[ricochet]

Hi guys,
I bought a road bike about a year ago, after years of mountain biking. I rode quite a bit last year, so I have a pretty good feel for my bike and my terrain. I have a FSA carbon pro 53-39 five arm isis drive crankset and a dura-ace 12-23 rear cassette. I hardly ever use the bottom half of my rear cassette and there are a few hills around here where I would like to have lower gears. I can't seem to find new chain rings without buying a whole new crankset. I have seen a new rear cassette in a 12-27. If I go with just a rear cassette I still won't use the bottom half.

Any suggestions or help is greatly appreciated.

thanks,

 

[fleck]

my guess is you are cross gearing a lot. As in using your 53t and your larger cogs. This in general isn't a great idea. Although chains are made to have lateral movement, this will wear it and your cogs out faster.

You might be an ideal canidate for a compact crank setup. Although that might mean a new front and rear derailuer.

 

[Cory]

Off-the-rack bikes are usually geared too high...

The racing influence has really been a curse for road bikes. Not many people need a 53-tooth big ring, and a 39-23 isn't much of a low gear, but the manufacturers think they can't sell anything that doesn't look like Lance rides it.
When I built my present bike, I put a 46-36-26 triple on it (I live in the Sierra, with 8000-foot passes all around), and I've never been sorry. You could do that, with some fiddling (new BB, or at least a longer spindle, probably new rear derailleur), but it would cost a couple of hundred dollars. If you decide to, a good, inexpensive crankset is the Sugino XD2 ( http://www.rivbike.com/webalog/cranks_bbs_c-rings/12067.html). I have about 6000 miles on one and 2500 on another, no problems ever.
The bolt circle on your crankset won't let you put on a smaller ring than 39 (maybe 38, I forget, but it's not enough difference to matter), so that's out. You could reduce the big ring to a 48 or so and get more usable gears, and when you swap the cassette, look for something like a 13-27, which in combination with the chainring will bring your whole range down a little.
I'm just doing this off the top of my head, so it might be a good idea to work out the new gear ratios before you spend the money, to see how many duplicates you'll have. The standard formula for that is to divide the number of teeth in the ring by the number in the cassette cog, them multiply by the wheel diameter in inches (use 27 for a 700c wheel). There are always gears so close together that one is superfluous, but you don't want to have a bunch of them.

Hi guys,
I bought a road bike about a year ago, after years of mountain biking. I rode quite a bit last year, so I have a pretty good feel for my bike and my terrain. I have a FSA carbon pro 53-39 five arm isis drive crankset and a dura-ace 12-23 rear cassette. I hardly ever use the bottom half of my rear cassette and there are a few hills around here where I would like to have lower gears. I can't seem to find new chain rings without buying a whole new crankset. I have seen a new rear cassette in a 12-27. If I go with just a rear cassette I still won't use the bottom half.

Any suggestions or help is greatly appreciated.

thanks,

 

[KeeponTrekkin]

Another option with Shimano...

is to get a Mountain bike derailleur and cassette or "custom" cassette from Harris Cyclery (harriscyclery.com) ; you could have 12-34 for example. The spacing is, naturally, wider than your current 12-23 so the changes between gears is greater. However, it's a small price to pay to get the usable gears. Unfortunately, you will need to buy the Mtn bike derailleur, but it's still cheaper than a new crank.

 

[ricochet]

calculations??

Let me see if I got the calcualtions right. I take the chain ring and divide by the cassette and then multiply by 27? (39/12)*27=87.75
I did this on a spreadsheet and none of the gears seem to be close at all(between chain rings) is this correct?

The racing influence has really been a curse for road bikes. Not many people need a 53-tooth big ring, and a 39-23 isn't much of a low gear, but the manufacturers think they can't sell anything that doesn't look like Lance rides it.
When I built my present bike, I put a 46-36-26 triple on it (I live in the Sierra, with 8000-foot passes all around), and I've never been sorry. You could do that, with some fiddling (new BB, or at least a longer spindle, probably new rear derailleur), but it would cost a couple of hundred dollars. If you decide to, a good, inexpensive crankset is the Sugino XD2 ( http://www.rivbike.com/webalog/cranks_bbs_c-rings/12067.html). I have about 6000 miles on one and 2500 on another, no problems ever.
The bolt circle on your crankset won't let you put on a smaller ring than 39 (maybe 38, I forget, but it's not enough difference to matter), so that's out. You could reduce the big ring to a 48 or so and get more usable gears, and when you swap the cassette, look for something like a 13-27, which in combination with the chainring will bring your whole range down a little.
I'm just doing this off the top of my head, so it might be a good idea to work out the new gear ratios before you spend the money, to see how many duplicates you'll have. The standard formula for that is to divide the number of teeth in the ring by the number in the cassette cog, them multiply by the wheel diameter in inches (use 27 for a 700c wheel). There are always gears so close together that one is superfluous, but you don't want to have a bunch of them.

 

[KeeponTrekkin]

See below

12 13 14 15 17 19 21 24 27<O</O

53 119.25 110.08 102.21 95.40 84.18 75.32 68.14 59.63 53.00<O</O

39 87.75 81.00 75.21 70.20 61.94 55.42 50.14 43.88 39.00


Not very pretty, but all the site will allow.

As mentioned by others, cross chaining is big ring, big cog (53 - 27) and small ring, small cog (39 - 12). With 53, 39 cranks, a change of the ring is about equal to 3 cogs.