Chainwheels sizes available

"cmcanulty" <[email hidden]> wrote in message
news:[email hidden]...

Quoted message said:

Is there anyplace I can find out what size chainwheels are available
in the different Bolt Circle Diameters? I have looked a lot and short
of just browsing all the online bike shops can't find out. Like is it
possible to put a <38 tooth chainring on a 130BCD?

No - the bolts will get in the way of the teeth.

Quoted message said:

Possibly by
redrilling the holes? I am trying to get a super low gear and super
high gear on my folding bicycle. Or is there a BCD that would allow me
to have 2 chainrings, 1 with 53 teeth and one with 22?

Road triple? 52/53 on the outside, 24t on the inside? I wouldn't do 53/22
spaced for a double - the chain will catch on the big ring if in
small/smallish.

Quoted message said:

I am NOT using
a front derailleur, will shift manually, so tooth difference doesn't
matter.

Except it does - you've still got to have something taking up the slack. And
there's an awful lot of slack to take up in what you want.

BTW it's Sheldon Brown.

cheers,
clive

cmcanulty said:

Is there anyplace I can find out what size chainwheels are available
in the different Bolt Circle Diameters? I have looked a lot and short
of just browsing all the online bike shops can't find out. Like is it
possible to put a <38 tooth chainring on a 130BCD? Possibly by
redrilling the holes? I am trying to get a super low gear and super
high gear on my folding bicycle. Or is there a BCD that would allow me
to have 2 chainrings, 1 with 53 teeth and one with 22? I am NOT using
a front derailleur, will shift manually, so tooth difference doesn't
matter. I want to achieve a super wide gear range of sub 18 to 125 or
so. It has a 9sp cassette on rear. I know to avoid the extreme cross
combinations, thanks. This is one of the few times Ricard Sheldon's
site didn't have the info or I didn't find it.

http://www.velo-orange.com/pro5viscr.html TA Pro 5 Vis and its now
discontinued Stronglight clone. Site says anything from 26 on the
inside to 64 on the outside. It comes in either double or triple. I
think the double will go 26 on the inside and whatever on the outside.

http://www.bikespecialties.com/site/parts2.html Canadian seller of
the TA Pro 5.

For something easier to find, but with less range, a 110mm bcd double
might work. Inner chainring can go down to 33 teeth from TA. Outer
is available into the 60s because tandems use the 110mm bcd.

cmcanulty said:

Is there anyplace I can find out what size chainwheels are available
in the different Bolt Circle Diameters? I have looked a lot and short
of just browsing all the online bike shops can't find out. Like is it
possible to put a <38 tooth chainring on a 130BCD? Possibly by
redrilling the holes? I am trying to get a super low gear and super
high gear on my folding bicycle. Or is there a BCD that would allow me
to have 2 chainrings, 1 with 53 teeth and one with 22? I am NOT using
a front derailleur, will shift manually, so tooth difference doesn't
matter. I want to achieve a super wide gear range of sub 18 to 125 or
so. It has a 9sp cassette on rear. I know to avoid the extreme cross
combinations, thanks. This is one of the few times Ricard Sheldon's
site didn't have the info or I didn't find it.

130mm was designed to run as low as 39t. SR-Sakae made a 38 but, just as
the 'cheater' 41t rings for classic Nuovo Record cranks, it may be
necessary to file the ends of the crank spider between the rings
if/where it fouls the chain sideplates. (if you can find one)

Usual limit of 151mm is 44t
for 144mm, 42t
for 110mm, 34t
for 74mm, 24t
No obvious solution comes to mind for a double 53/22. Internally geared
rear hubs can be an elegant solution to small wheel gearing, for example:
http://www.yellowjersey.org/suprsevn.html
--
Andrew Muzi
www.yellowjersey.org
Open every day since 1 April, 1971

"A Muzi" <[email hidden]> wrote in message
news:[email hidden]...

Quoted message said:

130mm was designed to run as low as 39t. SR-Sakae made a 38 but, just as
the 'cheater' 41t rings for classic Nuovo Record cranks, it may be
necessary to file the ends of the crank spider between the rings if/where
it fouls the chain sideplates. (if you can find one)

TA make a 130mm 38t ring. Never had any difficulty getting hold of one of
them.

cheers,
clive

On Tue, 29 Jan 2008 12:33:16 -0800 (PST), cmcanulty

may have said:

Is there anyplace I can find out what size chainwheels are available
in the different Bolt Circle Diameters? I have looked a lot and short
of just browsing all the online bike shops can't find out. Like is it
possible to put a <38 tooth chainring on a 130BCD? Possibly by
redrilling the holes? I am trying to get a super low gear and super
high gear on my folding bicycle. Or is there a BCD that would allow me
to have 2 chainrings, 1 with 53 teeth and one with 22? I am NOT using
a front derailleur, will shift manually, so tooth difference doesn't
matter. I want to achieve a super wide gear range of sub 18 to 125 or
so. It has a 9sp cassette on rear. I know to avoid the extreme cross
combinations, thanks. This is one of the few times Ricard Sheldon's
site didn't have the info or I didn't find it.

You're up against some problems here. First, to the best of my
knowledge, no manufacturer produces a front der that has a cage long
enough to accommodate a sprocket diameter difference that great.
Second, if you had a 53 custom-made to fit a BCD which allowed it to
be mounted on the same bolts with a 22, the 53 would get awfully
flexy; you'd have a good chance of encountering unintended shifting.
Third, you'll have trouble finding a rear der that could take up that
much slack, assuming that you're also running a Megarange cassette.
(And if you're not, then why engage in this exercise at all when a
Megarange will provide the same result?) Fourth, if you go with a
crank that has an adequately large BCD for the 53 to be properly
supported, the chain's probably going to foul on the mounting bolts
part of the time when you're on the 22.

--
My email address is antispammed; pull WEEDS if replying via e-mail.
Typoes are not a bug, they're a feature.
Words processed in a facility that contains nuts.

Werehatrack said:

On Tue, 29 Jan 2008 12:33:16 -0800 (PST), cmcanulty

may have said:

Is there anyplace I can find out what size chainwheels are available
in the different Bolt Circle Diameters? I have looked a lot and short
of just browsing all the online bike shops can't find out. Like is it
possible to put a <38 tooth chainring on a 130BCD? Possibly by
redrilling the holes? I am trying to get a super low gear and super
high gear on my folding bicycle. Or is there a BCD that would allow me
to have 2 chainrings, 1 with 53 teeth and one with 22? I am NOT using
a front derailleur, will shift manually, so tooth difference doesn't
matter. I want to achieve a super wide gear range of sub 18 to 125 or
so. It has a 9sp cassette on rear. I know to avoid the extreme cross
combinations, thanks. This is one of the few times Ricard Sheldon's
site didn't have the info or I didn't find it.

You're up against some problems here. First, to the best of my
knowledge, no manufacturer produces a front der that has a cage long
enough to accommodate a sprocket diameter difference that great....

I have run 62/52/39 chain-wheels with a long cage Shimano RSX front
derailer. The chain barely clears the crosspiece of cage when using the
"granny" ring, while the bottom of the cage plates barely clear the
outer ring. While the smaller radius of the 52T large ring will help
with derailer clearance, more than a 24T difference is unlikely to work
without a custom cage.

--
Tom Sherman - Holstein-Friesland Bovinia
"And never forget, life ultimately makes failures of all people."
- A. Derleth

On Tue, 29 Jan 2008 23:06:13 -0600, Tom Sherman

may have said:

Werehatrack said:

On Tue, 29 Jan 2008 12:33:16 -0800 (PST), cmcanulty

may have said:

Is there anyplace I can find out what size chainwheels are available
in the different Bolt Circle Diameters? I have looked a lot and short
of just browsing all the online bike shops can't find out. Like is it
possible to put a <38 tooth chainring on a 130BCD? Possibly by
redrilling the holes? I am trying to get a super low gear and super
high gear on my folding bicycle. Or is there a BCD that would allow me
to have 2 chainrings, 1 with 53 teeth and one with 22? I am NOT using
a front derailleur, will shift manually, so tooth difference doesn't
matter. I want to achieve a super wide gear range of sub 18 to 125 or
so. It has a 9sp cassette on rear. I know to avoid the extreme cross
combinations, thanks. This is one of the few times Ricard Sheldon's
site didn't have the info or I didn't find it.

You're up against some problems here. First, to the best of my
knowledge, no manufacturer produces a front der that has a cage long
enough to accommodate a sprocket diameter difference that great....

I have run 62/52/39 chain-wheels with a long cage Shimano RSX front
derailer. The chain barely clears the crosspiece of cage when using the
"granny" ring, while the bottom of the cage plates barely clear the
outer ring. While the smaller radius of the 52T large ring will help
with derailer clearance, more than a 24T difference is unlikely to work
without a custom cage.

Cogent data.

And 53/22 is a 31T difference, well beyond what's supported with
off-the-shelf hardware.

--
My email address is antispammed; pull WEEDS if replying via e-mail.
Typoes are not a bug, they're a feature.
Words processed in a facility that contains nuts.

Werehatrack said:

On Tue, 29 Jan 2008 23:06:13 -0600, Tom Sherman

may have said:

Werehatrack said:

On Tue, 29 Jan 2008 12:33:16 -0800 (PST), cmcanulty
<[email hidden]> may have said:

> Is there anyplace I can find out what size chainwheels are available
> in the different Bolt Circle Diameters? I have looked a lot and short
> of just browsing all the online bike shops can't find out. Like is it
> possible to put a <38 tooth chainring on a 130BCD? Possibly by
> redrilling the holes? I am trying to get a super low gear and super
> high gear on my folding bicycle. Or is there a BCD that would allow me
> to have 2 chainrings, 1 with 53 teeth and one with 22? I am NOT using
> a front derailleur, will shift manually, so tooth difference doesn't
> matter. I want to achieve a super wide gear range of sub 18 to 125 or
> so. It has a 9sp cassette on rear. I know to avoid the extreme cross
> combinations, thanks. This is one of the few times Ricard Sheldon's
> site didn't have the info or I didn't find it.

You're up against some problems here. First, to the best of my
knowledge, no manufacturer produces a front der that has a cage long
enough to accommodate a sprocket diameter difference that great....

I have run 62/52/39 chain-wheels with a long cage Shimano RSX front
derailer. The chain barely clears the crosspiece of cage when using the
"granny" ring, while the bottom of the cage plates barely clear the
outer ring. While the smaller radius of the 52T large ring will help
with derailer clearance, more than a 24T difference is unlikely to work
without a custom cage.

Cogent data.

And 53/22 is a 31T difference, well beyond what's supported with
off-the-shelf hardware.

However, C. McCanulty states that he (she?) will not use a front
derailer, but will shift by hand. There would still be the problem of a
rear derailer that could wrap enough chain, and the addition problem of
keeping the chain on the chain-wheels without a front derailer.

Florian Schlumpf has a solution for two widely spaced gear ratios on the
crank, but it is heavy, expensive and requires custom chamfering of the
BB shell: <http://www.schlumpf.ch/md_engl.htm>.

--
Tom Sherman - Holstein-Friesland Bovinia
"And never forget, life ultimately makes failures of all people."
- A. Derleth

On Jan 30, 6:31 am, Tom Sherman <[email hidden]>

Quoted message said:

Werehatrack said:

On Tue, 29 Jan 2008 23:06:13 -0600, Tom Sherman
<[email hidden]> may have said:

Quoted message said:

Quoted message said:

Werehatrack wrote:
> On Tue, 29 Jan 2008 12:33:16 -0800 (PST), cmcanulty
> <[email hidden]> may have said:

Quoted message said:

Quoted message said:

>> Is there anyplace I can find out what size chainwheels are available
>> in the different Bolt Circle Diameters? I have looked a lot and short
>> of just browsing all the online bike shops can't find out. Like is it
>> possible to put a <38 tooth chainring on a 130BCD? Possibly by
>> redrilling the holes? I am trying to get a super low gear and super
>> high gear on my folding bicycle. Or is there a BCD that would allow me
>> to have 2 chainrings, 1 with 53 teeth and one with 22? I am NOT using
>> a front derailleur, will shift manually, so tooth difference doesn't
>> matter. I want to achieve a super wide gear range of sub 18 to 125 or
>> so. It has a 9sp cassette on rear. I know to avoid the extreme cross
>> combinations, thanks. This is one of the few times Ricard Sheldon's
>> site didn't have the info or I didn't find it.

Quoted message said:

Quoted message said:

> You're up against some problems here. First, to the best of my
> knowledge, no manufacturer produces a front der that has a cage long
> enough to accommodate a sprocket diameter difference that great....

Quoted message said:

Quoted message said:

I have run 62/52/39 chain-wheels with a long cage Shimano RSX front
derailer. The chain barely clears the crosspiece of cage when using the
"granny" ring, while the bottom of the cage plates barely clear the
outer ring. While the smaller radius of the 52T large ring will help
with derailer clearance, more than a 24T difference is unlikely to work
without a custom cage.

Quoted message said:

Cogent data.

Quoted message said:

And 53/22 is a 31T difference, well beyond what's supported with
off-the-shelf hardware.

However, C. McCanulty states that he (she?) will not use a front
derailer, but will shift by hand. There would still be the problem of a
rear derailer that could wrap enough chain, and the addition problem of
keeping the chain on the chain-wheels without a front derailer.

Florian Schlumpf has a solution for two widely spaced gear ratios on the
crank, but it is heavy, expensive and requires custom chamfering of the
BB shell: <http://www.schlumpf.ch/md_engl.htm>.

--
Tom Sherman - Holstein-Friesland Bovinia
"And never forget, life ultimately makes failures of all people."
- A. Derleth

a quick nonsense posing.

On Tue, 29 Jan 2008 23:31:07 -0600, Tom Sherman

may have said:

Werehatrack said:

On Tue, 29 Jan 2008 23:06:13 -0600, Tom Sherman

may have said:

I have run 62/52/39 chain-wheels with a long cage Shimano RSX front
derailer. The chain barely clears the crosspiece of cage when using the
"granny" ring, while the bottom of the cage plates barely clear the
outer ring. While the smaller radius of the 52T large ring will help
with derailer clearance, more than a 24T difference is unlikely to work
without a custom cage.

Cogent data.

And 53/22 is a 31T difference, well beyond what's supported with
off-the-shelf hardware.

However, C. McCanulty states that he (she?) will not use a front
derailer, but will shift by hand. There would still be the problem of a
rear derailer that could wrap enough chain, and the addition problem of
keeping the chain on the chain-wheels without a front derailer.

Thank you; I had meant to point out that the der serves two purposes,
and intending its exclusion may be a goal that will not be feasible.

Quoted message said:

Florian Schlumpf has a solution for two widely spaced gear ratios on the
crank, but it is heavy, expensive and requires custom chamfering of the
BB shell: <http://www.schlumpf.ch/md_engl.htm>.

A less foot-centric shifting method would make it more attractive to
me, but it's out of my budgetary range in any event.

--
My email address is antispammed; pull WEEDS if replying via e-mail.
Typoes are not a bug, they're a feature.
Words processed in a facility that contains nuts.

Werehatrack said:

...

Quoted message said:

Florian Schlumpf has a solution for two widely spaced gear ratios on the
crank, but it is heavy, expensive and requires custom chamfering of the
BB shell: <http://www.schlumpf.ch/md_engl.htm>.

A less foot-centric shifting method would make it more attractive to
me, but it's out of my budgetary range in any event.

I have only ridden a couple of times on bicycles and trikes [1] with
Schlumpf bottom brackets, but was able to shift while clipped into SPD
pedals with my size 43 feet. The large gearing jump is more
disconcerting, as it requires shifting most to way across the cassette
to avoid a huge change in cadence.

[1] The trike also had a Rohloff hub, which makes for quite a pricey
drive train.

--
Tom Sherman - Holstein-Friesland Bovinia
"And never forget, life ultimately makes failures of all people."
- A. Derleth

"Clive George" <[email hidden]> wrote in message
news:[email hidden]...

Quoted message said:

"A Muzi" <[email hidden]> wrote in message
news:[email hidden]...

Quoted message said:

130mm was designed to run as low as 39t. SR-Sakae made a 38 but, just

as

Quoted message said:

Quoted message said:

the 'cheater' 41t rings for classic Nuovo Record cranks, it may be
necessary to file the ends of the crank spider between the rings

if/where

Quoted message said:

Quoted message said:

it fouls the chain sideplates. (if you can find one)

TA make a 130mm 38t ring. Never had any difficulty getting hold of one

of

Quoted message said:

them.

cheers,
clive

I have them running on several Shimano 600/105 cranksets without any
problems. The TA 130mm 49T outer chainrings with the pins shift really
well with the 38T inners.

Chas.

On Jan 30, 5:55 am, Tom Sherman <[email hidden]>

Quoted message said:

Werehatrack said:

...

Quoted message said:

Florian Schlumpf has a solution for two widely spaced gear ratios on the
crank, but it is heavy, expensive and requires custom chamfering of the
BB shell: <http://www.schlumpf.ch/md_engl.htm>.

Quoted message said:

A less foot-centric shifting method would make it more attractive to
me, but it's out of my budgetary range in any event.

I have only ridden a couple of times on bicycles and trikes [1] with
Schlumpf bottom brackets, but was able to shift while clipped into SPD
pedals with my size 43 feet. The large gearing jump is more
disconcerting, as it requires shifting most to way across the cassette
to avoid a huge change in cadence.

[1] The trike also had a Rohloff hub, which makes for quite a pricey
drive train.

--
Tom Sherman - Holstein-Friesland Bovinia
"And never forget, life ultimately makes failures of all people."
- A. Derleth

I haven't worked out the gear inches with whatever sets of chainrings,
but I looked in the Schlumpf drive with Rohlofff and Shimano
internally geared hubs. With Rohloff it makes very little sense, as
the Schlumpf Drive essentially gives you four extra gears (through
admittedly at the top, where the Rohloff by itself is pretty grim,
being a close-ratio box aimed at perpendicular mountains), the rest
being very close to what you get without the pricey Schlumpf addition.
With the Shimano 8-speed hub, the Schlumpf mountain drive becomes a
*very* attractive proposition, money and custom frame aside, because
the combination essentially gives you six gears added on at the
bottom, giving a wider touring range than the Rohloff on its own, and
a more usable range, and less waste as only two gears of the Shimano/
Schlumpf combination totalling 16 are duplicated or so close to
existing gears as likely in practice not to be used. I can publish a
gear-inch table of the two combinations if anyone is interested. The
price of a Schlumpf/Shimano combination on the bike is near enough
comparable with a Rohloff installation on its own.

I have no experience of the Schlumpf in the metal; I'm considering it
for a stainless custom frame I'm planning.

Andre Jute
My education was not wasted. I'm just broadening it with Excel.

"cmcanulty" <[email hidden]> wrote in message
news:[email hidden]...

Quoted message said:

Is there anyplace I can find out what size chainwheels are available
in the different Bolt Circle Diameters? I have looked a lot and short
of just browsing all the online bike shops can't find out. Like is it
possible to put a <38 tooth chainring on a 130BCD? Possibly by
redrilling the holes? I am trying to get a super low gear and super
high gear on my folding bicycle. Or is there a BCD that would allow me
to have 2 chainrings, 1 with 53 teeth and one with 22? I am NOT using
a front derailleur, will shift manually, so tooth difference doesn't
matter. I want to achieve a super wide gear range of sub 18 to 125 or
so. It has a 9sp cassette on rear. I know to avoid the extreme cross
combinations, thanks. This is one of the few times Ricard Sheldon's
site didn't have the info or I didn't find it.

Not doable unless you make yourself a custom rear derailleur that can wrap
up enough chain. With your projected chainrings and an 11-34 cassette, even
if you never use the two outer cogs with the small chainring or the two
inner cogs with the large chainring, you still exceed the chain wrap
capacity of any available derailleur. Also, if you try to run without a
front derailleur, you will find the chain falling off quite frequently over
bumps, particularly in gears where the chainline is not perfect.

One of Sheldon Brown's bikes has 50-28 chainrings on TA Cyclotouriste
cranks. See http://sheldonbrown.org/hetchins/index.html. I have a bike using
46-26 chainrings on the same model crank with a 13-28 7-speed freewheel, and
it works well enough.

TA apparently still make the crank -
http://www.specialites-ta.com/produits/trans_gb.htm - but you will have
problems finding anyone who sells it or the chainrings for it. Quite a few
web merchants still show the cranks and chainrings as available, but the
last few times I have tried to buy chainrings for the TA and Sugino cranks I
have that use that pattern, the selection available is very limited.

Nick

Nick Payne said:

"cmcanulty" <[email hidden]> wrote in message
news:[email hidden]...

Quoted message said:

Is there anyplace I can find out what size chainwheels are available
in the different Bolt Circle Diameters? I have looked a lot and short
of just browsing all the online bike shops can't find out. Like is it
possible to put a <38 tooth chainring on a 130BCD? Possibly by
redrilling the holes? I am trying to get a super low gear and super
high gear on my folding bicycle. Or is there a BCD that would allow me
to have 2 chainrings, 1 with 53 teeth and one with 22? I am NOT using
a front derailleur, will shift manually, so tooth difference doesn't
matter. I want to achieve a super wide gear range of sub 18 to 125 or
so. It has a 9sp cassette on rear. I know to avoid the extreme cross
combinations, thanks. This is one of the few times Ricard Sheldon's
site didn't have the info or I didn't find it.

Instead of trying to use an extreme gap between the chainrings, you
might try using the Shimano Capreo system in the rear, which is designed
to give a wide gearing range for small-wheeled bikes. You have to use
the Capreo hub, because it is specially designed to accommodate the
9-tooth small cog on the Capreo cassette.

Check it out here: http://www.sheldonbrown.com/harris/k7.html#capreo

The Capreo cassette is a 9-26. If you're running 28-406 tires, you could
use a 110/74 BCD triple crank and put a 25T on the inside with a 54T in
the middle or outer position to give you a double. I'd use the middle,
even though you plan to shift it manually, to avoid the chain jamming
between the rings if it jumps off. But, using the outer would reduce
interference in the small/small range. Your choice. The 25/26 low gear
would give you 17.49 inches. Unfortunately, 25T is not a common ring
size. You could go down to a 24, at 16.79 inches, or up to a 26 at 18.19
inches.

The 54/9 doesn't reach your high gear goal, you'd have to go to a 61 or
62 to hit that (good luck finding rings that large). But a 54/9 would
give you a 109 inch top gear, which is pretty respectable. That's about
what a compact 50/12 with 23-622 tires would give you. You can spin out
that gear on a steep downhill (at about 35 mph), but for riding on the
flats it's plenty of gear.

Those BCD sizes are easy to find rings for. Sugino and Salsa both make a
pretty good selection of 110 and 74 BCD rings. Plenty of Sugino
cranksets with 110/74 bolt circles around, too.

You can get a 54T 110 BCD Sugino ring (the only 54 I found) here:
http://aebike.com/page.cfm?PageID=30&action=details&sku=CR1171

A selection of 74 BCD rings in 24-26 range can be found here:
http://aebike.com/page.cfm?PageID=30&action=list&category=203&type=T&searchtype=attributesearch&searchDropDown97=5-Bolt&searchDropDown99=74&searchDropDown2=&searchDropDown71=&searchDropDown102=&searchFrom96=24&searchTo96=26&gobutnsearch=Search

An inexpensive 110/74 crank can be found here:
http://aebike.com/page.cfm?PageID=30&action=details&sku=CR2388

A new Sugino XD300 with 46/36/26 rings would run about $50. You could
maybe reuse the 26 ring, but you'd have to replace the others.

You'd have to use an SGS mountain derailleur on the rear to take up that
much chain slack. I doubt you'd be able to find a front derailleur (it'd
be a triple if you could) that would shift that setup. Might be worth a
try, though.

Be prepared to experiment.

Good luck,
Mike Johnson

Michael Johnson said:

Nick Payne said:

"cmcanulty" <[email hidden]> wrote in message
news:[email hidden]...

Quoted message said:

Is there anyplace I can find out what size chainwheels are available
in the different Bolt Circle Diameters? I have looked a lot and short
of just browsing all the online bike shops can't find out. Like is it
possible to put a <38 tooth chainring on a 130BCD? Possibly by
redrilling the holes? I am trying to get a super low gear and super
high gear on my folding bicycle. Or is there a BCD that would allow me
to have 2 chainrings, 1 with 53 teeth and one with 22? I am NOT using
a front derailleur, will shift manually, so tooth difference doesn't
matter. I want to achieve a super wide gear range of sub 18 to 125 or
so. It has a 9sp cassette on rear. I know to avoid the extreme cross
combinations, thanks. This is one of the few times Ricard Sheldon's
site didn't have the info or I didn't find it.

Instead of trying to use an extreme gap between the chainrings, you
might try using the Shimano Capreo system in the rear, which is designed
to give a wide gearing range for small-wheeled bikes. You have to use
the Capreo hub, because it is specially designed to accommodate the
9-tooth small cog on the Capreo cassette.

Check it out here:http://www.sheldonbrown.com/harris/k7.html#capreo

The Capreo cassette is a 9-26. If you're running 28-406 tires, you could
use a 110/74 BCD triple crank and put a 25T on the inside with a 54T in
the middle or outer position to give you a double. I'd use the middle,
even though you plan to shift it manually, to avoid the chain jamming
between the rings if it jumps off. But, using the outer would reduce
interference in the small/small range. Your choice. The 25/26 low gear
would give you 17.49 inches. Unfortunately, 25T is not a common ring
size. You could go down to a 24, at 16.79 inches, or up to a 26 at 18.19
inches.

The 54/9 doesn't reach your high gear goal, you'd have to go to a 61 or
62 to hit that (good luck finding rings that large).

Why would you need any luck to find a 60, 61, 62, 63 chainring? Just
call up a tandem shop and order one. No luck needed, just money. Big
chainrings are somewhat common on tandems.

This tandem shop offers 60, 61, 62, 63 in 110mm bcd. And 60 in 130mm
bcd. Vuelta brand. I suspect your local bike shop can order Vuelta
brand rings from their parts distributors.
http://www.precisiontandems.com/catframepart.htm

But a 54/9 would

Quoted message said:

give you a 109 inch top gear, which is pretty respectable. That's about
what a compact 50/12 with 23-622 tires would give you. You can spin out
that gear on a steep downhill (at about 35 mph), but for riding on the
flats it's plenty of gear.

Those BCD sizes are easy to find rings for. Sugino and Salsa both make a
pretty good selection of 110 and 74 BCD rings. Plenty of Sugino
cranksets with 110/74 bolt circles around, too.

You can get a 54T 110 BCD Sugino ring (the only 54 I found) here:http://aebike.com/page.cfm?PageID=30&action=details&sku=CR1171

A selection of 74 BCD rings in 24-26 range can be found here:http://aebike..com/page.cfm?PageID=30&action=list&category=203&type=T&...

An inexpensive 110/74 crank can be found here:http://aebike.com/page.cfm?PageID=30&action=details&sku=CR2388

A new Sugino XD300 with 46/36/26 rings would run about $50. You could
maybe reuse the 26 ring, but you'd have to replace the others.

You'd have to use an SGS mountain derailleur on the rear to take up that
much chain slack. I doubt you'd be able to find a front derailleur (it'd
be a triple if you could) that would shift that setup. Might be worth a
try, though.

Be prepared to experiment.

Good luck,
Mike Johnson

Other than having the world's widest crossover gearing, what is the
point of this exercise? It's hard to imagine the rider and terrain
that could actually make use of an 18"-125" range on a folding
bike...

JG

aka Russell Seaton said:

...
Why would you need any luck to find a 60, 61, 62, 63 chainring? Just
call up a tandem shop and order one. No luck needed, just money. Big
chainrings are somewhat common on tandems....

My RANS Rocket (ISO 406-mm drive wheel) came stock with a
62/52/39-tooth, 130-mm BCD crank.

--
Tom Sherman - Holstein-Friesland Bovinia
"And never forget, life ultimately makes failures of all people."
- A. Derleth

JG said:

Other than having the world's widest crossover gearing, what is the
point of this exercise? It's hard to imagine the rider and terrain
that could actually make use of an 18"-125" range on a folding
bike...

My Earth Cycles Sunset Lowracer has a stock gear range of 1.55 to 9.58
meters development (19 to 120 gear inches). However, a recumbent needs
both lower and higher gear than an upright.

--
Tom Sherman - Holstein-Friesland Bovinia
"And never forget, life ultimately makes failures of all people."
- A. Derleth