Chart Wanted: Cadence @ a Certain Speed..?

[Dave Noisy]

Hi all, i'm sure there's gotta be something like this out there..

I'm looking for a chart which shows what gear you need to be in to maintain a certain speed at a certain cadence.

For example, if i wanted to ride ~40kph and spin ~100rpm while at that speed, what gear would i need to be in?

Thanks!!

[goonda]

Not sure how scientific this is because it doesn't take into account weight of rider, flat vs. hills, etc. But I find it pretty useful to get the proper shifting sequence.

http://www.panix.com/~jbarrm/cycal/cycal.30f.html

[HereNT]

Man, I can't find it any more, but there's a forum that's all track bikes. I think that there was a chart here that listed gear vs cadence vs speed vs time per lap on different length tracks...

[Map tester]

Try this: HPV Drivetrain Analyzer (http://www.soulbikes.com/gears/) or Sheldon Brown's Gear Calculator (http://www.sheldonbrown.com/gears/)

[Dave Noisy]

Thanks guys, the Panix and Brown's ones are great!

HereNT - you prolly mean http://www.fixedgearfever.com/ - i'm on there as well, thanks!!

[HereNT]

Yeah, that was it.

[boyze]

For the math unchallenged here's how to figure it out:

the chain ring to rear cog tooth ratio is the gear ratio which means that for every turn of the crank the rear wheel turns front ring # teeth/rear cog # teeth times more. This ratio is then multiplied by the wheel circumference which you remember from geo as 3.14159 x the diameter (most wheels are 700mm(27.56 inches) or 27 inches). Therefore, multiple the 3.14159 x 27 x tooth ratio x cadence and that's your speed in inches per minute. To convert to mph multiple that number by 60/(12x5280).

Example: riding a 42/17 at 100 cadence on 27" wheels (if you ride 700's or other sizes just change to whatever diameter you have on the rear wheel

100 x (42/17) x 3.14159 x 27 x 60/(12 x 5280) = 19.84 mph

A mental exercise I used to do while training was simply scale the speed by the gear ratio knowing that a 42/17 or 66.7 inch gear is 20 mph at a 100 cadence. If I was riding a 52/14 which is a 100 inch gear than my speed would be close to 1/2 x faster or 30 mph. These were the days just before inexpensive speedometers were available ;)