Compact Cranks

For long term wear: big cog to big cog, more teeth meshed, means less wear, less ability for the chain to skip. More time allowed for a chain to peel off if it starts to suck up, more gap it has to fly through to slap the chain stays. Downside is less ground clearance, more weight.

Yet for power output and racing I feel cadence is key, so a smaller chain ring is better. Downside is you can run out of gears going downhill and I'm sure I feel the largest chainring bending sometimes. There again I break crank axles...

Wouldn't the compact be lighter? Or maybe that's what you said and I just misunderstood. I've looked at a couple of rollout charts and it looks like you can get almost just as much out of a 34/50 as you can a 39/53, with the proper cassette. Now that might mean you have to swap your cassettes more frequently but you can get close.

threaded said:

For long term wear: big cog to big cog, more teeth meshed, means less wear, less ability for the chain to skip. More time allowed for a chain to peel off if it starts to suck up, more gap it has to fly through to slap the chain stays. Downside is less ground clearance, more weight.

Yet for power output and racing I feel cadence is key, so a smaller chain ring is better. Downside is you can run out of gears going downhill and I'm sure I feel the largest chainring bending sometimes. There again I break crank axles...

threaded said:

For long term wear: big cog to big cog, more teeth meshed, means less wear, less ability for the chain to skip. More time allowed for a chain to peel off if it starts to suck up, more gap it has to fly through to slap the chain stays. Downside is less ground clearance, more weight.

Yet for power output and racing I feel cadence is key, so a smaller chain ring is better. Downside is you can run out of gears going downhill and I'm sure I feel the largest chainring bending sometimes. There again I break crank axles...

Don't quite understand the first paragraph either. With a 50 chainring, shouldn't there be more ground clearance?

As for running out of gears. You can get 11-25 cassette these days. 50/11 is pretty decent.

sogood said:

As for running out of gears. You can get 11-25 cassette these days. 50/11 is pretty decent.

50/11 is higher than 53/12. In that vein, I've rarely spun out a 53/13, but then I'm not Tom Boonen. Yeah, I've got 50/11 on my bike, but I only use it above 37 mph.

The main case for compact cranks is that you can get most of the lower ratios of a triple without the complications of the triple. With a 10-speed cassette the only reason for using a triple is to get ratios.

There is less duplication of gears on a compact double compared to a regular double. If you look on Sheldon Brown's site, there's a calculator that shows you all the combinations for a given setup. Pretty neat.

I switched over the summer, and I don't see an issue with running out of gears on the high end. I went from an 12 in back to an 11, and as oldbobcat said, my top gear is actually slightly higher than it was. The low end is definitely more forgiving, too, without putting the granny gear cassette on.

The only thing that took some getting used to for me was the transition from the big to the little ring and vice versa. It's a big jump, and while the mechanical bits handle it smoothly, I find that it's more comfortable for me if I shift a couple up or down in the back at the same time so that I am not suddenly spinning my brains out or mashing because of the difference in gear inches.

threaded said:

Downside is less ground clearance, more weight.

Why does a compact crankset give you less ground clearance? 😕

I've been using a compact crank on my road bike for a couple of years. It works out well for me.

The first thing to think about is if a compact will give you the gear range that you need. My advice is to take the time to calculate the gear inches of every potential gear combination on all of the drivetrain types you are considering. One will probably jump out as being right for you.

To me, the biggest issue with a compact crank has to do with flat road gears. You'd like your favorite flat road gear to fall right in the middle of the cassette when you're in the big ring. That way you'll have a couple of trim gears before you have to change chainrings and make the double shift.

A couple of the other posters have hinted at the reduced gear overlap when using a compact. Here's what that means in real life riding: On my bike when I change chainrings I have to make two rear shifts to get the equivlent next gear. Where you happen to be when you shift chainrings makes all of the difference of how well you are likely to enjoy a compact. If you are finding yourself making a lot of front shifts on a relatively flat road, you're likely to hate it. In my case the compact has allowed me to do most of my flat road riding on the big ring. I generally only shift into the small ring for climbing hills. Consequently, I love it.

Retro Grouch said:

The first thing to think about is if a compact will give you the gear range that you need. My advice is to take the time to calculate the gear inches of every potential gear combination on all of the drivetrain types you are considering. One will probably jump out as being right for you.

To me, the biggest issue with a compact crank has to do with flat road gears. You'd like your favorite flat road gear to fall right in the middle of the cassette when you're in the big ring. That way you'll have a couple of trim gears before you have to change chainrings and make the double shift.

I agree. This comes down to how strong a rider you are. If I had started my return to cycling with a CT, then I'd say I would hate it, as I would be regularly running large-large or swapping chainrings. Right now, I still often need that 50/25 for some of our hills here, but the amount of cross-chaining is much much less. Although not perfect yet, but I suspect another year of riding and I'd sit right in the sweat spot for CT/12-25 combo. 🙂

In retrospect, the triple was really a good setup for someone returning to cycling.

Retro Grouch said:

I've been using a compact crank on my road bike for a couple of years. It works out well for me.

The first thing to think about is if a compact will give you the gear range that you need. My advice is to take the time to calculate the gear inches of every potential gear combination on all of the drivetrain types you are considering. One will probably jump out as being right for you.

To me, the biggest issue with a compact crank has to do with flat road gears. You'd like your favorite flat road gear to fall right in the middle of the cassette when you're in the big ring. That way you'll have a couple of trim gears before you have to change chainrings and make the double shift.

A couple of the other posters have hinted at the reduced gear overlap when using a compact. Here's what that means in real life riding: On my bike when I change chainrings I have to make two rear shifts to get the equivlent next gear. Where you happen to be when you shift chainrings makes all of the difference of how well you are likely to enjoy a compact. If you are finding yourself making a lot of front shifts on a relatively flat road, you're likely to hate it. In my case the compact has allowed me to do most of my flat road riding on the big ring. I generally only shift into the small ring for climbing hills. Consequently, I love it.

+1 I think the better choice for all but top performing riders is a compact crank. Add gears that allow you to climb at a higher cadence, lose gears you don't really need. It's too bad that there's still a stigma with many riders that compacts are for 'beginners', 'old guys', etc.

Pad

grv said:

The only thing that took some getting used to for me was the transition from the big to the little ring and vice versa. It's a big jump, and while the mechanical bits handle it smoothly, I find that it's more comfortable for me if I shift a couple up or down in the back at the same time so that I am not suddenly spinning my brains out or mashing because of the difference in gear inches.

That's what I found, too. Just don't try to do it all at once or you end up dropping your chain.

Answering my own post as it looks like I wasn't as clear as I thought I was: 🙁

threaded said:

For long term wear: big cog to big cog, more teeth meshed, means less wear, less ability for the chain to skip. More time allowed for a chain to peel off if it starts to suck up, more gap it has to fly through to slap the chain stays. Downside is less ground clearance, more weight.

Here I am on about 130BCD, essentially you win on longevity because more cog teeth are involved at any time, but lose on weight and clearance.

threaded said:

Yet for power output and racing I feel cadence is key, so a smaller chain ring is better. Downside is you can run out of gears going downhill and I'm sure I feel the largest chainring bending sometimes. There again I break crank axles...

Here I discuss my experience of compact cranks, I find if I run a big chain ring I can feel it flexing, and if I don't have a big chain ring I run out of gears. If I run a very small cog at the back to compensate, I find I get the chain skipping.

My experience of compact cranks, much like a lot of this modern bicycle gear is that it feels right on the edge of failure, and doesn't last like old stuff. It doesn't last because they make design decisions that err on the side of wearing out quicker.

My Cyclo-cross bike is from the 1970s and still works, yet a full suspension mountain bike from a few years ago is more difficult to source spares for.

There again, most of what I see in the LBS is designed to be thrown after a season, so does longevity matter? And if longevity is your target, would you be choosing parts that are essentially just this years fashion?

Compact cranks this years fashion?

It's kind of the same here, you used to only hear the beginners, older riders or weaker riders were using the compacts. But now I'm starting to see some of our dominant racers using them and I'm starting to consider it.

threaded said:

My experience of compact cranks, much like a lot of this modern bicycle gear is that it feels right on the edge of failure, and doesn't last like old stuff. It doesn't last because they make design decisions that err on the side of wearing out quicker.
...
There again, most of what I see in the LBS is designed to be thrown after a season, so does longevity matter? And if longevity is your target, would you be choosing parts that are essentially just this years fashion?

After one season my cheap FSA Gossamer compact cranks feel just as rugged as the Campy record I'd used for over 30 years. Actually, they feel stiffer because of smaller spider radius and outboard bearings. The ring teeth might wear five percent faster but that's to be expected.

I'm happy with mine because it allows me to climb hills I hadn't touched in 20 years and helped me lose 25 pounds. If this bolsters your argument that compacts are for old farts, then so be it.

Compact cranks? If they work for you, then they're great. Of course, asking if compact cranks are good or bad is really a poorly posed question. The question that really should be asked is, "What gearing works best for me?" From there, you can figure out whether that gearing can be better achieved with a standard crank or a compact crank.

I've got a compact crank, 50/36, connected by the chain bone to a 11-25 cassette. That gearing is slightly more to my liking than what I had before on a standard crank. Slightly, but it was enough to make the difference to me.

There is one caveat to the gearing/crank answer: if your pennies are precious and you have a standard crank, it'll be loads cheaper to get a cassette with bigger cogs. If you're changing cranks anyway, then a compact crank can be excellent choice, depending on your needs. The one nice thing about a compact is that if you want, you can run standard sized chainrings, too.

Living in he Rockies, a compact is great.......gearing for you is the only important part.

Tim Lamkin said:

Living in he Rockies, a compact is great.......gearing for you is the only important part.

Bubbles,
How much did you get for those shopping carts?

Ricky

melslur said:

Bubbles,
How much did you get for those shopping carts?

Ricky

Woosh, that went completely over my head. How long is that darn shower going to take anyway?

kdelong said:

Woosh, that went completely over my head. How long is that darn shower going to take anyway?

Tim's avatar is from a tv show. Note the 4th line in "Character Summary":
en.wikipedia.orgBubbles %28Trailer Park Boys character%29Open ↗

Just having fun.

Too funny 😄