quad chainring

Quoted message said:

I'm trying to find the best way of adding higher gears to our tandem.
Rear wheel was originally 6 speed 14-28 which I've just swapped for 7
speed, currently 13-28, but will probably fit SRAM 12-32.

The bigger problem is the 22/32/42 chainrings. The crankset (compact
triple, 94mm BCD) is in very good condition and would be expensive to
change. I can change the middle and the outer to get 22/36/50 which
would be OK from the gearing point of view, but would give large
jumps.

Big jumps at the front don't matter much when you have small jumps at the
rear. How about upgrading to 9 or 10 speed at the back?

Quoted message said:

I found this website

http://www.bikexprt.com/bicycle/tancrank.htm

which describes how to put a 4th chainring on the outside of a
crankset and this one

http://www.abundantadventures.com/mtfaq/frontderail/fr.derail.mods.html

which desribes how to modify a front mech to work with four
chainrings.

Any chance I could use these methods to add a 50T chainring (biggest I
can find in 94 BCD) to the outside? My guess is the crank will hit the
front mech, any views?

I'd expect that to be a problem too.

~PB

[email hidden] wrote:
.....

Quoted message said:

Any chance I could use these methods to add a 50T chainring (biggest I
can find in 94 BCD) to the outside? My guess is the crank will hit the
front mech, any views?

Chainline will be poor as well.

~PB

Pete Biggs said:

Quoted message said:

Any chance I could use these methods to add a 50T chainring (biggest I
can find in 94 BCD) to the outside? My guess is the crank will hit the
front mech, any views?

Chainline will be poor as well.

Yes, I know, and I'm more likely to neglect it on a tandem because I
can't glance down and see it.

You can get excellent chainline on a tandem by moving the front mech
etc to the captain's BB. Chain is then so long that it doesn't matter
what combinations you use as the change in angle is tiny.

Rob

[email hidden] wrote in news:1188978771.596089.148660
@y42g2000hsy.googlegroups.com:

Quoted message said:

I'm trying to find the best way of adding higher gears to our tandem.
Rear wheel was originally 6 speed 14-28 which I've just swapped for 7
speed, currently 13-28, but will probably fit SRAM 12-32.

The bigger problem is the 22/32/42 chainrings. The crankset (compact
triple, 94mm BCD) is in very good condition and would be expensive to
change. I can change the middle and the outer to get 22/36/50 which
would be OK from the gearing point of view, but would give large
jumps.

I found this website

http://www.bikexprt.com/bicycle/tancrank.htm

which describes how to put a 4th chainring on the outside of a
crankset and this one

http://www.abundantadventures.com/mtfaq/frontderail/fr.derail.mods.html

which desribes how to modify a front mech to work with four
chainrings.

Any chance I could use these methods to add a 50T chainring (biggest I
can find in 94 BCD) to the outside? My guess is the crank will hit the
front mech, any views?

I would just go for the 22-36-50 and fit a road front derailleur to do
the shifting. Big gaps on the front really don't matter - on tandems you
are far better using the cassette for gear changing as it changes better
under load than the front and just using the front to select the
appropriate range for the current terrain.

Another option, but it might wear rather quickly, would be to consider a
Capreo cassette and hub which goes down to a 9 tooth sprocket. Really
designed for folding bikes but certainly would give you a much higher
gear.

--
Tony

" I would never die for my beliefs because I might be wrong."
Bertrand Russell

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

Quoted message said:

I'm trying to find the best way of adding higher gears to our tandem.
Rear wheel was originally 6 speed 14-28 which I've just swapped for 7
speed, currently 13-28, but will probably fit SRAM 12-32.

The bigger problem is the 22/32/42 chainrings. The crankset (compact
triple, 94mm BCD) is in very good condition and would be expensive to
change. I can change the middle and the outer to get 22/36/50 which
would be OK from the gearing point of view, but would give large
jumps.

I found this website

http://www.bikexprt.com/bicycle/tancrank.htm

which describes how to put a 4th chainring on the outside of a
crankset and this one

http://www.abundantadventures.com/mtfaq/frontderail/fr.derail.mods.html

which desribes how to modify a front mech to work with four
chainrings.

Any chance I could use these methods to add a 50T chainring (biggest I
can find in 94 BCD) to the outside? My guess is the crank will hit the
front mech, any views?

Just go for the big jumps - we've got 24/38/50 on the road tandem and it's
not that bad.

One note : You're on the slippery slope of upgrading now. There are an awful
lot of people who do this, spending more on upgrades than they would have
getting something rather better in the first place, and they still have eg a
lower quality frame.

Consider how much you're spending, and consider cutting your losses sooner
rather than later.

cheers,
clive

Clive George said:

Just go for the big jumps - we've got 24/38/50 on the road tandem and it's
not that bad.

One note : You're on the slippery slope of upgrading now. There are an awful
lot of people who do this, spending more on upgrades than they would have
getting something rather better in the first place, and they still have eg a
lower quality frame.

Consider how much you're spending, and consider cutting your losses sooner
rather than later.

Yes, that's in the back of my mind all the time. This is a consciously
a cheap tandem to see if we like using a tandem. If we really take to
it, I'd like to get something better in the future, ideally a Pino,
but who knows.

I'm actually pleased with the quality of the thing, it rides very
well. I'm mystified by the provenance of the frame. It has felt fine
on everything we've done on it, it coped with a previous heavy team on
rough tracks, and it's light enough for me lift into the car by myself
without difficulty. Other bits are a mishmash, but at least decent if
not good.

The only thing that spoils our enjoyment is the gearing, which I'm
trying to change as cheaply as possible. Upgrade from 6 to 7 gears at
the back has been achieved for £2.20, the price at auction of an old
MTB that's in good condition, which will donate its STI shifter, rear
mech + wheel. Cassette was only 13-28, so will probably spend £15 on
replacing that with a 12-32. 8 speed would have been good, but I might
wait a long time to see one.

I didn't recognize the compact chainset (never had one before) until I
discovered my spare 48T chainring didn't fit, which was going to be my
major cheap gear upgrade, so now I'm looking at other possibilities.
Finding a 2nd hand bike with a 94 BCD 48/50T chainring seems highly
improbably. I'll have another look at cassettes with 11T sprockets.
Last time I looked I could only find ones that went up to the mid 20s
or the 11-34 megarange which has a huge jump to the 34 I don't like.
An 11T sprocket on the back might give enough of a boost to live with
the front chainrings for a while.

I see what I am doing as configuring rather than upgrading - if we'd
got a better 2nd hand one, there's still a fair chance the options
wouldn't suit us and we'd have to make some changes.

Rob

Tony Raven said:

I would just go for the 22-36-50 and fit a road front derailleur to do
the shifting. Big gaps on the front really don't matter - on tandems you
are far better using the cassette for gear changing as it changes better
under load than the front and just using the front to select the
appropriate range for the current terrain.

I find I have to shift the front quite a lot at the moment, probably
because 14-28 isn't a big enough range at the back. 12-32 should
improve this.

Quoted message said:

Another option, but it might wear rather quickly, would be to consider a
Capreo cassette and hub which goes down to a 9 tooth sprocket. Really
designed for folding bikes but certainly would give you a much higher
gear.

Interesting idea, I've never heard of these, not being in to folding
bikes. A quick google only found the 32 hole hub on sale in the UK,
but even with the 36H I'd be a bit worried about longevity. And ISTR
someone here making caustic remarks about the efficiency of 11T
sprockets, so I dread to think what they'd say about about 9T. But
thanks, always nice to hear of different approaches.

Rob

[email hidden] wrote in
news:[email hidden]:

Quoted message said:

Tony Raven said:

I would just go for the 22-36-50 and fit a road front derailleur to
do the shifting. Big gaps on the front really don't matter - on
tandems you are far better using the cassette for gear changing as it
changes better under load than the front and just using the front to
select the appropriate range for the current terrain.

I find I have to shift the front quite a lot at the moment, probably
because 14-28 isn't a big enough range at the back. 12-32 should
improve this.

Then consider revising your changing style - you need more anticipation and
planning on a tandem than a single. For example if you are coming down a
hill and about to hit an upslope it is worth first measuring your speed at
a comfortable cadence in the small/small combination. On a tandem you then
put it in small small at the bottom of the hill, wait till your speed drops
to the above measured one and then start pedalling, working steadily down
the rear gears as necessary. You wouldn't do this on a single but on a
tandem it can be very difficult to shift the front gear under load.
Similarly in other situations anticipate and be in the right front gear to
begin with and then use the rear gears to give you changes for local
variations as needed.

--
Tony

" I would never die for my beliefs because I might be wrong."
Bertrand Russell

Quoting <[email hidden]>:

Quoted message said:

The bigger problem is the 22/32/42 chainrings. The crankset (compact
triple, 94mm BCD) is in very good condition and would be expensive to
change. I can change the middle and the outer to get 22/36/50 which
would be OK from the gearing point of view, but would give large
jumps.

You might have a concern that in 94mm BCD the 50t would be insufficiently
stiff, which causes the chain to fall down the gap between it and the
middle ring. We definitely had this problem in 86mm Stronglight. It is
much easier to induce on a tandem, of course.
--
OPTIONS=name:Kirsty,menustyle:C,female,lit_corridor,standout,time,showexp,hilit
e_pet,catname:Akane,dogname:Ryoga,fruit:okonomiyaki,pickup_types:"!$?=/,scores:
5 top/2 around,color,boulder:0,autoquiver,autodig,disclose:yiyayvygyc,pickup_bu
rden:burdened,!cmdassist,msg_window:reversed,!sparkle,horsename:Rumiko,showrace

In news:[email hidden],
David Damerell <[email hidden]> tweaked the Babbage-Engine
to tell us:

Quoted message said:

You might have a concern that in 94mm BCD the 50t would be
insufficiently stiff, which causes the chain to fall down the gap
between it and the middle ring. We definitely had this problem in
86mm Stronglight. It is much easier to induce on a tandem, of course.

I've put in 2000-odd km on a 20/36/50 94/58 chainset in the past month or so
and haven't had any problems of this nature. Just the left crank attempting
to escape...

--
Dave Larrington
<http://www.legslarry.beerdrinkers.co.uk>
Mr. Charles Kennedy (Krankieburgh): Would the Prime Minister
care to comment on a report in today's Guardian that he: "arrived
late for a meeting with Jacques Chirac, smelling of alcohol, and
with body language suggesting a total disregard for the rights
of ethnic minorities, lone parents and laboratory animals"?

Quoting Dave Larrington <[email hidden]>:

Quoted message said:

David Damerell <[email hidden]> tweaked the Babbage-Engine

Quoted message said:

You might have a concern that in 94mm BCD the 50t would be
insufficiently stiff, which causes the chain to fall down the gap
between it and the middle ring. We definitely had this problem in
86mm Stronglight. It is much easier to induce on a tandem, of course.

I've put in 2000-odd km on a 20/36/50 94/58 chainset in the past month or so
and haven't had any problems of this nature.

But not on a tandem? And, perhaps, also on a design of bike that doesn't
encourage stomping on the pedals? It's obviously a lot easier with twice
as much lard to pull the chain into that gap.

Sure, you won't have that problem if you slack off all the way before
shifting up, but you're going to push it sometimes.

Mind you, it might just be that the difference between 86mm and 94mm is
enough.
--
OPTIONS=name:Kirsty,menustyle:C,female,lit_corridor,standout,time,showexp,hilit
e_pet,catname:Akane,dogname:Ryoga,fruit:okonomiyaki,pickup_types:"!$?=/,scores:
5 top/2 around,color,boulder:0,autoquiver,autodig,disclose:yiyayvygyc,pickup_bu
rden:burdened,!cmdassist,msg_window:reversed,!sparkle,horsename:Rumiko,showrace

In news:[email hidden],
David Damerell <[email hidden]> tweaked the Babbage-Engine
to tell us:

Quoted message said:

Quoting Dave Larrington <[email hidden]>:

Quoted message said:

David Damerell <[email hidden]> tweaked the
Babbage-Engine

Quoted message said:

You might have a concern that in 94mm BCD the 50t would be
insufficiently stiff, which causes the chain to fall down the gap
between it and the middle ring. We definitely had this problem in
86mm Stronglight. It is much easier to induce on a tandem, of
course.

I've put in 2000-odd km on a 20/36/50 94/58 chainset in the past
month or so and haven't had any problems of this nature.

But not on a tandem? And, perhaps, also on a design of bike that
doesn't encourage stomping on the pedals? It's obviously a lot easier
with twice as much lard to pull the chain into that gap.

Sure, you won't have that problem if you slack off all the way before
shifting up, but you're going to push it sometimes.

Mind you, it might just be that the difference between 86mm and 94mm
is enough.

And possibly because the 86 mm "Strong"light chainrings have a well-deserved
reputation for being made of cheese. I know of a Several of people who have
borken chainrings while using said cranks on fixers, myself included.

--
Dave Larrington
<http://www.legslarry.beerdrinkers.co.uk>
Mushroom! Mushroom!