Help me understand cranks/cassette ratio

It is simply a way to manipulate your gear ratios:

http://www.sheldonbrown.com/gain.html

FWIW, I love my compact crank and 12-25 cassette.  I switched from a 53/39 to my 50/34 a couple years ago.  The step between gears is better spaced, I picked up one more "gear", and I have to be well over 30 MPH to "spin out"!  And for hills, the extra low end is a real help.

I used the links the other posters listed and plugged in my sizes and looked at the differences to help me make my decision.

The whole gearing argument gets complicated, quick. I took the term to learn it all recently (the Sheldon Brown website is one of the key references), but you don't need it to such an extreme.

I like sticking with what works. Here's my breakdown.

- TRIPLE RINGS: Have the most hill-friendly gearing of any setup. If you want easier gears than your triple, you're likely out of luck. If you know you're a weaker hill climber, or are a beginner, a triple may be your best bet.

- COMPACT CRANK DOUBLE 50/34 - "Compact" because it allows your lowest gear to be easier than the standard crank. This will suffice for the vast majority of cyclists, on almost all terrain, even hilly onse. You can still go 30mph+ with this crank. If in doubt, get this.

- STANDARD CRANK DOUBLE 53/39 - A good bet for stronger riders/racers or mostly flat courses. It will be tougher to climb big hills because the small gear is not so small, but you get a faster top speed in return. Most pure bike racers use this setup, but they are generally stronger riders than the general triathlete. Most triathlon races are on flat courses, so this is a good racing setup as well, even for triathletes. Get this if you're riding mostly flattish stuff or making a dedicated flat-racing bike. If you're doing mountain-type climbs, get the compact crank.

- TRIPLE vs DOUBLE? - Shifting is a bit smoother on the double due to the simpler drivetrain. Still, this difference will be irrelevant if you are caught on a super-steep climb that you cannot climb on your gearing.

I am a fairly good rider (2nd AG M30-35 in last sprint tri), and I suffer on hills of 8+% with my standard gearing. I can't imagine back-of-pack cyclists even being able to ride those hills unless they had a compact, or better yet, triple.

Then you are basically already riding a hybrid of a compact.  You have the top end detriment of the compact (meaning you lose top speed ability with only a 50) but have the advantage of the granny gear with the small chainring.

Not sure why you are looking to change gearing?  I would not own a triple because of the shifting issues they have, but that is my choice.  If it is working for you, why change it?

Pace per gear has nothing to do with watts unless you are talking about a straight road.  And it will still vary based on position and rider size.

I spin out my 53/11 often on descents.  It is not uncommon at all.

DAREMO

Not sure why you are looking to change gearing?  I would not own a triple because of the shifting issues they have, but that is my choice.  If it is working for you, why change it?

Only reson for change "Upgrading to TRI Bike" Still keeping road bike for group ride and some training.

Blasphemy!!! (although I know it's mostly true)

All kidding aside, there are other gear ratios.  I recently saw one on Bonktown that was a 56/44.  I'd hate to try and climb hills with that, but the top speed must be pretty fast!

I use a triple on my road bike (52/42/30) and a double on my tri bike (53/39)  Oh, and my MTB has a triple (42/32/22)  Now that's some hill climbing gears!

Ahhhhhh.  Then I would evaluate what gearing you typically use on your roadbike and set the tri bike up accordingly (same pretty much).

I also have some questions about gearing and combinations of compact crank or not vs. changing the rear cassette, etc ....

But just a quick question about spinning out in 53/11 ... I have this happen to be as well on downhills ... although I probably spin out at around 90-95 rpm's whereas I think yours would be much higher ... but generally how fast do you think I'm going if I spin out on the 53/11 gear?

I have a 2008 Felt S32 with the 53/39 crank and 10 speed 11-23 rear cassette.

My next question(s) is about the best method to gain an extra low gear or two.

Some have advised me to change out my 11-23 rear cassette for a 12-25 and some say go with the 12-27 ... I'm really weak on going up hills ... I hate to mash and would much rather spin in a super low granny gear vs. mashing on it or getting up out of the saddle.

So, would it be better to change up the rear cassette or to instead get a compact crank?

Is there a chart that shows what would be comparable, such as a 50/34 compact crank with an 11-23 rear is the same as a standard 54/39 crank with a 12-5 rear ... or a 12-27 rear, etc ....

Is it possbile to use a compact crank and that effectively changes an 11-23 rear to a 12-27 ?? as I'm leaning toward getting a 12-27 rear (vs. a 12-25).

Finally, what is cheaper and/or easier to change.  Get a different rear or get a compact crank?

Thanks for the help!

Give you the benefit of the doubt and say 100rpm, giving you 37.7mph:

Cool!

So I was close to going 40 mph!!

How do the pro's and FOP AG's go 45 and more?  Are they using an even higher geared crank or rear cassette, or just pedaling their damn legs off?

Steeper downhills!

RNH - 2009-03-08 10:12 PM Stay aero on a really steep hill, you can get going really fast in any gear with a cadence of zero Just don't touch the brakes Last year I was going downhill at Black Bear, hitting 40, and a guy passed me who had to be going 55. I was astonished someone had the nerve to stay aero at that speed. Use the gear tool to see the speeds you would get with different combinations. Changing the cassette is a much cheaper option, but the compact crank may give you better gearing choices since you don't need a wide range of gears on the cassette, causing 'skips' where you don't have certain cogs.

Yep!

I posted a thread about a week or so ago about whether or not people pedal going down hill or use it as a rest period.

I'm 250 lbs. and so I get going really fast even if I don't pedal or just pedal very little.  Even when I had just an old Diamondback hybrid bike at my sprint race, I was zipping past really FOP riders on their $2,000 tri bikes on the down hills ... and I was just pedal about 1/3 the way down then lean over into a pseudo aero postions (the best you can do on a hybrid) ... and I would zoom by.

I started using this as a rest period.  But the advice I got was to keep pedaling down the hills, to get even more speed and to help getting to the top of the hill once it bottomed out and started  going back up.

So, I've been pedaling down the hills lately and today on my ride I was in my higest gear of 53/11 and was spining out ... I could no longer pedal any faster and feel any tension from the crank ... meaning that any more pedaling just wasn't getting me any faster.

Bear posted that chart and so I estimate I was going between 37 and 40 mph.

My question is about up hills though ... I  need more climbing power.  So trying to figure out of it would be better to go from my 11-23 rear cassette to a 12-25 or 12-27 ... or keep the 11-23 and go to a compact crank.

double post ... how does that happen?