What's a Compact Crank, anyway?

[Bad JuJu]

Will someone please explain to me what a "compact crank" is and why they're so popular?

I know what "compact" means, and I know what a "crank" is--yes, on the bike as well as in other areas of life ;) . But put them together and all I can do is display my ignorance. Please enlighten me. Thanks!

Because I know you can't all be talking about some short guy who's hard to get along with. ;)

[caligurl]

it's something between a triple and a standard double....

if this were a testosterone forum... i'd stir the pot and say they are too weak for a straight double and too egotistical to admit they need a triple....

however... they have a purpose!

if you need easier gearing... but don't have the hills... then a compact is a good compromise (i see you are in florida... so you are probably a good candidate for a compact!)

by the way.... i had a triple put on my ruby cuz i like to climb gruesome hills!

[DebW]

It's a wide-gap double. Think granny gear for inside chainring.

[Adventure Girl]

A triple might be something like 52/39/30.
A double might be something like 53/39.

A compact double is a double that has a smaller big ring and a larger small ring. Something like 50/34.

You don't get a big big ring. But you get a smaller small ring than a conventional double.

[caligurl]

It's a wide-gap double. Think granny gear for inside chainring.


oh... that's good! except it's not quite granny easy... nor is the big ring a "regular" big ring hard... both are in the middle... OR.... if you choose one or the other to be the same size as a standard big ring or standard granny... you will lose gears on the other ring!

that's why i didn't get a compact... i wanted my easiest gears... but i would have lost my harder gears... and i'm often out of gears when descending a hill already! didn't need to lose more!

[mimitabby]

but why are we calling a chainring or gears a crank? I am confused.

[DebW]

but why are we calling a chainring or gears a crank? I am confused.

A crank consists of chainrings, spider, and pedal arms. Because you need different spider arms with a different bolt circle diameter for a triple, double, or compact double, the chainrings aren't interchangeable. And the right pedal arm attaches to the spider. So you need the whole shooting match to switch from one to the other, ie, you have to replace the crank.

[mimitabby]

so the gizmo that the pedal sits on is NOT a crank, it's a pedal arm?

[Fredwina]

(i see you are in florida... so you are probably a good candidate for a compact!)

That depends. I spent a year in Tallahassee. I can remember a hill or two in Leon county that I was glad to have a triple. The Panhandle (JuJu, I know "Tally" really insn't consdered the panhandle) can get hilly, as in short but steep.

[Bad JuJu]

Wow, thanks everyone--this has been hugely enlightening. The reason I asked the question is that I'm getting my Bianchi Veloce soon, and it's a 2005, which has a triple. But someone said the 2006 has a compact crank, so I wondered whether I was getting a bad deal, even though the price on the 05 Veloce is the deal of the century.

But now that I know what a compact crank is, I'm glad I'm getting the triple. While this area is free of actual mountains, there are some hills that have you reaching for your granny gears, as Fredwina noted. Also, I do ride in other areas occasionally, and I'm not too proud to go for the grannies when I need them.:)

[mimitabby]

when are you getting your bike Bad JUJU?

[DebW]

so the gizmo that the pedal sits on is NOT a crank, it's a pedal arm?

You can say that the pedals are attached to the crank, because the pedal arm is part of the crank. The arm, spider, and chainrings go on and off the bike in one unit, collectively called "the crank".

[mimitabby]

You can say that the pedals are attached to the crank, because the pedal arm is part of the crank. The arm, spider, and chainrings go on and off the bike in one unit, collectively called "the crank".

Thank you Deb, you are making sense to me. So what about a short crank?
there was a thread just a little while ago about a short woman wanting a short crank. for that matter, the average woman IS shorter, should women's bikes have shorter cranks, and is that a big problem?
(Do they sell them?)

[DebW]

Thank you Deb, you are making sense to me. So what about a short crank?
there was a thread just a little while ago about a short woman wanting a short crank. for that matter, the average woman IS shorter, should women's bikes have shorter cranks, and is that a big problem?
(Do they sell them?)

You are full of questions today, Mimi. I suppose I should add that a crankset includes the left crank arm as well. A short crank means that the arms are short, sized to match a smaller person's leg length. Crank arms come in 165, 170, and 175 mm and maybe some in-between lengths. So yes, a well-designed woman's bike would have 165 mm arms matched with smaller frame sizes, 170 mm arms for larger sizes. A good fitter would determine the proper crank arm length independent of frame size. Crank arm length has nothing to do with the chainring size or gearing per se, but of course a longer crank arm gives you more leverage for turning over a bigger gear.

[Bad JuJu]

when are you getting your bike Bad JUJU?
Thanks for asking, Mimi! I get paid tomorrow, so possibly next week. *drooling at the thought* :D

Don't worry, TE forums and the other TE Bianchi girls will be among the first to know!

[roadfix]

I'm not strong enough to push a traditional 53 ring and the 39 wasn't small enough despite running a large 26 cog......therefore I replaced my traditional double with a compact double 50/34. Now I'm happy...:)

[Kano]

Spider???

Karen in Boise

[DebW]

Spider???

The short radial arms that connect the pedal arm to the chainrings. Usually there are 5 of them radiating out from the center of the crank. You can think of them as spokes on a wheel. Their length sets the bolt circle diameter and limits the size of the smallest chainring that can be attached. A couple of the avatars on this page should make it clear.

[KnottedYet]

I'm looking at a 50/34, too. And maybe a cassette 13-26T. My "new" bike should arrive today! Might need to change out to get lower gears for my hill climbing (in)ability.

[roadfix]

I'm looking at a 50/34, too. And maybe a cassette 13-26T. My "new" bike should arrive today! Might need to change out to get lower gears for my hill climbing (in)ability.

I'm currently running a 13-26 Campy cassette with my compact cranks. Although I don't have a problem, some may find the 50x13 top end (103 gear inches) not high enough.

[jenxxs]

I'm about to try my first compact double, and I think I'll be going with 48/33. I'm fairly new to road cycling, and so I wish I knew a bit more about my gearing preferences before making this investment, but at least it's not that expensive to swap rings - at least I think it shouldn't be!

[7rider]

Bad JuJu...You should check out some gear charts before deciding that you need the triple for the occasional hill.
http://www.fullspeedahead.com/downloads/Compact%20Gear%20Ratio%20comparison.pdf#search=%22compact%20gearing%20chart%22
The gearing you get with a standard road triple (52/42/30 and a 12/25 cassette) isn't all that different from a 50/34 compact set up with the 1-25 in the back. I think just the weight savings alone will help make up for any gearing loss (what's the weight of the '05 bike vs. the '06?).
With the compact, you could even put a 27 on the back, and you'll be flying up the hill on a less complicated drive train.
Just my $0.02.

[Bad JuJu]

Thanks for the tip, Regina. I'll check it out. It's funny that I've always been a language person, vs. numbers (I'm an English teacher), but I LOVE studying anything having to do with the science and math of cycling.

[Triskeliongirl]

I have 50/34s on both my bikes with a 700c rear wheel and love it. I pair it with a 12/27 casette for MOST riding, and on one bike I installed a mountain (XT) rear derailleur, so I can swap out the 12/27 for an 11/34 when I got to serious mountains or for loaded touring. They are mechanically simpler and easier to keep in adjustment, and ligter than triples. Just run the numbers through sheldon's caluclator to figure out what you need. What you give up is tightly spaced gearing with the wide range casettes like the 11/34. The 12/27 is just great though, and gets me up anything in the texas hill country.

[winddance]

I have a compact double (50/34) paired with a 12/27 in the hilly SF Bay area, and while it gets me up most hills, I definitely see the benefits of a triple or a mountain cassette for sustained climbing. I'm sure I could eventually make it to the top of Mt. Diablo if I worked at it, but it'd sure be nice to have a triple so I didn't have to burn myself out trying to get there.

Still, it's a nice way to equip a bike for hills without the expense of converting from double to triple. That's ultimately the reason that I chose to go this route. And whatever doesn't kill you...