I have a HIM this weekend with a 6 mile climb at 4.9% grade (1400 feet rise over the 6 miles). I have a compact crank set up, 172.5 crank arm length, 700cc tires and an FTP of 260. I wanted to make sure that I have an large enough cog in back that I don’t blow up the climb but I’m not sure how to figure that out using the online calculators. Any advice/instructions appreciated.
You’re overcomplicating/over analysing … that’s not an especially big climb and you’ve got a reasonably decent FTP as long as you’re not huge. With a compact I reckon you’d be absolutely fine on a 25t but, if you’re worried, fit a 28t.
syracuse ?
how much do you weigh ?
HITS North Country. And I’m 158 lbs (although I’ll probably be 160 by race day, can’t stop eating during taper).
Thanks for the reassurance. Just wanted to make sure.
Sheldon Brown has the most thorough gear calculator I’ve come across. http://sheldonbrown.com/gears/
Type in your rim and tire size, likely you’re running 700-23 or 700-25. Tire width is needed because a wider tire increases the diameter of your wheel, and thus increases your speed at any given gear and cadence.
Then select your crank length, enter your chain ring sizes (50x34 or 52x36 since you’re running a compact crank) and select your cassette range from the drop-down menu.
For gear units, select mph at 90 or 80 rpm (Your optimal cadence on a 5% gradient is probably between 80 and 90 rpm. ) , then hit calculate. The output will be a table with your mph at 80/90 rpm in every gear combination.
To make sure your current cassette will work for the race though, just find a local hill that’s right about 5%, and ride up at 260W in the 80-90 rpm range and make sure you’ve got a gear that you can climb comfortably in, if not, you might want to switch out the cassette for a 11-28 or 12-28.
Sheldon Brown has the most thorough gear calculator I’ve come across. http://sheldonbrown.com/gears/
Type in your rim and tire size, likely you’re running 700-23 or 700-25. Tire width is needed because a wider tire increases the diameter of your wheel, and thus increases your speed at any given gear and cadence.
Then select your crank length, enter your chain ring sizes (50x34 or 52x36 since you’re running a compact crank) and select your cassette range from the drop-down menu.
For gear units, select mph at 90 or 80 rpm (Your optimal cadence on a 5% gradient is probably between 80 and 90 rpm. ) , then hit calculate. The output will be a table with your mph at 80/90 rpm in every gear combination.
To make sure your current cassette will work for the race though, just find a local hill that’s right about 5%, and ride up at 260W in the 80-90 rpm range and make sure you’ve got a gear that you can climb comfortably in, if not, you might want to switch out the cassette for a 11-28 or 12-28.
No need for a gear calculator at all if you’re using that method 
Great explanation. Thanks!
Is there any tool that allows you to enter that same information in addition to %grade of incline to get the power required to turn the cranks at X RPM?
Great explanation. Thanks!
Is there any tool that allows you to enter that same information in addition to %grade of incline to get the power required to turn the cranks at X RPM?
You can use http://bikecalculator.com/
Put in your weight, altitude distance, percent grade and the power you plan to ride the climb at and it will give you a speed.
Once you have that use Sheldon Brown’s calculator using the speed at X RPM option where X is your preferred cadence. From there you can figure out what gear will work for your situation.
Sheldon Brown has the most thorough gear calculator I’ve come across. http://sheldonbrown.com/gears/
Good old Sheldon, he was quite the local character, bike mechanic and a great resource. He as been gone since 2008 but lives on in his website!
I really like http://gear-calculator.com/. It doesn’t have any analytics built in, but it is the most user-friendly interface that I’ve come across.
Thanks again. The work-around/combination you suggested provided the info I was looking for. Not thrilled about the 43 minutes it reports will be the time needed for that climb, but what can you do, it’s just math.