Comparing gears

Judith said:

What I am really trying to figure out is whether I *need* a six speed
Brommie or will a 3-speed be enough? I think, from reading what
people here have said, I'll go for the 12% reduction anyway, but I'd
like to be able to go faster than my current bike allows. Also, I
feel that a 3-speed would be less likely to fail/be damaged etc

You can convert the three to the six for a parts cost not much different
from the price difference. I would suggest getting a 3-speed with an
agreement with the shop that if you decide you need the six they will
fit it for the price difference.

--
Tony

"I did make a mistake once - I thought I'd made a mistake but I hadn't"
Anon

Judith said:

I currently have a 26 inch wheel, 3-speed Sturmey Archer
tourer/road-bike. I do not know how to work out the gear ratio for
gears I cannot see - ie inside the hub.

If I *could* work out my existing gear ratios, can I directly relate
that to the ratios on the Brompton?

Yes. And more to the point, you can measure the gears relatively
easily. Tools: 1 piece of chalk and a bit of road or pavement, and
one tape measure, preferably a good sized one.

Mark the road with the chalk where one of the tyres touches the
road. Move the bike along 1 full turn of the pedals and mark the
road there, repeating this for each gear. That is the gear
measurement as given in meters.

Then relate those numbers to the Brompton's gears, which are:

3 speed 3.71m 5.05m 6.87m
6 speed 3.22m 3.71m 4.38m 5.05m 5.96m 6.87m

Don't forget the 3 speed can be changed by 12 or 18% down, and the
6 by 12% down.

Quoted message said:

Or ..... and this is the bit I
don't know how to ask ..... will the gears "feel" different because of
the different sized wheels and shape of the bikes?

Possibly a little, depending on the riding position and the way you
ride the bike. For example, Bromptons really don't respond well to
climbing while stood up out of the saddle, so that would probably
seem like harder work than on another bike with the same gears.
But overall an Xm gear is an Xm gear.

Quoted message said:

What I am really trying to figure out is whether I *need* a six speed
Brommie or will a 3-speed be enough?

"need" is a big word... One speed is, strictly speaking, all you
need, and is now a standard option on the Brom, but not one I'd
take. I know for experience that a 3 with the 18% reduction is
enough for me in Dundee, which has its share of quite respectable
hills. OTOH I'm probably a fitter cyclist than you at this point
in time and a bigger engine makes quite a difference. Having said
that, there's no shame in walking up a big hill until you have got
the puff to take it directly.

Quoted message said:

I think, from reading what
people here have said, I'll go for the 12% reduction anyway, but I'd
like to be able to go faster than my current bike allows.

The easy way to do that is work on the engine. Even with the -18%
reduction on a 3 it's quite capable of a good turn of speed on the
flat if the tyres are running at 100 psi and you're got a bit of
practice spinning highish cadences. Better to learn higher
cadences than just mash bigger gears. It is fairly easy to spin it
out down any sort of Real Hill, but that's what gravity is for. On
the flat I find 3rd is for tailwinds and hard work.

Quoted message said:

Also, I
feel that a 3-speed would be less likely to fail/be damaged etc

The 6 appears to be quite reliable and is built in to the degree it
shouldn't suffer too much from untoward damage. But I didn't
bother with it because I didn't need the extra complexity. One
point to note is that all you need for a 6 can be bought as a
retro-fit kit (~£65 IIRC) and added to any 3 from the last few
years, so if you do save your money for now you can always upgrade
without losing much.

Quoted message said:

If I could get ANY 2nd-hand Brompton I'm sure it would be fine .....
but I want to get things right if I'm paying full whack.

If you do get a 2nd hand it's likely to be a pre-Mk 3, and that
can't be retrofitted with the 6 speed kit.

Quoted message said:

PS How *DO* you work out SA gear ratios?

measure them directly, as above.

Quoted message said:

Perhaps I'll have to count how many times the wheel spins for each
turn of the crank.

That's basically the same as above, though the chalk marks make it
more accurate and rule out any accidental freewheeling.

Pete.
--
Peter Clinch Medical Physics IT Officer
Tel 44 1382 660111 ext. 33637 Univ. of Dundee, Ninewells Hospital
Fax 44 1382 640177 Dundee DD1 9SY Scotland UK
net [email hidden] http://www.dundee.ac.uk/~pjclinch/

Judith said:

I'm still toying with the idea of buying a Brompton. If only there
was a very stupid person offering a second-hand one for sale cheaply
in the local freebie paper.

I currently have a 26 inch wheel, 3-speed Sturmey Archer
tourer/road-bike. I do not know how to work out the gear ratio for
gears I cannot see - ie inside the hub.

If I *could* work out my existing gear ratios, can I directly relate
that to the ratios on the Brompton? Or ..... and this is the bit I
don't know how to ask ..... will the gears "feel" different because of
the different sized wheels and shape of the bikes?

The gear is directly proportional to the tyre size, so if you had the
same sprocket sizes on a bike with 26" wheels and on a bike with 20"
wheels, the 20" wheel bike would be geared significantly lower.

Generally, small wheel bikes make it easy to get low gears for
climbing, but it's difficult to get high gears for pedaling downhill
without using unusually large (and hard to find) chainwheels.

Quoted message said:

What I am really trying to figure out is whether I *need* a six speed
Brommie or will a 3-speed be enough?

If 3 was enough on one bike, it will be enough on another. You can
easily change the gearing on a Sturmey-Archer hub by installing a
larger (or smaller) sprocket to lower (raise) all of the gears.
Replacement sprockets shouldn't cost more than 8-10 quid.

If you do go to a much larger one, you may also need to replace the
chain with a longer one, but chains are also cheap.

Quoted message said:

PS How *DO* you work out SA gear ratios? Sheldon's gear calculator
lists loads of different SA hubs and I don't know what I have.

You almost certainly have an AW or equivalent, with gears of 4:3, 1:1,
and 3:4. The model number will be stamped on the hubshell, all you
need to do is look.

See also: http://sheldonbrown.com/english
+------------------------------------------------------------+
| Aerodynamics don't make a difference. |
| How much do you hate riding that your ten mile ride |
| has to take you fifteen seconds less? - Grant Petersen |
| http://sheldonbrown.com/podcasts.html#grant |
+------------------------------------------------------------+
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

Quoted message said:

Quoted message said:

PS How *DO* you work out SA gear ratios? Sheldon's gear calculator
lists loads of different SA hubs and I don't know what I have.

You almost certainly have an AW or equivalent, with gears of 4:3, 1:1,
and 3:4. The model number will be stamped on the hubshell, all you
need to do is look.

You're right. I've just been out to the shed and I can see it's an
AW.

As for whether 3 gears have been enough for me so far..... I'd like
one more gear at each end of my current range. Around town they're
fine, but I could do with being able to drop down a little more on
very long hills and being able to go a bit faster on long flats (and
gentle downhill slopes).

I wouldn't be using the Brompton as my main long-distance bike, so the
3 gears - with an option to upgrade - sounds fine.

Thanks
Judith

Judith said:

I currently have a 26 inch wheel, 3-speed Sturmey Archer
tourer/road-bike. I do not know how to work out the gear ratio for
gears I cannot see - ie inside the hub.

In a typical Sturmey 3-speed, middle gear is direct drive, top gear is
direct drive multiplied by 4/3, and bottom gear is direct drive multiplied
by 3/4. Gear ratios are most commonly measured in inches, calculated by
multiplying the diameter of the driven wheel by the ratio of the number of
teeth on the chainring to the number of teeth on the sprocket.

Quoted message said:

If I *could* work out my existing gear ratios, can I directly relate
that to the ratios on the Brompton? Or ..... and this is the bit I
don't know how to ask ..... will the gears "feel" different because of
the different sized wheels and shape of the bikes?

A bike with smaller wheels will generally have a bigger chainring to give
an overall gearing equivalent to a big-wheeled bike. If two bikes with
different wheel sizes have the same chainring, sprocket, and hub gear, the
smaller-wheeled bike will have gearing that is lower by the ratio of wheel
sizes.

Quoted message said:

PS How *DO* you work out SA gear ratios? Sheldon's gear calculator
lists loads of different SA hubs and I don't know what I have.
Perhaps I'll have to count how many times the wheel spins for each
turn of the crank.

By far the most common Sturmey 3-speed was the AW, giving the ratios I
listed above.

James Thomson

Peter Clinch said:

Quoted message said:

Also, I
feel that a 3-speed would be less likely to fail/be damaged etc

The 6 appears to be quite reliable and is built in to the degree it
shouldn't suffer too much from untoward damage. But I didn't
bother with it because I didn't need the extra complexity. One
point to note is that all you need for a 6 can be bought as a
retro-fit kit (~£65 IIRC) and added to any 3 from the last few
years, so if you do save your money for now you can always upgrade
without losing much.

I hadn't realised this. That sounds like the easy answer.

All I need to figure out now is L3 (with dynamo hub) or T3 .... but
you seem to think the front luggage options are good enough? It seems
odd to me to have weight on the handle bars.

Judith

Judith wrote:
...........

Quoted message said:

Or ..... and this is the bit I
don't know how to ask ..... will the gears "feel" different because of
the different sized wheels and shape of the bikes?

A smaller wheel effectively makes the same gear lower. Wheel size can be
included in gear calculations to help with comparisons between different
bikes. Using "gear inch" units helps for that. See
http://sheldonbrown.com/gears/

Shape/stiffness of the bike may make a small difference to what gears you
need as a more efficient bike can be ridden faster for the same effort. But
weight is a more important factor. A heavier bike will benefit from having
a slightly lower bottom gear, or much lower if carrying much heavier
luggage.

Quoted message said:

What I am really trying to figure out is whether I *need* a six speed
Brommie or will a 3-speed be enough?

Sorry I can't answer that, but in my general experience with bikes, I've
never regretted getting more gears (or lower gears, except for one exception
on a road bike). More chance of being safe than sorry that way.

~PB

Judith said:

Peter Clinch said:

Quoted message said:

Also, I
feel that a 3-speed would be less likely to fail/be damaged etc

The 6 appears to be quite reliable and is built in to the degree it
shouldn't suffer too much from untoward damage. But I didn't
bother with it because I didn't need the extra complexity. One
point to note is that all you need for a 6 can be bought as a
retro-fit kit (~£65 IIRC) and added to any 3 from the last few
years, so if you do save your money for now you can always upgrade
without losing much.

I hadn't realised this. That sounds like the easy answer.

All I need to figure out now is L3 (with dynamo hub) or T3 .... but
you seem to think the front luggage options are good enough? It seems
odd to me to have weight on the handle bars.

Again you can always add the luggage rack later but its of limited use
IMO because with stuff on it you can't fold the bike. The front pannier
system works a treat and is where I would recommend starting. I just
have the shopping basket and throw whatever - waterproofs, briefcase,
rucksack, shopping... - into it but you may prefer one of the other options.

--
Tony

"I did make a mistake once - I thought I'd made a mistake but I hadn't"
Anon

Judith said:

All I need to figure out now is L3 (with dynamo hub)

Also remeber that a dynohub can be retrofitted. It will cost you
more than an up-front fitting because you'll need a wheel build
too, but it can be done (until recently all dynohub Bromptons were
retrofitted units, mine is one of them).

Quoted message said:

you seem to think the front luggage options are good enough? It seems
odd to me to have weight on the handle bars.

The weight isn't on the handlebars, the pannier mounts onto a block
on the main frame, independently of the bars, so there's much less
effect than you may have imagined on the steering.

But is the front luggage setup good enough on its own? Well,
depends on what you're carrying, but just how much can go at either
end[1] is illustrated here...
http://users.belgacom.net/bn886679/brompton/chapters/Luggage.html

You can get more on if you have the rear carrier, but whether
that's useful depends on the jobs in hand. I don't miss it because
if I have a cargo job I have the 8 Freight for that, but I can
certainly imagine riders for whom the rear rack would be
invaluable. I imagine you could wangle one from a Brompton dealer
as a retrofit, but have no idea of the cost.

Pete.

[1] Dave Halliday is rumoured to have earned a personal exception
to the Brompton frame guarantee!
--
Peter Clinch Medical Physics IT Officer
Tel 44 1382 660111 ext. 33637 Univ. of Dundee, Ninewells Hospital
Fax 44 1382 640177 Dundee DD1 9SY Scotland UK
net [email hidden] http://www.dundee.ac.uk/~pjclinch/

Tony Raven said:

You can convert the three to the six for a parts cost not much different
from the price difference. I would suggest getting a 3-speed with an
agreement with the shop that if you decide you need the six they will
fit it for the price difference.

Nigel Cliffe just sent me this (he can't post News where he is now,
and can't de-mung Judith's address).
********************************************** quote starts
According to both the Folding Society and Velovision websites, from
January 2005, Brompton removed the 3-6 speed easy upgrade path.
This is the statement from December 2004 from Brompton reproduced
on the Folding Society webpages, I've seen nothing since which
changes things:

"From January 1 2005, all Brompton three speed bikes will use the
new Sunrace Sturmey Archer 3 speed and Brompton 6 speed bikes will
use the Sram Sachs 3 speed hub. The performance of the two hubs is
similar. The SRAM 3 speed has a gear range of 1.33:1:0.75. The new
Sunrace Sturmey Archer hub has a range of 1.36:1:0.73 and is 50
grams heavier. Both hubs fit a newly designed Universal rear frame:
dual applicability being made possible through a combination of
washers.

Brompton owners or customers considering a Brompton, will need to
keep in mind that upgrading from 3 to 6 speed version will now no
longer be possible without the expense of buying a new wheel and
hub. This is because the Brompton derailleur system does not work
with the Sturmey Archer hub."
********************************************** quote ends

So it's stll possible, but will cost much more than £65.

I'd taken the gear rations in my post from Brompton's own web site,
but they don't appear to have updated it as the basic ratios given
are the same between 3 and 6 speeds there.

Pete.
--
Peter Clinch Medical Physics IT Officer
Tel 44 1382 660111 ext. 33637 Univ. of Dundee, Ninewells Hospital
Fax 44 1382 640177 Dundee DD1 9SY Scotland UK
net [email hidden] http://www.dundee.ac.uk/~pjclinch/

Judith said:

Peter Clinch said:

Quoted message said:

Also, I
feel that a 3-speed would be less likely to fail/be damaged etc

The 6 appears to be quite reliable and is built in to the degree it
shouldn't suffer too much from untoward damage. But I didn't
bother with it because I didn't need the extra complexity. One
point to note is that all you need for a 6 can be bought as a
retro-fit kit (~£65 IIRC) and added to any 3 from the last few
years, so if you do save your money for now you can always upgrade
without losing much.

I hadn't realised this. That sounds like the easy answer.

Except you can't do it anymore !

The cheap retro upgrade has not been possible since Jan 2005 when Brompton
changed the hub on the 3-speed from Sachs to Sturmey, but left the 6-speed
using Sachs. The 6-speed bits only work with a Sachs hub. The upgrade to 6
speed now requires a new rear hub building into the wheel (info in Brompton
press release on the Folding Society website, also in post which Pete made
on my behalf earlier today).
I guess the upgrade is likely to cost £250 rather than £65, though you will
have a spare 3-speed hub to sell at the end of the process.

--
Nigel Cliffe,
Webmaster at http://www.2mm.org.uk/

On Mon, 3 Oct 2005 19:22:47 +0100, "Nigel Cliffe" <[email hidden]>

Quoted message said:

One

Quoted message said:

Quoted message said:

point to note is that all you need for a 6 can be bought as a
retro-fit kit (~£65 IIRC) and added to any 3 from the last few
years, so if you do save your money for now you can always upgrade
without losing much.

I hadn't realised this. That sounds like the easy answer.

Except you can't do it anymore !

The cheap retro upgrade has not been possible since Jan 2005 when Brompton
changed the hub on the 3-speed from Sachs to Sturmey, but left the 6-speed
using Sachs. The 6-speed bits only work with a Sachs hub. The upgrade to 6
speed now requires a new rear hub building into the wheel (info in Brompton
press release on the Folding Society website, also in post which Pete made
on my behalf earlier today).
I guess the upgrade is likely to cost £250

Eeek!

Quoted message said:

rather than £65, though you will
have a spare 3-speed hub to sell at the end of the process.

But I wouldn't sell it. I'd keep it forever in my come-in-handy box
(with all the other junk!)

I phoned my local Brompton supplier (as listed on the Brompton
website) today. They have a C3E and a M6R Plus in stock. I think the
C3E would be a false economy but I think I'll visit to compare a
"fully featured" Brommie against a "cheap" one. I presume the M6R
Plus dynamo is NOT a hub dynamo..... that's why it's sooooooo cheap!
(£635 on http://www.cycle-heaven.co.uk/folding_bikes.html). Something
I have noticed in the last few days is how many webpages devoted to
folding bikes there are.

Someone has suggested I get a Birdy instead ...... but if I'm not
going to get a Brompton, I'll probably save the cash and get a Dahon.
Too much choice!

Judith

Peter Clinch said:

Quoted message said:

you seem to think the front luggage options are good enough? It seems
odd to me to have weight on the handle bars.

The weight isn't on the handlebars, the pannier mounts onto a block
on the main frame, independently of the bars, so there's much less
effect than you may have imagined on the steering.

Yes, I see now. I've never had an open basket on a bike but it seems
like a nice, simple idea. I'm not sure why it's 58 quid but in for a
penny in for a pound!

I would not be using the bike as a load carrier, but would not want to
have to use a rucksack even for small loads eg a few groceries. I
have always had a rear rack and a saddle bag or panniers, so I suppose
that is what seems "right" to me. However, a well-balanced basket/bag
on the front would be fine.

Quoted message said:

But is the front luggage setup good enough on its own? Well,
depends on what you're carrying, but just how much can go at either
end[1] is illustrated here...
http://users.belgacom.net/bn886679/brompton/chapters/Luggage.html

Another interesting and amusing Brompton website. Ta.

Judith

Judith said:

Yes, I see now. I've never had an open basket on a bike but it seems
like a nice, simple idea. I'm not sure why it's 58 quid but in for a
penny in for a pound!

If you want a more traditional effect, you might consider speaking to
David Hembrow: http://homepage.ntlworld.com/hembrow/bicycle.html.

Jon

Judith said:

Yes, I see now. I've never had an open basket on a bike but it seems
like a nice, simple idea. I'm not sure why it's 58 quid but in for a
penny in for a pound!

In defence of the price it's not just a bag, but includes the mounting
block and an alloy frame that supports the bag and is removable so you
can lash outsize loads directly that don't fit in the bag.

In material terms it's still overpriced, but what you're really paying
for is the design excellence: it works /very/ well and I don't think
I've ever heard much of a word against Brompton's bags except Guy
whingeing a bit that they won't keep out water if submerged.

Quoted message said:

I would not be using the bike as a load carrier, but would not want to
have to use a rucksack even for small loads eg a few groceries.

It does that no problems at all.

Pete.
--
Peter Clinch Medical Physics IT Officer
Tel 44 1382 660111 ext. 33637 Univ. of Dundee, Ninewells Hospital
Fax 44 1382 640177 Dundee DD1 9SY Scotland UK
net [email hidden] http://www.dundee.ac.uk/~pjclinch/

Judith said:

Quoted message said:

I guess the upgrade is likely to cost £250

Quoted message said:

Eeek!

This seems a bit steep... 65 for the upgrade kit, let's say 40 for a
wheel and a 3 speed hub... are they /really/ £150? (I don't know)

But if it is that much it brings it into line with adding a Schlumpf,
which would extend the range of gearing rather than add intermediate
steps between the main shifts. Whether that's better depends on your
particular use, but it would suit me better.

Quoted message said:

I phoned my local Brompton supplier (as listed on the Brompton
website) today. They have a C3E and a M6R Plus in stock. I think the
C3E would be a false economy but I think I'll visit to compare a
"fully featured" Brommie against a "cheap" one.

Consensus here is that if you can afford anything else then the C3 is
indeed a false economy. Note that when you're comparing a lot of the
price difference is in less good componentry which won't necessarily
make itself obvious until it wears out in rather less time. The tyres
on a test might not all be pumped up to the 100 psi the Brompton and
Schwalbe tyres can do, but the C3's Raleigh tyres can only manage 60
IIRC, which makes a tangible difference to Whizz factor.

Quoted message said:

Someone has suggested I get a Birdy instead ...... but if I'm not
going to get a Brompton, I'll probably save the cash and get a Dahon.

Dahon's come in at a range of prices including Serious Money for very
respectable bits of kit, so you're not necessarily saving money.

Pete.
--
Peter Clinch Medical Physics IT Officer
Tel 44 1382 660111 ext. 33637 Univ. of Dundee, Ninewells Hospital
Fax 44 1382 640177 Dundee DD1 9SY Scotland UK
net [email hidden] http://www.dundee.ac.uk/~pjclinch/

On Tue, 04 Oct 2005 08:47:33 +0100, Jon Senior

jon_AT_restlesslemon_DOT_co_DOT_uk said:

Quoted message said:

Yes, I see now. I've never had an open basket on a bike but it seems
like a nice, simple idea. I'm not sure why it's 58 quid but in for a
penny in for a pound!

If you want a more traditional effect, you might consider speaking to
David Hembrow: http://homepage.ntlworld.com/hembrow/bicycle.html.

I like the map basket.

Judith

Sorry for the delay however I am not a regular here.
You probably have it by now🙂

Quoted message said:

Quoted message said:

3 speed 3.71m 5.05m 6.87m
6 speed 3.22m 3.71m 4.38m 5.05m 5.96m 6.87m
Don't forget the 3 speed can be changed by 12 or 18% down, and the
6 by 12% down.

Quoted message said:

As for whether 3 gears have been enough for me so far..... I'd like
one more gear at each end of my current range.

Well, with the 6 speed you do get a lower one at the bottom
however top is still the same.

Here are the options, this is hard to follow and may be line wrapped.
#3 3.71 5.05 6.87
#3 -12 3.31 4.51 6.13
#3 -18 2.81 3.82 5.20

#6 3.22 3.71 4.38 5.05 5.96 6.87
#6 -12 2.88 3.31 3.91 4.51 5.32 6.13

Quoted message said:

Quoted message said:

As for whether 3 gears have been enough for me so far..... I'd like
one more gear at each end of my current range.

Well, with the 6 speed you do get a lower one at the bottom
however top is still the same.

Here are the options, this is hard to follow and may be line wrapped.
#3 3.71 5.05 6.87
#3 -12 3.31 4.51 6.13
#3 -18 2.81 3.82 5.20

#6 3.22 3.71 4.38 5.05 5.96 6.87
#6 -12 2.88 3.31 3.91 4.51 5.32 6.13

That makes sense.

Thanks
Judith