Cross-chaining and correct gearing: My solution

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09-07-2006, 04:46 PM
Kalidurga

Cross-chaining and correct gearing: My solution

After my thread on cross-chaining over in Bike Maintenance, I've been determined to grasp the whole gearing issue. I feel that I know physically when I'm in the proper gear, but going purely by feel has often meant that I've ended up riding cross-chained. Since I don't wanna screw up my drivetrain, I've gotta understand this on an intellectual level, too-- Not just what I feel, but what's happening with the mechanism of the bike.

So, I took SadieKate's recommendation of Sheldon Brown's Gear Calculator and DebW's advice from the other thread, and created the following chart that I then taped to the stem of my bike (my nifty, color-coded chart didn't paste properly, but hopefully you get the idea):

MPH @ 90 RPM

34 48
25, 9.8, 13.9
23, 10.7, 15.1
21, 11.7, 16.5
19, 12.9, 18.3
17, 14.5, 20.4
15, 16.4, 23.1
13, 18.9, 26.7
12, 20.5, 28.9

The top and left columns are the chainrings and cassette of my bike, laid out so that I can visualize the rings/cogs from left to right. The middle and right columns are the speeds that I should achieve in that gear combo at a cadence of 90rpm (usually my most comfortable, most sustainable cadence). I tested it today and the numbers matched the cadence/speed on my computer. It ended up being so easy to stay out of those cross-chained gears. It's simple to keep track of which ring I'm in up front, so I could judge by cadence/speed which gear I was in on the rear cassette.

My only issue is exactly what Deb pointed out: On a flat surface such as I rode today, my ideal gear combos are 34/15 up to 48/19, which involves a double-shift. I didn't want to screw up my rythm today, so I just spun it up to 100 or so rpm a few times instead of shifting up to the higher gear. Maybe a few weeks of squats and lunges will get me up into that 48/19 permanently ;)

I need to ride a hilly route next time out so that I can see what combos I end up in (and to practice that damned double-shift...). Oh, and the chart on the stem isn't worth beans on a gravelly path-- the bike vibrates too much for me to read it!

I don't know if this sort of idea would help other folks trying to learn gearing, but I thought I'd throw it out there. Thanks again to SadieKate and Deb for your recommendations!
09-08-2006, 08:07 AM
DebW

Quote:

Originally Posted by Kalidurga

My only issue is exactly what Deb pointed out: On a flat surface such as I rode today, my ideal gear combos are 34/15 up to 48/19, which involves a double-shift. I didn't want to screw up my rythm today, so I just spun it up to 100 or so rpm a few times instead of shifting up to the higher gear. Maybe a few weeks of squats and lunges will get me up into that 48/19 permanently ;)

Good for you for working it all out and practicing. Nice chart. I think your approach was perfect. Practicing spinning at 100 or 110 is really good for your legs and will improve your riding. That double shift is not something you want to do constantly, so if your cadence has some flexibility you'll be better off. Besides, I'm betting that you WILL get stronger and can begin spending more time in the larger chainring. Does the 48/21 feel too cross-chained to ride? It shouldn't hurt to at least use it every once in awhile for short periods.
09-08-2006, 08:24 AM
mimitabby

Quote:

Originally Posted by Kalidurga

After my thread on cross-chaining over in Bike Maintenance, I've been determined to grasp the whole gearing issue. I feel that I know physically when I'm in the proper gear, but going purely by feel has often meant that I've ended up riding cross-chained. Since I don't wanna screw up my drivetrain, I've gotta understand this on an intellectual level, too-- Not just what I feel, but what's happening with the mechanism of the bike.

So, I took SadieKate's recommendation of Sheldon Brown's Gear Calculator and DebW's advice from the other thread, and created the following chart that I then taped to the stem of my bike (my nifty, color-coded chart didn't paste properly, but hopefully you get the idea):

MPH @ 90 RPM

34 48
25, 9.8, 13.9
23, 10.7, 15.1
21, 11.7, 16.5
19, 12.9, 18.3
17, 14.5, 20.4
15, 16.4, 23.1
13, 18.9, 26.7
12, 20.5, 28.9

The top and left columns are the chainrings and cassette of my bike, laid out so that I can visualize the rings/cogs from left to right. The middle and right columns are the speeds that I should achieve in that gear combo at a cadence of 90rpm (usually my most comfortable, most sustainable cadence). I tested it today and the numbers matched the cadence/speed on my computer. It ended up being so easy to stay out of those cross-chained gears. It's simple to keep track of which ring I'm in up front, so I could judge by cadence/speed which gear I was in on the rear cassette.

My only issue is exactly what Deb pointed out: On a flat surface such as I rode today, my ideal gear combos are 34/15 up to 48/19, which involves a double-shift. I didn't want to screw up my rythm today, so I just spun it up to 100 or so rpm a few times instead of shifting up to the higher gear. Maybe a few weeks of squats and lunges will get me up into that 48/19 permanently ;)

I need to ride a hilly route next time out so that I can see what combos I end up in (and to practice that damned double-shift...). Oh, and the chart on the stem isn't worth beans on a gravelly path-- the bike vibrates too much for me to read it!

I don't know if this sort of idea would help other folks trying to learn gearing, but I thought I'd throw it out there. Thanks again to SadieKate and Deb for your recommendations!

nope, i don't get it. I would like to because a very experienced rider told me
"you always want to stay in the center of your chainrings" whatever that means. I would like to do this, understand this, but so far... nope.

okay, i'm over in your cross chain thread now...
09-08-2006, 08:41 AM
Kalidurga

Quote:

Originally Posted by DebW

Practicing spinning at 100 or 110 is really good for your legs and will improve your riding. That double shift is not something you want to do constantly, so if your cadence has some flexibility you'll be better off. Besides, I'm betting that you WILL get stronger and can begin spending more time in the larger chainring. Does the 48/21 feel too cross-chained to ride? It shouldn't hurt to at least use it every once in awhile for short periods.

Actually, I usually spin anywhere from 90-105rpm, depending on the surface where I'm riding. I've recently realized that even though my legs can handle the higher rpm, I become fatigued more quickly. I've had asthma issues, so it's a matter of building up my cardiovascular strength. I'm also determined to get my legs even stronger, though, so I can spend more time in the big ring. Funny how you can think you're soooo strong, but then when you learn a bit more about your sport you realize how much room for improvement you really have... :rolleyes:

And, yeah, when I look at the 48/21, the chain is at an obvious angle coming out of the bottom of the pulley. I could do it for short stretches, but will probably try to avoid it.

Mimi, cross-chaining is exactly what it sounds like. Try putting your bike into each combination of big ring/rear cog, then look at the chain from the rear of the bike. When you have the chain on, for example, the smallest ring in front and the smallest ring in back, you can see that the chain is angled from front to back, instead of running in a more or less straight line. That's what that experienced rider was telling you, in a not so clear way. It's less stress on your drivetrain to stay in gear combos that keep your chain running as straight as possible instead of at an angle. What's hard is learning a way to know when you're in the proper gear without craning your head down to look at the cogs while you're riding, which will cause you to swerve all over the darned trail...