Wide gearing for 20" wheel travel bike

Kendall said:

I have a Bike Friday with the 20" wheels for my travel bike. To compensate
for the small wheels it has a 45x58 chainrings with an 11x23 cassette but
I'd like a lower gear for a ride I am about to do in the mountains with some
steeps. Using the gear calculator I think I'd like to go with a 28 tooth on
the cassette to get something comparable what I have used on the same ride
with a normal bike. I put on my 13x28 from another bike and while this has
low enough gearing I am spinning out in the flats. I'd rather have the 11
tooth small cog but would settle for a 12 if I had to. I have a few
different cassettes with loose cogs so I could construct an 11x28 or 12x28.
I might settle for a 12x26 if I have to.

My question is: With a Campy loose cogs (9 spd), what would you recommend
going with while hopefully maintaining decent shifting. Are their any
considerations or rules. Could this work? 11-12-14-16-18-21-23-25-28

I would make the last steps at the big end much larger. There's not
much difference in pedal effort between the 25 and the 28; it's less
of a percentage change than 12-14. I'd take the original 11x23 and
just swap the 28 on in place of the 23, or better still, build it so
that the last step is 23-28.
--
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"Kendall" <[email hidden]> wrote in message
news:[email hidden]...

Quoted message said:

I have a Bike Friday with the 20" wheels for my travel bike. To

compensate

Quoted message said:

for the small wheels it has a 45x58 chainrings with an 11x23 cassette but
I'd like a lower gear for a ride I am about to do in the mountains with

some

Quoted message said:

steeps. Using the gear calculator I think I'd like to go with a 28 tooth

on

Quoted message said:

the cassette to get something comparable what I have used on the same ride
with a normal bike. I put on my 13x28 from another bike and while this

has

Quoted message said:

low enough gearing I am spinning out in the flats. I'd rather have the 11
tooth small cog but would settle for a 12 if I had to. I have a few
different cassettes with loose cogs so I could construct an 11x28 or

12x28.

Quoted message said:

I might settle for a 12x26 if I have to.

My question is: With a Campy loose cogs (9 spd), what would you recommend
going with while hopefully maintaining decent shifting. Are their any
considerations or rules. Could this work? 11-12-14-16-18-21-23-25-28

FWIW, I modified the 13-29 10s cassette I have to an 11-29 by taking the
smallest three cogs off an 11-23 and using them in place of the existing
cogs, and also reusing the third smallest cog off the 13-29 (15t) as the
fourth smallest. That gives me 11-12-13-15-17... instead of
13-14-15-16-17...

I can't detect that the changing is any worse on the modified cassette
compared to the original. I'm using it on a standard road bike with 48-34
chainrings.

I also have a Bike Friday. I'm using 53-42 chainrings and a 13-26 9s
cassette. The bike came with larger chainrings such as you have, but I got
tired of having to remove the right crankarm to fit the bike into its travel
case. With the smaller chainrings I don't have to, and the 53-11 is still
good for bursts of 50kph.

Nick

Werehatrack said:

On Thu, 22 Jul 2004 22:17:57 -0400, "Kendall"

Quoted message said:

I have a Bike Friday with the 20" wheels for my travel bike. To compensate
for the small wheels it has a 45x58 chainrings with an 11x23 cassette but
I'd like a lower gear for a ride I am about to do in the mountains with some
steeps. Using the gear calculator I think I'd like to go with a 28 tooth on
the cassette to get something comparable what I have used on the same ride
with a normal bike. I put on my 13x28 from another bike and while this has
low enough gearing I am spinning out in the flats. I'd rather have the 11
tooth small cog but would settle for a 12 if I had to. I have a few
different cassettes with loose cogs so I could construct an 11x28 or 12x28.
I might settle for a 12x26 if I have to.

My question is: With a Campy loose cogs (9 spd), what would you recommend
going with while hopefully maintaining decent shifting. Are their any
considerations or rules. Could this work? 11-12-14-16-18-21-23-25-28

I would make the last steps at the big end much larger. There's not
much difference in pedal effort between the 25 and the 28; it's less
of a percentage change than 12-14. I'd take the original 11x23 and
just swap the 28 on in place of the 23, or better still, build it so
that the last step is 23-28.
--
Typoes are a feature, not a bug.
Some gardening required to reply via email.
Words processed in a facility that contains nuts.

There is a further reason to select small sprockets closely together.
The smaller sprockets are more likely to be used at higher speeds so aero-resistance comes into play. Aero drag goes up with the square of speed, power with the cube of speed, so it's better to have tight ratios correspoinding to percent effort changes rather than percent speed changes.