38 rear gear with a 20 front gear - Page 2

"Willy Smallboy" <soreass@yahoo.com> wrote in message
news:ml6o40hur0k3l2268lmghrogiaer466ctk@4ax.com...
> has anyone got a SunTour 14-34 rear to work with a 20-32-
> 42 Suntour ?? got the 38 on eBay and was told that I need
> a AG der or Duet (?). Best to find someone that got this
> working.
>
> I have a 34 rear and a 22 front on a 27" bike that works
> but I would like to get the lowest gear possible (I have a
> bad right leg) to build a 26" or 700c
>
> thanks
>

Don't forget that you can lace any size rim to your rear hub
and as long as the cranks don't hit the ground then you're
good to go. Consider lacing a 20" rim to your rear hub. When
this is combined w/ your 38 tooth rear and 20t front, you
will be able to climb mount everest using the little piggy
that stayed home!

And when your leg gets better please do consider a normal
bike because this would obviously be a solution to your
(hopefully temporary) handicap.

Dave

"Willy Smallboy" <soreass@yahoo.com> wrote in message
news:ml6o40hur0k3l2268lmghrogiaer466ctk@4ax.com...
> has anyone got a SunTour 14-34 rear to work with a 20-32-
> 42 Suntour ?? got the 38 on eBay and was told that I need
> a AG der or Duet (?). Best to find someone that got this
> working.
>
> I have a 34 rear and a 22 front on a 27" bike that works
> but I would like to get the lowest gear possible (I have a
> bad right leg) to build a 26" or 700c
>
> thanks
>

Don't forget that you can lace any size rim to your rear hub
and as long as the cranks don't hit the ground then you're
good to go. Consider lacing a 20" rim to your rear hub. When
this is combined w/ your 38 tooth rear and 20t front, you
will be able to climb mount everest using the little piggy
that stayed home!

And when your leg gets better please do consider a normal
bike because this would obviously be a solution to your
(hopefully temporary) handicap.

Dave

"Willy Smallboy" <soreass@yahoo.com> wrote in message
news:ml6o40hur0k3l2268lmghrogiaer466ctk@4ax.com...
> has anyone got a SunTour 14-34 rear to work with a 20-32-
> 42 Suntour ?? got the 38 on eBay and was told that I need
> a AG der or Duet (?). Best to find someone that got this
> working.
>
> I have a 34 rear and a 22 front on a 27" bike that works
> but I would like to get the lowest gear possible (I have a
> bad right leg) to build a 26" or 700c
>
> thanks
>

Don't forget that you can lace any size rim to your rear hub
and as long as the cranks don't hit the ground then you're
good to go. Consider lacing a 20" rim to your rear hub. When
this is combined w/ your 38 tooth rear and 20t front, you
will be able to climb mount everest using the little piggy
that stayed home!

And when your leg gets better please do consider a normal
bike because this would obviously be a solution to your
(hopefully temporary) handicap.

Dave

"Bob Taylor" <ritaylor1@mchsi.com> wrote:

> I used a freewheel with this 38 tooth cog and a Huret
> Duopar rear derailleur on my 1985 Cannondale ST400 touring
> bike. This combination worked just fine but I should
> mention that this Cannondale has a very long derailleur
> tab. Bikes with the more usual tab length may not work
> with this combination.

Duopars were rated for a 38 tooth big sprocket, and a mighty
52 tooth wrap.

The tab length is an interesting point. The OP might
consider trying a modern mtb derailleur (typically rated to
34t) with an extended tab.

James Thomson

"David Damerell" <damerell@chiark.greenend.org.uk> wrote:

> You're looking for the SRAM "Dual Drive" hubs; HU2591 in
> 36-hole. Sheldon sells them, amongst others.
>
> One of these will effect a considerably greater reduction
> - .73:1 - than switching a 34 for a 38.

One point of caution: most hub gears specify a minimum
chainring:sprocket ratio, as excessive input torque can lead
to damage. I appreciate that the OP has an injury that
limits the loads he can apply.

James Thomson

Willy Smallboy <soreass@yahoo.com> wrote in message news:<ml6o40hur0k3l2268lmghrogiaer466ctk@4ax.com>...
> has anyone got a SunTour 14-34 rear to work with a 20-32-
> 42 Suntour ?? got the 38 on eBay and was told that I need
> a AG der or Duet (?). Best to find someone that got this
> working.
>
> I have a 34 rear and a 22 front on a 27" bike that works
> but I would like to get the lowest gear possible (I have a
> bad right leg) to build a 26" or 700c
>
> thanks

Try this link:

http://abundantadventures.com/quads.html

It requires the use of a 110/74mm bolt pattern triple crank.
You can use the triple adapter, or the quad, or even the
triple as a quad. I depends if the crank has seperate
spacers for the inner ring or if the spacers are built into
the crank. I have an XTR 5 bolt crank that I have ran a 17
ring with a 34 rear cog. It was great for climbing very
steep paved roads. But off road, it was almost too low to be
rideable. It was difficult to keep the momentum up on rough
dirt trails (it was easy to fall over). Off road, I find a
19 tooth ring to be about the limit with a 34 rear cog.

I also ran a 48,36,20 with a 11x28 cassette on a
recumbent. It worked great for a hilly century ride. I
have yet to get a quad setup to work well. Since you need
a longer BB axle, you need a crank with a very low Q
factor, like an old Ritchy or Sugino. You also need
friction shifting for the front.

God luck...

russellseaton1@yahoo.com (Russell Seaton) wrote in message news:<e90052be.0403090752.5bf21bd6@posting.google.com>...
> > >
> > > We're talking about a difference of 1.8 gear inches on
> > > the 700C wheeled bike between 20x34 and 20x38. And a
> > > difference of 1.5 gear inches on the 26" 1.25" width
> > > tire bike between 20x34 and 20x38. Not enough
> > > difference to matter. Your current low gear of 22x34
> > > on a 27" wheel bike gives 17.5 gear inches.
> >
> > Dear Russell,
> >
> > When the gear-inches are so small, it's hard to remember
> > that apparently tiny differences become important. You
> > may have lost sight of the forest for the trees.
> >
> > Given the same crank length, rear wheel size, and front
> > sprocket teeth, replacing a 34-tooth rear cog with a 38-
> > tooth will provide an 11.8% increase in overall
> > mechanical advantage, which is likely to be quite
> > noticeable on steep hills.
> >
> > Carl Fogel
>
> Dear Carl,
>
> When the gear inches are so small, one must remember to
> disregard the percentage change and look at the real
> numbers. Very similar to buying 100 shares of a penny
> stock and getting a 100% return. $1 or $2 makes no
> difference. In contrast, having 1 share of Berkshire and
> getting a 10% return, you can afford two Record equipped
> pro bikes. Two of the cheaper pro bikes anyway.
>
> Going from a 22x34, which the question asker already has,
> to a 22x38, gives a decrease of 1.9 gear inches. Too small
> of a difference to matter.

Dear Russell,

I'm afraid that it matters exactly 38/34ths, no matter what
the size of the rear wheel is.

A percentage change in leverage (mechanical advantage) is
relentlessly indifferent. The difference between a foot-
pound differs from a ten-inch-pound roughly as a kg-meter
differs from a kg-90cm. Double the length of a two-inch
lever and you get twice the mechanical advantage, which is
why stubby little allen keys benefit from small absolute
increases in length.

Here's how the financial analogy actually works out. Whether
we buy 100 shares of stock at $1 each, or just a single
share at $100, both kinds of investment yield exactly the
same profit if the price per share rises 10%.

The profit on each $1 stock is only a dime, not the
ten dollars of the $100 version, but a hundred dimes
add up to $10.

Similarly, the absolute gear-inch difference in how far the
wheel rolls for a 38 versus a 34 rear cog is aboslutely
tiny, like the dime profit. But there are so many tiny
advantages that they add up to exactly the same as a 380
versus a 340, if such cogs existed.

The gears are really just an endless series of levers
rotating around a common center and combined by a chain
(think of each tooth as the end of a lever).

A lever 38 units long always offers the same mechanical
advantage over a lever 34 units long. It converts a small
force (our arm pushing down on the car-jack) over a large
distance (the jack-handle moves two feet) into a large force
(enough to raise a car) over a short distance (the car rises
only a quarter of an inch). force spreads the

No matter what the rear wheel size may be, we pedal 38 times
to cover a given distance with a 38-tooth cog, spreading the
work out over 4 more pedal cycles than a 34-tooth cog.

Another way to see why it's the percentage that matters is
is to use not gear-inches, but gear-football-fields. The gear-
inch calculations will always work out to show that a 34 cog
goes about 12% further than a 38 tooth cog for each turn of
the pedal, an inch or two for a normal wheel.

An inch or two doesn't sound like much. But convert it into
football fields and you'll find that 34 football fields
versus 38 football fields is around 400 extra yards over a
distance of about two miles. The percentage remains the
same, but now it's expressed on a scale that we can more
easily appreciate.

Carl Fogel

A shimano tourney megarange might work they are only $12.
There is a man named frank berto who wrote a book called the
dancing chain about the history of derailers if any knows he
does I will try to find his email adress for you.

For a 26" tire:

Dual drive with 34T with 20T ring gets you to : 11.2 gear inches
Dual drive with 38T with 20T ring gets you to : 10.0 gear inches

Not sure what the smallest available Schlumpf Chainring is, I know they have a 29.

Schlumpf Mountain Drive 29T + Dual drive with 34T 6.5 gear inches (extreme overkill)
Schlumpf Mountain Drive 29T + Dual drive with 38T 5.8 gear inches

I assume there must be a rder that handles 38T since Sun made those 38T freewheels.

Spicer Industries makes a cassette chainring adapter so that you can put 58bcd or 74bcd chainring on a cassette/single speed rear hub splines. These are primarily used in 2 speed fixed gear mountain bike applications (2 chainrings up front, to cogs in back at least on a chainring). If you find a rder that can handle more than 38T, you should really be able to get a ratio through the floor.

http://www.spicercycles.com/index.cg..._desc=Mountain

Another option would be a Shimano Nexus 7 or SRAM S7 internal gear hub with the Spicer adapter putting a chainring

Shimano Nexus internal gear hub 7 with 20T ring and 24T sprocket: 13.7 gear inches.

The expensive Rohloff internal gear hub with 20T ring and 18T sprocket: 8.1 gear inches

I’d start out with the dual drive 11/34 Megarange cassette and 20T granny chainring. If you need more, add the Spicer then Schlumpf parts.

artisticwill@worldnet.att.net (rocketman58) wrote in message news:<70ce0d5a.0403091155.53b286ec@posting.google.com>...
> Willy Smallboy <soreass@yahoo.com> wrote in message
> news:<ml6o40hur0k3l2268lmghrogiaer466ctk@4ax.com>...
> > has anyone got a SunTour 14-34 rear to work with a 20-32-
> > 42 Suntour ?? got the 38 on eBay and was told that I
> > need a AG der or Duet (?). Best to find someone that got
> > this working.
> >
> > I have a 34 rear and a 22 front on a 27" bike that works
> > but I would like to get the lowest gear possible (I have
> > a bad right leg) to build a 26" or 700c
> >
> > thanks
>
> Try this link:
>
> http://abundantadventures.com/quads.html
>
> It requires the use of a 110/74mm bolt pattern triple
> crank. You can use the triple adapter, or the quad, or
> even the triple as a quad. I depends if the crank has
> seperate spacers for the inner ring or if the spacers are
> built into the crank. I have an XTR 5 bolt crank that I
> have ran a 17 ring with a 34 rear cog. It was great for
> climbing very steep paved roads. But off road, it was
> almost too low to be rideable. It was difficult to keep
> the momentum up on rough dirt trails (it was easy to fall
> over). Off road, I find a 19 tooth ring to be about the
> limit with a 34 rear cog.
>
> I also ran a 48,36,20 with a 11x28 cassette on a
> recumbent. It worked great for a hilly century ride. I
> have yet to get a quad setup to work well. Since you need
> a longer BB axle, you need a crank with a very low Q
> factor, like an old Ritchy or Sugino. You also need
> friction shifting for the front.
>
> God luck...

Dear Rocketman and Willy,

Here are a few RPM values for 2045 mm ATB tires and 2124 mm
700c tires for 3 to 4 mph. I used the gears that have been
mentioned. The lower you go on the table, the lower the
gearing and the faster you spin to maintain 3 or 4 mph,
which is a fair walking pace on level ground.

2045 mm 175 mm 2124 mm 175 mm ATB crank road
crank front rear rpm@ rpm@ mech rpm@ rpm@ mech
teeth teeth 3mph 4mph advt 3mph 4mph advt

22t 34t 61 81 1.203 59 78 1.250 22t 38t 68 91 1.077 65 87
1.118 19t 34t 70 94 1.039 68 90 1.079 17t 34t 79 105
0.930*** 76 101 0.966 17t 38t 88 117 0.832 85 113 0.864 22t
50t 89 119 0.818 86 115 0.850

*** "good on pavement, easy to fall over in dirt"

The overall mechanical advantage (feet the pedal moves per
foot of rear wheel roll) is shown for 175 mm cranks, which
are fairly common. Using a smaller ATB wheel and tire lowers
the gearing.

At around 80-100 rpm at 3-4 mph on an ATB tire, Rocketman
says that steep pavement is good, but that falling is a
danger on dirt. This seems quite plausible.

At this point, the mechanical advantage has dropped below
1.00 and the rider's feet on the pedals are going slightly
further than his rear wheel is rolling. He might well find
that he could push the bike just as fast.

Lower gearing than this will be noticeably slower than walking--
90 to 120 rpm for 3 to 4 mph is faster than typical paces
per minute for that speed.

Carl Fogel

On Wed, 10 Mar 2004 04:15:29 GMT, meb
<usenet-forum@cyclingforums.com> wrote:
>If you find a rder that can handle more than 38T, you
>should really be able to get a ratio through the floor.

A custom derailer hanger ought to make any large-capacity
rder handle the >38T.
--
Rick Onanian

On 9 Mar 2004 22:10:16 -0800, carlfogel@comcast.net (Carl Fogel)
wrote:
>At this point, the mechanical advantage has dropped below
>1.00 and the rider's feet on the pedals are going slightly
>further than his rear wheel is rolling. He might well find
>that he could push the bike just as fast.

IIRC, the OP has a bum leg and is pedalling with only that
leg. Presumably, walking or walking while pushing a bike
with that leg is unpleasant or very difficult. Better to
roll very slowly than to stand still...of course, at the
low, difficult-balance speeds, the balance may be further
thrown off by the one-legged pedalling.
--
Rick Onanian

carlfogel@comcast.net (Carl Fogel) wrote in message news:<8bbde8fc.0403092210.7a864f67@posting.google.com>...

> Here are a few RPM values for 2045 mm ATB tires and 2124
> mm 700c tires for 3 to 4 mph. I used the gears that have
> been mentioned. The lower you go on the table, the lower
> the gearing and the faster you spin to maintain 3 or 4
> mph, which is a fair walking pace on level ground.
>
> 2045 mm 175 mm 2124 mm 175 mm ATB crank road
> crank front rear rpm@ rpm@ mech rpm@ rpm@
> mech teeth teeth 3mph 4mph advt 3mph 4mph
> advt
>
> 22t 34t 61 81 1.203 59 78 1.250 22t 38t 68 91 1.077 65 87
> 1.118 19t 34t 70 94 1.039 68 90 1.079 17t 34t 79 105
> 0.930*** 76 101 0.966 17t 38t 88 117 0.832 85 113 0.864
> 22t 50t 89 119 0.818 86 115 0.850
>
> *** "good on pavement, easy to fall over in dirt"
>
> The overall mechanical advantage (feet the pedal moves per
> foot of rear wheel roll) is shown for 175 mm cranks, which
> are fairly common. Using a smaller ATB wheel and tire
> lowers the gearing.
>
> At around 80-100 rpm at 3-4 mph on an ATB tire, Rocketman
> says that steep pavement is good, but that falling is a
> danger on dirt. This seems quite plausible.
>
> At this point, the mechanical advantage has dropped below
> 1.00 and the rider's feet on the pedals are going slightly
> further than his rear wheel is rolling. He might well find
> that he could push the bike just as fast.
>
> Lower gearing than this will be noticeably slower than walking--
> 90 to 120 rpm for 3 to 4 mph is faster than typical paces
> per minute for that speed.
>
> Carl Fogel

The problem with using such low gearing off road occurs
mostly on rougher sections of steep trails. It it often
dificult to maintain a constant rpm when you are responding
to changing terrain. With such low gearing you can drop to 1
or 2 mph with a slight drop in cadence. At that point, you
are better off walking.

Such gearing can be a lot of fun. You can amaze you fellow
cyclist as you spin past them as they are walking up a steep
hill. Super low gears can be a lot of fun in low speed
contests at local cycling events. They are also very nice on
a recumbent trike (you can't fall over).

Shorter cranks typically work better with the lower gears as
well. They make it easier to maintain a higher cadence.

Getting back to the original post, I would probably just go
with an older compact crank running 44,32,20 chainrings,
with a 12x34 9speed XT cassette. This should be low enough
for any paved hill. I run the same cassette with a 41,30,20
chainring setup on my MTB. On by road bike, I run a 48,36,24
chainring set with a 12x27 9speed cassette.

I have used the shimano mr40 derailer with a 13 15 18 21 24
29 34 on the back and a 20 32 42 on the front it worked fine
the the pulley was not close to the cogs it looks like it
will clime a 38 easly. Frank berto wrote about the 38 tooth
cog set in bicycling magazine about 1981 here is his email
address fberto@ix.netcom.com

Carl Fogel wrote:

> ... At the even more extreme ratio of a 20 front x 50
> rear, your foot actually moves farther than the rear
> wheel rolls. The ratio is 0.77, meaning that for every
> foot that you crank the pedal, the rear wheel moves only
> about 9 inches.
>
> You'd probably find it easier and faster to walk next to
> the bike than to use such an extreme ratio. Its only use
> will be if your leg problems are so bad that you can't
> walk up the slope.
>
> Even then, balance would present a problem. It's hard
> enough to balance a smoothly pedalled bike heading uphill
> at such low gearing. An uneven power stroke would make
> balancing even more difficult....

Dear Carl,

The obvious solution is to add a third wheel. For example,
an 11-34 cassette and a SRAM Dual Drive hub on a 406-mm
wheel combined with a 44-32-22 MTB crank on a trike would
have a gear range of 9 to 106 gear inches, or 2.2 mph at 80
rpm in low gear. This would allow an average rider to pull a
heavy load up almost any hill found on paved roads.

Tom Sherman - Quad Cities (Illinois Side)