Great Lakes - hey Mr Engineer, can you figure this out for me?

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dannwilliams
02-08-09, 01:59 PM
I changed rear cassettes and I'm wondering how it will affect my top speed. I went from a 50 - 12 to a 50 - 11 top gear. I run 700 23 at 110 #'s of pressure. I turn the crank at 110 rpm in a dead sprint for the famed town line sign. How fast will I be going this year?

recursive
02-08-09, 02:22 PM
If you were spinning out the 12, your speed will increase by a maximum of ~9% if you can spin the 11 at the same speed.

That's also my sprinting gear. It's big enough for pretty much any reasonable circumstance I see on the road.
Galoot
02-08-09, 02:23 PM
Slower than me (and pcad).

Actually, it works out to a skosh over 39 mph, assuming that your wheel circumference is 2100 mm.

"Fred"
02-08-09, 02:27 PM
To answer your question your speed would go from 33.5 MPH to 36.5 MPH at 110 RPM.

However On a dead sprint 110 RPM is very low. If you are only spinning at 110 RPM I would assume that your max power is the limiting factor and your top speed will stay the same if not get lower with your new gear combo. Try to sprint in your 50x13 or 50x14 gear combo at a higher cadence and see what happens.
dannwilliams
02-08-09, 03:11 PM
I do not have a cadence on my Garmin, so I was just throwing out a number. What I do know is I hit 39 mph and I pegged my heart rate at 198. Took me a half hour to recover....but I won that sprint!
cyclpsycho
02-08-09, 04:14 PM
Bicycle gear calculator (http://www.panix.com/~jbarrm/cycal/cycal.30f.html)
Crast
02-08-09, 06:03 PM
Bicycle gear calculator (http://www.panix.com/~jbarrm/cycal/cycal.30f.html)
I find it quite amusing that that gear calculator allows for up to 10 front chainrings. Useful for comparisons between cranks, I suppose.

another bicycle gear calculator (http://sheldonbrown.com/gears) I like this one because it allows a lot of different measurements including a "speed @100RPM" number for each gear, also has useful presets for common cassettes
dannwilliams
02-08-09, 08:12 PM
another bicycle gear calculator (http://sheldonbrown.com/gears) I like this one because it allows a lot of different measurements including a "speed @100RPM" number for each gear, also has useful presets for common cassettes

That is what I am looking for
cyclpsycho
02-09-09, 04:53 PM
another bicycle gear calculator (http://sheldonbrown.com/gears) I like this one because it allows a lot of different measurements including a "speed @100RPM" number for each gear, also has useful presets for common cassettes

I like that one better :thumb:

I should have known Sheldon would have something. Thanks! I update my bookmark ;)