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Folding dilemas...

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  1. Smudge
    Member

    Well, as some of the twitterati know already, I now have an old Brompton T3 sat in the front room B-)
    The good news is that whilst it is a little scruffy and well used, it is basically sound (and arrived at the right price!)
    The bad news is that either my current folder (lovely Dahon Helios SL) or the Brompton will have to be sold soon to restore "S-1".

    I've tried the Brommie today on the big hill back from the station and tbh it's a bit brutal. Max effort still resulted in having to walk the last 20m or so.
    I can stand up and power on the Brommie which I can't on the Dahon, but then the Dahon is lighter, faster and has a much larger spread of gears. Otoh the Brommie has pretty much unlimited spares availability and is infinitely customisable...

    Hmmmm tough choices!! :-/

    Posted 12 years ago #

  2. wee folding bike
    Member

    You might be able to lower the gearing on the Brompton.

    Do you know how many teeth are on the chainring and sprocket?

    Smaller tyres can drop the effective gearing too.

    If it was made after early 2001 you can probably convert it to a 6 speed.

    Posted 12 years ago #

  3. BikeFan
    Member

    Contact this guy http://www.tillercycles.co.uk/page6.html about re-gearing Bromptons. Scroll down to "Lower gearing for all Bromptons (1,2,3,6, 8 and 11 speed)" for more information.

    Not that I know anything about Bromptons, he featured in an article in a magazine earlier this year. He has the only bike repair shop on a barge that I know of - maybe one needs to start on the Union Canal and berth alongside Zazou?

    Posted 12 years ago #

  4. Smudge
    Member

    Ok finally got Smudge minor to calm down and go to sleep(!)
    Thanks for the replies.
    The sprockets are 50t front 14t rear with a Sturmey-Archer 3 speed "AW" hub on the back. It's a 1998 model so a 1/2" x 1/8" chain.

    I guess I either need to learn to push instead of spinning or fit a new chain and sprockets with the newer (1/2" x 3/32") size. :-/

    Posted 12 years ago #

  5. splitshift
    Member

    "smudge minor !" good to hear alls well mate,cant really help with your folding dilemas, last folder i had was a raleigh stowaway !I still owe you a tube ! see you out there !
    Scott

    Posted 12 years ago #

  6. Uberuce
    Member

    I'd look into a bigger rear sprocket. Unless there's some folder witchcraft going on, the hub'll take any standard S-A cog, which go up to 20t.

    Posted 12 years ago #

  7. wee folding bike
    Member

    There is indeed some folder witchcraft. Big sprockets will start to grind the inside of the RHS chain stay.

    There is a 15t sprocket available for the SRAM 6 speed which has the Sturmey Archer 3 tit spline pattern but I don't know if the 3 speed transmission works OK with that. I've never used it on a 3 speed set up but I do have it on a couple of 6 speed wheels. The spacing might be different. OTOH it might work just fine.

    http://www.sjscycles.co.uk/brompton-sprocket-15t-r-2-mm-sram-6-spd-for-3-32-inch-chain-iso-qrspr15dr-prod22346/

    You can get a 44t chainring for about £33 which will drop your current gearing by 12%. That's a fairly simple way round the issue. You can run a 1/8" chain on a 3/32" chainring. I don't think they make any 1/8" chainrings anymore.

    http://www.sjscycles.co.uk/brompton-44t-chainwheel-only-3-32-qcw44-prod4825/

    A cheaper option is to build up some muscle…

    Posted 12 years ago #

  8. Smudge
    Member

    Thanks all, decision made, the Brommie stays and the Dahon sadly must find a new home (sniff, I shall miss upsetting the faux roadies on it!).
    First batch of refurb parts ordered for the Brompton, time for a cuppa and a think about the gearing options now :-)

    Posted 12 years ago #

  9. wee folding bike
    Member

    Brompton S2L-X is a nice Q bike.

    Anyone watching carefully would spot that I'm spinning like crazy with no higher gears because the top is only 74" but apparently being passed by a folder upsets a person's critical faculties. Flying start is great because of the wee wheels, standing start less so because of the 56" other gear.

    Expect to wear out chains at an accelerated rate. There is a Yahoo group called Bromptontalk which can answer lots of questions.

    Posted 12 years ago #

  10. Smudge
    Member

    74" is quite low! The paperwork with this three speed quotes the gears as 46", 62", 82"
    Can't remember what the Dahon's gear range is, but at about 7 1/2 kilos on Schwalbe GP tyres it's really quick when you start to spin, as you say, it plays with peoples minds when a folder passes them and they can't catch it* :-))

    *not that I'm fast, I'm not! It's just that some people are slower than they think (and don't realise that buying a carbon bike wont make your legs any stronger)!

    Posted 12 years ago #

  11. fimm
    Member

    I have a 3-speed Brompton. I can pass people on mountain bikes but proper fast people fly past me.
    I can "honk" it up Dundas Street or Market Street. I have no idea what the gear ratios or whatever are.

    Posted 12 years ago #

  12. chdot
    Admin

    "and don't realise that buying a carbon bike wont make your legs any stronger"

    My first impression with my first light/fast bike was that it 'made' me go faster.

    Limitation wasn't legs but lungs - got puffed out quickly!

    Posted 12 years ago #

  13. wee folding bike
    Member

    Yes, at least some of the S2L-X advantage is in the mind of the rider. It invites you to go faster so you turn the effort up to 11.

    Posted 12 years ago #

  14. Smudge
    Member

    "Limitation wasn't legs but lungs - got puffed out quickly! "

    I think 'cause I'm a bit lazy and tend to spin rather than power up hills (the Surly's lowest gear will see you doing approx 5mph at 80-90rpm!) my heart/lungs do ok on climbs, but if I try to "power" up hills my legs give out long before I run out of puff. I guess pushing a taller gear will do me good on the whole :-) (I hope!)

    Not sure how I'd check the gear ratios on a hub gear bike, I suppose bits of chalk and a tape measure! Much easier to work out with a pair of cogs to count teeth on!

    Posted 12 years ago #

  15. cb
    Member

    I think my seven speed Birdy is 36" to 92". Can only really pedal it up to about 25mph downhill and it can be a bit hard work up steep hills but it's nippy away from the lights, certainly a fast bike about town and fairly easy to accelerate past people.
    Apart from all the times when other people accelerate past me.

    Posted 12 years ago #

  16. wee folding bike
    Member

    There is a Brompton calculator here:

    http://xldev.co.uk/bgc.html

    If you want to do it by hand the ratios are 75%, 100% and 133%.

    Posted 12 years ago #

  17. Uberuce
    Member

    74" is what wee blue floofy's set to these days, by wacky coincidence.

    It was at 63" up until last weekend, and like chdot noticed upon getting a lighter bike, I just ride everywhere quicker now - it's apparently easier to ride at my natural cadence and shove the extra friction than it is to grind.

    Posted 12 years ago #

  18. wee folding bike
    Member

    My old Claud Butler has a 74" fixed gear. It's had that since the '80s.

    Posted 12 years ago #

  19. Smudge
    Member

    "74" is quite low!"

    I feel I should qualify that statement(!), low for top gear on a multi-gear bike, pretty blooming tall to be pushing uphill imo :-o

    Great link for the gear calculator thanks :)

    Posted 12 years ago #

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