Compact Chainrings: How much difference do they make?
 

While I haven't yet met a grade I couldn't climb, I have been thinking about switching from my 53/39 12-25 set up to a compact. If I can spin up a little more easily and efficiently it should make me faster too, right? I don't know how much difference it really makes though, so I'm worried that I may not even notice a difference? Or should I change the cassette? Tell me your experiences And what are your thoughts and advice? By the way I'm 46 and I also think the compact set-up may help preserve the health of my knees.

There's a huge difference -- it's totally different gearing and there is no doubt you'll notice. However, if you're doing fine with the 39, why bother with lower gears? But if you're hurting, go for it.

I'm using a 50/36 with a 23-11, and it's a lot easier to go through the gears. So much so that I can get up to the upper end of the cassette in combination with the 50 quite easily if there's any kind of negative grade. Going down SoMo, I'll run out of gears and just tuck. I don't find a need for anything less than the 21 either so all my gearing is super tight which is really nice.

My road bike on the other hand is a 53/39 and I hardly go into the upper range of the cassette in the 53. I use a 25-11 and find it fine for almost everything.

Basically, since TTing is staying in one comfortable gear and having easier gears for grades to stay in aero, I have the compact. Road biking, I need bursts of power and a range for climbing so bigger cassette and larger chain rings.

If you don't need the compact, why bother getting one?

I recently switched to a mid-compact (52/36) and that's been spectacular for the hills and small mountains near me. I also have an 11-28 in the back.

I'm tempted to put the compact chainrings back on and switch the back out for a 12-25 simply because it would put me in the fun part of the cassette more often and the ratios would be closer at the large end of the cassette.

The difference between 39 and 34 in front is 13% required effort per pedal crank revolution. To get the same difference only using the rear you would have to change from a 25 to a 29 largest cog (if it existed). If you do both, go from 39/25 lowest gear to 34/28, you can get a total of 23% reduction. Assuming you want to stay with a road rear dearailleur and don't want or have Apex, that is the best you can do. That is huge. The good news is that is doesn't much hurt your top end. Not too long ago, 12t was the smallest rear cog. Now with 11t cogs, you can have a very slightly higher top gear with 50/11 than you used to have with 53/12. What does change a lot is the spacing of the gears and the changeover point that you have to go from small front ring to large and vice-versa. That is a new learning process. You may not like the arrangement of gears in a compact setup, but it is the price you pay for easier climbing. One way to analyze things is to take note of which cruising gears you use most now and see how close you can get to them (not the same combinations, but just the same ratios) with the compact gearing. Don't forget to take into account any new rear cassette you would opt for. Can you cruise at the same exertion or not? Are your three favorite cruising gears reasonably situated to each other to make shifts convenient. That is what you really need to determine. For example, say you like 53/17. That is a ratio of 3.12. With a 50 front, that corresponds to a 16 rear nearly perfectly. Not too bad if you have it or can get it on a new cassette. And so on...

Shimano are moving to 30T cassettes. 105/Ultegra reportedly available later this year.
I'm running the 30T 4600 cassette + 5700A derailleur on my compact, climbs pretty nicely.

OP: a 28 cassette would be a good place to start.

I would keep what you have, but be open to it for your next bike.

Realize you would need a new CRANKSET, you can't just get a compact chainring...it won't fit on your standard crank.

I would also look at a gear calculator (there are tons online) just to get a sense of what options are out there before you make a choice.

FWIW I am 47 and run 39-53 and 12-23 with no problems...but you should pick the gearing that's best for YOU and your style and your terrain.

Me as well. It is a beautiful combination.

Also 47, and would have a stroke with that combo.

It is a huge difference..... I run 50/34 with a 11/25 cassette and I almost never shift to the 34T ring. We have only a couple big hills here, and I dropped to the 34T ring but did not need to get up to the 25T cog. For my style of riding and the terrain, I could ride 50/25 exclusively, but it's nice to have that cushion if needed.

For what it's worth, I'm 51........

The difference it makes is you'll have a couple more lower gears and a couple less high gears. In between extremes, there really is no difference.

Or you can do the math yourself. There will be ratios with your present gearing that are similar to those you'd have with a compact. Figure out what they are and take a ride using those gears. Formula is the number of teeth on the chainring divided by the number of teeth on the rear cog, multiplied by the wheel diameter (27 for 700 wheels, 26 for mountain bikes). Result is in "gear inches," a standard measure.

I would have had a stroke with that combo when I was 27...

That's funny, I have no problems with my gearing.

I rarely use my "bailout" 39/23 gear...there is a local hill that is 15% and I use it for that.

I am at the base of the Rockies, so it was more about geography, but still. 23 big is too gnarly for me.




I need to HTFU.

I'm riding a Roubaix with the 50/34 and 11-32 set up. I really like the range of the gearing but with the spacing it is sometimes challenging to maintain a set speed.

Go to Sheldon Brown and plug in you present ratios into their gear calculator. I'm building a new road bike and am going to use a 50/34 crank married to a 13-25 cassette. That gives me 101 GI's at the top and 35.9 at the bottom. That'll do for me. I do group rides at a fairly sporty pace with my club and at 58, that setup will work for me.

Figure out what you need and go from there. Nashbar has a nice selection of cassettes. Al

I certainly like the compact crank, and the 11/28 cassette. I've only been riding a year since a 25 or so year hiatus, so I am not strong enough to stay out of the small/big combo all the time. Getting better, but even if I htfu significantly, I don't see that my ego will outstrip the fact that I like having a bailout gear. I know it is only a small difference, but I am seriously considering a 30T big cog in the back - just because I'm 54 and a cycling rookie, and I can only get so strong before the years intervene.

Thanks for all the replies so far. I live in N. AZ and I climb a lot on every ride, not that there's not flat rides available, but more because I WANT to be a climber! Part of the reason I'm looking into other gearing options is that while climbing, I am in my lowest gear combination ALOT. Like somebody suggested, maybe a good place to start would be an 11-28 cassette?

I live in a pretty hilly place and I am a Clyde at 6'4" and 255.

Rain bike is 53/39 with 12-29 11 speed cassette and the Climbing bike is 50/34 with 12-29. When I first made switch to compact I was slower on steep hills as I reflexively bailed out out - in time have really benefitted from being able to keep cadence up on steeper inclines.

I just imagine I'm Christian VdeV leading Ryder up the Stelvio....

Get a triple!

/runs, hides.

But seriously, this is one reason I like my triple. Lots of options, no significant gaps.