Granny vs. the hill

Is there any reasonable table of granny ratios to hill inclines for a
typical rider? Thanks.

Dave Wrote:
Is there any reasonable table of granny ratios to hill inclines for a
typical rider? Thanks.

Not that I know of. But in general, with all other things being equa
and for grades steeper than about 8%, the gear you need is roughl
inversely proportional to the steepness of the hill. So if you need
30/21 to get up a 10% grade, you'll need a 30/25 to get up a 12% grade

--
Gonzo Bob

Can anything be determined from this "Gain ratio" stuff? I have no
clue how to interpret it. Does this provide any way to relate an
incline to a required torque?

http://www.sheldonbrown.com/gain.html


Gonzo Bob wrote:

Not that I know of. But in general, with all other things being equal
and for grades steeper than about 8%, the gear you need is roughly
inversely proportional to the steepness of the hill. So if you need a
30/21 to get up a 10% grade, you'll need a 30/25 to get up a 12% grade.

Dave Wrote:
Is there any reasonable table of granny ratios to hill inclines for a
typical rider? Thanks.

(Dave) wrote in
om:

Can anything be determined from this "Gain ratio" stuff? I have no
clue how to interpret it. Does this provide any way to relate an
incline to a required torque?

It's a ratio between *force* at the pedal spindle and *force* at the rear
wheel rim. You can't relate force to incline unless you have numbers for
things like air resistance and rolling resistance.

However, the gravitational force along the ground (pushing you down the
hill) is mg sin \theta, where m is your total mass, g is the local
gravitational field strength, and \theta is the slope angle. For small
\theta, sin \theta ~= \theta (in radians); I think this works up to about
1 in 10.


--
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RE/
Is there any reasonable table of granny ratios to hill inclines for a
typical rider? Thanks.

I back into that ratio. For my upper gear, I choose a ratio where I'm spun
out at about 5 mph faster than the highest speed I can maintain aerobically.

For me, that gives a really low, stump-pulling granny gear. Others might want
to start with the high ration as described, then kick it up a couple steps if
the resulting granny is just *too* low.
--
PeteCresswell

qtq wrote in message ...
(Dave) wrote in
om:

Can anything be determined from this "Gain ratio" stuff? I have no
clue how to interpret it. Does this provide any way to relate an
incline to a required torque?

It's a ratio between *force* at the pedal spindle and *force* at the rear
wheel rim. You can't relate force to incline unless you have numbers for
things like air resistance and rolling resistance.

However, the gravitational force along the ground (pushing you down the
hill) is mg sin \theta, where m is your total mass, g is the local
gravitational field strength, and \theta is the slope angle. For small
\theta, sin \theta ~= \theta (in radians); I think this works up to about
1 in 10.

Maybe what I need to ask is this -- at what gear ratio will you simply
lack enough wheelspeed to maintain adequate balance and instead tend
to fall over?

qtq wrote in message ...
(Dave) wrote in
om:

Can anything be determined from this "Gain ratio" stuff? I have no
clue how to interpret it. Does this provide any way to relate an
incline to a required torque?

It's a ratio between *force* at the pedal spindle and *force* at the rear
wheel rim. You can't relate force to incline unless you have numbers for
things like air resistance and rolling resistance.

However, the gravitational force along the ground (pushing you down the
hill) is mg sin \theta, where m is your total mass, g is the local
gravitational field strength, and \theta is the slope angle. For small
\theta, sin \theta ~= \theta (in radians); I think this works up to about
1 in 10.

Maybe what I need to ask is this -- at what gear ratio will you simply
lack enough wheelspeed to maintain adequate balance and instead tend
to fall over?

Dave wrote:

Can anything be determined from this "Gain ratio" stuff? I have no
clue how to interpret it. Does this provide any way to relate an
incline to a required torque?

It's a ratio between *force* at the pedal spindle and *force* at the re=
ar=20
wheel rim. You can't relate force to incline unless you have numbers f=
or=20
things like air resistance and rolling resistance.

However, the gravitational force along the ground (pushing you down the=
=20
hill) is mg sin \theta, where m is your total mass, g is the local=20
gravitational field strength, and \theta is the slope angle. For small=
=20
\theta, sin \theta ~=3D \theta (in radians); I think this works up to =
about=20
1 in 10.
=20
=20
Maybe what I need to ask is this -- at what gear ratio will you simply
lack enough wheelspeed to maintain adequate balance and instead tend
to fall over?

Actually, when you get "too low" the limit is often the tendency of the=20
bike to "wheelie" which is partly related to the frame geometry and=20
rider height.

Once you get below about a 1.5 gain ratio (20 inches, 1 meter) the gears =

tend to become impractical for a bicycle.

Tricycles can effectively use lower gears than this in some cases.

Sheldon "Greenspeed" Brown
+------------------------------------------------+
| I=92ll be appearing in: |
| Gilbert & Sullivan's Iolanthe at M.I.T. |
| November 12, 13, 14 and 18, 19, 20, 21 |
| http://web.mit.edu/gsp/www |
| http://sheldonbrown.com/music.html |
+------------------------------------------------+
Harris Cyclery, West Newton, Massachusetts
Phone 617-244-9772 FAX 617-244-1041
http://harriscyclery.com
Hard-to-find parts shipped Worldwide
http://captainbike.com http://sheldonbrown.com

Dave wrote:

Can anything be determined from this "Gain ratio" stuff? I have no
clue how to interpret it. Does this provide any way to relate an
incline to a required torque?

It's a ratio between *force* at the pedal spindle and *force* at the re=
ar=20
wheel rim. You can't relate force to incline unless you have numbers f=
or=20
things like air resistance and rolling resistance.

However, the gravitational force along the ground (pushing you down the=
=20
hill) is mg sin \theta, where m is your total mass, g is the local=20
gravitational field strength, and \theta is the slope angle. For small=
=20
\theta, sin \theta ~=3D \theta (in radians); I think this works up to =
about=20
1 in 10.
=20
=20
Maybe what I need to ask is this -- at what gear ratio will you simply
lack enough wheelspeed to maintain adequate balance and instead tend
to fall over?

Actually, when you get "too low" the limit is often the tendency of the=20
bike to "wheelie" which is partly related to the frame geometry and=20
rider height.

Once you get below about a 1.5 gain ratio (20 inches, 1 meter) the gears =

tend to become impractical for a bicycle.

Tricycles can effectively use lower gears than this in some cases.

Sheldon "Greenspeed" Brown
+------------------------------------------------+
| I=92ll be appearing in: |
| Gilbert & Sullivan's Iolanthe at M.I.T. |
| November 12, 13, 14 and 18, 19, 20, 21 |
| http://web.mit.edu/gsp/www |
| http://sheldonbrown.com/music.html |
+------------------------------------------------+
Harris Cyclery, West Newton, Massachusetts
Phone 617-244-9772 FAX 617-244-1041
http://harriscyclery.com
Hard-to-find parts shipped Worldwide
http://captainbike.com http://sheldonbrown.com

Sheldon Brown wrote:

Actually, when you get "too low" the limit is often the tendency of the
bike to "wheelie" which is partly related to the frame geometry and
rider height.

Once you get below about a 1.5 gain ratio (20 inches, 1 meter) the gears
tend to become impractical for a bicycle.

Tricycles can effectively use lower gears than this in some cases.

Sheldon "Greenspeed" Brown

Sheldon Brown has been assimilated.
http://www.sheldonbrown.com/harris/greenspeed/index.html.

--
Tom Sherman