Cycling question: gearing, chainrings and cassettes

I need some insight from the cycling gurus here. I ride a Scott with a Campy Chorus 10 speed grupo. I mostly ride while training for triathlons and average 18-19 mph while riding solo. I'd like to bump my average speed up to around 21 while competing in tris.

As for my question, here is the scenario. Often, when riding here in relatively flat north FL, I find myself riding on the small front derailleur and at the far (small) end of the rear derailleur. My cadence will be around 95 at that point. My question is should I be on the big front ring and on a lower rear gear? I'll admit that I don't understand the relationship between the front rings, the rear rings, the cassette, etc. I do know that my front chain ring is a compact (34/50) and wonder if a different size would make the situation better or worse.

Can someone offer some advice? ECM, are you out there? Can you dumb it down for me?

Basically, no it doesn't matter. You're using roughly the same gear ratio either way, the only deciding factor would be driveline alignment. A chain running in a straight line between the front chainring and the rear cassette instead of at an angle to the gears is more efficient, and lasts longer.

In a race, though, it's more about strategy than perfect drivetrain alignment. First, think about what you're good at. If you have great cardio but weak legs, you should push a small gear and shift often to keep your cadence up. In this case, I'd probably (I don't know the range of your rear cassette) use the small chainring and be continuously shifting to keep my legs spinning. On the other hand, if you have bad cardio and strong legs, it would probably be faster for you to push a big gear and lower your cadence, so you don't overtax your lungs and heart. In this case, I'd use the large chainring up front and power through it all. Either way, pick the gear combination that works for you.

Of course, pushing a lot of gear inches all the time is bad for your knees, so be careful.

Oh, and just a heads up about vocabulary since you don't seem to know much about all the stupid names given to bike parts (no offense meant to anyone), derailleurs are the little "sticks" that move your chain around on the gears. Chainrings are the gears on the front, and the cassette is the stack of gears on the back.

Drivetrain alignment does contribute to wear, and by the time you are close to that smallest cog on the back you should go ahead and move up to the big ring on the front. Don't push the big ring all the time, but when you need to put the hammer down, that's where you should be.

Once you start down shifting into easier gears on the back you will want to think about the timing of your downshift on the front. Down shift on the front before you get too far down the cassette or it will mess with your cadence.

To be fair, the best way to train is to get a heart rate monitor, learn how to use it, and base your workout level/ intensity on that. Focus on being smooth when you pedal versus being in a specific gear, too low a gear and you hop around in the saddle because we tend to pedal in squares. To tall a gear and we can't use our leverage to the best advantage, so finding the right cadence and tweaking it and becoming smooth will get you far in your training and help prevent injury.

There are plenty of good cycling workout/training videos like the Carmichael series that will help you understand the gearing and when to use what gear.

I find the good basic rule of thumb is to visually divide the rear cogs in the middle. If I shift past the halfway point I make the front ring match that position. As I shift to the outside on the rear I will shift to the outside on the front. This keeps the chain line straight and you make the most effective use of the gear range without to much of a dramatic jump from one gear to another.

...aaaaand that probably made it sound way more complicated than it really is.

a HR monitor and cadance sensor make not over exerting yourself but keeping consistent so much easier to keep going strong for the entire ride.

In reply to dyintorace:

Okey Dokey, dyintorace. I'm a former bike shop owner and racer. Tommy's got it right, but here's alittle more detail and a place you go to find even more! Going for a better chain line is an important "kind to your drive-line thing". What you're doing (small front chainring to rear small cog) is called cross chaining. It causes MUCH earlier drive-line wear as well as wasting a surprising amount your energy. You gotta remember that we are small motors, so small losses have big impacts.

The 50-34 or "compact" gearing is fine for most of us mere mortals. It's only a problem if you're trying to sprint at 40 mph. If you can do that, get down to your closest weekend crit and race! If you travel and plan to ride out of state keep it.

One of the common miss conceptions about bike drive trains is that if it has 20 combinations it has twenty different gear ratios. It doesn't because there are many repeats (or near repeats) in the gearing. They are there on purpose. As you work your way up through the gears you will find yourself heading for the cross chain situation you've been experiencing. So lets say that you have the rear cogs shifted to position seven (with one being closest to the center of the bike and 10 farthest away) and you're on the small (inner) chainring. When you need a next higher gear you actually shift the rear BACK to position 5 as you shift to the bigger (outer) chainring. This is called a "Cross over shift". You soft pedal for a rotation as you do it (half a rotaion when you get good at it) to take the strain off the chain for a quick shift. You do the same thing in reverse when you are working your way back down the gears (this will happen when you go ride in Georgia, or some other place with a hill that's not also an overpass). Which ever direction you're going, do your crossovers just past the mid-cassette (say 6-7-8 cog on the way up and 5-4-3 cog on the way down).

Every rider will find a sweet spot cadence that they are most efficient at. Some guys are happier at 85 some at 95, but most will fall somewhere in that range for motoring along the flats. It seems you're a 95 guy, so experiment with your gears and find the duplicates in your gear set so you can try 'em out. Not knowing what cassette (the rear set of cogs) you're running (11-23, 12-27, etc.) it's hard to say if you'll need a two cog difference or a three cog difference for the smoothest transition when you cross over (on a compact it's usually two or three, sometimes four of you have a really tight cassette like an 11-21), but you'll find you can almost exactly duplicate the gear you are in on either the large or small chainring.

You can really drive yourself crazy by going to Sheldon Brown's website (google it) and down loading a gearing calculator. You can put your exact gearing in and print out a little chart to tape to the stem that shows your actual gear inches or ratio in each combination. That will give you a visual representation of where there are duplicates. Last word here is that if you see say a 52" gear on a big chainring combo and a nearby 51" gear in the small chainring combo, don't obsess! You wouldn't be able to tell the difference blind folded. Treat them as identical...also don't ride into a mailbox while focusing on the gearing chart.

Thanks for the insight. I understand it much better now, including the terminology. Intuitively, the cross chaining didn't seem good. On my next ride (tomorrow morning hopefully), I'm going to experiment with getting onto the big front ring and a bigger rear ring. The notion of the "cross over shift" makes sense too. Thanks for the explanation GTCEB!

Shouldn't this be in SPROCKETS?

4eyes wrote: Shouldn't this be in SPROCKETS?

Meh, bicycle threads seem to end up here and motorcycle threads go over there, for the most part. I'm content with that, since I'm not into motorcycles but I like the GRM bicycle threads.

MmmmmKay

Wow, Gladly, that really was a great explanation. I'll say from personal experience that an equivalent gear in the big ring is somehow easier than the same gear in the small ring. The only time I wear out the little-little combo is when I'm riding in very rolling hills and know I'll be down in the low gears often.

Interesting side tip since you ride the same Chorus gruppo I do - if you're cruising along in the big ring and a middle-size rear cog when you start up a hill, you can easily jump to an equivalent gear in the small ring by nailing both thumb levers at the same time. The left thumb lever drops from big ring to small ring at the same time the right thumb lever goes 2-3 gears harder in the back. With a little practice you can hit the equivalent small-ring gear with no loss in cadence and be ready for downshifting as the terrain continues to kick up.

word of warning - this can cause all kinds of exciting chain wrap problems if your driveline isn't pretty well line dout and maintained. Proceed with caution.