compact cranks

[debdownunder]

i am an older rider (54) and have a felt 35 racing bike. i am having a bit of trouble keeping up on hills....any hill, i seem to fall behind the group.
all the girls seem to have compact cranks, apart from myself. a friend who is a top triathlete says a compact crank would help me, but the local bloke from the bike shop says it wouldnt make much difference.
dont know what to think....we generally ride about about 150k+ per week, covering a range of hilly, undulating and flat terrain.

[Andrea]

A compact won't necessarily make you faster, it will just make it a little easier to "spin" up hills, which is easier. It's actually a little slower, but won't give you quite the leg burn that turning a harder gear would.

[bounceswoosh]

i am an older rider (54) and have a felt 35 racing bike. i am having a bit of trouble keeping up on hills....any hill, i seem to fall behind the group.
all the girls seem to have compact cranks, apart from myself. a friend who is a top triathlete says a compact crank would help me, but the local bloke from the bike shop says it wouldnt make much difference.
dont know what to think....we generally ride about about 150k+ per week, covering a range of hilly, undulating and flat terrain.

I'm assuming you have a double now -- what about trying a triple? A lot of people use them around here.

[alpinerabbit]

It's usually easier to switch to a compact than a triple.

I did it on my first bike. No, it will not make you faster, as Andrea says, but +1 to what she said: it may preserve your strength on hills so you last longer. And it will save your knees (I hurt a ligament grinding up hills in my first year).

Folks call the regular double the "hero crank" and that's what it's for. I don't see how amateurs should have much use for it unless they live in a flat area. I see how shops sell them because it is "the standard" of old times.

[mimitabby]

I may not be right here, but I believe we're talking about leverage. The bigger the lever, the less work to get it to move.
If you get a compact crank, you're not going to have to turn it as far to move the same distance, but you're going to have to work harder.


to illustrate to yourself the difference between what you have and a compact
just put your bike in a higher gear next time you're going up a hill. you won't have to pedal as much, but IT WILL BE HARDER.

tell me if i'm wrong guys, but i just checked Sheldon Brown's website and from what it said, I believe I understand the concept.

I agree, get a triple if you want to have more options going up a hill.

[bounceswoosh]

I may not be right here, but I believe we're talking about leverage. The bigger the lever, the less work to get it to move.
If you get a compact crank, you're not going to have to turn it as far to move the same distance, but you're going to have to work harder.


to illustrate to yourself the difference between what you have and a compact
just put your bike in a higher gear next time you're going up a hill. you won't have to pedal as much, but IT WILL BE HARDER.

tell me if i'm wrong guys, but i just checked Sheldon Brown's website and from what it said, I believe I understand the concept.

I agree, get a triple if you want to have more options going up a hill.

I looked up the term, too, but I got a different description --

http://www.chainreaction.com/triples.htm

(search "compact")

"Just when you thought you had it all figured out, along comes the "Compact" crank. A new way (actually it's been around for some time, but forgotten) to get lower gears without a triple. Instead of the classic 53/39 front chainrings, you have a 50/36 (sometimes 50/34) combination that gets you quite a bit lower gears, while giving up a very small amount from the high end... all using standard double-compatible shifters & derailleurs. A high-quality compact setup is actually lighter weight than a standard double! The downside? You don't get as low a gear as a triple will offer, and you lose just a bit off your high end (the gears you'd be drafting trucks downhill in, but nothing you'd ever miss in day-to-day riding)."

[mimitabby]

I looked up the term, too, but I got a different description --

http://www.chainreaction.com/triples.htm

(search "compact")

"Just when you thought you had it all figured out, along comes the "Compact" crank. A new way (actually it's been around for some time, but forgotten) to get lower gears without a triple. Instead of the classic 53/39 front chainrings, you have a 50/36 (sometimes 50/34) combination that gets you quite a bit lower gears, while giving up a very small amount from the high end... all using standard double-compatible shifters & derailleurs. A high-quality compact setup is actually lighter weight than a standard double! The downside? You don't get as low a gear as a triple will offer, and you lose just a bit off your high end (the gears you'd be drafting trucks downhill in, but nothing you'd ever miss in day-to-day riding)."

thanks Monique, that's better than what Sheldon said about it.
The compact isn't going to help you up harder hills, it doesn't have the gearing options of the triple. sounds nice for moderate riding; for folks that don't want to go too fast and don't have a lot of hills to climb.

[DebW]

I may not be right here, but I believe we're talking about leverage. The bigger the lever, the less work to get it to move.
If you get a compact crank, you're not going to have to turn it as far to move the same distance, but you're going to have to work harder.

Mimi, the term leverage would apply to the length of the crank arms. Longer crank arms would in theory make it easier to grind up a hill in too big a gear. The first consideration on crank length is leg (femur) length. But a spinner would tend to prefer a shorter crank while a rider who favors lower rpms may prefer a longer crank length for the leverage.

In the discussion of compact vs regular double vs triple, gear ratio is the appropriate concept, ie how far the bike travels for one revolution of the cranks. This is the ratio of the chainring size (# of teeth) to the rear sprocket size (# of teeth) multiplied by wheel circumference.

Traditional doubles were 42-52 because a bigger spread produced a very slow and awkward shift. With modern ramped and pinned chainrings, you can get a good shift over a wider range. You also want a front derailleur designed for the chainring spread and size of the largest chainring. A triple front needs extra travel in the front derailleur, and a design to maximize shifts for the given chainrings. Note that the rear derailleur has a maximum capacity (tooth difference of cassette plus tooth difference of chainrings) because it need to keep tension on the chain at all times. Sometimes swapping the cassette to a wider range can give the same low gear as going to a compact double, but for less money. Depends on what gears the bike currently has and how much extra capacity the rear derailleur has.

[aicabsolut]

Mimi, the term leverage would apply to the length of the crank arms. Longer crank arms would in theory make it easier to grind up a hill in too big a gear. The first consideration on crank length is leg (femur) length. But a spinner would tend to prefer a shorter crank while a rider who favors lower rpms may prefer a longer crank length for the leverage.

In the discussion of compact vs regular double vs triple, gear ratio is the appropriate concept, ie how far the bike travels for one revolution of the cranks. This is the ratio of the chainring size (# of teeth) to the rear sprocket size (# of teeth) multiplied by wheel circumference.

Traditional doubles were 42-52 because a bigger spread produced a very slow and awkward shift. With modern ramped and pinned chainrings, you can get a good shift over a wider range. You also want a front derailleur designed for the chainring spread and size of the largest chainring. A triple front needs extra travel in the front derailleur, and a design to maximize shifts for the given chainrings. Note that the rear derailleur has a maximum capacity (tooth difference of cassette plus tooth difference of chainrings) because it need to keep tension on the chain at all times. Sometimes swapping the cassette to a wider range can give the same low gear as going to a compact double, but for less money. Depends on what gears the bike currently has and how much extra capacity the rear derailleur has.

Correct.

There are generally 2 options for going with a compact: 50/36 (harder to find, and you must use a 110BCD), or 50/34 (often available with the more standard 130BCD--meaning you wouldn't have to buy new crank arms necessarily, just rings). Most double front derailleurs can handle the 50-34 tooth drop. One thing to keep in mind is your chain position on the rear cog when making shifts in a compact. You will also have to be very very precise with your front derailleur adjustments. Index shifters that give you the ability to move the FD half a click will help with cross-chain issues, but when making full shifts in the front (esp large to small), it can be easier to drop your chain if you are in the wrong rear cog.

I believe that compact cranksets are much nicer than triples. For one, you have many more usable rear gears per front ring. SEcond, you can really tweak a compact to suit your style of riding and terrain. I like a 36T small ring, because I ride a lot on flat ground in traffic when I don't really want to be in the big ring. It also gives me all the gears I need to climb pretty long steep hills that I encounter. If I were to build a climbing rig for more serious climbing, I would go with a 34T small ring. My next move will be to get a cassette with an 11 cog instead of a 12, for sprinting and descending.

Look up a good gear inches calculator. I believe Sheldon Brown's site has one. The reason I'd want an 11 cog for races instead of getting a regular double? A 50-11 is bigger than a 53-12. It also lets me see what kind of cassette I might want with a 34T ring or how I might change things up with my current crankset.

The ladies are right that the compact won't necessarily make you faster, at least at first. It depends on your fitness. Obviously, the best thing is to be able to "spin" a BIG gear. It definitely helps to start out spinning small gears and saving some muscle power on the climbs. Then just work on climbing. Do it a lot. Then you'll be able to do it as easily in harder gears. You aren't really going to lose much by switching to a compact. You may spin out easier while descending, but you can compensate for that some with a new cassette. But then, if you rarely ever use your hardest gear, you may be just fine with the cassette you have. You can always just try to spin like crazy or get as aero as possible on descents that are too steep in the compact. In my races, I tend to attack on descents. If I can do that in a compact, then it shows they aren't so wussy, even though I want an 11 cog.

You will save weight by going with a compact over a triple, and you will have to change fewer components--no need for a different derailleur or shifters.

[bounceswoosh]

It's usually easier to switch to a compact than a triple.

Is that because of the adjustment to shifting across three rings?

[debdownunder]

forgot to mention that i dont have a triple...just the regular double...
and trying to make my riding even more enjoyable
playing catch ups is really hard work.