Cranks

[bikerchas55]

I'm 6'4" and on my summer bike I have 180 cranks and 53/42 13/23..... on my rain/winter bike I have 170 cranks with the same gearing. The 180 cranks give me a more "effortless" feel during big gear high speed cruising on level ground. On hill climbing there seems to be a real advntage with the 180s. For some reason though the winter bike gives me consistently higher average speeds on frequently traveled training circuits. The geometry of the 2 bikes is different so it is definitely not a scentific comparison.

 

[cwdzoot]

Have a look at the new FSA compact cranks:

awsome idea.

http://store.yahoo.com/glorycycles/cranks.html

This blows former crank ideas away eliminates the need for a tripple and the need for 10 speed rear.

 

[wadoflove]

Originally posted by cwdzoot
Have a look at the new FSA compact cranks:

awsome idea.

http://store.yahoo.com/glorycycles/cranks.html

This blows former crank ideas away eliminates the need for a tripple and the need for 10 speed rear.

That looks really interesting. I checked the gear ratios and it seems that you have 15 non-overlapping gear sizes with the 50-34 11-23 setup (gear inches from 38.4 - 118.2) as compared to 13 with the standard 53-39 and 12-25 setup (gear inches 40.6 - 114.8). But if you have a triple with 53-39-30 and 12-25 you would have 17 (gear inches from 31.2 - 114.8). So for the double it is an advantage over the standard setup in both overall gear range and number of non-overlaps. Whereas the triple gives you a smaller gear and only 2 more non-overlapping gear sizes...
But its not cheap at $320 cause you might need to change to an ISIS bottom bracket for betwen $40-90... A Campy Record crank set is only $190 on the same website, granted its not carbon.

 

[dhk]

Originally posted by wadoflove
That looks really interesting. I checked the gear ratios and it seems that you have 15 non-overlapping gear sizes with the 50-34 11-23 setup (gear inches from 38.4 - 118.2) as compared to 13 with the standard 53-39 and 12-25 setup (gear inches 40.6 - 114.8). But if you have a triple with 53-39-30 and 12-25 you would have 17 (gear inches from 31.2 - 114.8). So for the double it is an advantage over the standard setup in both overall gear range and number of non-overlaps. Whereas the triple gives you a smaller gear and only 2 more non-overlapping gear sizes...
But its not cheap at $320 cause you might need to change to an ISIS bottom bracket for betwen $40-90... A Campy Record crank set is only $190 on the same website, granted its not carbon.

Good analysis. I also looked at the FSA Compact for my new bike. It may be a good choice for some, but ended up going with the FSA triple for two primary reasons. First, gain a lower gear all the way down to 30/25 for our long steep hills. Second, minimize the need to shift chainrings, particularly in a tight club pace line on rolling hills. The 42 tooth middle ring, with a 12-25, should allow me gears to cover the speed range I ride the great majority of the time without a lot of extra shifting.

If a guy is strong enough to ride in the 50 ring most all the time, that would tend to tip the scales more in favor of the Compact. Lots of options out there.

Dan

 

[boudreaux]

Originally posted by cwdzoot
Have a look at the new FSA compact cranks:



This blows former crank ideas away eliminates the need for a tripple and the need for 10 speed rear.

Well, actually it doesn't in every case,but if you are buying it ...go ahead.

 

[BaCardi]

Originally posted by boudreaux
Well, actually it doesn't in every case,but if you are buying it ...go ahead.

No joke, but thanks for the obvious.

 

[boudreaux]

Originally posted by BaCardi
No joke, but thanks for the obvious.

Must not have been to the poster. You do realize how silly you make yourself? Don't you? Try and have a good day.

 

[BaCardi]

Originally posted by boudreaux
Must not have been to the poster. You do realize how silly you make yourself? Don't you? Try and have a good day.

Sorry dude, but you're totally out in left field on this one.

 

[drewski]

Originally posted by boudreaux
Must not have been to the poster. You do realize how silly you make yourself? Don't you? Try and have a good day.

you're both look pretty silly, imo.

boudreaux, you do add interesting pearls, but i have to agree with Bacardi that you often state the obvious or even paraphrase others responses while alledgely "correcting them". pearls/post ratio definitely gets impacted by some of the other fluff you post.

BaCardi, this is an online forum, if you find his posts silly just ignore them or tune them to a different level. that's what i did after a few posts where boudreaux's tone sounded like he was contradicting me with new insights, but really just restated what i said using some different lingo. though you were guilty of the same thing on that "I'm building a bike, need a headtube" thread. tubing is tubing whether the end result is a frame or complete bike.

now that i've offended both of you, i'm going out for an evening on the town! feel free to flame me as i've just purchased some new Nomex underwear!!

 

[boudreaux]

Originally posted by drewski
that's what i did after a few posts where boudreaux's tone sounded like he was contradicting me with new insights, but really just restated what i said using some different lingo.

Maybe the different lingo made the water less muddy?

 

[JAPANic]

Why is everybody on this thread getting CRANKY?

 

[Cipher]

Originally posted by JAPANic
Why is everybody on this thread getting CRANKY?

(You forgot yo add No pun intended...)

 

[wadoflove]

Originally posted by dhk
Good analysis. I also looked at the FSA Compact for my new bike. It may be a good choice for some, but ended up going with the FSA triple for two primary reasons. First, gain a lower gear all the way down to 30/25 for our long steep hills. Second, minimize the need to shift chainrings, particularly in a tight club pace line on rolling hills. The 42 tooth middle ring, with a 12-25, should allow me gears to cover the speed range I ride the great majority of the time without a lot of extra shifting.

If a guy is strong enough to ride in the 50 ring most all the time, that would tend to tip the scales more in favor of the Compact. Lots of options out there.

Dan

Hi Dan,

How is the shifting on the front derailleur with this setup? Also do you have a medium or long rear derailleur?

Wad

 

[dhk]

Originally posted by wadoflove
Hi Dan,

How is the shifting on the front derailleur with this setup? Also do you have a medium or long rear derailleur?

Wad

It's the long Dura Ace rear derailleur...the 7700 GS. But, can't tell you how it shifts since we're still waiting for the fork to come in. Should be ready this week, or at least in time for Christmas! I'll plan to give you a report then.

Dan

 

[dhk]

Have taken my first ride now. This is my first bike with STI, and also my first triple. I've found shifting the chainrings is easy, whether going up or down. You do have to hold the lever over until the front shift is completed, but it's farily quick. No problems with shifting or trimming at all...it just works as it should.

Dan

 

[herbert.nrp]

Fascinating thread.

Actually, I'm pretty sure Ant is right. Leverage and gearing are the same thing. A gear is just a bunch of levers stuck together - each cog is a little lever. The physics are the same.

Anyway, this doesn't answer the question of ideal crank length, though. Hasn't everybody left out one important part of the equation - flexibility?

A rider with very tight hamstrings is going to need a relatively lower saddle to maintain power through the bottom of the stroke while remaining aero. If that rider is also not tall, a long crank is going to bend the knee to an acute angle at the top of the stroke, and jam the knee into the chest if she is in an aero position.

So, it seems to me that small, inflexible riders might not do better with longer cranks. (Did the Velo News study normalize for hamstring and lower back flexibility?)

Any thoughts? (Boudreaux?)

(Irrelevant, but maybe interesting to a small subset of readers of this forum - the principle that an equity investor in a successful business can make more money faster if the business also has debt is called "leverage" in the US, and the same principle is called "gearing" in the UK. Just like the physics of leverage and gearing, the finance is the same.)

 

[ewenn]

At 6'5" and 210lbs I love my Dura Ace 180 mm cranks. Of course they have to be Dura Ace because Shimano doesn't make a 180 in Ultegra or 105. They have slowed my cadence slightly from the 175s I used formerly, but the power output is greater.

 

[davek]

This discussion has made absolutely fascinating reading for me - I never even considered crank size until I started looking at a new bike and found I had to make a decision.

I've got a shortish inside leg - 31" - so according to the various formulas I should be on a 165mm crank but my current bike has a 172.5mm crank and a 52-42 chainset, so now I begin to understand why my knees are always so sore after a long slog.

I can never manage much more than 90rpm for very long even on the flat, so based on what I've read here I reckon I ought to switch down to a 165mm crank.

I can understand the notional benefits of a longer crank on the big hills, but with my dodgy knees, would I be better off with a shorter crank and a triple chainset? Or will I manage with a smaller double? I'm not really into racing, touring/randonnees are more my thing so what do people advise?

 

[drewski]

I have a 30" inseam and dodgy knees. I use a 172.5mm crank and have used one for over a decade.

In my experience, other fit characteristics like saddle height and position (fore-aft) as well as the choice of pedals (speedplays have reduced/eliminated my any pain tremendously vs. my old Time's) impacted my knees more than my crank-length . . . though the only lengths I've used have been 170 & 172.5mm

that said, a triple could help reduce strain on longer climbs and some rollers could improve your spin over 90rpm.

 

[Ted B]

Originally posted by drewski
I have a 30" inseam and dodgy knees. I use a 172.5mm crank and have used one for over a decade...In my experience, other fit characteristics like saddle height and position (fore-aft) as well as the choice of pedals (speedplays have reduced/eliminated my any pain tremendously...

Agreed.

My inseam is 31.5" (~80cm) and I have used both 172.5mm and even 175mm comfortably. Seat height and position is absolutely critical, and should be set correctly using a goniometer. Also worthy of note is cleat alignment and position on one's shoes.