on how hard you want to work. I'm old and get by with an 11-25 in the Colorado mountains, but they are not that steep, for the most part.

You can always buy more than one cassette. Just buy Chorus cassettes, that cost far less than Record or SR. The Chorus cassette will last far longer.


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Posted: Thu Dec 30, 2010 4:13 pm 


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PostPosted: Thu Dec 30, 2010 4:50 pm 
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Location: Canada
For terrain like that, I would always err on the side of caution. If you are having a bad day, at least you will be able to get to the finish...


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PostPosted: Thu Dec 30, 2010 7:15 pm 
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Why can't you get the 12-29 cassette with the compact 50-34 crankset? Why does the 12-29 have to come with a 54-39? 54? Personally I think the 50-34 with the 12-29 is the best choice for the terrain you described. A 34x29 low gear is 31 gear inches. Pretty low. Great for mountains.

But regarding your two choices of 50-34 and 12-27 or 54-39 and 12-29. It does not really make any difference except on the high end. The 54x12 is a lot higher than the 50x12. But so what, you get to pedal a bit more going down the mountain before you start coasting. Big whoop. The low of 34x27 is 33.4 gear inches. The low of 39x29 is 35.6 gear inches. Not much difference. If these are really your only choices, then the 54-39 and 12-29 may be better. But the 50-34 and 12-29 is best of all.

Campagnolo 11 speed 12-27 is 12-13-14-15-16-17-19-21-23-25-27. Campagnolo 11 speed 12-29 is 12-13-14-15-16-17-19-21-23-26-29. So only the last two cogs are different between these two cassettes. I much prefer big jumps on the end of cassettes. Have all the other cogs tightly spaced and then big jumps when you really need low gears.


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PostPosted: Thu Dec 30, 2010 8:57 pm 
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The only reason that I like a 53/12 or 50/11 top gear is that I ride more moderate descents in the Colorado mountains. Just coasting is quite often too slow for me and right in the range where a 50/11 allows me to boost the speed.

Obviously, is you're descending grades of 8% or more, you'll be doing 45+ real quick and your top gear won't matter.


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PostPosted: Thu Dec 30, 2010 9:47 pm 
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Brilliant replies, esp Russell thank you. Very helpful.

By going with 12/29, there'll be weight penalties of added chain links and two larger sprockets. I don't really want to over gear on a whim.

Currently the bike comes with 50/34 & 12/27 standard - my only worry is this set up is more suited to professional climbers, i.e. the same gearing ratio Andy Schleck rode at the TDF during the Mountain stages.

Should I try 12/27 first and see how I get on? That way I'll know for certain if I need to go lower?

Thank you again


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PostPosted: Thu Dec 30, 2010 11:48 pm 
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Location: Reading, UK
hatone wrote:
Currently the bike comes with 50/34 & 12/27 standard - my only worry is this set up is more suited to professional climbers, i.e. the same gearing ratio Andy Schleck rode at the TDF during the Mountain stages.


Are you sure about that? A pro won't need a gear anywhere near that low except for maybe the Angliru in the Vuelta. The Alpine climbs used in the Tour are rarely steeper than 10%.

For normal riding for a normal rider, ie not pro or elite, a 34x27 will get up most hills. If you're doing long events in the mountains then you might appreciate 34x29 when you face either supersteep climbs, as British sportives like to find, or repeated long climbs, as an Alpine or Pyrenean sportive will feature. Altitude will also increase your gratitude at possessing a low gear.


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PostPosted: Fri Dec 31, 2010 12:54 am 
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How long are your crankarms?

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PostPosted: Fri Dec 31, 2010 1:57 am 
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hatone wrote:
By going with 12/29, there'll be weight penalties of added chain links and two larger sprockets. I don't really want to over gear on a whim.

Currently the bike comes with 50/34 & 12/27 standard - my only worry is this set up is more suited to professional climbers, i.e. the same gearing ratio Andy Schleck rode at the TDF during the Mountain stages.

Should I try 12/27 first and see how I get on? That way I'll know for certain if I need to go lower.


Sounds like 50-34 and 12-27 is the "no extra cost" option. And trying the 12-29 is an extra cost. So go with the 50-34 and 12-27 and see how it works for you. The extra weight of 1-2 chain links and the bigger cogs to go with a 12-29 is minor. 50 grams extra maybe. A low gear of 34x27 is 33.4 gear inches. A low gear of 34x29 is 31.1 gear inches. Not a lot but maybe enough to be noticed. Personally i want the lowest gear I can get for mountain climbing. Even if I don't use the lowest gear. It doesn't bother me to carry the unused big cogs up the mountain.


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PostPosted: Fri Dec 31, 2010 8:49 am 
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Cool guys. Crank length is 170 mm. What effect does crank length have?

I'll try 12/27 and see how I get on. In the meantime, better lose a kg for the New Year..!!

Thank you all very much for your help.


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PostPosted: Fri Dec 31, 2010 9:46 am 
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Location: Santa Barbara
Theres a book i read a while back called The Rider, by Tim Krabbé. Its depicts in first person the experiences of a young amateur cyclist in the early 70's in the biggest race of the season. The morning before the race, each cyclist stopped to have a important meeting with themselves, hunched over the box of cogs in the back of their car, stealing furtive glances at opponents bicycles, pondering what sized cogs they would rely on to deliver themselves over the mountain pass. It was a personal choice then and it stil can be today. If worse comes to worse you'll just have to push your pedals at 60rpm, swaying your head side to side as you grind up the mountain just like they did in the bad old days. Only you can really know what gearing you can push up 20km of a 8.5%- none of us know your body like you do.

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PostPosted: Fri Dec 31, 2010 5:53 pm 
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I think you have to bear in mind the 'average' riders on L'Etape use 12-27.

I think the pros only used the 29 for the steepest climbs Monte Zoncolan and Plan de Corones in the Giro this year, otherwise they use 12-27 on mountain stages.


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PostPosted: Fri Dec 31, 2010 9:39 pm 
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I switched my wife from a Shimano triple to a Campy compact setup with a 13-29 cassette (they didn't offer 12-29 at the time). Since then of course SRAM actually marketed this with Apex and everyone thought they were brilliant, when in fact they were years and years behind what we already knew.

One item that hasn't been brought up is the RD. I setup my wife with a mid-cage Centaur for this gearing and it works great. The short cage will handle the 12-27 cassette but I'm not so sure that a short cage will handle the 50/34 - 12/29 combination. Please someone correct me if they are using this.

On the other end, I wouldn't be concerned at all with the high gear. I race with a 50/34 and 12/25 and I still always gain time on every other rider on the descents with good coasting and tucking technique. (now if only I could go as fast on the flats). Once you spin out a 50-12 its usually time to coast anyway and enjoy it especially if not racing.


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PostPosted: Fri Dec 31, 2010 10:18 pm 
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The Campy 11 speed RD, 2010 or newer will handle a 50/34 with a 12-29. The 2009 model needs a new part in the B screw mechanism to allow the upper pulley to swing further away from the 29T cog.


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Posted: Fri Dec 31, 2010 10:18 pm 


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PostPosted: Fri Dec 31, 2010 11:46 pm 
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hatone wrote:
Cool guys. Crank length is 170 mm. What effect does crank length have?

I'll try 12/27 and see how I get on. In the meantime, better lose a kg for the New Year..!!

Thank you all very much for your help.
Crank length is dependent on your leg length but in particular the ratio between the thigh and lower leg.

How tall are you? If you're a fit 74 kg I wonder if you are on too short a crank length. I'm 5'9" and I should be 70-72 kg, my cranks are 172.5.

Plus where are you riding? 15% is steep, but if they're short steep hills then power rather than gearing should get you up them. On the other hand 15% for several km is better done with gearing.


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