Compact will allow you to use two different gear cassette with two different outcomes.
For hills, us a 12~25 and you will have a lower gear than a 39x27.
For most other riding use 11~23 and you will have a lower gear on the bottom and a higher gear on top - comparred to a 39x25 or 53x11.
Here's why. 1 tooth up front is equal to 4 teeth in the rear!
You can do the math and come up with a better perfoming gear, a LOT LESS gear overlap, and a finer transition between all the gears on the cassette!
This page will help you out - put in what you are running now, and what you think you would like to run, print it out and compare - you'll notice a lot finer transition over what you are running, even with a triple.
A compact allows tighter gearing. You can run a 11-23 cassette in a 53/39 is almost the same as a 12-27 cassette. You can also run a 12-25 or 12-27 on a compact to get a lower gear if you need it.
I ride a regular crankset and I sometimes (not often) wish for a triple. But that's until I tried a compact. I think it's a more useful combination of gears without losing the crisp shifting of a double crankset. You only lose some gearing that is ultralow and the high gears you need to cruise along at over 33mph comfortably (and who does that on a regular basis). Plus you lose some weight and the smaller rings could be arguably stiffer.
Shimano compact? As in the R700 compact that Team Discovery took to the 2006 Tour de France along with Shimano 12-27 gearing? That one?
Okay,
Well, any compact crankset is going to have high reliance on the 12 tooth and smaller cogs.
Those smaller cogs can be extremely inefficient and are affected greatly by:
1) Bearings inside the Freehub ("clickity" deal the cassette sits on) must be in tiptop shape and of really excellent design.
2) Need an all-plated (completely bright shiny) chain like Dura Ace to reduce friction.
3) Precise derailleur adjustment to increase the efficiency (reduce vibration) of the smallest rear cogs.
As far as #1 goes, mechanics have been recommending to disassemble Shimano branded rear hubs (and many others) to install Slick 50 One Grease (automotive) because it allows for a higher tension with less drag. Shimano hubs below Ultegra/XT must be refitted with an Ultegra Freehub, $28, in order to further avoid vibration at the smallest rear cogs.
In addition to increasing the chance of drag when you're trying to go fast, the compact crankset hits you hard where you need it least.
That's on a hill.
A classic triple does about a 30% slowdown from large to middle rings.
A classic double does almost a 40% slowdown when you change from large to smaller ring.
As you can imagine, the compact double hits hardest at over 45% slowdown right when you're trying to climb a hill.
Not even comfort bikes have such foul gearing with their 40% jump on Tourney Mega-Range systems.
The compact double is even worse, and the hardest hitter (largest gap!) of all to slam down your speed on steep hills.
The compact double is so successful because it makes the bike feel easier on the low gears.
Comparison:
39-53 with 13-29 Ultegra cassette
34-50 with 12-27 cassette
*The 13t cog will not chain drag, but the 12t cog will drag when you're trying to go fast.
*The gap in the 34-50 causes a larger slowdown on shifting due to the very huge "gap".
Instead, use the following equipment and leave your more efficient large crankset right where it is:
Make up your low range with quality wheels that are not rim-centric in weight. This makes up for about 2 low gears. One of these:
(in order by price)
Neuvation R28SL2 (27mm Reynolds)
TailwindTour Tornado (30mm T10)
Rol de-Huez (27mm Reynolds, fine spokes)
Easton Velomax Tempest 2 (30mm T10)
*Or a "climber" wheel (low profile rim), such as Performance.com's super-inexpensive Forte Gemini ($175 and always out of stock). Climber wheels skip the speeds above 30 for faster uphill rates--maybe a better average on very hilly terrain. They have super tiny rims and fine double-butted spokes for dramatically decreased weight at the rim. Also known as a sprinter wheel. A climber front can be used with an areo rear in 24/24 layout, to knock the resistance off the front of the bike.
*Do not run a front wheel with WIDE blade spokes such as Sapim CX. Use 20 CX-Ray skinny blade instead of 16 CX wide blade on areo front wheels. Any power delivery into the front wheel pushes the bike backwards, forcing you to seek a lower gear.
Tire:
If you run a racer tire, use a "supple" tire on the front. If you run Anti-Flat, use Serfas Seca RS on the front. A firm tire is fine on the back and its nature should be judged appropriate for body weight.
Cranksets:
1) 39-52 or 39-53 crankset
2) Triple changed to 34-42-52 (increase grandma) so that the "gaps" are very tiny between gears. This makes a "racing triple" because you can change any gear and not get hit with a gap.
*Ultegra, 105, and TA Specalities replacement rings are very useful to make this.
*Team Discovery refused to take this one uphill in France because of its embarassing "Triple" appearance.
It was offered along with 12-25, and would have been much faster according to team member comments after the fact.
They used the compact double for its modern appearance and reported wishing and wishing for a gear "somewhere in the middle" so it wouldn't be so exhausting.
These two bits of information were reported seperately, but it adds up to the fact that the team mechanics were right and Shimano was wrong. This is not a surprise.
Cassette:
Now that other hill climbing issues have been overcome, a 12-25 in 10 cogs, a 13-26 in 10 cogs, or a 13-25 in 9 cogs will do the job just fine.
*If you have 8 rear cogs (Shimano Sora), use the 13-23 "T" 8 cog cassette with the "racing triple" described above, except 32-42-52 layout. Or, you can make a 13-24 8 cog racing model with. . . a 12-21 HG90 cassette, a 13t top cog, an 8 speed spacer and a 24t LX cog. File the "fat" tab inside the 13t and 24t to align the spiral shift pattern for excellent results. Harris Cyclery and TailwindTour can make this for you if you've got a Sora in need of speed.
In summary, use efficient wheels; and, use efficient gearing with as little gaps as possible. Increasing the gaps in your gearing will hurt at exactly the same points it is marketed to help.
Comments
Compact will allow you to use two different gear cassette with two different outcomes.
For hills, us a 12~25 and you will have a lower gear than a 39x27.
For most other riding use 11~23 and you will have a lower gear on the bottom and a higher gear on top - comparred to a 39x25 or 53x11.
Here's why. 1 tooth up front is equal to 4 teeth in the rear!
You can do the math and come up with a better perfoming gear, a LOT LESS gear overlap, and a finer transition between all the gears on the cassette!
This page will help you out - put in what you are running now, and what you think you would like to run, print it out and compare - you'll notice a lot finer transition over what you are running, even with a triple.
http://www.campagnolo.com/sviluppo.php
A compact allows tighter gearing. You can run a 11-23 cassette in a 53/39 is almost the same as a 12-27 cassette. You can also run a 12-25 or 12-27 on a compact to get a lower gear if you need it.
I ride a regular crankset and I sometimes (not often) wish for a triple. But that's until I tried a compact. I think it's a more useful combination of gears without losing the crisp shifting of a double crankset. You only lose some gearing that is ultralow and the high gears you need to cruise along at over 33mph comfortably (and who does that on a regular basis). Plus you lose some weight and the smaller rings could be arguably stiffer.
Compact with 11-23 or the new SRAM 11-26 can't be beat. Not matter where you live.
Shimano compact? As in the R700 compact that Team Discovery took to the 2006 Tour de France along with Shimano 12-27 gearing? That one?
Okay,
Well, any compact crankset is going to have high reliance on the 12 tooth and smaller cogs.
Those smaller cogs can be extremely inefficient and are affected greatly by:
1) Bearings inside the Freehub ("clickity" deal the cassette sits on) must be in tiptop shape and of really excellent design.
2) Need an all-plated (completely bright shiny) chain like Dura Ace to reduce friction.
3) Precise derailleur adjustment to increase the efficiency (reduce vibration) of the smallest rear cogs.
As far as #1 goes, mechanics have been recommending to disassemble Shimano branded rear hubs (and many others) to install Slick 50 One Grease (automotive) because it allows for a higher tension with less drag. Shimano hubs below Ultegra/XT must be refitted with an Ultegra Freehub, $28, in order to further avoid vibration at the smallest rear cogs.
In addition to increasing the chance of drag when you're trying to go fast, the compact crankset hits you hard where you need it least.
That's on a hill.
A classic triple does about a 30% slowdown from large to middle rings.
A classic double does almost a 40% slowdown when you change from large to smaller ring.
As you can imagine, the compact double hits hardest at over 45% slowdown right when you're trying to climb a hill.
Not even comfort bikes have such foul gearing with their 40% jump on Tourney Mega-Range systems.
The compact double is even worse, and the hardest hitter (largest gap!) of all to slam down your speed on steep hills.
The compact double is so successful because it makes the bike feel easier on the low gears.
Comparison:
39-53 with 13-29 Ultegra cassette
34-50 with 12-27 cassette
*The 13t cog will not chain drag, but the 12t cog will drag when you're trying to go fast.
*The gap in the 34-50 causes a larger slowdown on shifting due to the very huge "gap".
Instead, use the following equipment and leave your more efficient large crankset right where it is:
Make up your low range with quality wheels that are not rim-centric in weight. This makes up for about 2 low gears. One of these:
(in order by price)
Neuvation R28SL2 (27mm Reynolds)
TailwindTour Tornado (30mm T10)
Rol de-Huez (27mm Reynolds, fine spokes)
Easton Velomax Tempest 2 (30mm T10)
*Or a "climber" wheel (low profile rim), such as Performance.com's super-inexpensive Forte Gemini ($175 and always out of stock). Climber wheels skip the speeds above 30 for faster uphill rates--maybe a better average on very hilly terrain. They have super tiny rims and fine double-butted spokes for dramatically decreased weight at the rim. Also known as a sprinter wheel. A climber front can be used with an areo rear in 24/24 layout, to knock the resistance off the front of the bike.
*Do not run a front wheel with WIDE blade spokes such as Sapim CX. Use 20 CX-Ray skinny blade instead of 16 CX wide blade on areo front wheels. Any power delivery into the front wheel pushes the bike backwards, forcing you to seek a lower gear.
Tire:
If you run a racer tire, use a "supple" tire on the front. If you run Anti-Flat, use Serfas Seca RS on the front. A firm tire is fine on the back and its nature should be judged appropriate for body weight.
Cranksets:
1) 39-52 or 39-53 crankset
2) Triple changed to 34-42-52 (increase grandma) so that the "gaps" are very tiny between gears. This makes a "racing triple" because you can change any gear and not get hit with a gap.
*Ultegra, 105, and TA Specalities replacement rings are very useful to make this.
*Team Discovery refused to take this one uphill in France because of its embarassing "Triple" appearance.
It was offered along with 12-25, and would have been much faster according to team member comments after the fact.
They used the compact double for its modern appearance and reported wishing and wishing for a gear "somewhere in the middle" so it wouldn't be so exhausting.
These two bits of information were reported seperately, but it adds up to the fact that the team mechanics were right and Shimano was wrong. This is not a surprise.
Cassette:
Now that other hill climbing issues have been overcome, a 12-25 in 10 cogs, a 13-26 in 10 cogs, or a 13-25 in 9 cogs will do the job just fine.
*If you have 8 rear cogs (Shimano Sora), use the 13-23 "T" 8 cog cassette with the "racing triple" described above, except 32-42-52 layout. Or, you can make a 13-24 8 cog racing model with. . . a 12-21 HG90 cassette, a 13t top cog, an 8 speed spacer and a 24t LX cog. File the "fat" tab inside the 13t and 24t to align the spiral shift pattern for excellent results. Harris Cyclery and TailwindTour can make this for you if you've got a Sora in need of speed.
In summary, use efficient wheels; and, use efficient gearing with as little gaps as possible. Increasing the gaps in your gearing will hurt at exactly the same points it is marketed to help.