Gearing

amattinson

I normally ride my entry level roady in hilly territory with several 4km ascents of about 5% with a 23-11 cassette. While not the best climber I don't think the gearing is the problem. I am going to a quite mountainous region (Switzerland) for work and taking the bike so as not to miss the oportunity of riding some of those awesome cols.
Anyway.... what gearing does anyone with any idea recommend or even just general opinion. I am considering 27-12 but wondering whether I need to go to the 27 or whether 25 will be sufficient.

ator539

Hey, I do not have very particular advice for whether you ought to go with a 27 or 25 in the back for your trip. My feeling generally is that the more teeth in back, the better. There are even some Shimano-compatible 11-28 cassettes out there which shift quite nicely with typical shimano rear road derrailleurs (nashbar sells one which is OK, but not great).

If you really want to get into a precise calculation, you can look to the speed and cadence meters availalbe online. For example, check out sheldonbrown.com's gear chart

http://www.sheldonbrown.com/gears/

and this can give you a speed for a gear, given a cadence. For example, if you want to maintain 10mph up your 5% climb at 90 cadence, then you need to have a 39 up front and a 27 in the rear (actually, you would go 10.2mph for typical wheels at the cadence and gearing mentioned). Playing around with this gear calculator and other calculators online will give you a better idea of what you might need.

Alternatively, a gear/power online calculator can be found at

http://www.kreuzotter.de/english/espeed.htm

Playing around with that will give you an idea of the power needed to go a certain speed at a given incline, and this can be compared to what you would need to put out for a speed on flat land. My hunch is that most people are over-geared rather generally and these tools help people to see that. For example, it shows that to go up a 10% incline, such and such a power is needed, and this power would put the person at 26mph on flat land, etc.

Hope this helps. Sorry I could not be of more particular assistance.

dhk2

Going to a 25 from 23 isn't worth the effort; 27 is a no-brainer. Beyond that, if you'll be on 10% and steeper climbs, I'd suggest you consider switching to a compact crankset. Remember, on a 10% slope you'll be climbing at half the speed you do on a 5% slope (keeping power output constant). So, it follows that to maintain the same cadence with the same effort at half speed you'll need "half" the gear. Since you can't put on a 46 rear cog, going to a smaller chainring is the only solution.

I've got a triple, with 30/25 low, and on 10% grades it's just deep enough. With that gearing, 6 mph is about 60 rpm cadence. 6 mph sounds like cupcake territory, but that requires ~ 250 watts on a 10% gradient. For me, that's a hard effort @ 60 rpm if the climb lasts more than a few minutes, or comes near the end of the day after a thousand meters of climbing.

Solanog

Don't know if it will fit your bike but I rode with a guy that installed a Mountain bike's cassette so he had huge cogs maybe 11-32. If your rear deraileur supports it then it will be an option.

dhk2

Yes, I've seen the 11-34 MTB cassette used here on road bikes as well.
Believe an MTB rear derailleur is necessary, but for a week of mountain riding, it might be worth the cost and time to make the change. If the big jumps in cogs proved to much back home, it's easy enough to change things back to stock.

A buddy here has a Madone which came with the standard double. He's bought a triple set up for it, as well as a compact. For the big mountain century in spring, he uses the triple, otherwise he rides with the standard double or compact. Seems a bit over the top to have three crankset options for one bike, but he's kind of a gearhead who likes to optimize his equipment for the job at hand.

kdelong

FYI- www.nashbar.com has MTB rear derailleurs on sale. You can pick up a Shimano Alivio for $14.99US or Shimano Deore 8 or 9 speed compatible for $17.99US. The Deore will accept a 34T rear cog. That's bigger than some compact crankset chainrings.

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Powerful Pete

If you are going to do serious riding in the Alps and come from areas where you do not have long hard mountain roads, I would go with something along the lines of what dhk2 is recommending - a compact (50-34 up front) with a 27 in the back...

If you are in relatively good shape and are not racing, but rather riding for training and enjoyment a 34x27 should get you up just about everything in... relative comfort.

Or, if you are really concerned, go for a triple with an MTB derailleur. But I do not think you would need that if you are not doing extended rides with a number of cols every day.

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Solanog

Add a long chain to that.

benkoostra

I knew a guy in Sacramento, CA, who used an XTR cassette and derailleur on his Madone. It worked fine.