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  1. #1
    Bromptonaut 14R's Avatar
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    Merc rear wheel options

    I am looking for a ultra compact, trouble free bicycle that I can use and fix without getting a degree in mechanics. My goal is to upgrade the attached Merc into something like this:



    (picture used without permission, let me know if this bothers you Easy Racer)

    OK. i am not really thrilled with the plastic chain tensioner that came on the merc. If I count labor hours, I would rather buy ANYTHING than continue working on the internal hub/chain tensioner to make it work the way I want, so based on that, what are my options to achieve a better setup for a brompton-like Merc?

    For sure, I am going with single front chainring (bigger, probably 50T);

    Buy a better, 8 spd internal hub?

    Fixed gear? I like versatility, so this is the last case scenario

    Would a real derailleur work as a chain tensioner for folding purposes? If that's the case, I may go with a nice 9spd rear setup.
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  2. #2
    Senior Member
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    Quote Originally Posted by Rafael Guerra
    For sure, I am going with single front chainring (bigger, probably 50T);

    Buy a better, 8 spd internal hub?

    Fixed gear? I like versatility, so this is the last case scenario

    Would a real derailleur work as a chain tensioner for folding purposes? If that's the case, I may go with a nice 9spd rear setup.
    Bigger chainring is easy, Brompton run 54T as their largest factory option. Others have fitted bigger aftermarket.
    Most 8sp hubs are wider than the Brompton swingarm OLN (don't know about the copies) but that can be changed.
    Fixed gear is difficult with any sort of chain tensioner and you'll need one to fold the swingarm.
    Rear derailleurs on Bromptons can work but generally require tweaking in use and some care when folding (certain gears only, etc). Hub width can be a problem as mentioned previously.

    Most of these changes will make the bike heavier...

  3. #3
    Raleigh20 PugFixie, Merc LittlePixel's Avatar
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    My gut feeling is maybe a Rohloff tensioner might be a good upgrade from the plasticcy thing it comes with. Don't really know why Rohloff's need a tensioner but the one's I've seen are pretty well engineered...

    http://www.sjscycles.co.uk/product-R...250)-12312.htm

    In my own current Brompy/Merc thread I mused about fixed and pretty much everyone is saying it's impossible; this is because the hinge of the rear triangle and the centre of the cranks is not the same so that when you flip the triangle underneath the chain tension changes.

  4. #4
    Senior Member Fear&Trembling's Avatar
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    @Rafael - Did you get that Merc from Wav? I ask, as I have still not seen the "souped-up" version for sale. How do you find it?

  5. #5
    Bromptonaut 14R's Avatar
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    I did get the Merc from Wav. Although, the souped-up Merc is already available for sale if you contact them (their web site sucks, but their customer service is above average).

    I can't tell if I like the bike or not because I only rode it for 3.6 miles. I spent about 40 hours trying to fix a miss aligned rear tensioner and now I finally took it to the professionals (bike will be ready tomorrow). So fat, the geometry is nice, the brakes are by far the most impressive I've seen and the smaller wheels did not make a big difference compared to 20" wheels.

    If the Merc end up not being the bike I want, I honestly don't know what to get. Ideally, the bike that I want is a 24speed Merc with a trouble free mechanism that I can travel with without disassembly and ride a century after arrival. Any suggestions?

  6. #6
    Senior Member
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    A Rohloff tensioner will not wrap enough chain.

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