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  1. #1
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    Brompton Mods - for a newbie

    Hi All,
    So I bought my Arctic Blue M3L Brompton about three months ago and commute on it daily. Within two days of owning it I had modified some skate wheels to replace the factory fitted castors and that is as far as I have got, until now...

    I want to change the M handlebar I have for a lower riser bar. I also think the stick gear shifter for my standard 3 gear sturmey archer is ugly and want to replace it. If I am doing that... then let's also look at the brake levers, grips and bar ends.

    My question to you bike gurus out there is, what components would you recommed and will go together? They should not interfere with the fold (hence a riser bar should be perfect) and the total weight should be comparable if not lower than what is there already.

    Brompton bars are 25.4mm at the clamp. What about gear shifters, do they have specific mounting diameters? Same question for brake levers?

    Also, what complications do I need to look out for? Do I need to replace my factory fitted cables or will they slot straight into the new 3 speed gear shifter and brake levers?

    Lots to get wrong here, and as a bike lover but a newbie bike tech, I need your help.

  2. #2
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    I'll be reading this with interest. I'm very curious to know the weight of stock Brompton components, particularly the stem and handlebars for all 3 types. I'm guessing the M bar is heavy. Perhaps Dahon's Andros stem plus a flat bar could offer a highly adjustable solution with more space for brakes/shifter/lights etc..

  3. #3
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    If you check Bromptons web site "bike explorer" you can see all the different weights for the various components and options.

    http://www.brompton.co.uk/explorer/bikes/index.asp?s=1

    This link will give you the weights for each model both standard and TI

    http://www.brompton.co.uk/page.asp?p=3060

    Move your mouse over the model to see price and weight.

    You will see for example that a M3L TI will cost you 450 more than the M3L standard. At 1kg difference that's 450/kg

    If I had the money, I would buy a M3L-X remove back brake, 3 speed hub, brake lever, gear changer & cables and replace them with a S/A Duomatic 2 speed kickback hub with coaster brake. I would then fit Kojaks which would probably bring it down to between 9.5-10kgs

    Regards

    Jerry
    Last edited by jerrysimon; 03-22-11 at 07:06 AM.

  4. #4
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    Will the coaster brake work with the chain tensioner?
    Dahon Jifo
    Dawes Kingpin 2speed

  5. #5
    Senior Member dorkypants's Avatar
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    I replaced my stock Brompton bars with a cheap aluminum MTB straight bar from a closeout sale. I got a SRAM GripShift 3-speed shifter (intended for the front derailleur of an MTB) to replace the SA trigger shifter. The shifter came with its own cable. The only oddities are (a) it's "backwards" if you mount it on the right side of the handlebar, (b) it moves the brake lever quite far inboard if you use standard MTB grips w/o cutting them short. Neither mod interferes with the fold.

  6. #6
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    Quote Originally Posted by Dynocoaster View Post
    Will the coaster brake work with the chain tensioner?
    Yes it does because I have tried it. Its not perfect but works ok. The fold is not compromised and the coaster brake works fine.

    I am told it is better to use the tensioner on the two speed changer whereas I used the one from my three speed.

    Regards

    Jerry
    Last edited by jerrysimon; 03-22-11 at 11:39 AM.

  7. #7
    Bromptonaut 14R's Avatar
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    All the mods must be based on what you want to achieve. Is it speed, comfort, style or any combination of these topics? I have about 5 years of experience "mod'ing" Bromptons, I can point you in the right direction.

    Before we start, please let me know your hight and your overall budget available for these improvements.

    Let the fun begin!

  8. #8
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    Jerrysimon, I'd like to know the specific weights of the individual components that differentiate the models. I would have weighed the M bars and stem already if they were easier to get off the bike.

  9. #9
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    Quote Originally Posted by 14R View Post
    Is it speed, comfort, style or any combination of these topics? I have about 5 years of experience "mod'ing" Bromptons, I can point you in the right direction.
    Do you think speed and comfort are mutually exclusive ?

    Regards

    Jerry

  10. #10
    Bromptonaut 14R's Avatar
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    Quote Originally Posted by jerrysimon View Post
    Do you think speed and comfort are mutually exclusive ?

    Regards

    Jerry
    Yes. For speed, you need a rigid bike where all forces generated from you are transferred, through the bike, to the pavement.

    For comfort, you need all forces generated from irregular pavement NOT transferred through the bike, to you.

    Besides, comfy stuff are typically heavier than racing stuff.

    Does it make sense?

  11. #11
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    Here is my experience with what i have changed (will change) on my 2009 M3L. I did learn that using stuff that is not stock/designed for Brompton rarely fits. You can still mod the bike but try to stick to stock-ish components.

    Bottom Bracket: Phil Wood 120 mm Campagnolo taper (The stock one developed some grind in about ~4000km and quite some play after ~5000; it lasted me through 2 winters and LOTS of rain). Overall this seems to be a weak spot for the Brompton.

    Crankset: You can change it but remember 170mm crank length MAX, 119mm spindle; square taper JIS or ISO (Campagnolo) on BOTH the crank and the BB.

    P-type stem+handlebars: I am pretty tall so although the M-types are OK, I want something a little higher and more forward. It would also give me a lower position as well. I have the stem on order from SJS Cycles, so when it arrives I will change it (and will have an M-type stem+handlebars+brake levers spare if anyone is interested). In your case you can put a S-type straight bars on the P-type stem to get an even lower sporty position and that would leave you plenty of space for risers without compromising the fold. If you decide you can go back and put P-type bars for a multi-position at the cost of some weight. In addition I am not sure but you can probably substitute the M type handlebars for S-type as well.

    Sturmey-Archer AM Medium ratio three speed hub: Look up "Some hub gear tinkering in Google" done by rogerzilla, it is a very simple conversion and would give you nice gears for some fast cycling.

    2 speed derailleur: I did consider the hub gear/derailleur hybrid gearing a monstrosity, however, getting to think about it it is a way to add some gear range. When using the 13-15 cog combination and the AM hub you have overlapping ranges but it would give me the same low end as the AW hub and another top gear if needed (I currently run 54/14). I see it as Low Range and High Range 3-speed rather than a 6 speed. Newer SA hubs have a narrower driver so you might have trouble fitting 2 cogs, you can swap the hub internals for an older model ones with no trouble.

    You can upgrade the headset to a Chris King 1-1/8 inch (Gripnut or 2Nut) if you are so inclined/have the money, however, the Brompton headset seems to do its job just fine.

    As I mentioned earlier the Brompton in it's current state is what has crystallized over the years, so there is pretty much stock parts to suit every rider's need. Anything else looks like a Frankenbike, I particulalry I am not a fan of that look (nice looking rides go fast, eh?=))

    Without actually trying, it is tough to say what will work or not for you, however, if you ride a lot you learn through trial and error what needs to be changed. Also always remember, if it ain't broken, don't fix it. Trust me on that last one. =)

    If you want to save weight, you can buy the titanium frame parts but they do cost quite a chunk of change. You can get an the alloy seatpost for some weight savings and at a reasonable price

    -Carcinogent

  12. #12
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    Hi All, thanks for the keen responses.
    To summarise where my head is at so far.... I am cycling through London daily and hence my standard 3 gear SA drive train is perfectly acceptable so thanks for the recommendations but right now I want to focus on the cockpit - I want to lose the granny bars (too upright for me) and improve the brompton gear shifter. If I can make the cockpit look more streamlined and less happy-shopper that would be good.

    I am 64kg and 5'7" - yep I'm small and light so no broken spokes for me, it means I am able to accelerate from those flaming London traffic lights considerably quicker that most other riders. I am looking for a ride that is more quick than comfortable otherwise I would stick with the M bars... however, this bike is my commuter not my racer so flat bars are out and a small riser bar would seem to suit. Plus, (no offence meant) I don't like the look of the S-Type Brompton. I also use the C-Bag daily so for functionality and cost I am not intending to change the steering post.

    Cost wise I am flexible... but I'm not rich so need to be realistic, maybe aim for under 150 all in? (that seems a lot to me but do not want to restrict the component solutions). That should cover: Riser Bar / Gear Shifter / Brake Levers / Grips / Bar Caps / Bolts and Cables-if needed.

    Oh and Chagzuki, I found on SJSCycles web site that they reckon the P-Type bar is 465g.... however, I don't think you can then use Bromptons quoted weight difference on their Bike Explorer page because it would make the M-bar something like 197g.... which would rival carbon fibre! So closer to an answer but not there yet.

    J.
    Last edited by cityjim; 03-23-11 at 07:17 AM. Reason: correction to gear shifter descripiton in 1st para

  13. #13
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    Quote Originally Posted by 14R View Post
    Does it make sense?
    Yep

    I just popped into town on my M3L and tried a S2L-X. It was actually quite nippy though I just can't ride that stooped over for any length of time. I found I had to sit up and put my fingers tips on the bars after a short power ride to get my breath back. I guess being older my back just can't take that riding position for long.

    I guess that is where the P bars come in.

    I am still not sure the TI (X) premium is worth it, though I must admit the ride feels a little different so I guess its not just a weight thing ?

    Regards

    Jerry

  14. #14
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    Quote Originally Posted by jerrysimon View Post
    I am still not sure the TI (X) premium is worth it, though I must admit the ride feels a little different so I guess its not just a weight thing ?

    Regards

    Jerry
    The way i see it Ti is just less carrying weight/minimalistic without that much effect on ride quality. Steel and Ti are in the same boat when it comes to comfort, etc. And of course Ti doesn't rust, a desirable quality in an all weather commuter.

    -Cacinogent
    Last edited by Carcinogent; 03-23-11 at 08:08 AM.

  15. #15
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    Quote Originally Posted by cityjim View Post
    Oh and Chagzuki, I found on SJSCycles web site that they reckon the P-Type bar is 465g.... however, I don't think you can then use Bromptons quoted weight difference on their Bike Explorer page because it would make the M-bar something like 197g.... which would rival carbon fibre! So closer to an answer but not there yet.
    Does seem a bit odd. Dunno, downhill bars are overbuilt and tend to be around 300g. They're probably about the same length overall. . . actually the M bars would be about 80cm if straightened. I'm wondering how much of the flex in the front is down the bars rather than stem. I was surprised when first riding the brompton that the ride wasn't as harsh as I expected, which I initially put down to the steel frame. But perhaps the suspension effect of the M bars has a lot to do with it. . . unfortunately the degree of flex is annoying when hill climbing.

  16. #16
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    Quote Originally Posted by cityjim View Post


    I am 64kg and 5'7" - yep I'm small and light so no broken spokes for me, it means I am able to accelerate from those flaming London traffic lights considerably quicker that most other riders. I am looking for a ride that is more quick than comfortable otherwise I would stick with the M bars... however, this bike is my commuter not my racer so flat bars are out and a small riser bar would seem to suit. Plus, (no offence meant) I don't like the look of the S-Type Brompton. I also use the C-Bag daily so for functionality and cost I am not intending to change the steering post.

    Cost wise I am flexible... but I'm not rich so need to be realistic, maybe aim for under 150 all in? (that seems a lot to me but do not want to restrict the component solutions). That should cover: Riser Bar / Gear Shifter / Brake Levers / Grips / Bar Caps / Bolts and Cables-if needed.
    Well P-type might be the bike for you after all. It meets all of the above-mentioned requirements including price. =P

    -Carcinogent

  17. #17
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    Having just inspected my bike I can see that the M bars don't flex much front-to-back but they do vertically. Actually seems like quite an effective design. Unfortunately most of the front-to-back flex does appear to come from the stem. I'm guessing from the quill section. Dahon's A-head design strikes me as superior, though there's still plenty of flex in that too.

  18. #18
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    Quote Originally Posted by Carcinogent View Post
    Well P-type might be the bike for you after all. It meets all of the above-mentioned requirements including price. =P

    -Carcinogent
    Hi Carcinogent, I see where you are coming from, combining my wish for speed and commuting! :-)
    Althought you present an interesting option, I am still keen on a low riser bar, somewhere between the flat bar of the S and the high rise of the M (and in between the two of a P).

  19. #19
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    The S-type bars are apparently around 8 cm lower than the m-type and the M bar has around 16cm of rise. So the S stem must be 8 cm higher than the M stem. Add a riser bar and you'd have a little control over reach too.

    The only way I could see a solution with the M or P stem would be in conjunction with something akin to Dahon's Andros stem, unless a different handlebar with around 12 cm rise is available.

  20. #20
    Bromptonaut 14R's Avatar
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    I would go with used mountain bike raised bar like seen here:



    Ergon grips with or without bar extension. Most ergons don't require bar caps.

    Google flat bar road bike brake lever. Make sure you get ROAD BIKE compatible, otherwise they will not have the long reach you need. Believe me on this one.

    Good luck on your final mods.

  21. #21
    Bromptonaut 14R's Avatar
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    Quote Originally Posted by Carcinogent View Post

    Bottom Bracket: Phil Wood 120 mm Campagnolo taper

    -Carcinogent
    Is there any Chris King BB that is compatible with the Brompton? I am quite ignorant about BBs...

  22. #22
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    S Bar has a taller front steer stem.. such as :
    http://www.sjscycles.co.uk/brompton-...att-prod20013/

    the trad klick lever is what i use, but now there is a thumb-shifter for the 3 speed..

  23. #23
    coprolite fietsbob's Avatar
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    Chris K and Phil W are both in the external bearing BB game,
    but CK does not do square taper (Phil has, since founding of company)

    http://chrisking.com/bottombracket so you need an the new type crankset too..

    No personal experience... on bromptons,
    [ have Phil for BB on trad road bike].


    For my Brompton, I adopted Schlumpf Mountain drive 2 speed crankset.
    a 54t..Use with AW3/BSR hub, 15t, low range in crank is
    at between a 21,22t equivalent, so the 3 speed is used twice..

    Ergon GR3, folds, [GR5 sticks out so fold down of stem
    won't reach the catch..]
    Mountain Drive is offered in a Brompton version, it's a quick install..

    .. but inappropriate, I expect, for Flatlands like Florida .

    Speed Drive crank, perhaps if you can turn monster gears ,
    as the overdrive is 165% then a small chainring acts much larger
    in high range

    but the gear system is not weightless. and some frame install mods.

    Looks like they fit one on this bike: http://www.flickr.com/photos/3513132...-68401638@N00/
    Last edited by fietsbob; 07-08-12 at 12:22 AM.

  24. #24
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    Quote Originally Posted by cityjim View Post
    Hi All,
    So I bought my Arctic Blue M3L Brompton about three months ago and commute on it daily. Within two days of owning it I had modified some skate wheels to replace the factory fitted castors and that is as far as I have got, until now...

    I want to change the M handlebar I have for a lower riser bar. I also think the stick gear shifter for my standard 3 gear sturmey archer is ugly and want to replace it. If I am doing that... then let's also look at the brake levers, grips and bar ends.

    My question to you bike gurus out there is, what components would you recommed and will go together? They should not interfere with the fold (hence a riser bar should be perfect) and the total weight should be comparable if not lower than what is there already.

    Brompton bars are 25.4mm at the clamp. What about gear shifters, do they have specific mounting diameters? Same question for brake levers?

    Also, what complications do I need to look out for? Do I need to replace my factory fitted cables or will they slot straight into the new 3 speed gear shifter and brake levers?

    Lots to get wrong here, and as a bike lover but a newbie bike tech, I need your help.
    It depends on what you wish to accomplish on your modifications. I tend to go for the simple and true approach to modifications to both my Brompton & Raleigh Twenty. If you visit my Google Website (for the recent Raleigh Twenty's restoration), and my Flickr sites for the Brompton over the 5 years I had it, you will see the changes for yourself.

  25. #25
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    Interesting discussion...

    I'll just list some of my changes and see if it applies to you. I started with an M6L in Seattle to cover some big hills. I found the shifting routine cumbersome and the 2 speed derailleur would jam too easily because of all the road grime sticking to it. To combat the shifting situation, I switched to a 5 speed S-RF5 rear hub. I love it...covers enough range without being much heavier than the 3 speed. Singlespeed-style drivetrain is much better...not a problem for you if you have a 3 speed.

    For the cockpit, I also started out with the M-bars because I like the looks better. I thought I might be able to get a high rise MTB bar, but nothing was high enough (other than some steel ones). So, I purchased an S-stem and put on a 2" (50cm) riser and it's spot on (I'm 5'9" and about 80kg). For shifting, I went with the SA thumbie-style shifter after unsuccessfully modifying a gripshifter. For the other cockpit mods, I went with Paul Component Cantilevers (any road-compatible flat bar brake will work fine, but I have wanted a reason to buy these) and Ergon Biokorks.

    I absolutely love my Brompton. I had a Bike Friday Tikit for about 4 months, but the fold just didn't cut it. The Brompton is as close to a perfect multimodal commuter as I could imagine

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