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Dahon Impulse P21 is a Dream Bike

Started by Elisa Francesca Roselli · · Last activity · 13 posts · 1,454 views

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UK and Europe
Published
15 November 2004
Last activity
12 December 2004
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Elisa Francesca Roselli
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  1. A while ago I posted a thread about the horoscope of a new bike, a Dahon
    Impulse P21, that was causing me a lot of grief. However, since the bike
    had not been delivered in a rideable condition, but needed further
    intervention from a cycling professional to make it road ready, I
    deemed, with the help of the forum, that the horoscope could be recast
    for the time I picked him up from the shop. This must optimally have
    been around 11:30 on November 6th. In the event, I paid for Flyzipper's
    assembly at 11:25 and rode my first few yards on him at 11:38. This was
    just in time for a cycling holiday I was planning to take from 9th to
    14th November in the Touraine region of France where I used to live.

    This bike is a winner!

    Flyzipper has 20" wheels, weighs 12 kg, and is equipped with a fabulous
    21-speed SRAM DualDrive shifter - three speeds in the front hub and
    seven on the rear derailleur. It is a whole new world of comfort to have
    so light and small a bicycle! After a year of struggling with Behemoth,
    a 20 kg Dutch monster whose geometry has never really suited me, I feel
    as though I have finally come home. Flyzipper starts in a breath and
    rides extremely straight. Weight on the handlebars is minimal. I was
    right to choose this model with its straight T-bar handles, as this puts
    so much less stress on my wrists than Behemoth's swept-back bars. My
    wrists tend to start aching after only about 20 mins on Behemoth. On
    Flyzipper, I rode more than 4 hours on my first big day out and didn't
    even have to put on my gloves. I feel much more balanced on Flyzipper
    for not teetering so high from the ground. And the SRAM is the best
    shifter I have dealt with so far. All 21 gears are useable, but most of
    the time, I just change between the 3 front speeds. When I have a
    stretch of long, clear riding ahead, I up the rear shifter a notch or
    two; when the ground is hilly or the paths are shorter or a stop-start
    situation threatens, I put the rear shifter into a neutral 4th gear. I
    have not yet tried the granny gears but will soon have occasion to do
    so. What is great about this system is that it cuts down on needless
    complexity. Behemoth has a Nexus 7 shifter, meaning that split-second
    decisions have to be made between all 7 gears. With Flyzipper, there are
    only 3, but each of those can be modulated through a whole spectrum of
    shades when there is leisure.

    I am amazed at the speed of this lil critter! He seems to be the fastest
    of my bikes. Can it be that the advantage of lightness compensates for
    the smaller wheels? My second outing in the Touraine was my first
    accompanied cycle. My friend was on a 21-gear bike with 700mm wheels. I
    was in 2/5 for most of our flat 7.5 km stint and she was in 2/7, but she
    had trouble keeping up with me! We finished the circuit in just half an
    hour, despite a nasty head-wind.

    The Impulse P21 folds more easily and compactly than the Speed TR,
    another model I considered. I worried that the addition of lights would
    compromise the folding action, but this didn't happen. OTOH, the counter
    did pop off when I had the bike folded. Fortunately I spotted it in time
    and didn't lose it, but I now recommend pocketing it before folding. I
    made a little mark on the seat-post to show how far I need to pull it
    out to have the seat at the right height. As for the front bar, once
    adjusted, the folding action affects neither its height nor its angle,
    so this does not have to be recalculated every time.

    Unlike the Speed TR, the Impulse has a chain guard, and to my delight,
    after a week of stopping against lamp-posts and walls, I discovered a
    small strut. It does not come with lights, but I discovered from
    Behemoth that I hate dynamos anyway. I fitted Flyzipper with lights that
    run on ordinary rechargeable AA batteries such as I already use for my
    TV earphones and am well equipped to handle.

    A few small demerits. It took me a week to figure out how to fold in the
    pedals, and I reproach the manual for giving no clear instructions on
    that point. (You have to push them _in_, towards their axis, then they
    can be pivoted flat.) The magnetic catch that holds the bike together
    when folded is rather weak and the two halves easily come apart. The
    bike is extremely lumbersome to carry in its folded condition. Unlike
    even the heaviest luggage which today almost always has wheels, the
    Dahon needs to be hoiked and heaved over the smallest distance. I
    quickly learned that, on train platforms, the folding must happen at the
    last possible minute, when you are just in front of the door of your
    wagon, and you must unfold the minute you alight from the train. At
    Tours St Pierre station, elevators are only supposed to be used by the
    disabled. I'm afraid I had to disregard this rule, because if I had
    tried the stairs with that bike and my bags, I would have risked a heart
    attack. (But why anyone should be expected to carry enormous
    portmanteaus up and down great flights of stairs remains for me one of
    the great ineptitudes of station architecture...)

    The baggage rack is small and carrying capacity is limited. I used only
    my one small Vaude pannier. I have various over-the-rack double panniers
    but they hang too low to the ground. Also, I did nearly kick the pannier
    off several times with my heel, so it could not have been any wider.
    However, the Speed TR model has a special, high-set baggage rack for
    touring that can be ordered for the Impulse as an add-on, should I
    project a longer trip.

    The most important drawback is that this bike is totally unupported in
    France. Unlike Behemoth, who needs practically no maintenance, Flyzipper
    has parts that rain and my weight and rougher riding could damage. I was
    paranoid about getting a flat. Why are there no local sellers? Is Dahon
    one of those American firms that has made a policy not to sell to "Old
    Europe" out of redneck jingoism? From the fascinated glances Flyzipper
    was attracting from all sides, I cannot doubt that there would be a good
    market. The policy of the SNCF, the French Railway System, towards bikes
    is hugely incoherent, but suffice it to say that many trips cannot be
    made with a full-size bike. On the other hand, few folding models are
    available in this generally bike-friendly country, and none with the
    touring capacities of my Flyzipper.

    I can't wait for the Spring!

    EFR
    Ile de France

  2. On Mon, 15 Nov 2004 17:55:51 +0100,

    Elisa Francesca Roselli said:

    accompanied cycle. My friend was on a 21-gear bike with 700mm wheels. I
    was in 2/5 for most of our flat 7.5 km stint and she was in 2/7, but she
    had trouble keeping up with me! We finished the circuit in just half an
    hour, despite a nasty head-wind.

    Good to see you are getting on well with it (despite the horoscope
    wierdness). At that speed (and maybe a little faster if there is no
    head-wind) you should be fine for getting to and from work if or when
    they move - as you seem to be much faster than on your old bike.

    --
    Andy Leighton => [email hidden]
    "The Lord is my shepherd, but we still lost the sheep dog trials"
    - Robert Rankin, _They Came And Ate Us_

  3. Elisa Francesca Roselli said:

    This bike is a winner!

    *snip review*

    Nice write up, thanks. Can you tell us how long it takes you to fold
    and unfold the bike?

    --

    Email address is spam trapped, to reply directly remove the beverage.

  4. Elisa Francesca Roselli said:

    .....Dahon Impulse P21....... This bike is a winner!

    Quoted message said:

    ....... Weight on
    the handlebars is minimal. I was right to choose this model with its
    straight T-bar handles, as this puts so much less stress on my wrists
    than Behemoth's swept-back bars.......

    I guess this is one clue towards sorting Behemoth - new handlebars -
    assuming that bike is staying with you.

    Quoted message said:

    A few small demerits........... The magnetic catch that
    holds the bike together when folded is rather weak and the two halves
    easily come apart.

    A bit of webbing or velcro strap to tie the two bits together can fix that
    easily. So light and cheap that it can be left attached to handlebar or
    somewhere else which is convinient.

    Quoted message said:

    The baggage rack is small and carrying capacity is limited.

    Carradice (a UK cycle luggage maker of legends) make some bags adapted to
    fit Dahon's (or, I think, have spotted a niche to sell their standard bags
    to Dahon owners).
    http://www.carradice.co.uk/dahon-sqr-products.htm

    Digging around Carradice's site also shows an "uplift" mount for a
    conventional saddle bag (wider designs rather than the longer SQR bag
    shapes), which fits onto a SQR mounting block:
    http://www.carradice.co.uk/sqr-products.htm

    Otherwise, I wonder if its possible to get the Brompton front luggage
    bracket fitted to a Dahon ? Its something which would need some thought, so
    not one for someone without knowledge of both machines. If it can be fitted
    there are a range of useful front bags made for Bromptons.

    Quoted message said:

    The most important drawback is that this bike is totally unupported in
    France. ..... I was paranoid about getting a flat. Why are there no local
    sellers? Is Dahon one of those American firms that has made a policy
    not to sell to "Old Europe" out of redneck jingoism?

    Probably as likely that French cycle shops cannot cope with unusual bicycles
    ? In the UK most cycle shops have little out of the ordinary.
    Even so, Dahon are available in the UK, arguably easier to find than a UK
    made Brompton folder.
    Dahon.com suggests these are the French importer:
    http://www.josealvarez.fr/public/ who in turn hint that "Bouticycle" are the
    dealer outlet(s) http://www.bouticycle.com

    Tyres shouldn't be too hard - Schwalbe make a range of types of the required
    sizes, covering everything from extreme racing through urban sensible, to
    mud-plugging off-road.

    - Nigel

    --
    NC - Webmaster for http://www.2mm.org.uk/
    Replies to newsgroup postings to the newsgroup please.

  5. Elisa Francesca Roselli said:

    The most important drawback is that this bike is totally unupported in
    France. Unlike Behemoth, who needs practically no maintenance, Flyzipper
    has parts that rain and my weight and rougher riding could damage. I was
    paranoid about getting a flat. Why are there no local sellers? Is Dahon
    one of those American firms that has made a policy not to sell to "Old
    Europe" out of redneck jingoism?

    I can't imagine any American firm, or American Government official, ever
    exhibiting anything like jingoism. You must have us confused with some
    other country...

    --

    David L. Johnson

    __o | It is a scientifically proven fact that a mid life crisis can
    _`\(,_ | only be cured by something racy and Italian. Bianchis and
    (_)/ (_) | Colnagos are a lot cheaper than Maserattis and Ferraris. --
    Glenn Davies

  6. Elisa Francesca Roselli said:

    Flyzipper has 20" wheels, weighs 12 kg, and is equipped with a fabulous
    21-speed SRAM DualDrive shifter - three speeds in the front hub and
    seven on the rear derailleur.

    No, the 3 speed hub is at the back and the derailleur mounts onto it.

    Quoted message said:

    so. What is great about this system is that it cuts down on needless
    complexity. Behemoth has a Nexus 7 shifter, meaning that split-second
    decisions have to be made between all 7 gears. With Flyzipper, there are
    only 3, but each of those can be modulated through a whole spectrum of
    shades when there is leisure.

    But the Dualdrive is more complex, so you seem to be misunderstanding
    something somewhere... With the Nexus 7 if you want to change up,
    change up, if you want to change down, change down. There's no "split
    second decisions" you have to make at all, so I think basically it's all
    a problem in your head. The point of a DD is more finely graduated
    gears and a greater overall range than a hub, but it really is more
    complex because you've got two independent shifting mechanisms. If it
    works for you then that's Good, but for future reference don't get hung
    up on hubs on their own being more complex to use, because they're not!

    Quoted message said:

    I am amazed at the speed of this lil critter! He seems to be the fastest
    of my bikes. Can it be that the advantage of lightness compensates for
    the smaller wheels?

    Lightness makes you quicker and as Dr, Moulton proved back in the 60s,
    small wheels aren't nearly the problem that lots of people seem to
    assume as long as you have a reasonably good surface, and "reasonably
    good" certainly doesn't require a billiard table.

    Quoted message said:

    paranoid about getting a flat. Why are there no local sellers? Is Dahon
    one of those American firms

    Dahon are Far Eastern, and are the largest manufacturer of folding bikes
    in the world.

    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/

  7. In uk.rec.cycling NC <[email hidden]> wrote:

    : I guess this is one clue towards sorting Behemoth - new handlebars -
    : assuming that bike is staying with you.

    Sadly, I guess that this is a clue towards sorting Behemoth. That bike
    is too bike. This isn't a fixable problem.

    --
    Arthur Clune PGP/GPG Key: http://www.clune.org/pubkey.txt
    "Blogs are neither necessary nor sufficient for evil to triumph.
    They're just what we call an enabling technology" - Danny O'Brien

  8. Arthur Clune said:

    Sadly, I guess that this is a clue towards sorting Behemoth. That bike
    is too bike. This isn't a fixable problem.

    Why be sad about it? The new bike suits the rider better even for jobs
    where the roadster is nominally better (why anyone would prefer battery
    lights to a dynohub on an urban utility bike and how anyone can find a
    Nexus 7 more complex than a DualDrive are both beyond me, but if that's
    how Elisa feels then that's how she feels) so get some money and space
    back and sell it on.

    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/

  9. Peter Clinch said:
    Elisa Francesca Roselli said:

    Flyzipper has 20" wheels, weighs 12 kg, and is equipped with a fabulous
    21-speed SRAM DualDrive shifter - three speeds in the front hub and
    seven on the rear derailleur.

    No, the 3 speed hub is at the back and the derailleur mounts onto it.

    Quoted message said:

    so. What is great about this system is that it cuts down on needless
    complexity. Behemoth has a Nexus 7 shifter, meaning that split-second
    decisions have to be made between all 7 gears. With Flyzipper, there are
    only 3, but each of those can be modulated through a whole spectrum of
    shades when there is leisure.

    But the Dualdrive is more complex, so you seem to be misunderstanding
    something somewhere... With the Nexus 7 if you want to change up,
    change up, if you want to change down, change down. There's no "split
    second decisions" you have to make at all, so I think basically it's all
    a problem in your head. The point of a DD is more finely graduated
    gears and a greater overall range than a hub, but it really is more
    complex because you've got two independent shifting mechanisms. If it
    works for you then that's Good, but for future reference don't get hung
    up on hubs on their own being more complex to use, because they're not!

    Hi, I meant to post earlier and then deleted the OP's original
    message. I think she could benefit from reading Sheldon's write up on
    gear shifting. It talks of maintaining a reasonably even cadence.
    Something that Elisa may not be doing. So, for the OP, here is the
    link:
    http://www.sheldonbrown.com/gears.html

    And here is the the link, that includes that article, as well as many
    others. It is titled "Articles For New Cyclists", but I believe there
    is info that is helpful to more than just "new" cyclists.
    http://www.sheldonbrown.com/beginners/index.html

    Life is Good!
    Jeff

  10. Call me Bob said:

    Nice write up, thanks. Can you tell us how long it takes you to fold
    and unfold the bike?

    It doesn't take long. I'm not sure of the time, since I wasn't clocking
    myself and was more concerned to do it right than to do it fast.
    Basically you fold down the front bar, shunt in the seat and fold it in
    half in the middle. A few seconds, I suppose.

    EFR
    Ile de France

  11. "Elisa Francesca Roselli" <[email hidden]> wrote in message
    news:[email hidden]...

    Quoted message said:

    This bike is a winner!

    Flyzipper has 20" wheels, weighs 12 kg, and is equipped with a fabulous
    21-speed SRAM DualDrive shifter -
    EFR
    Ile de France

    Glad you like it, and were able to manipulate it's birth date so favourably,
    but "Flyzipper" is the thing we (male) Brits use to keep the breeze out of
    our trousers, so I guess it loses something in the translation.

    --

    Martin Bulmer

  12. Martin Bulmer said:

    Glad you like it, and were able to manipulate it's birth date so favourably,
    but "Flyzipper" is the thing we (male) Brits use to keep the breeze out of
    our trousers, so I guess it loses something in the translation.

    I'm perfectly aware that this name describes something small, straight and fast
    that lives between the legs!
    ;°>

    EFR
    Ile de France

  13. Peter Clinch said:
    Arthur Clune said:

    Sadly, I guess that this is a clue towards sorting Behemoth. That


    bike

    Quoted message said:
    Quoted message said:

    is too bike. This isn't a fixable problem.

    Why be sad about it? The new bike suits the rider better even for


    jobs

    Quoted message said:

    where the roadster is nominally better (why anyone would prefer


    battery

    Quoted message said:

    lights to a dynohub on an urban utility bike and how anyone can find


    a

    Quoted message said:

    Nexus 7 more complex than a DualDrive are both beyond me, but if


    that's

    Quoted message said:

    how Elisa feels then that's how she feels) so get some money and


    space

    Quoted message said:

    back and sell it on.

    I looked into a dynohub for a Dahon Speed that I ordered. By the time I
    would get the wheel with the dynohub, and a set of lights, I was
    looking at well over $300. I ordered a lithium-ion rechargeable battery
    powered light for less than 1/2 the cost, with twice the intensity.
    Another advantage is that it serves as a flashlight for night time
    repairs.

    The Dual Drive is indeed more complex.

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